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  • 1.
    Akiyama, Reiko
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Conflicting selection on the timing of germination in a natural population of Arabidopsis thaliana2014In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 27, no 1, p. 193-199Article in journal (Refereed)
    Abstract [en]

    The timing of germination is a key life-history trait that may strongly influence plant fitness and that sets the stage for selection on traits expressed later in the life cycle. In seasonal environments, the period favourable for germination and the total length of the growing season are limited. The optimal timing of germination may therefore be governed by conflicting selection through survival and fecundity. We conducted a field experiment to examine the effects of timing of germination on survival, fecundity and overall fitness in a natural population of the annual herb Arabidopsis thaliana in north-central Sweden. Seedlings were transplanted at three different times in late summer and in autumn covering the period of seed germination in the study population. Early germination was associated with low seedling survival, but also with high survival and fecundity among established plants. The advantages of germinating early more than balanced the disadvantage and selection favoured early germination. The results suggest that low survival among early germinating seeds is the main force opposing the evolution of earlier germination and that the optimal timing of germination should vary in space and time as a function of the direction and strength of selection acting during different life-history stages.

  • 2.
    Akiyama, Reiko
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Magnitude and timing of leaf damage affect seed production in a natural population of Arabidopsis thaliana (Brassicaceae)2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 1, p. e30015-Article in journal (Refereed)
    Abstract [en]

    Background: The effect of herbivory on plant fitness varies widely. Understanding the causes of this variation is of considerable interest because of its implications for plant population dynamics and trait evolution. We experimentally defoliated the annual herb Arabidopsis thaliana in a natural population in Sweden to test the hypotheses that (a) plant fitness decreases with increasing damage, (b) tolerance to defoliation is lower before flowering than during flowering, and (c) defoliation before flowering reduces number of seeds more strongly than defoliation during flowering, but the opposite is true for effects on seed size.

    Methodology/Principal Findings: In a first experiment, between 0 and 75% of the leaf area was removed in May from plants that flowered or were about to start flowering. In a second experiment, 0, 25%, or 50% of the leaf area was removed from plants on one of two occasions, in mid April when plants were either in the vegetative rosette or bolting stage, or in mid May when plants were flowering. In the first experiment, seed production was negatively related to leaf area removed, and at the highest damage level, also mean seed size was reduced. In the second experiment, removal of 50% of the leaf area reduced seed production by 60% among plants defoliated early in the season at the vegetative rosettes, and by 22% among plants defoliated early in the season at the bolting stage, but did not reduce seed output of plants defoliated one month later. No seasonal shift in the effect of defoliation on seed size was detected.

    Conclusions/Significance: The results show that leaf damage may reduce the fitness of A. thaliana, and suggest that in this population leaf herbivores feeding on plants before flowering should exert stronger selection on defence traits than those feeding on plants during flowering, given similar damage levels.

  • 3.
    Boberg, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Alexandersson, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Jonsson, Magdalena
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Maad, Johanne
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Nilsson, Anders L.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Pollinator shifts and the evolution of spur length in the moth-pollinated orchid Platanthera bifolia2014In: Annals of Botany, ISSN 0305-7364, E-ISSN 1095-8290, Vol. 113, no 2, p. 267-275Article in journal (Refereed)
    Abstract [en]

    Plantpollinator interactions are thought to have shaped much of floral evolution. Yet the relative importance of pollinator shifts and coevolutionary interactions for among-population variation in floral traits in animal-pollinated species is poorly known. This study examined the adaptive significance of spur length in the moth-pollinated orchid Platanthera bifolia. Geographical variation in the length of the floral spur of P. bifolia was documented in relation to variation in the pollinator fauna across Scandinavia, and a reciprocal translocation experiment was conducted in south-east Sweden between a long-spurred woodland population and a short-spurred grassland population. Spur length and pollinator fauna varied among regions and habitats, and spur length was positively correlated with the proboscis length of local pollinators. In the reciprocal translocation experiment, long-spurred woodland plants had higher pollination success than short-spurred grassland plants at the woodland site, while no significant difference was observed at the grassland site. The results are consistent with the hypothesis that optimal floral phenotype varies with the morphology of the local pollinators, and that the evolution of spur length in P. bifolia has been largely driven by pollinator shifts.

  • 4.
    Boberg, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Despite their apparent integration, spur length but not perianth size affects reproductive success in the moth-pollinated orchid Platanthera bifolia2009In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 23, no 5, p. 1022-1028Article in journal (Refereed)
    Abstract [en]

    The evolution of many floral traits is thought to have been shaped  by pollinator-mediated selection for increased attractiveness or an   improved mechanical fit of flowers to pollinators. Yet, few studies have examined experimentally the independent and interactive effects of   different aspects of flower morphology on plant reproductive success.   In the orchid Platanthera bifolia, perianth size and spur length are   positively correlated within and among populations. To test the hypothesis that pollination success and seed output increases with   increasing perianth size and spur length, we manipulated the two traits   in a factorial design in a long-spurred population of P. bifolia   pollinated by long-tongued hawkmoths. Additionally, to determine   whether differences in selfing rate can explain variation in fruit set   and fruit size, we performed controlled self- and cross-pollination.   Plants with long spurs had more flowers pollinated, more pollen removed   and produced more and larger fruits compared to plants with short   spurs. In contrast, perianth size did not affect the pollination   success or fruit production of P. bifolia.   Fruit production and fruit size did not differ among flowers pollinated   with self- and cross pollen, respectively. This indicates that reduced   pollen deposition rather than pollinator-mediated self-pollination   caused the reduction in fruit set and fruit volume observed after   shortening of the spur.   The results demonstrate that spur length, but not perianth size, is   critical for reproductive success in P. bifolia, and suggest that   among-population differentiation in perianth size may reflect a  correlated response to selection on spur length. The results are  consistent with the hypothesis that visual display is less important   than other cues for the reproductive success of P. bifolia, and   underscore the necessity to experimentally examine the functional   significance of putatively adaptive traits.

  • 5.
    Chapurlat, Elodie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Sletvold, Nina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Spatial variation in pollinator-mediated selection on phenology, floral display and spur length in the orchid Gymnadenia conopsea2015In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 208, no 4, p. 1264-1275Article in journal (Refereed)
    Abstract [en]

    Spatial variation in plant-pollinator interactions may cause variation in pollinator-mediated selection on floral traits, but to establish this link conclusively experimental studies are needed. We quantified pollinator-mediated selection on flowering phenology and morphology in four populations of the fragrant orchid Gymnadenia conopsea, and compared selection mediated by diurnal and nocturnal pollinators in two of the populations. Variation in pollinator-mediated selection explained most of the among-population variation in the strength of directional and correlational selection. Pollinators mediated correlational selection on pairs of display traits, and on one display trait and spur length, a trait affecting pollination efficiency. Only nocturnal pollinators selected for longer spurs, and mediated stronger selection on the number of flowers compared with diurnal pollinators in one population. The two types of pollinators caused correlational selection on different pairs of traits and selected for different combinations of spur length and number of flowers. The results demonstrate that spatial variation in interactions with pollinators may result in differences in directional and correlational selection on floral traits in a plant with a semi-generalized pollination system, and suggest that differences in the relative importance of diurnal and nocturnal pollinators can cause variation in selection.

  • 6.
    Colautti, Robert I.
    et al.
    Queens Univ, Dept Biol, 116 Barrie St, Kingston, ON K7L 3N6, Canada..
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Anderson, Jill T.
    Univ Georgia, Dept Genet, 120 Green St, Athens, GA 30602 USA.;Univ Georgia, Odum Sch Ecol, 120 Green St, Athens, GA 30602 USA..
    Phenological shifts of native and invasive species under climate change: insights from the Boechera - Lythrum model2017In: Philosophical Transactions of the Royal Society of London. Biological Sciences, ISSN 0962-8436, E-ISSN 1471-2970, Vol. 372, no 1712, article id 20160032Article, review/survey (Refereed)
    Abstract [en]

    Warmer and drier climates have shifted phenologies of many species. However, the magnitude and direction of phenological shifts vary widely among taxa, and it is often unclear when shifts are adaptive or how they affect long-term viability. Here, we model evolution of flowering phenology based on our long-term research of two species exhibiting opposite shifts in floral phenology: Lythrum salicaria, which is invasive in North America, and the sparse Rocky Mountain native Boechera stricta. Genetic constraints are similar in both species, but differences in the timing of environmental conditions that favour growth lead to opposite phenological shifts under climate change. As temperatures increase, selection is predicted to favour earlier flowering in native B. stricta while reducing population viability, even if populations adapt rapidly to changing environmental conditions. By contrast, warming is predicted to favour delayed flowering in both native and introduced L. salicaria populations while increasing long-term viability. Relaxed selection from natural enemies in invasive L. salicaria is predicted to have little effect on flowering time but a large effect on reproductive fitness. Our approach highlights the importance of understanding ecological and genetic constraints to predict the ecological consequences of evolutionary responses to climate change on contemporary timescales. This article is part of the themed issue 'Human influences on evolution, and the ecological and societal consequences'.

  • 7. Dalin, Peter
    et al.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Björkman, Christer
    Huttunen, Piritta
    Kärkkäinen, Katri
    Leaf trichome formation and plant resistance to herbivory2008In: Induced plant resistance to herbivory, Springer , 2008, p. 89-105Chapter in book (Other academic)
  • 8. Dittmar, Emily L.
    et al.
    Oakley, Christopher G.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Schemske, Douglas W.
    Flowering time QTL in natural populations of Arabidopsis thaliana and implications for their adaptive value2014In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 23, no 17, p. 4291-4303Article in journal (Refereed)
    Abstract [en]

    The genetic basis of phenotypic traits is of great interest to evolutionary biologists, but their contribution to adaptation in nature is often unknown. To determine the genetic architecture of flowering time in ecologically relevant conditions, we used a recombinant inbred line population created from two locally adapted populations of Arabidopsis thaliana from Sweden and Italy. Using these RILs, we identified flowering time QTL in growth chambers that mimicked the natural temperature and photoperiod variation across the growing season in each native environment. We also compared the genomic locations of flowering time QTL to those of fitness (total fruit number) QTL from a previous three-year field study. Ten total flowering time QTL were found, and in all cases, the Italy genotype caused early flowering regardless of the conditions. Two QTL were consistent across chamber environments, and these had the largest effects on flowering time. Five of the fitness QTL colocalized with flowering time QTL found in the Italy conditions, and in each case, the local genotype was favoured. In contrast, just two flowering time QTL found in the Sweden conditions colocalized with fitness QTL and in only one case was the local genotype favoured. This implies that flowering time may be more important for adaptation in Italy than Sweden. Two candidate genes (FLC and VIN3) underlying the major flowering time QTL found in the current study are implicated in local adaptation.

  • 9. Ehlers, B. K.
    et al.
    Olesen, J. M.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Floral morphology and reproductive success in the orchid Epipactis helleborine: regional and local across-habitat variation2002In: Plant Systematics and Evolution, ISSN 0378-2697, E-ISSN 1615-6110, Vol. 236, no 1-2, p. 19-32Article in journal (Refereed)
    Abstract [en]

    The terrestrial orchid Epipactis helleborine is a morphologically variable species with a wide distribution in Europe. It is pollinated by social wasps, and most populations show the morphological characteristics of outcrossing species. However, local predominantly selfing subspecies and varieties have been documented from drier habitats. To document geographic variation in floral morphology, ability to produce seeds through autogamy, and reproductive success in E. helleborine, we sampled 13 populations from three geographic regions along a latitudinal gradient of c. 1000 km from northern to southern Sweden. In the southernmost region, populations in dry and mesic habitats were compared. Supplemental hand-pollination was conducted to determine whether among-population variation in fruit set could be explained by differences in the natural level of pollination, and whether any relationship between floral morphology and fruit production could be explained by interactions with pollinators. Bagging experiments showed no evidence of autogamy in any of the study populations. Number of flowers, pollinia removal and fruit set varied significantly among populations but did not differ among regions. Pollinia removal was positively correlated with population size and both pollinia removal and fruit set were lower in dry than in mesic habitats. At the level of the individual plant, the number of pollinia removed increased more rapidly with flower number than did number of fruits produced. The hand-pollination experiment indicated that the positive relationship between number of flowers and fruit production was due to a higher degree of pollen limitation in plants with few flowers than in plants with many flowers. The experiment also showed that variation in the level of pollen limitation could only partly explain variation in fruit set among populations.

  • 10.
    Ehrlén, Johan
    et al.
    Dept of Botany, Stockholm Univ..
    Käck, Sofia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Pollen limitation, seed predation and scape length in Primula farinosa2002In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 97, no 1, p. 45-51Article in journal (Refereed)
    Abstract [en]

    Floral display and reward production may affect the attractiveness of a plant to a range of interacting animals including pollinators, herbivores, and vectors of pathogenic fungi. The optimal floral phenotype should therefore depend on the relative importance of selection exerted by both mutualistic and antagonistic animals. The perennial, rosette herb Primula farinosa is polymorphic for scape length. Natural populations may include both plants with flowers displayed well above the ground (the long-scaped morph) and those with flowers positioned very close to the ground (the short-scaped morph). In this study, we conducted a field experiment to examine how the relative fitness of the two scape morphs is affected by interactions with pollinators and fruit predators in two different microhabitats (high and low vegetation). As predicted based on the difference in floral display, supplemental hand-pollination showed that fruit initiation was more strongly pollen-limited in the short-scaped than in the long-scaped morph, and that this difference was significantly larger in high than in low vegetation. Moreover, plants with a short scape experienced lower levels of fruit predation than plants with a long scape. Among open-pollinated controls, there was no significant difference in seed output between the two scape morphs. However, among plants receiving supplemental hand-pollination, short-scaped plants produced significantly more seeds than long-scaped plants. The results suggest that the positive and negative effects of a prominent floral display (increased pollination and seed predation, respectively) balance in the study population, but also that the short-scaped morph would have an advantage at higher pollination intensities. Spatial and temporal variation in pollinator activity and seed predation should result in associated variation in the relative fecundity of the two scape morphs.

  • 11. Falahati-Anbaran, Mohsen
    et al.
    Lundemo, Sverre
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Stenoien, Hans K.
    Genetic consequences of seed banks in the perennial herb Arabidopsis lyrata subsp. petraea (Brassicaceae)2011In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 98, no 9, p. 1475-1485Article in journal (Refereed)
    Abstract [en]

    Premise of the Study: Seed banks may increase the effective population size (N(e)) of plants as a result of elevated coalescence times for alleles residing in the populations. This has been empirically demonstrated in populations of the annual Arabidopsis thaliana, whereas comparable data for perennial species are currently lacking. We studied the contribution of seed banks to effective sizes of natural populations of the self-incompatible, perennial Arabidopsis lyrata subsp. petraea, a close relative of A. thaliana. Methods: Fourteen populations of A. lyrata collected throughout the Norwegian distribution range were analyzed using micro-satellite markers. Key Results: The genetic composition of seed-bank and aboveground cohorts was found to be highly similar, with little genetic differentiation between cohorts in most populations. However, the proportion of private alleles was higher in aboveground than in seed-bank cohorts. The presence of seed banks significantly increased total N(e), but the contribution from seed banks to overall N(e) were lower than the contribution from aboveground cohorts in most populations. Estimated historical N(e) values, reflecting the effective sizes of populations throughout the history of the species, were considerably higher than estimates of contemporary N(e), reflecting number of reproducing individuals within the past few generations. Conclusions: The results show that the seed bank contributes to total N(e) in the perennial herb A. lyrata. However, the contribution is similar to or lower than that of the above-ground fraction of the population and markedly weaker than that previously documented in the annual A. thaliana.

  • 12.
    Fogelqvist, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics.
    Niittyvuopio, Anne
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Savolainen, Outi
    Lascoux, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics.
    Cryptic population genetic structure: the number of inferred clusters depends on sample size2010In: Molecular Ecology Resources, ISSN 1755-098X, Vol. 10, no 2, p. 314-323Article in journal (Refereed)
    Abstract [en]

    Clustering methods have been used extensively to unravel cryptic population genetic structure. We investigated the effect of the number of individuals sampled in each location on the resulting number of clusters. Our study was motivated by recent results in Arabidopsis thaliana: studies in which more than one individual was sampled per location apparently have led to a much higher number of clusters than studies where only one individual was sampled in each location, as is generally done in this species. We show, using computer simulations and microsatellite data in A. thaliana, that the number of sampled individuals indeed has a strong impact on the number of resulting clusters. This effect is smaller if the sampled populations have a hierarchical structure. In most cases, sampling 5-10 individuals per population should be enough. The results argue for abandoning the concept of 'accessions' in partially selfing organisms.

  • 13. Frenkel, Martin
    et al.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Jansson, Stefan
    Improper excess light energy dissipation in Arabidopsis results in a metabolic reprogramming2009In: BMC Plant Biology, ISSN 1471-2229, E-ISSN 1471-2229, Vol. 9, p. 12-Article in journal (Refereed)
    Abstract [en]

    Background. Plant performance is affected by the level of expression of PsbS, a key photoprotective protein involved in the process of feedback de-excitation (FDE), or the qE component of non-photochemical quenching, NPQ. Results. In studies presented here, under constant laboratory conditions the metabolite profiles of leaves of wild-type Arabidopsis thaliana and plants lacking or overexpressing PsbS were very similar, but under natural conditions their differences in levels of PsbS expression were associated with major changes in metabolite profiles. Some carbohydrates and amino acids differed ten-fold in abundance between PsbS-lacking mutants and over-expressers, with wild-type plants having intermediate amounts, showing that a metabolic shift had occurred. The transcriptomes of the genotypes also varied under field conditions, and the genes induced in plants lacking PsbS were similar to those reportedly induced in plants exposed to ozone stress or treated with methyl jasmonate (MeJA). Genes involved in the biosynthesis of JA were up-regulated, and enzymes involved in this pathway accumulated. JA levels in the undamaged leaves of field-grown plants did not differ between wild-type and PsbS-lacking mutants, but they were higher in the mutants when they were exposed to herbivory. Conclusion. These findings suggest that lack of FDE results in increased photooxidative stress in the chloroplasts of Arabidopsis plants grown in the field, which elicits a response at the transcriptome level, causing a redirection of metabolism from growth towards defence that resembles a MeJA/JA response.

  • 14.
    Gaudeul, Myriam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Stenøien, Hans K.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Landscape structure, clonal propagation, and genetic diversity in Scandinavian populations of Arabidopsis lyrata (Brassicaceae)2007In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 94, no 7, p. 1146-1155Article in journal (Refereed)
    Abstract [en]

    Colonization history, landscape structure, and environmental conditions may influence patterns of neutral genetic variation because of their effects on gene flow and reproductive mode. We compared variation at microsatellite loci within and among 26 Arabidopsis lyrata populations in two disjunct areas of its distribution in northern Europe (Norway and Sweden). The two areas probably share a common colonization history but differ in size (Norwegian range markedly larger than Swedish range), landscape structure (mountains vs. coast), and habitat conditions likely to affect patterns of gene flow and opportunities for sexual reproduction. Within-population genetic diversity was not related to latitude but was higher in Sweden than in Norway. Population differentiation was stronger among Norwegian than among Swedish populations (F-ST = 0.23 vs. F-ST = 0.18). The frequency of clonal propagation (proportion of identical multilocus genotypes) increased with decreasing population size, was higher in Norwegian than in Swedish populations, but was not related to altitude or substrate. Differences in genetic structure are discussed in relation to population characteristics and range size in the two areas. The results demonstrate that the possibility of clonal propagation should be considered when developing strategies for sampling and analyzing data in ecological and genetic studies of this emerging model species.

  • 15. Hambäck, PA
    et al.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Plant Ecology.
    Ericson, L
    Associational resistance: insect damage to purple loosestrife reduced in thickets of sweet gale2000In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 81, no 7, p. 1784-1794Article in journal (Refereed)
    Abstract [en]

    Associational resistance occurs when herbivore damage to a focal plant is reduced by the presence of other plant species. Neighboring plants can reduce herbivore damage (1) by their effects on the predator community, (2) by reducing the ability of herbivores to find their host plants, and (3) by reducing the time herbivores remain on their host plants. We examined how the presence of the aromatic low shrub Myrica gale and of predatory lady beetles affected herbivore damage and reproductive output in a population of the perennial herb Lythrum salicaria in northern Sweden. An observational study showed that L. salicaria growing in Myrica thickets were less damaged by herbivores, had a lower abundance of the monophagous, leaf-feeding, chrysomelid beetle Galerucella calmariensis, and had higher flower and seed production than L. salicaria outside Myrica thickets. To test whether these differences could be explained by (a) differences in some aspect of plant quality, or (b) differences in predator abundance, we placed potted L. salicaria within and outside Myrica thickets. To determine whether differences in the abundance of G. calmariensis were primarily the result of different rates of colonization or emigration, we marked adult beetles and placed them on a second set of potted plants in the two micro-habitats. The results show that differences in herbivore abundance, plant damage, and reproductive output between potted L. salicaria placed within and outside Myrica thickets were in the same direction and of the same magnitude as those observed for naturally occurring plants, indicating that the observed patterns were not an effect of differences in the chemical composition of the host plant. Moreover, we found no support for the hypothesis that a higher abundance of insect predators could explain the lower abundance of G. calmariensis on L. salicaria in Myrica thickets. On the contrary, lady beetles (Coccinella quinqempunctata and Coccinella septempunctata) were observed on a greater proportion of the plants placed outside the Myrica thickets. The monitoring of marked beetles indicated that differences in the abundance of G. calmariensis were the result of a markedly higher colonization rate and a somewhat lower emigration rate from L. salicaria outside Myrica thickets. Outside the Myrica thickets, the survival of G. calmariensis and the magnitude of herbivore damage were lower, and fruit and seed output were higher on plants with observations of lady beetles than on plants without lady beetles. The results indicate that the abundance of the specialist herbivore G. calmariensis, and the herbivore damage and reproductive output of its host plant, L. salicaria, are affected both by the presence of the nonhost Myrica and by predation from lady beetles. We suggest that the most likely mechanism causing decreased feeding on L. salicaria growing in Myrica thickets is that Myrica affects the ability of G. calmariensis to find its host, either through visual or olfactory interference.

  • 16. Handley, RJ
    et al.
    Ekbom, B
    Ågren, Jon
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Plant Ecology.
    Variation in trichome density and resistance against a specialist herbivore in natural populations of Arabidopsis thaliana2005In: Ecological Entomology, Vol. 30, p. 284-292Article in journal (Refereed)
  • 17. Huttunen, Piritta
    et al.
    Karkkainen, Katri
    Loe, Geir
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Rautio, Pasi
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Leaf trichome production and responses to defoliation and drought in Arabidopsis lyrata (Brassicaceae)2010In: Annales Botanici Fennici, ISSN 0003-3847, E-ISSN 1797-2442, Vol. 47, no 3, p. 199-207Article in journal (Refereed)
    Abstract [en]

    Leaf trichomes can protect plants against herbivory and drought, but can be costly to produce. Theory suggests that selection for reduced costs of resistance may result in the evolution of inducible defences. We quantified variation in tolerance to drought and defoliation, and tested the hypotheses that (a) tolerance is associated with cost, (b) leaf trichome production increases tolerance to drought, and (c) trichome production is increased in response to defoliation and drought stress in Arabidopsis lyrata (Brassicaceae). Eight maternal half-sib families were exposed to two watering regimes and four defoliation treatments in a factorial design. Tolerance to drought varied among families and was inversely related to leaf size, but was not related to trichome density. Family mean performance in the low-watering treatment tended to correlate negatively with that in the control treatment. Trichome production was not induced by defoliation or drought stress. The results suggest that there is genetic variation in tolerance to drought in the study population, that tolerance to drought is associated with a cost, and that trichome production does not increase tolerance to drought in A. lyrata.

  • 18.
    Jakobsson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Padrón, Benigno
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Distance-dependent effects of invasive Lupinus polyphyllus on pollination and reproductive success of two native herbs2015In: Basic and Applied Ecology, ISSN 1439-1791, E-ISSN 1618-0089, Vol. 16, no 2, p. 120-127Article in journal (Refereed)
    Abstract [en]

    A comprehensive understanding of the effects of invasive plants on native species requires identification of both the mechanisms of interaction and the spatial scale over which they act. Indirect interactions involving mobile organisms such as pollinators are likely to be scale-dependent, yet most studies examining effects of invasive species on pollination of native plants have considered effects across a single distance between interacting species. We examined the effects of the invasive herb Lupinus polyphyllus on pollination of two native herbs using multiple distances between the invasive and the natives. We recorded pollinator visitation and seed production in the native herbs Lotus corniculatus and Lychnis viscaria at 0, 5 m or 200 m away from L. polyphyllus. To reduce the influence of confounding factors, we used experimentally established populations of the invasive and potted individuals of the natives. In the immediate vicinity to L. polyphyllus, visitation to L. corniculatus was higher than 200 m away, and seed production per flower was higher than 5 m and 200 m away. In L. viscaria, bumblebee visitation was higher adjacent to L. polyphyllus than 5 m and 200 m away, but total pollinator visitation and reproductive success did not vary with distance. The results indicate that L. polyphyllus facilitates pollination of the native plants, and that this occurs at a very local spatial scale as effects dropped off already at a distance of 5 m. Presence of L. polyphyllus could benefit both pollinators and pollination of native herbs, and these positive effects should be considered along with likely negative effects due to resource competition. Moreover, the results illustrate the necessity to consider scale-dependent effects when assessing the impact of invasive flowering plants on native pollination interactions.

  • 19.
    Jakobsson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Distance to semi-natural grassland influences seed production of insect-pollinated herbs2014In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 175, no 1, p. 199-208Article in journal (Refereed)
    Abstract [en]

    Marginal grassland fragments, such as road verges and field margins, may act as important supplemental habitats for grassland plants in the modern agricultural landscape. However, abundance of pollinators in such fragments has been found to decline with distance to larger natural and semi-natural habitats, and this could have corresponding effects on plant pollination. In this study, we performed a field experiment on road verges with three insect-pollinated grassland herbs to examine the relationship between distance to semi-natural grassland and plant reproductive success in two landscapes with contrasting farming intensities. In Lychnis viscaria and Lotus corniculatus, seed production tended to decrease with increasing distance to semi-natural grassland, but only in the landscape with high farming intensity. Seed production in Armeria maritima spp. maritima decreased with distance in both landscapes. Although many studies have investigated effects of natural habitat on crop pollination, little is known about the impact on pollination in native plants. The results from this study indicate that management of semi-natural grasslands improves not only biodiversity within the actual grassland but also pollination of native plants in the surrounding agricultural landscape.

  • 20. Johnson, S.D.
    et al.
    Collin, C.L.
    Wissman, H.J.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Halvarsson, E
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Ågren, Jon
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Factors contributing to variation in seed production among remnant populations of the endangered daisy Gerbera aurantiaca2004In: Biotropica, Vol. 36, p. 148-155Article in journal (Refereed)
  • 21. Johnson, S.D.
    et al.
    Peter, C.I.
    Ågren, Jon
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    The effect of nectar addition on pollen removal and geitonogamy in the non-rewarding orchid Anacamptis morio2004In: Proceedings of the Royal Society of London B, Vol. 271, p. 803-809Article in journal (Refereed)
  • 22. Johnson, Steven D.
    et al.
    Peter, Craig I.
    Nilsson, L. Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Pollination success in a deceptive orchid is enhanced by co-ocurring rewarding magnet plants2003In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 84, no 11, p. 2919-2927Article in journal (Refereed)
    Abstract [en]

    It has been debated whether pollination success in nonrewarding plants that flower in association with nectar-producing plants will be diminished by competition for pollinator visits or, alternatively, enhanced through increased local abundance of pollinators (the magnet species effect). We experimentally evaluated these effects using the nonrewarding bumblebee-pollinated orchid Anacamptis morio and associated nectar-producing plants at a site in Sweden. Pollination success (estimated as pollen receipt and pollen removal) in A. morio was significantly greater for individuals translocated to patches of nectar-producing plants (Geum rivale and Allium schoenoprasum) than for individuals placed outside (20 m away) such patches. These results provide support for the existence of a facilitative magnet species effect in the interaction between certain nectar plants and A. morio. To determine the spatial scale of these interactions, we correlated the visitation rate to flowers of A. morio with the density of sympatric nectar plants in 1-m2 and 100-m2 plots centered around groups of translocated plants, and at the level of whole meadows (0.5–2 ha). Visitation rate to flowers of A. morio was not correlated with the 1-m2 patch density of G. rivale and A. schoenoprasum, but showed a significant positive relationship with density of these nectar plants in 100-m2 plots. In addition, visitation to flowers of A. morio was strongly and positively related to the density of A. schoenoprasum at the level of the meadow. Choice experiments showed that bees foraging on the purple flowers of A. schoenoprasum (a particularly effective magnet species) visit the purple flowers of A. morio more readily (47.6% of choices) than bees foraging on the yellow flowers of Lotus corniculatus (17% of choices). Overall similarity in flower color and shape may increase the probability that a pollinator will temporarily shift from a nectar-producing “magnet” plant to a nonrewarding plant. We discuss the possibility of a mimicry continuum between those orchids that exploit instinctive food-seeking behavior of pollinators and those that show an adaptive resemblance to nectar-producing plants.

  • 23. Johnson, Steven D.
    et al.
    Torninger, Erica
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Relationships between population size and pollen fates in a moth-pollinated orchid2009In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 5, no 2, p. 282-285Article in journal (Refereed)
    Abstract [en]

    Management of small plant populations requires an understanding of their reproductive ecology, particularly in terms of sensitivity to Allee effects. To address this issue, we explored how components of pollen transfer and pollination success of individual plants varied among 36 populations of the self-compatible moth-pollinated orchid Satyrium longicauda in South Africa. Mean fruit set, seed production, proportion of flowers with pollen deposited or removed and proportion of removed pollen that reached stigmas (approx. 8% in this species) were not significantly related to population size (range: 1–450 flowering individuals), density or isolation. Plants in small populations did, however, have significantly higher levels of pollinator-mediated self-pollination (determined using colour-labelled pollen) than those in larger populations. Our results suggest that small populations of this orchid species are resilient to Allee effects in terms of overall pollination success, although the higher levels of pollinator-mediated self-pollination in small populations may lead to inbreeding depression and long-term erosion of genetic diversity.

  • 24. Kivimäki, Maarit
    et al.
    Kärkkäinen, Katri
    Gauldeul, Myriam
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Løe, Geir
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Gene, phenotype and function: GLABROUS1 and resistance to herbivory in natural populations of Arabidopsis lyrata2007In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 16, no 2, p. 453-462Article in journal (Refereed)
    Abstract [en]

    The molecular genetic basis of adaptive variation is of fundamental importance for evolutionary dynamics, but is still poorly known. Only in very few cases has the relationship between genetic variation at the molecular level, phenotype and function been established in natural populations. We examined the functional significance and genetic basis of a polymorphism in production of leaf hairs, trichomes, in the perennial herb Arabidopsis lyrata. Earlier studies suggested that trichome production is subject to divergent selection. Here we show that the production of trichomes is correlated with reduced damage from insect herbivores in natural populations, and using statistical methods developed for medical genetics we document an association between loss of trichome production and mutations in the regulatory gene GLABROUS1. Sequence data suggest that independent mutations in this regulatory gene have provided the basis for parallel evolution of reduced resistance to insect herbivores in different populations of A. lyrata and in the closely related Arabidopsis thaliana. The results show that candidate genes identified in model organisms provide a valuable starting point for analysis of the genetic basis of phenotypic variation in natural populations.

  • 25. Kärkkäinen, K
    et al.
    Løe, Geir
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Ågren, Jon
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Population structure in Arabidopsis lyrata: evidence for divergent selection on trichome production2004In: Evolution, Vol. 58, p. 2831-2836Article in journal (Refereed)
  • 26.
    Kärkkäinen, K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology.
    Ågren, J.
    Genetic basis of trichome production in Arabidopsis lyrata.2002In: Hereditas, Vol. 136, p. 219-226Article in journal (Refereed)
  • 27.
    Külheim, Carsetn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Jansson, Stefan
    Rapid Regulation of Light Harvesting and Plant Fitness in the Field.2002In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 297, no 5578, p. 91-93Article in journal (Refereed)
    Abstract [en]

    We used Arabidopsis thaliana mutants to examine how a photosynthetic regulatory process, the qE-type or ΔpH-dependent nonphotochemical quenching, hereafter named feedback de-excitation, influences plant fitness in different light environments. We show that the feedback de-excitation is important for plant fitness in the field and in fluctuating light in a controlled environment but that it does not affect plant performance under constant light conditions. Our findings demonstrate that the feedback de-excitation confers a strong fitness advantage under field conditions and suggest that this advantage is due to the increase in plant tolerance to variation in light intensity rather than tolerance to high-intensity light itself.                      

  • 28.
    Laenen, Benjamin
    et al.
    Stockholm Univ, Sci Life Lab, Dept Ecol Environm & Plant Sci, SE-10691 Stockholm, Sweden..
    Tedder, Andrew
    Stockholm Univ, Sci Life Lab, Dept Ecol Environm & Plant Sci, SE-10691 Stockholm, Sweden..
    Nowak, Michael D.
    Stockholm Univ, Sci Life Lab, Dept Ecol Environm & Plant Sci, SE-10691 Stockholm, Sweden..
    Toräng, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Wunder, Jörg
    Max Planck Inst Plant Breeding Res, D-50829 Cologne, Germany..
    Wötzel, Stefan
    Max Planck Inst Plant Breeding Res, D-50829 Cologne, Germany..
    Steige, Kim A.
    Stockholm Univ, Sci Life Lab, Dept Ecol Environm & Plant Sci, SE-10691 Stockholm, Sweden.;Univ Cologne, Inst Bot, Biozentrum, D-50674 Cologne, Germany..
    Kourmpetis, Yiannis
    Wageningen Univ & Res Ctr, Biometris, NL-6700 AC Wageningen, Netherlands.;Nestle Inst Hlth Sci, CH-1015 Lausanne, Switzerland..
    Odong, Thomas
    Wageningen Univ & Res Ctr, Biometris, NL-6700 AC Wageningen, Netherlands..
    Drouzas, Andreas D.
    Aristotle Univ Thessaloniki, Sch Biol, Thessaloniki 54124, Greece..
    Bink, Marco C. A. M.
    Wageningen Univ & Res Ctr, Biometris, NL-6700 AC Wageningen, Netherlands.;Hendrix Genet Res Technol & Serv, NL-5830 AC Boxmeer, Netherlands..
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Coupland, George
    Max Planck Inst Plant Breeding Res, D-50829 Cologne, Germany..
    Slotte, Tanja
    Stockholm Univ, Sci Life Lab, Dept Ecol Environm & Plant Sci, SE-10691 Stockholm, Sweden..
    Demography and mating system shape the genome-wide impact of purifying selection in Arabis alpina2018In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 115, no 4, p. 816-821Article in journal (Refereed)
    Abstract [en]

    Plant mating systems have profound effects on levels and structuring of genetic variation and can affect the impact of natural selection. Although theory predicts that intermediate outcrossing rates may allow plants to prevent accumulation of deleterious alleles, few studies have empirically tested this prediction using genomic data. Here, we study the effect of mating system on purifying selection by conducting population-genomic analyses on whole-genome resequencing data from 38 European individuals of the arctic-alpine crucifer Arabis alpina. We find that outcrossing and mixed-mating populations maintain genetic diversity at similar levels, whereas highly self-fertilizing Scandinavian A. alpina show a strong reduction in genetic diversity, most likely as a result of a postglacial colonization bottleneck. We further find evidence for accumulation of genetic load in highly self-fertilizing populations, whereas the genome-wide impact of purifying selection does not differ greatly between mixed-mating and outcrossing populations. Our results demonstrate that intermediate levels of outcrossing may allow efficient selection against harmful alleles, whereas demographic effects can be important for relaxed purifying selection in highly selfing populations. Thus, mating system and demography shape the impact of purifying selection on genomic variation in A. alpina. These results are important for an improved understanding of the evolutionary consequences of mating system variation and the maintenance of mixed-mating strategies.

  • 29.
    Lehndal, Lina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Hambäck, Peter
    Stockholm Univ, Dept Ecol Environm & Plant Sci, S-10691 Stockholm, Sweden.
    Ericson, Lars
    Umea Univ, Dept Ecol & Environm Sci, S-90187 Umea, Sweden.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Herbivory strongly influences among-population variation in reproductive output of Lythrum salicaria in its native range2016In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 180, no 4, p. 1159-1171Article in journal (Refereed)
    Abstract [en]

    Herbivory can negatively affect several components of plant reproduction. Yet, because of a lack of experimental studies involving multiple populations, the extent to which differences in herbivory contribute to among-population variation in plant reproductive success is poorly known. We determined experimentally the effects of insect herbivory on reproductive output in nine natural populations of the perennial herb Lythrum salicaria along a disturbance gradient in an archipelago in northern Sweden, and we quantified among-population differentiation in resistance to herbivory in a common-garden experiment in the same area. The intensity of leaf herbivory varied >500-fold and mean female reproductive success >400-fold among the study populations. The intensity of herbivory was lowest in populations subject to strong disturbance from ice and wave action. Experimental removal of insect herbivores showed that the effect of herbivory on female reproductive success was correlated with the intensity of herbivory and that differences in insect herbivory could explain much of among-population variation in the proportion of plants flowering and seed production. Population differentiation in resistance to herbivory was limited. The results demonstrate that the intensity of herbivory is a major determinant of flowering and seed output in L. salicaria, but that differences in herbivory are not associated with differences in plant resistance at the spatial scale examined. They further suggest that the physical disturbance regime may strongly influence the performance and abundance of perennial herbs not only because of its effect on interspecific competition, but also because of effects on interactions with specialized herbivores.

  • 30.
    Lehndal, Lina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Herbivory Differentially Affects Plant Fitness in Three Populations of the Perennial Herb Lythrum salicaria along a Latitudinal Gradient2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 9, article id e0135939Article in journal (Refereed)
    Abstract [en]

    Herbivory can negatively and selectively affect plant fitness by reducing growth, survival and reproductive output, thereby influencing plant population dynamics and evolution. We documented intensity of herbivory and experimentally examined its effect on survival, growth and reproductive output in three natural populations of the perennial herb Lythrum salicaria along a latitudinal gradient from southern to northernmost Sweden over two years. The intensity of herbivory and the effects of herbivory on plant fitness were strongest in the southern population and intermediate in the central population. The mean proportion of the leaf area removed ranged from 11% in the southern to 3% in the northern population. Herbivore removal increased plant height 1.5-fold in the southern and 1.2-fold in the central population, the proportion plants flowering 4-fold in the southern and 2-fold in the central population, and seed production per flower 1.6-fold in the southern and 1.2-fold in the central population, but did not affect plant fitness in the northern population. Herbivore removal thus affected the relative fecundity of plants in the three populations: In the control, seed output per plant was 8.6 times higher in the northern population compared to the southern population, whereas after herbivore removal it was 2.5 times higher in the southern population compared to the northern. Proportion of leaf area removed increased with plant size, but tolerance to damage did not vary with size. The results demonstrate that native herbivores may strongly affect the demographic structure of L. salicaria populations, and thereby shape geographic patterns of seed production. They further suggest that the strength of herbivore-mediated selection varies among populations and decreases towards the north.

  • 31.
    Lehndal, Lina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Latitudinal variation in resistance and tolerance to herbivory in the perennial herb Lythrum salicaria is related to intensity of herbivory and plant phenology2015In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 28, no 3, p. 576-589Article in journal (Refereed)
    Abstract [en]

    Both the length of the growing season and the intensity of herbivory often vary along climatic gradients, which may result in divergent selection on plant phenology, and on resistance and tolerance to herbivory. In Sweden, the length of the growing season and the number of insect herbivore species feeding on the perennial herb Lythrum salicaria decrease from south to north. Previous common-garden experiments have shown that northern L. salicaria populations develop aboveground shoots earlier in the summer, and finish growth before southern populations do. We tested the hypotheses that resistance and tolerance to damage vary with latitude in L. salicaria, and are positively related to the intensity of herbivory in natural populations. We quantified resistance and tolerance of populations sampled along a latitudinal gradient by scoring damage from natural herbivores and fitness in a common-garden experiment in the field, and by documenting oviposition and feeding preference by specialist leaf beetles in a greenhouse experiment. Plant resistance decreased with latitude of origin, whereas plant tolerance increased. Oviposition and feeding preference in the greenhouse, and leaf damage in the common-garden experiment were negatively related to damage in the source populations. The latitudinal variation in resistance was thus consistent with reduced selection from herbivores towards the northern range margin of L. salicaria. Variation in tolerance may be related to differences in the timing of damage in relation to the seasonal pattern of plant growth, as northern genotypes have developed further than southern have when herbivores emerge in early summer.

  • 32. Leinonen, Päivi H.
    et al.
    Sandring, Saskia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Quilot, Bénédicte
    Clauss, Maria J.
    Mitchell-Olds, Thomas
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Savolainen, Outi
    Local adaptation in European populations of Arabidopsis lyrata (Brassicaceae)2009In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 96, no 6, p. 1129-1137Article in journal (Refereed)
    Abstract [en]

    We studied local adaptation to contrasting environments usingan organism that is emerging as a model for evolutionary plantbiology—the outcrossing, perennial herb Arabidopsis lyratasubsp. petraea (Brassicaceae). With reciprocal transplant experiments,we found variation in cumulative fitness, indicating adaptivedifferentiation among populations. Nonlocal populations didnot have significantly higher fitness than the local population.Experimental sites were located in Norway (alpine), Sweden (coastal),and Germany (continental). At all sites after one year, thelocal population had higher cumulative fitness, as quantifiedby survival combined with rosette area, than at least one ofthe nonlocal populations. At the Norwegian site, measurementswere done for two additional years, and fitness differencespersisted. The fitness components that contributed most to differencesin cumulative fitness varied among sites. Relatively small rosettearea combined with a large number of inflorescences producedby German plants may reflect differentiation in life history.The results of the current study demonstrate adaptive populationdifferentiation in A. lyrata along a climatic gradient in Europe.The studied populations harbor considerable variation in severalcharacters contributing to adaptive population differentiation.The wealth of genetic information available makes A. lyrataa highly attractive system also for examining the functionaland genetic basis of local adaptation in plants.

  • 33.
    Løe, Geir
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Toräng, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Gauldeul, Myriam
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Trichome production and spatiotemporal variation in herbivory in the perennial herb Arabidopsis lyrata2007In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 116, no 1, p. 134-142Article in journal (Refereed)
    Abstract [en]

    Allocation theory suggests that the optimal level of resistance against herbivores should vary with the risk of herbivory if allocation to resistance is costly. The perennial herb Arabidopsis lyrata has a genetically based polymorphism for- trichome production and occurs in a glabrous and a trichome-producing form. Leaf trichomes (hairs) can protect plants against insect herbivores, and may increase tolerance to drought and UV-radiation. To examine the functional significance of trichome production, we documented the frequency of glabrous plants and damage by insect herbivores in 30 A. lyrata populations in Sweden and Norway. The proportion of glabrous plants ranged from 0.10 to 0.71 (median = 0.44) in polymorphic populations; 7 of 12 populations in Norway and 14 of 18 populations in Sweden were monomorphic glabrous, i.e. with fewer than 5% trichome-producing plants. The mean proportion of the leaf area removed by herbivores varied substantially among populations and years. With few exceptions, glabrous plants were more damaged than trichome-producing plants in polymorphic populations. The intensity of herbivory quantified as the mean damage to glabrous plants tended to be higher in polymorphic populations than in populations monomorphic for the glabrous morph and was higher in Sweden than in Norway. In Norway, both the magnitude of herbivore damage and the frequency of trichome-producing plants tended to decrease with increasing altitude. The results indicate that leaf trichomes contribute to resistance against herbivorous insects in A. lyrata, and suggest that herbivore-mediated selection contributes to the maintenance of the polymorphism in trichome production.

  • 34.
    Menzel, Mandy
    et al.
    Lund Univ, Lund, Sweden.
    Sletvold, Nina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Hansson, Bengt
    Lund Univ, Lund, Sweden.
    Inbreeding Affects Gene Expression Differently in Two Self-Incompatible Arabidopsis lyrata Populations with Similar Levels of Inbreeding Depression2015In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 32, no 8, p. 2036-2047Article in journal (Refereed)
    Abstract [en]

    Knowledge of which genes and pathways are affected by inbreeding may help understanding the genetic basis of inbreeding depression, the potential for purging (selection against deleterious recessive alleles), and the transition from outcrossing to selfing. Arabidopsis lyrata is a predominantly self-incompatible perennial plant, closely related to the selfing model species A. thaliana. To examine how inbreeding affects gene expression, we compared the transcriptome of experimentally selfed and outcrossed A. lyrata originating from two Scandinavian populations that express similar inbreeding depression for fitness ((partial derivative approximate to 0.80). The number of genes significantly differentially expressed between selfed and outcrossed individuals were 2.5 times higher in the Norwegian population (approximate to 500 genes) than in the Swedish population (approximate to 200 genes). In both populations, a majority of genes were upregulated on selfing (approximate to 80%). Functional annotation analysis of the differentially expressed genes showed that selfed offspring were characterized by 1) upregulation of stress-related genes in both populations and 2) upregulation of photosynthesis-related genes in Sweden but downregulation in Norway. Moreover, we found that reproduction-and pollination-related genes were affected by inbreeding only in Norway. We conclude that inbreeding causes both general and population-specific effects. The observed common effects suggest that inbreeding generally upregulates rather than downregulates gene expression and affects genes associated with stress response and general metabolic activity. Population differences in the number of affected genes and in effects on the expression of photosynthesis-related genes show that the genetic basis of inbreeding depression can differ between populations with very similar levels of inbreeding depression.

  • 35.
    Nilsson, Emil
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Ågren, Jon
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Population size, female fecundity, and sex ratio variation in gynodioecious Plantago maritima2006In: Journal of Evolutionary Biology, Vol. 19, p. 825-833Article in journal (Refereed)
  • 36. Oakley, C. G.
    et al.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Schemske, D. W.
    Heterosis and outbreeding depression in crosses between natural populations of Arabidopsis thaliana2015In: Heredity, ISSN 0018-067X, E-ISSN 1365-2540, Vol. 115, no 1, p. 73-82Article in journal (Refereed)
    Abstract [en]

    Understanding the causes and architecture of genetic differentiation between natural populations is of central importance in evolutionary biology. Crosses between natural populations can result in heterosis if recessive or nearly recessive deleterious mutations have become fixed within populations because of genetic drift. Divergence between populations can also result in outbreeding depression because of genetic incompatibilities. The net fitness consequences of between-population crosses will be a balance between heterosis and outbreeding depression. We estimated the magnitude of heterosis and outbreeding depression in the highly selfing model plant Arabidopsis thaliana, by crossing replicate line pairs from two sets of natural populations (C <-> R, B <-> S) separated by similar geographic distances (Italy <-> Sweden). We examined the contribution of different modes of gene action to overall differences in estimates of lifetime fitness and fitness components using joint scaling tests with parental, reciprocal F-1 and F-2, and backcross lines. One of these population pairs (C <-> R) was previously demonstrated to be locally adapted, but locally maladaptive quantitative trait loci were also found, suggesting a role for genetic drift in shaping adaptive variation. We found markedly different genetic architectures for fitness and fitness components in the two sets of populations. In one (C <-> R), there were consistently positive effects of dominance, indicating the masking of recessive or nearly recessive deleterious mutations that had become fixed by genetic drift. The other set (B <-> S) exhibited outbreeding depression because of negative dominance effects. Additional studies are needed to explore the molecular genetic basis of heterosis and outbreeding depression, and how their magnitudes vary across environments.

  • 37. Oakley, Christopher G.
    et al.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Atchison, Rachel A.
    Schemske, Douglas W.
    QTL mapping of freezing tolerance: links to fitness and adaptive trade-offs2014In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 23, no 17, p. 4304-4315Article in journal (Refereed)
    Abstract [en]

    Local adaptation, defined as higher fitness of local vs. nonlocal genotypes, is commonly identified in reciprocal transplant experiments. Reciprocally adapted populations display fitness trade-offs across environments, but little is known about the traits and genes underlying fitness trade-offs in reciprocally adapted populations. We investigated the genetic basis and adaptive significance of freezing tolerance using locally adapted populations of Arabidopsis thaliana from Italy and Sweden. Previous reciprocal transplant studies of these populations indicated that subfreezing temperature is a major selective agent in Sweden. We used quantitative trait locus (QTL) mapping to identify the contribution of freezing tolerance to previously demonstrated local adaptation and genetic trade-offs. First, we compared the genomic locations of freezing tolerance QTL to those for previously published QTL for survival in Sweden, and overall fitness in the field. Then, we estimated the contributions to survival and fitness across both field sites of genotypes at locally adaptive freezing tolerance QTL. In growth chamber studies, we found seven QTL for freezing tolerance, and the Swedish genotype increased freezing tolerance for five of these QTL. Three of these colocalized with locally adaptive survival QTL in Sweden and with trade-off QTL for overall fitness. Two freezing tolerance QTL contribute to genetic trade-offs across environments for both survival and overall fitness. A major regulator of freezing tolerance, CBF2, is implicated as a candidate gene for one of the trade-off freezing tolerance QTL. Our study provides some of the first evidence of a trait and gene that mediate a fitness trade-off in nature.

  • 38.
    Olsson, K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Latitudinal population differentiation in phenology, life history and flower morphology in the perennial herb Lythrum salicaria.2002In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 15, no 6, p. 983-996 Article in journal (Refereed)
    Abstract [en]

     In plants with a wide distribution, phenological characters can be expected to vary clinally along climatic gradients, whereas other characters important for adaptation to local biotic and abiotic factors may vary in a more mosaic fashion. We used common-garden experiments and controlled crosses to examine population differentiation in phenology, life history and morphology in the perennial herb Lythrum salicaria along a latitudinal transect through Sweden (57°N to 66°N). Northern populations initiated growth and flowering earlier, flowered for a shorter period, were shorter, produced more and larger winter buds, and were older at first reproduction than southern populations. Flower morphology varied significantly among populations, but was, with the exception of calyx length, not significantly related to latitude of origin. Survival in the common garden (at 63°49′N) was positively correlated with latitude of origin and the size and number of winter buds produced in the preceding year. The results suggest that the among-population differences in phenology and life history have evolved in response to latitudinal variation in length of the growing season. Further studies are required to determine whether population differentiation in flower morphology is maintained by selection.

  • 39. Platt, Alexander
    et al.
    Horton, Matthew
    Huang, Yu S.
    Li, Yan
    Anastasio, Alison E.
    Mulyati, Ni Wayan
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Bossdorf, Oliver
    Byers, Diane
    Donohue, Kathleen
    Dunning, Megan
    Holub, Eric B.
    Hudson, Andrew
    Le Corre, Valerie
    Loudet, Olivier
    Roux, Fabrice
    Warthmann, Norman
    Weigel, Detlef
    Rivero, Luz
    Scholl, Randy
    Nordborg, Magnus
    Bergelson, Joy
    Borevitz, Justin O.
    The Scale of Population Structure in Arabidopsis thaliana2010In: PLoS Genetics, ISSN 1553-7390, Vol. 6, no 2, p. e1000843-Article in journal (Refereed)
    Abstract [en]

    The population structure of an organism reflects its evolutionary history and influences its evolutionary trajectory. It constrains the combination of genetic diversity and reveals patterns of past gene flow. Understanding it is a prerequisite for detecting genomic regions under selection, predicting the effect of population disturbances, or modeling gene flow. This paper examines the detailed global population structure of Arabidopsis thaliana. Using a set of 5,707 plants collected from around the globe and genotyped at 149 SNPs, we show that while A. thaliana as a species self-fertilizes 97% of the time, there is considerable variation among local groups. This level of outcrossing greatly limits observed heterozygosity but is sufficient to generate considerable local haplotypic diversity. We also find that in its native Eurasian range A. thaliana exhibits continuous isolation by distance at every geographic scale without natural breaks corresponding to classical notions of populations. By contrast, in North America, where it exists as an exotic species, A. thaliana exhibits little or no population structure at a continental scale but local isolation by distance that extends hundreds of km. This suggests a pattern for the development of isolation by distance that can establish itself shortly after an organism fills a new habitat range. It also raises questions about the general applicability of many standard population genetics models. Any model based on discrete clusters of interchangeable individuals will be an uneasy fit to organisms like A. thaliana which exhibit continuous isolation by distance on many scales.

  • 40.
    Postma, Froukje M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Lundemo, Sverre
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution. WWF Norway, Postboks 6784, N-0130 Oslo, Norway..
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Seed dormancy cycling and mortality differ between two locally adapted populations of Arabidopsis thaliana2016In: Annals of Botany, ISSN 0305-7364, E-ISSN 1095-8290, Vol. 117, no 2, p. 249-256Article in journal (Refereed)
    Abstract [en]

    Background and Aims Intraspecific variation in seed bank dynamics should contribute to local adaptation, but is not well studied. The extent to which genetic and environmental factors affect dormancy cycling and seed mortality was investigated in the annual herb Arabidopsis thaliana by conducting a reciprocal seed burial experiment. Methods Seeds from two locally adapted populations (from Italy and Sweden) were buried at both of the sites of origin, and seed mortality and germinability were determined during the following 2 years for initially non-dormant glasshouse-matured seeds and dormant field-matured seeds. Key Results Mean soil temperature was higher at the Italian site compared with the Swedish site throughout the year, and the germination proportions were in general higher for seeds buried in Italy than in Sweden. The rate of secondary dormancy induction of the Italian genotype was faster than that of the Swedish genotype at both sites, while the opposite was true for the rate of dormancy release, at least at the Swedish site. The comparison of nondormant glasshouse seeds with dormant field seeds demonstrated that A. thaliana seeds can adjust their dormancy levels to current environmental conditions, and suggests that maternal environmental conditions have only minor effects on dormancy cycles. At both sites, locally produced seeds had low germinability in the first year compared with the second year, suggesting that a considerable fraction of the seeds would enter the seed bank. In Italy, but not in Sweden, seed mortality increased rapidly during the second year of burial. Conclusions This is the first demonstration of intraspecific genetic differentiation in the annual seed dormancy cycle of any species, and the documented difference is likely to contribute to local adaptation. The results suggest that the contribution of a seed bank to seedling recruitment should vary among environments due to differences in the rate of seed mortality.

  • 41.
    Postma, Froukje M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Early life stages contribute strongly to local adaptation in Arabidopsis thaliana2016In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 113, no 27, p. 7590-7595Article in journal (Refereed)
    Abstract [en]

    The magnitude and genetic basis of local adaptation is of fundamental interest in evolutionary biology. However, field experiments usually do not consider early life stages, and therefore may underestimate local adaptation and miss genetically based tradeoffs. We examined the contribution of differences in seedling establishment to adaptive differentiation and the genetic architecture of local adaptation using recombinant inbred lines (RIL) derived from a cross between two locally adapted populations (Italy and Sweden) of the annual plant Arabidopsis thaliana. We planted freshly matured, dormant seeds (> 180 000) representing >200 RILs at the native field sites of the parental genotypes, estimated the strength of selection during different life stages, mapped quantitative trait loci (QTL) for fitness and its components, and quantified selection on seed dormancy. We found that selection during the seedling establishment phase contributed strongly to the fitness advantage of the local genotype at both sites. With one exception, local alleles of the eight distinct establishment QTL were favored. The major QTL for establishment and total fitness showed evidence of a fitness tradeoff and was located in the same region as the major seed dormancy QTL and the dormancy gene DELAY OF GERMINATION 1 (DOG1). RIL seed dormancy could explain variation in seedling establishment and fitness across the life cycle. Our results demonstrate that genetically based differences in traits affecting performance during early life stages can contribute strongly to adaptive differentiation and genetic tradeoffs, and should be considered for a full understanding of the ecology and genetics of local adaptation.

  • 42.
    Postma, Froukje M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Maternal environment affects the genetic basis of seed dormancy in Arabidopsis thaliana2015In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 24, no 4, p. 785-797Article in journal (Refereed)
    Abstract [en]

    The genetic basis of seed dormancy, a key life history trait important for adaptive evolution in plant populations, has yet been studied only using seeds produced under controlled conditions in greenhouse environments. However, dormancy is strongly affected by maternal environmental conditions, and interactions between seed genotype and maternal environment have been reported. Consequently, the genetic basis of dormancy of seeds produced under natural field conditions remains unclear. We examined the effect of maternal environment on the genetic architecture of seed dormancy using a recombinant inbred line (RIL) population derived from a cross between two locally adapted populations of Arabidopsis thaliana from Italy and Sweden. We mapped quantitative trait loci (QTL) for dormancy of seeds produced in the greenhouse and at the native field sites of the parental genotypes. The Italian genotype produced seeds with stronger dormancy at fruit maturation than did the Swedish genotype in all three environments, and the maternal field environments induced higher dormancy levels compared to the greenhouse environment in both genotypes. Across the three maternal environments, a total of nine dormancy QTL were detected, three of which were only detected among seeds matured in the field, and six of which showed significant QTLxmaternal environment interactions. One QTL had a large effect on dormancy across all three environments and colocalized with the candidate gene DOG1. Our results demonstrate the importance of studying the genetic basis of putatively adaptive traits under relevant conditions.

  • 43.
    Price, Nicholas
    et al.
    Colorado State Univ, Dept Bioagr Sci & Pest Management, Ft Collins, CO 80523 USA.
    Moyers, Brook T.
    Colorado State Univ, Dept Bioagr Sci & Pest Management, Ft Collins, CO 80523 USA.
    Lopez, Lua
    Penn State Univ, Dept Biol, University Pk, PA 16802 USA.
    Lasky, Jesse R.
    Penn State Univ, Dept Biol, University Pk, PA 16802 USA.
    Monroe, J. Grey
    Colorado State Univ, Dept Bioagr Sci & Pest Management, Ft Collins, CO 80523 USA.
    Mullen, Jack L.
    Colorado State Univ, Dept Bioagr Sci & Pest Management, Ft Collins, CO 80523 USA.
    Oakley, Christopher G.
    Purdue Univ, Dept Bot & Plant Pathol, W Lafayette, IN 47907 USA;Purdue Univ, Ctr Plant Biol, W Lafayette, IN 47907 USA.
    Lin, Junjiang
    Colorado State Univ, Dept Bioagr Sci & Pest Management, Ft Collins, CO 80523 USA.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Schrider, Daniel R.
    Rutgers State Univ, Dept Genet, Piscataway, NJ 08854 USA.
    Kern, Andrew D.
    Rutgers State Univ, Dept Genet, Piscataway, NJ 08854 USA.
    McKay, John K.
    Colorado State Univ, Dept Bioagr Sci & Pest Management, Ft Collins, CO 80523 USA.
    Combining population genomics and fitness QTLs to identify the genetics of local adaptation in Arabidopsis thaliana2018In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 115, no 19, p. 5028-5033Article in journal (Refereed)
    Abstract [en]

    Evidence for adaptation to different climates in the model species Arabidopsis thaliana is seen in reciprocal transplant experiments, but the genetic basis of this adaptation remains poorly understood. Field-based quantitative trait locus (QTL) studies provide direct but low-resolution evidence for the genetic basis of local adaptation. Using high-resolution population genomic approaches, we examine local adaptation along previously identified genetic trade-off (GT) and conditionally neutral (CN) QTLs for fitness between locally adapted Italian and Swedish A. thaliana populations [angstrom gren J, et al. (2013) Proc Natl Acad Sci USA 110: 21077-21082]. We find that genomic regions enriched in high F-ST SNPs colocalize with GT QTL peaks. Many of these high F-ST regions also colocalize with regions enriched for SNPs significantly correlated to climate in Eurasia and evidence of recent selective sweeps in Sweden. Examining unfolded site frequency spectra across genes containing high F-ST SNPs suggests GTs may be due to more recent adaptation in Sweden than Italy. Finally, we collapse a list of thousands of genes spanning GT QTLs to 42 genes that likely underlie the observed GTs and explore potential biological processes driving these trade-offs, from protein phosphorylation, to seed dormancy and longevity. Our analyses link population genomic analyses and field-based QTL studies of local adaptation, and emphasize that GTs play an important role in the process of local adaptation.

  • 44.
    Puentes, Adriana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Additive and non-additive effects of simulated leaf and inflorescence damage on survival, growth and reproduction of the perennial herb Arabidopsis lyrata2012In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 169, no 4, p. 1033-1042Article in journal (Refereed)
    Abstract [en]

    Herbivores may damage both leaves and reproductive structures, and although such combined damage may affect plant fitness non-additively, this has received little attention. We conducted a 2-year field experiment with a factorial design to examine the effects of simulated leaf (0,12.5, 25, or 50% of leaf area removed) and inflorescence damage (0 vs. 50% of inflorescences removed) on survival, growth and reproduction in the perennial herb Arabidopsis lyrata. Leaf and inflorescence damage negatively and independently reduced flower, fruit and seed production in the year of damage; leaf damage also reduced rosette size by the end of the first season and flower production in the second year. Leaf damage alone reduced the proportion of flowers forming a fruit and fruit production per plant the second year, but when combined with inflorescence damage no such effect was observed (significant leaf × inflorescence damage interaction). Damage to leaves (sources) caused a greater reduction in future reproduction than did simultaneous damage to leaves and inflorescences (sinks). This demonstrates that a full understanding of the effects of herbivore damage on plant fitness requires that consequences of damage to vegetative and reproductive structures are evaluated over more than 1 year and that non-additive effects are considered.

  • 45.
    Puentes, Adriana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    No trade-off between trichome production and tolerance to leaf and inflorescence damage in a natural population of Arabidopsis lyrata2014In: Journal of Plant Ecology, ISSN 1752-9921, E-ISSN 1752-993X, Vol. 7, no 4, p. 373-383Article in journal (Refereed)
    Abstract [en]

    Early models of plant defense conceived resistance and tolerance to herbivore damage as mutually exclusive strategies. Support for this idea has been equivocal and studies on these two strategies are still needed to understand the evolution of defenses in natural populations. In Arabidopsis lyrata, the production of trichomes, a documented resistance trait, has been associated with a fitness cost in the absence of herbivores. We examined whether trichome production is also associated with reduced tolerance to simulated herbivore damage. We conducted a field experiment in a natural Swedish population of A. lyrata where we inflicted leaf (0 vs. 50% of the area of each leaf removed) and inflorescence damage (0 vs. 50% of inflorescences removed) to trichome-producing and glabrous plants in a factorial design. We examined the response (survival, growth and reproduction) of the plants to the imposed damage over 2 years. Trichome-producing plants were not less tolerant than glabrous plants to simulated herbivore damage (no significant morph x leaf damage or morph x inflorescence damage interactions). Inflorescence and leaf damage had independent negative effects on the performance of damaged plants. Leaf damage reduced rosette size the year of damage, but effects on reproductive output in the year of damage, and on survival and reproductive performance the following year were weak and not statistically significant. Inflorescence damage significantly reduced the number of flowers, fruits and seeds the year of damage, but not in the following year. Irrespective of morph, the study population was more tolerant to leaf than to inflorescence damage. The results indicated no trade-off between trichome production and tolerance, suggesting that these two defense mechanisms have the potential to evolve independently in this A. lyrata population.

  • 46.
    Puentes, Adriana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Trichome production and variation in young plant resistance to the specialist insect herbivore Plutella xylostella among natural populations of Arabidopsis lyrata2013In: Entomologia Experimentalis et Applicata, ISSN 0013-8703, E-ISSN 1570-7458, Vol. 149, no 2, p. 166-176Article in journal (Refereed)
    Abstract [en]

    The strength of plant-herbivore interactions varies spatially and through plant ontogeny, which may result in variable selection on plant defenses against herbivory both among populations and among different life-history stages. The perennial herb Arabidopsis lyrata occurs in a trichome-producing and a glabrous morph, and previous work has shown that glabrous plants tend to receive more damage than trichome-producing plants. In this study, we quantified oviposition preference and larval feeding by P. xylostella on very young A. lyrata (5-6 weeks old), originating from twelve natural populations, six from Sweden and six from Norway. Six of the populations (three from each region) were polymorphic for trichome production and allowed a comparison of resistance against P. xylostella between the glabrous and the trichome-producing morph at a stage when trichome density is low in trichome-producing plants. There was considerable variation among populations in the number of eggs received and the proportion of leaf area consumed, but not between regions (Sweden and Norway) or trichome morphs. Rosette size explained a significant portion of the variation in oviposition and larval feeding. The results demonstrate that among-population variation in resistance to insect herbivory can also be detected among very young individuals of the perennial herb A. lyrata. They further suggest that trichome densities are too low at this developmental stage to contribute to resistance, and that the observed among-population variation in resistance is related to differences in other plant traits.

  • 47.
    Sandring, Saskia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Riihimäki, Mona
    Savolainen, Outi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Selection on flowering time and floral display in an alpine and a lowland population of Arabidopsis lyrata2007In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 20, no 2, p. 558-567Article in journal (Refereed)
    Abstract [en]

    To determine whether population differentiation in flowering time is consistent with differences in current selection, we quantified phenotypic selection acting through female reproductive success on flowering phenology and floral display in two Scandinavian populations of the outcrossing, perennial herb Arabidopsis lyrata in two years. One population was located in an alpine environment strongly affected by grazing, whereas the other was close to sea level and only moderately affected by herbivory. Multiple regression models indicated directional selection for early end of flowering in one year in the lowland population, and directional selection for early start of flowering in one year in the alpine population. As expected, there was selection for more inflorescences in the lowland population. However, in the alpine population, plants with many inflorescences were selectively grazed and the number of inflorescences produced was negatively related to female fitness in one year and not significantly related to female fitness in the second year. The results are consistent with the hypothesis that genetic differentiation in flowering phenology between the study populations is adaptive, and indicate that interactions with selective grazers may strongly influence selection on floral display in A. lyrata.

  • 48.
    Sandring, Saskia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Pollinator-mediated selection on floral display and flowering time in the perennial herb Arabidopsis lyrata2009In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 63, no 5, p. 1292-1300Article in journal (Refereed)
    Abstract [en]

    The evolution of floral display and flowering time in animal-pollinated plants is commonly attributed to pollinator-mediated selection. Yet, the causes of selection on flowering phenology and traits contributing to floral display have rarely been tested experimentally in natural populations. We quantified phenotypic selection on morphological and phenological characters in the perennial, outcrossing herb Arabidopsis lyrata in two years using female reproductive success as a proxy of fitness. To determine whether selection on floral display and flowering   phenology can be attributed to interactions with pollinators, selection   was quantified both for open-pollinated controls and for plants receiving supplemental hand-pollination. We documented directional selection for many flowers, large petals, late start of flowering, and early end of flowering. Seed output was pollen-limited in both years   and supplemental hand-pollination reduced the magnitude of selection on number of flowers, and reversed the direction of selection on end of flowering. The results demonstrate that interactions with pollinators may affect the strength of selection on floral display and the   direction of selection on phenology of flowering in natural plant populations. They thus support the contention that pollinators can drive the evolution of both floral display and flowering time.

  • 49. Sletvold, Nina
    et al.
    Grindeland, John M.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Pollinator-mediated selection on floral display, spur length and flowering phenology in the deceptive orchid Dactylorhiza lapponica2010In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 188, no 2, p. 385-392Article in journal (Refereed)
    Abstract [en]

    Nonrewarding animal-pollinated plants commonly experience severe pollen limitation, which should result in strong selection on traits affecting the success of pollination. However, the importance of pollinators as selective agents on floral traits in deceptive species has not been quantified experimentally. Here, we quantified pollinator-mediated selection (Delta beta(poll)) on floral morphology and start of flowering in the deceptive orchid Dactylorhiza lapponica by subtracting estimates of selection gradients for plants receiving supplemental hand-pollination from estimates obtained for open-pollinated control plants. There was directional selection for taller plants with more flowers and longer spurs, but no statistically significant selection on corolla size or flowering start. Pollinator-mediated selection accounted for all observed selection on spur length (Delta beta(poll) = 0.32), 76% of the selection on plant height (Delta beta(poll) = 0.19) and 42% of the selection on number of flowers (Delta beta(poll) = 0.30). Sixteen per cent of developing fruits were consumed by insect herbivores, but fruit herbivory had only minor effects on the strength of pollinator-mediated selection. Our results demonstrate that pollinators mediate selection on floral traits likely to affect both pollinator attraction and pollination efficiency, and are consistent with the hypothesis that deceptive species experience strong selection for increased display and mechanical fit between flower and pollinator.

  • 50.
    Sletvold, Nina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Grindeland, John Magne
    Zu, Pengjuan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Strong inbreeding depression and local outbreeding depression in the rewarding orchid Gymnadenia conopsea2012In: Conservation Genetics, ISSN 1566-0621, E-ISSN 1572-9737, Vol. 13, no 5, p. 1305-1315Article in journal (Refereed)
    Abstract [en]

    Conservation of species threatened by habitat fragmentation is a major global challenge, and determining the genetic and demographic processes associated with isolation and reductions in population size will be critical for an increasing number of species. We conducted controlled crosses and field germination experiments to quantify the effects of inbreeding and outbreeding in the declining orchid Gymnadenia conopsea in two Norwegian populations that differ in size. We further compared our results with published estimates of inbreeding depression in orchids. There was severe inbreeding depression for seed production (delta = 0.41-0.67) and germination (delta = 0.46-0.66) in both populations, with stronger inbreeding depression in the large population. Compared to outcrossing, selfing reduced female fitness (number of seeds per fruit x proportion of seeds germinating) by 76 and 54 % in the large and small population, respectively. The magnitude of inbreeding depression for seed production was higher than the average reported for orchids, while for germination it was similar to earlier estimates. The large population also experienced considerable outbreeding depression for seed production (delta = 0.23-0.27), germination (delta = 0.33) and female fitness (delta = 0.47) following crosses with a population 1.6 km away. The strong inbreeding depression indicates that both populations harbour a substantial genetic load, and suggests that fragmentation may reinforce population decline in G. conopsea via increased inbreeding. Moreover, the local outbreeding depression indicates substantial genetic differentiation at a moderate spatial scale. This has important implications for the use of crosses between populations or plant translocations as conservation approaches.

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