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Publications (10 of 97) Show all publications
Chapurlat, E., Ågren, J., Anderson, J., Friberg, M. & Sletvold, N. (2019). Conflicting selection on floral scent emission in the orchid Gymnadenia conopsea. New Phytologist, 222(4), 2009-2022
Open this publication in new window or tab >>Conflicting selection on floral scent emission in the orchid Gymnadenia conopsea
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2019 (English)In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 222, no 4, p. 2009-2022Article in journal (Refereed) Published
Abstract [en]

Floral scent is a crucial trait for pollinator attraction. Yet only a handful of studies have estimated selection on scent in natural populations and no study has quantified the relative importance of pollinators and other agents of selection. In the fragrant orchid Gymnadenia conopsea, we used electroantennographic data to identify floral scent compounds detected by local pollinators and quantified pollinator-mediated selection on emission rates of 10 target compounds as well as on flowering start, visual display and spur length. Nocturnal pollinators contributed more to reproductive success than diurnal pollinators, but there was significant pollinator-mediated selection on both diurnal and nocturnal scent emission. Pollinators selected for increased emission of two compounds and reduced emission of two other compounds, none of which were major constituents of the total bouquet. In three cases, pollinator-mediated selection was opposed by nonpollinator-mediated selection, leading to weaker or no detectable net selection. Our study demonstrates that minor scent compounds can be targets of selection, that pollinators do not necessarily favour stronger scent signalling, and that some scent compounds are subject to conflicting selection from pollinators and other agents of selection. Hence, including floral scent traits into selection analysis is important for understanding the mechanisms behind floral evolution.

Keywords
agents of selection, conflicting selection, diurnal and nocturnal scent emission, floral evolution, floral scent, pollinator-mediated selection, volatile organic compounds
National Category
Evolutionary Biology Ecology
Identifiers
urn:nbn:se:uu:diva-384056 (URN)10.1111/nph.15747 (DOI)000467301100029 ()30767233 (PubMedID)
Funder
Lars Hierta Memorial FoundationSwedish Research Council FormasSwedish Research Council
Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-06-20Bibliographically approved
Oakley, C. G., Lundemo, S., Ågren, J. & Schemske, D. W. (2019). Heterosis is common and inbreeding depression absent in natural populations of Arabidopsis thaliana. Journal of Evolutionary Biology, 32(6), 592-603
Open this publication in new window or tab >>Heterosis is common and inbreeding depression absent in natural populations of Arabidopsis thaliana
2019 (English)In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 32, no 6, p. 592-603Article in journal (Refereed) Published
Abstract [en]

The importance of genetic drift in shaping patterns of adaptive genetic variation in nature is poorly known. Genetic drift should drive partially recessive deleterious mutations to high frequency, and inter-population crosses may therefore exhibit heterosis (increased fitness relative to intra-population crosses). Low genetic diversity and greater genetic distance between populations should increase the magnitude of heterosis. Moreover, drift and selection should remove strongly deleterious recessive alleles from individual populations, resulting in reduced inbreeding depression. To estimate heterosis, we crossed 90 independent line pairs of Arabidopsis thaliana from 15 pairs of natural populations sampled across Fennoscandia and crossed an additional 41 line pairs from a subset of four of these populations to estimate inbreeding depression. We measured lifetime fitness of crosses relative to parents in a large outdoor common garden (8,448 plants in total) in central Sweden. To examine the effects of genetic diversity and genetic distance on heterosis, we genotyped parental lines for 869 SNPs. Overall, genetic variation within populations was low (median expected heterozygosity = 0.02), and genetic differentiation was high (median F-ST = 0.82). Crosses between 10 of 15 population pairs exhibited significant heterosis, with magnitudes of heterosis as high as 117%. We found no significant inbreeding depression, suggesting that the observed heterosis is due to fixation of mildly deleterious alleles within populations. Widespread and substantial heterosis indicates an important role for drift in shaping genetic variation, but there was no significant relationship between fitness of crosses relative to parents and genetic diversity or genetic distance between populations.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
genetic distance, genetic drift, heterosis, inbreeding depression, outbreeding depression
National Category
Genetics
Identifiers
urn:nbn:se:uu:diva-390597 (URN)10.1111/jeb.13441 (DOI)000472662300007 ()30883966 (PubMedID)
Funder
Swedish Research Council
Available from: 2019-08-13 Created: 2019-08-13 Last updated: 2019-08-13Bibliographically approved
Ågren, J. (2019). Pollinators, herbivores, and the evolution of floral traits. Science, 364(6436), 122-123
Open this publication in new window or tab >>Pollinators, herbivores, and the evolution of floral traits
2019 (English)In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 364, no 6436, p. 122-123Article in journal, Editorial material (Other academic) Published
Place, publisher, year, edition, pages
AMER ASSOC ADVANCEMENT SCIENCE, 2019
National Category
Ecology Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-383048 (URN)10.1126/science.aax1656 (DOI)000464620000018 ()30975872 (PubMedID)
Funder
Swedish Research CouncilSwedish Research Council Formas
Available from: 2019-05-13 Created: 2019-05-13 Last updated: 2019-05-13Bibliographically approved
Trunschke, J., Sletvold, N. & Ågren, J. (2019). The independent and combined effects of floral traits distinguishing two pollination ecotypes of a moth-pollinated orchid. Ecology and Evolution, 9(3), 1191-1201
Open this publication in new window or tab >>The independent and combined effects of floral traits distinguishing two pollination ecotypes of a moth-pollinated orchid
2019 (English)In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 9, no 3, p. 1191-1201Article in journal (Refereed) Published
Abstract [en]

Identifying traits and agents of selection involved in local adaptation is important for understanding population divergence. In southern Sweden, the moth-pollinated orchid Platanthera bifolia occurs as a woodland and a grassland ecotype that differ in dominating pollinators. The woodland ecotype is taller (expected to influence pollinator attraction) and produces flowers with longer spurs (expected to influence efficiency of pollen transfer) compared to the grassland ecotype. We examined whether plant height and spur length affect pollination and reproductive success in a woodland population, and whether effects are non-additive, as expected for traits influencing two multiplicative components of pollen transfer. We reduced plant height and spur length to match trait values observed in the grassland ecotype and determined the effects on pollen removal, pollen receipt, and fruit production. In addition, to examine the effects of naturally occurring variation, we quantified pollinator-mediated selection through pollen removal and seed production in the same population. Reductions of plant height and spur length decreased pollen removal, number of flowers receiving pollen, mean pollen receipt per pollinated flower, and fruit production per plant, but no significant interaction effect was detected. The selection analysis demonstrated pollinator-mediated selection for taller plants via female fitness. However, there was no current selection mediated by pollinators on spur length, and pollen removal was not related to plant height or spur length. The results show that, although both traits are important for pollination success and female fitness in the woodland habitat, only plant height was sufficiently variable in the study population for current pollinator-mediated selection to be detected. More generally, the results illustrate how a combination of experimental approaches can be used to identify both traits and agents of selection.

National Category
Ecology
Research subject
Biology with specialization in Ecological Botany
Identifiers
urn:nbn:se:uu:diva-349138 (URN)10.1002/ece3.4808 (DOI)000461112200022 ()30805152 (PubMedID)
Funder
Swedish Research CouncilSwedish Research Council Formas
Available from: 2018-04-24 Created: 2018-04-24 Last updated: 2019-04-10Bibliographically approved
Postma, F. M. & Ågren, J. (2018). Among-year variation in selection during early life stages and the genetic basis of fitness in Arabidopsis thaliana. Molecular Ecology, 27(11), 2498-2511
Open this publication in new window or tab >>Among-year variation in selection during early life stages and the genetic basis of fitness in Arabidopsis thaliana
2018 (English)In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 27, no 11, p. 2498-2511Article in journal (Refereed) Published
Abstract [en]

Incomplete information regarding both selection regimes and the genetic basis of fitness limits our understanding of adaptive evolution. Among-year variation in the genetic basis of fitness is rarely quantified, and estimates of selection are typically based on single components of fitness, thus potentially missing conflicting selection acting during other life-history stages. Here, we examined among-year variation in selection on a key life-history trait and the genetic basis of fitness covering the whole life cycle in the annual plant Arabidopsis thaliana. We planted freshly matured seeds of >200 recombinant inbred lines (RILs) derived from a cross between two locally adapted populations (Italy and Sweden), and both parental genotypes at the native site of the Swedish population in three consecutive years. We quantified selection against the nonlocal Italian genotype, mapped quantitative trait loci (QTL) for fitness and its components, and quantified selection on timing of germination during different life stages. In all 3years, the local Swedish genotype outperformed the nonlocal Italian genotype. However, both the contribution of early life stages to relative fitness, and the effects of fitness QTL varied among years. Timing of germination was under conflicting selection through seedling establishment vs. adult survival and fecundity, and both the direction and magnitude of net selection varied among years. Our results demonstrate that selection during early life stages and the genetic basis of fitness can vary markedly among years, emphasizing the need for multiyear studies considering the whole life cycle for a full understanding of natural selection and mechanisms maintaining local adaptation.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-302861 (URN)10.1111/mec.14697 (DOI)000434152100002 ()29676059 (PubMedID)
Funder
Swedish Research Council, 2016-05435
Available from: 2016-09-12 Created: 2016-09-12 Last updated: 2018-08-31Bibliographically approved
Price, N., Moyers, B. T., Lopez, L., Lasky, J. R., Monroe, J. G., Mullen, J. L., . . . McKay, J. K. (2018). Combining population genomics and fitness QTLs to identify the genetics of local adaptation in Arabidopsis thaliana. Proceedings of the National Academy of Sciences of the United States of America, 115(19), 5028-5033
Open this publication in new window or tab >>Combining population genomics and fitness QTLs to identify the genetics of local adaptation in Arabidopsis thaliana
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2018 (English)In: 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) Published
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.

Place, publisher, year, edition, pages
NATL ACAD SCIENCES, 2018
Keywords
divergent selection, ecotype, FST, selective sweep, tradeoff
National Category
Genetics Ecology
Identifiers
urn:nbn:se:uu:diva-356386 (URN)10.1073/pnas.1719998115 (DOI)000431639100071 ()29686078 (PubMedID)
Funder
Swedish Research CouncilNIH (National Institute of Health), R01GM078204
Available from: 2018-08-15 Created: 2018-08-15 Last updated: 2018-08-15Bibliographically approved
Laenen, B., Tedder, A., Nowak, M. D., Toräng, P., Wunder, J., Wötzel, S., . . . Slotte, T. (2018). Demography and mating system shape the genome-wide impact of purifying selection in Arabis alpina. Proceedings of the National Academy of Sciences of the United States of America, 115(4), 816-821
Open this publication in new window or tab >>Demography and mating system shape the genome-wide impact of purifying selection in Arabis alpina
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2018 (English)In: 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) Published
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.

Place, publisher, year, edition, pages
NATL ACAD SCIENCES, 2018
Keywords
self-fertilization, demographic history, bottleneck, fitness effects, genetic load
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-343798 (URN)10.1073/pnas.1707492115 (DOI)000423097800070 ()29301967 (PubMedID)
Funder
Swedish National Infrastructure for Computing (SNIC), snic2014-1-194, b2013022, b2013237Swedish Research CouncilScience for Life Laboratory - a national resource center for high-throughput molecular bioscience
Available from: 2018-03-05 Created: 2018-03-05 Last updated: 2018-03-05Bibliographically approved
Chapurlat, E., Anderson, J., Ågren, J., Friberg, M. & Sletvold, N. (2018). Diel pattern of floral scent emission matches the relative importance of diurnal and nocturnal pollinators in populations of Gymnadenia conopsea. Annals of Botany, 121, 711-721
Open this publication in new window or tab >>Diel pattern of floral scent emission matches the relative importance of diurnal and nocturnal pollinators in populations of Gymnadenia conopsea
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2018 (English)In: Annals of Botany, ISSN 0305-7364, E-ISSN 1095-8290, Vol. 121, p. 711-721Article in journal (Refereed) Published
Abstract [en]

Background and Aims

Floral scent is considered an integral component of pollination syndromes, and its composition and timing of emission are thus expected to match the main pollinator type and time of activity. While floral scent differences among plant species with different pollination systems can be striking, studies on intraspecific variation are sparse, which limits our understanding of the role of pollinators in driving scent divergence.

Methods

Here, we used dynamic headspace sampling to quantify floral scent emission and composition during the day and at night in the natural habitat of six Scandinavian populations of the fragrant orchid Gymnadenia conopsea. We tested whether diel scent emission and composition match pollinator type by comparing four populations in southern Sweden, where nocturnal pollinators are more important for plant reproductive success than are diurnal pollinators, with two populations in central Norway, where the opposite is true. To determine to what extent scent patterns quantified in the field reflected plasticity, we also measured scent emission in a common growth chamber environment.

Key Results

Both scent composition and emission rates differed markedly between day and night, but only the latter varied significantly among populations. The increase in scent emission rate at night was considerably stronger in the Swedish populations compared with the Norwegian populations. These patterns persisted when plants were transferred to a common environment, suggesting a genetic underpinning of the scent variation.

Conclusions

The results are consistent with a scenario where spatial variation in relative importance of nocturnal and diurnal pollinators has resulted in selection for different scent emission rhythms. Our study highlights the importance of adding a characterization of diel variation of scent emission rates to comparative studies of floral scent, which so far have often focused on scent composition only.

Keywords
diel variation, diurnal and nocturnal pollination, floral evolution, floral scent, geographic variation, Gymnadenia conopsea (fragrant orchid), plasticity, population differentiation, scent emission rate, scent rhythm, semi-generalkized pollination, spatial variation
National Category
Evolutionary Biology Ecology
Identifiers
urn:nbn:se:uu:diva-358243 (URN)10.1093/aob/mcx203 (DOI)000427884200015 ()29360931 (PubMedID)
Funder
Swedish Research Council FormasSwedish Research Council
Available from: 2018-08-26 Created: 2018-08-26 Last updated: 2019-06-28Bibliographically approved
Thomann, M., Ehrlen, J. & Ågren, J. (2018). Grazers affect selection on inflorescence height both directly and indirectly and effects change over time. Ecology, 99(10), 2167-2175
Open this publication in new window or tab >>Grazers affect selection on inflorescence height both directly and indirectly and effects change over time
2018 (English)In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 99, no 10, p. 2167-2175Article in journal (Refereed) Published
Abstract [en]

Selection mediated by one biotic agent will often be modified by the presence of other biotic interactions, and the importance of such indirect effects might change over time. We conducted an 11-yr field experiment to test the prediction that large grazers affect selection on floral display of the dimorphic herb Primula farinosa not only directly through differential grazing damage, but also indirectly by affecting vegetation height and thereby selection mediated by pollinators and seed predators. Exclusion of large grazers increased vegetation height and the strength of pollinator-mediated selection for tall inflorescences and seed-predator-mediated selection for short inflorescences. The direct effect of grazers on selection resulting from differential grazing damage to the two scape morphs showed no temporal trend. By contrast, the increase in vegetation height in exclosures over time was associated with an increase in selection mediated by pollinators and seed predators. In the early years of the experiment, the indirect effects of grazers on selection mediated by pollinators and seed predators were weak, whereas at the end of the experiment, the indirect effects were of similar magnitude as the direct effect due to differential grazing damage. The results demonstrate that the indirect effects of a selective agent can be as strong as its direct effects, and that the relative importance of direct vs. indirect effects on selection can change over time. A full understanding of the ecological processes governing variation in selection thus requires that both direct and indirect effects of biotic interactions are assessed.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
biotic interactions, conflicting selection, context-dependence, diffuse evolution, floral traits, indirect ecological effects, non-additive selection, pollination, Primula farinosa, seed predation
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-367406 (URN)10.1002/ecy.2470 (DOI)000446270400005 ()30047592 (PubMedID)
Funder
Swedish Research Council FormasSwedish Research Council
Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2018-12-03Bibliographically approved
Urbina, H., Breed, M. F., Zhao, W., Gurrala, K. L., Andersson, S. G. .., Ågren, J., . . . Rosling, A. (2018). Specificity in Arabidopsis thaliana recruitment of root fungal communities from soil and rhizosphere. Fungal Biology, 122(4), 231-240
Open this publication in new window or tab >>Specificity in Arabidopsis thaliana recruitment of root fungal communities from soil and rhizosphere
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2018 (English)In: Fungal Biology, ISSN 1878-6146, E-ISSN 1878-6162, Vol. 122, no 4, p. 231-240Article in journal (Refereed) Published
Abstract [en]

Biotic and abiotic conditions in soil pose major constraints on growth and reproductive success of plants. Fungi are important agents in plant soil interactions but the belowground mycobiota associated with plants remains poorly understood. We grew one genotype each from Sweden and Italy of the widely studied plant model Arabidopsis thaliana. Plants were grown under controlled conditions in organic topsoil local to the Swedish genotype, and harvested after ten weeks. Total DNA was extracted from three belowground compartments: endosphere (sonicated roots), rhizosphere and bulk soil, and fungal communities were characterized from each by amplification and sequencing of the fungal barcode region ITS2. Fungal species diversity was found to decrease from bulk soil to rhizosphere to endo-sphere. A significant effect of plant genotype on fungal community composition was detected only in the endosphere compartment. Despite A. thaliana being a non-mycorrhizal plant, it hosts a number of known mycorrhiza fungi in its endosphere compartment, which is also colonized by endophytic, pathogenic and saprotrophic fungi. Species in the Archaeorhizomycetes were most abundant in rhizosphere samples suggesting an adaptation to environments with high nutrient turnover for some of these species. We conclude that A. thaliana endosphere fungal communities represent a selected subset of fungi recruited from soil and that plant genotype has small but significant quantitative and qualitative effects on these communities.

Keywords
Arabidopsis, Archaeorhizomcyetes, Brassicaceae, Ion Torrent, ITS metabarcoding, Rhizosphere
National Category
Botany
Identifiers
urn:nbn:se:uu:diva-354246 (URN)10.1016/j.funbio.2017.12.013 (DOI)000430773300005 ()29551197 (PubMedID)
Funder
Swedish Research Council, 349-2007-8731Swedish Research Council, 2012-3950Australian Research Council, DE150100542Australian Research Council, DP150103414
Note

De 2 första författarna delar förstaförfattarskapet.

Available from: 2018-06-19 Created: 2018-06-19 Last updated: 2019-08-28Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-9573-2463

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