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  • 51. Ericsson, D.L.
    et al.
    Fenster, C.B.
    Stenøien, Hans K.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Quantitative trait locus analyses and the study of evolutionary process2004In: Molecular Ecology, Vol. 13, p. 2505-2522Article in journal (Refereed)
  • 52.
    Eriksson, B. K. and Johansson, G.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. PLANT ECOLGY.
    Sedimentation reduces recruitment success of Fucus vesiculosus (Phaeophyceae) in the Baltic Sea2003In: European Journal of Phycology, Vol. 38, p. 217-222Article in journal (Refereed)
  • 53.
    Eriksson, B. Klemens
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Sandström, A
    Isaeus, M
    Schreiber, H
    Karås, P
    Effects of boating activities on aquatic vegetation in the Stockholm archipelago, Baltic Sea2004In: Estuarine Coastal Shelf Science, Vol. 61, p. 339-349Article in journal (Refereed)
  • 54.
    Eriksson, Britas Klemens
    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.
    Bergström, L
    Local distribution patterns of macroalgae in relation to environmental variables in the northern Baltic Proper2005In: Estuarine Coastal Shelf Science, Vol. 62, p. 109-117Article in journal (Refereed)
  • 55.
    Eriksson, Britas Klemens
    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.
    Johansson, Gustaf
    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.
    Effects of sedimentation on macroalgae: species-specific responses are related to reproductive traits2005In: Oecologia, Vol. 143, p. 438-448Article in journal (Refereed)
  • 56.
    Eriksson, I
    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.
    Teketay, Demel
    Granström, A
    Response of plant communities to fire in an Acacia woodland and a dry Afromontane forest, southern Ethiopia2003In: Forest Ecology and Management, Vol. 177, p. 39-50Article in journal (Refereed)
  • 57.
    Eriksson, Olof
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Niva, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Biology Education Centre.
    Caruso, Alexandro
    Use and abuse of reindeer range2007Book (Other academic)
    Abstract [en]

    In consequence of variations in geology and soils, in climate, and in its wide extent in longitude, latitude and altitude, the Scandinavian mountain chain exhibits major variations in natural conditions. Nature is constantly influenced by processes that include both natural forces and human activity.

    In the early 1990s, there was an intense media debate about current damage to the montane vegetation, which many believed they could observe.

    In 1992, the World Wide Foundation for Nature, WWF, invited representatives of responsible authorities, reindeer-husbandry interests, voluntary conservation bodies and interested researchers to a conference, which, somewhat erroneously, came to be called the 'Reindeer grazing conference', but which included a spectrum of factors that can affect the montane vegetation.

    One result of this conference was that, in 1993, WWF initiated a research project, extending over several years, intended to provide information about temporal changes in montane vegetation.

    Experimental areas distributed along the Swedish mountain chain were selected: the southernmost are on Fulufjället in Dalama, and the northernmost are ea. 15 km S of Tavvavuoma in Swedish Lapland. (Some placenames are given in modern North-Saamish spelling in Appendix 2) The vegetation types studied were Grass heath, Meadow with low herbs, Dry heath, Birch forest-heath type with lichens and Birch forest-heath with mosses. These cover all major montane areas and are important grazing areas for reindeer.

    At all study sites, six adjacent plots were selected, half of which were fenced to deny access to larger herbivores, and half were left open for grazing by all herbivores. The composition of plant communities in the field, bottom and tree layer in plots was estimated in 1995-96, and re-estimated three to four years later.

    Generally, marginal or no effects of enclosure were seen on the vegetation communities, and there were no differences between vegetation types.

    Up to the end of the 19th century, travellers in the montane region, both Saami and outsiders, ocularly assessed the plant cover. As a rule, they reported a good supply of reindeer fodder plants, especially lichen species.

    From the end of the 19th century, there began to be observations of severely denuded lichen cover, especially in areas exposed to a veritable invasion of Saami and reindeer from the north-Norwegian and north-Finnish reindeer grazing areas. Incomers from those areas introduced an extensive form of reindeer husbandry, developed to suit conditions on the Finnmarksvidda and in northernmost Finland, where large reindeer herds could readily find grazing on well-demarcated headlands and islands during the snowfree season, without much supervision.

    The conflicts of interest between the incomers, and indigenous Saami who wished to carry on an intensive form of reindeer husbandry, with closely supervised herds, were great. From the beginning of the 20th century, state interventions, in the form of commissions of enquiry and field surveys, were instituted. Their aim was to resolve existing conflicts, to ensure a sustainable access to grazing, and satisfactory profitability. The results cannot be said to have been satisfactory.

  • 58. Finni, T
    et al.
    Kononen, K
    Olsonen, R
    Wallström, Kerstin
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    The history of cyanobacterial blooms in the Baltic Sea2001In: Ambio, Vol. 30, p. 172-178Article in journal (Refereed)
  • 59. Flodin, Lars-Åke
    et al.
    Gunnarsson, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Vegetationsförändringar på mossar och kärr i Halland2008In: Svensk Botanisk Tidskrift, ISSN 0039-646X, Vol. 102, no 3-4, p. 177-188Article in journal (Refereed)
  • 60. Franzen, Markus
    et al.
    Larsson, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Seed set differs in relation to pollen and nectar foraging flower visitors in an insect-pollinated herb2009In: Nordic Journal of Botany, ISSN 0107-055X, E-ISSN 1756-1051, Vol. 27, no 4, p. 274-283Article in journal (Refereed)
    Abstract [en]

    Assessing the relative contributions to seed sets of each of a plant species' floral visitors provides an indication of the relative influence of these visitors on the plants' reproductive success. In this study we compared the seed set of the gynodioecious Knautia arvensis (Dipsacaceae) in 49 local plant populations in two regions of southern Sweden. We measured the seed set for hermaphroditic and female plant individuals. In both plant sexes and both regions, the seed set was positively related to the abundance of Apidae. The seed set was negatively related to the abundance of pollen-foraging solitary bees (Halictidae, Megachilidae) and beetles (Oedemeridae, Malachidae). The seed set was not related to plant population size, plant density or female frequency. Our results confirm that pollination success in generalised plant-pollinator systems varies between pollinator groups. Flower-visitors foraging for pollen might not contribute to increased pollination success in generalised pollination systems.

  • 61. Franzén, M.
    et al.
    Larsson, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Pollen harvesting and reproductive rates in specialized solitary bees2007In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 44, no 6, p. 405-414Article in journal (Refereed)
    Abstract [en]

    Andrena humilis is an endangered oligolectic solitary bee and has declined in recent decades throughout western Europe. The aim of this study was to explore the pollen harvesting pattern and to determine the reproductive rate in specialized andrenid bees. We measured the amount of pollen required to produce one brood-cell, the pollen harvesting rate and compared our results with data for other specialized andrenid bee species. Pollen-foraging trips were registered and the activity events (entering, leaving or digging) recorded at the nests. The mean number of pollen-foraging trips per day was 5.3 and an average bee nest was active (and open) 88 min day(-1). The bees were highly efficient in harvesting pollen and spent on average 10.7 min to complete one pollen-foraging trip. Most pollen-foraging trips (77%) were completed in less than 15 min. The duration of pollen-foraging trips increased over the day, presumably because pollen became more costly to harvest. Based on pollen counts (pollen loads on bees and pollen provisions) an average bee required 3.85 foraging trips to complete one brood cell and one bee managed to accomplish 1.37 brood cells in one day with suitable weather. In the literature we found data on an additional 19 specialized andrenid bee species. Andrena humilis seems to be extremely efficient compared with most other species, with an average trip for pollen lasting almost one hour (average for andrenid bees = 46 min). An extremely low reproductive rate seems to be a common trait among specialized bees in the family Andrenidae with an average 0.9 offspring produced per day and less than ten offspring produced during the whole lifetime. The high degree of specialisation and the low reproductive rate among andrenid bees can explain the severe decline in many species today.

  • 62. Franzén, Markus
    et al.
    Larsson, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Nilsson, Sven G.
    Small local population sizes and high habitat patch fidelity in a specialized solitary bee2009In: Journal of Insect Conservation, ISSN 1366-638X, E-ISSN 1572-9753, Vol. 13, no 1, p. 89-95Article in journal (Refereed)
    Abstract [en]

    Andrena hattorfiana is a rare solitary bee which has declined during the last decades throughout western Europe. It is specialised to forage pollen from plants of the family Dipsacaceae. Knowledge of distribution, dispersal propensity, and local population sizes is essential for successful conservation of A. hattorfiana. The investigated local bee populations (n = 78) were dominated by small local populations and 60% were smaller than 10 female individuals and 80% were smaller than 50 female individuals. The area of the median occupied habitat patch was 1.25 hectare and harboured 7 female bees. Mark-release-recapture studies of female A. hattorfiana revealed a sedentary behaviour. Among pollen-foraging female bees the average registered distance moved was 46 m. The patch emigration rate was about 2%, with an observed maximum colonization distance of 900 m. Only 10% of the individuals crossed areas without the pollen plant within grassland patches, such as unpaved roads, stone walls and small tree-stands, even if these areas were less than 10 m wide. This study shows that solitary bees can occur in local populations of extremely small size and they have a sedentary behaviour. These are features that usually increase the risk of local population extinction.

  • 63. Freitas, Leandro
    et al.
    Bolmgren, Kjell
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Synchrony is more than overlap:  measuring phenological synchronization considering time length and intensity2008In: Revista Brasileira de Botânica, ISSN 0100-8404, Vol. 31, p. 721-724Article in journal (Refereed)
    Abstract [en]

    Synchrony is more than overlap: measuring phenological synchronization considering time length andintensity). The degree of flowering and fruiting synchronization is believed to have ecological and evolutionary relevance atseveral scales. Here we discuss some measures that have been used to estimate synchrony and propose an index that incorporatesboth the entire length of an individual phenophase and variation in the number of flowers or fruits over that time period.This new index describes more accurately the phenological synchrony among individuals and populations.

  • 64. 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.

  • 65. Fresco, LFM
    et al.
    van der Maarel, Eddy
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Kazmierczak, E
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    VEGRON v. 7. Numerical analysis in vegetation ecology: Program package and Introduction2001Other (Other scientific)
  • 66.
    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.

  • 67.
    Gerhardt, Karin
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Tree seedling development in a tropical dry forest in Costa Rica2001In: Vegetation Science in retrospect and perspective. Proc. 41 IAVS Symposium, 2001, p. 243-245Conference paper (Refereed)
  • 68.
    Granath, Gustaf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Strengbom, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Breeuwer, Angela
    Heijmans, Monique M. P. D.
    Berendse, Frank
    Rydin, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Photosynthetic performance in Sphagnum transplanted along a latitudinal nitrogen deposition gradient2009In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 159, no 4, p. 705-715Article in journal (Refereed)
    Abstract [en]

    Increased N deposition in Europe has affected mire ecosystems. However, knowledge on the physiological responses is poor. We measured photosynthetic responses to increasing N deposition in two peatmoss species (Sphagnum balticum and Sphagnum fuscum) from a 3-year, north-south transplant experiment in northern Europe, covering a latitudinal N deposition gradient ranging from 0.28 g N m(-2) year(-1) in the north, to 1.49 g N m(-2) year(-1) in the south. The maximum photosynthetic rate (NPmax) increased southwards, and was mainly explained by tissue N concentration, secondly by allocation of N to the   photosynthesis, and to a lesser degree by modified photosystem II activity (variable fluorescence/maximum fluorescence yield). Although climatic factors may have contributed, these results were most likely attributable to an increase in N deposition southwards. For S. fuscum, photosynthetic rate continued to increase up to a deposition level of 1.49 g N m(-2) year(-1), but for S. balticum it seemed to level out at 1.14 g N m(-2) year(-1). The results for S. balticum suggested that transplants from different origin (with low or intermediate N   deposition) respond differently to high N deposition. This indicates that Sphagnum species may be able to adapt or physiologically adjust to high N deposition. Our results also suggest that S. balticum might be more sensitive to N deposition than S. fuscum. Surprisingly, NPmax was not (S. balticum), or only weakly (S. fuscum) correlated with biomass production, indicating that production is to a great extent is governed by factors other than the photosynthetic capacity.

  • 69.
    Granath, Gustaf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Vicari, M.
    Bazely, Dawn R.
    Ball, John P.
    Puentes, Adriana
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Rakocevic, T.
    Variation in the abundance of fungal endophytes in fescue grasses along altitudinal and grazing gradients2007In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 30, no 3, p. 422-430Article in journal (Refereed)
    Abstract [en]

    Epichloë festucae, a common fungal symbiont of the genus Festuca (family Poaceae), can provide its host plant with protection against herbivores. However, infection might also be associated with a cost to its host plant. We examined the distribution of Epichloë festucae infection in natural populations of three fescue grasses, Festuca rubra, F. ovina and F. vivipara, on mountains in northern Sweden to determine whether infection frequency varied with reindeer Rangifertarandus grazing pressure and altitude. Two differently-scaled approaches were used: 1) infection frequency was measured at a local scale along ten elevational transects within a ca 400 km2 area and 2) infection frequency was measured on a regional scale along elevational transects on 17 mountains classified as having a history of high or low reindeer grazing pressure. Mean infection frequencies in F. rubra were 10% (vegetative tillers at a local scale), and 23% (flowering culms at a regional scale), and in F. ovina they were 13% (local scale) and 15% (regional scale). Endophyte infection frequency in F. vivipara, was, on average, 12% (local scale) and 37% (regional scale). In F. rubra, infection decreased significantly with increasing altitude at both the local and regional scale, and was positively correlated with grazing pressure. In F. ovina, an opposite trend was found at the regional scale: infection frequency increased significantly with increasing altitude, while no discernible distribution pattern was observed at the local scale. No elevational trends were observed in infection of F. vivipara. These patterns in the distribution of endophyte-infected grasses in non-agricultural ecosystems may be explained by both biotic (grazing) and abiotic factors (altitude). Differences in ecology and life history of the studied grass species may also be of importance for the different results observed among species.

  • 70.
    Granath, Gustaf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Wiedermann, Magdalena M.
    Strengbom, Joachim
    Physiological responses to nitrogen and sulphur addition and raised temperature in Sphagnum balticum2009In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 161, no 3, p. 481-490Article in journal (Refereed)
    Abstract [en]

    Sphagnum, the main genus which forms boreal peat, is strongly affected by N and S deposition and raised temperature, but the physiological mechanisms behind the responses are largely unknown. We measured maximum photosynthetic rate (NPmax), maximum efficiency of photosystem II [variable fluorescence (F v)/maximum fluorescence yield (F m)] and concentrations of N, C, chlorophyll and carotenoids as responses to N and S addition and increased temperature in Sphagnum balticum (a widespread species in the northern peatlands) in a 12-year factorial experiment. NPmax did not differ between control (0.2 g N m−2 year−1) and high N (3.0 g N m−2 year−1), but was higher in the mid N treatment (1.5 g N m−2 year−1). N, C, carotenoids and chlorophyll concentration increased in shoot apices after N addition. F v/F m did not differ between N treatments. Increased temperature (+3.6°C) had a small negative effect on N concentration, but had no significant effect on NPmax or F v/F m. Addition of 2 g S m−2 year−1 showed a weak negative effect on NPmax and F v/F m. Our results suggest a unimodal response of NPmax to N addition and tissue N concentration in S. balticum, with an optimum N concentration for photosynthetic rate of ~13 mg N g−1. In conclusion, high S deposition may reduce photosynthetic capacity in Sphagnum, but the negative effects may be relaxed under high N availability. We suggest that previously reported negative effects on Sphagnum productivity under high N deposition are not related to negative effects on the photosynthetic apparatus, but differences in optimum N concentration among Sphagnum species may affect their competitive ability under different N deposition regimes.

  • 71.
    Grandin, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Short-term and long-term variation in seed bank/vegetation relations along an environmental and successional gradient2001In: Ecography, Vol. 24, p. 731-741Article in journal (Refereed)
  • 72. Grandin, Ulf
    et al.
    Lönn, Mikael
    Rydin, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Allozyme variation at a PGI locus in differently aged populations of Moehringia trinervia (Caryophyllaceae) in a successional area2002In: Nordic Journal of Botany, ISSN 0107-055X, E-ISSN 1756-1051, Vol. 22, no 3, p. 303-311Article in journal (Refereed)
    Abstract [en]

    We studied genetic effects of the colonisation process during primary succession by analysing allozyme variation at a PGI locus in differently aged populations of Moehringia trinervia, which is a selfing annual with low dispersal ability. The populations studied come from islands and shores created in the 1880s by a drop in the water table of a Swedish lake and from old parts of a large island and of the mainland. The population age is known from five vegetation analyses over a century. We have also analysed the genetic composition of M. trinervia derived from seeds in the soil. Mainland populations had a higher genetic diversity than island populations that were little differentiated and differed genetically from the mainland populations. There was no temporal trend in the distribution of genetic variation on the new islands. The presence of alleles in the extant populations was associated with the proportion of that allele in the seed bank, indicating a main recruitment from the seed bank and not by repeated immigrations. We suggest that some of the new islands were colonised by a few early founders from the mainland. Later colonisation has occurred between adjacent islands, which preserves the founder effect and could explain the uniform, low genetic variation in the island populations.

  • 73.
    Gunnarsson, Urban
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Boresjö Bronge, L
    Rydin, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ohlson, M
    Near-zero recent carbon accumulation in a bog with high nitrogen deposition in SW Sweden2008In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 14, p. 2152-2165Article in journal (Refereed)
    Abstract [en]

    We present data on the accumulation of carbon and nitrogen into an open oceanic ombrotrophic bog, SW Sweden, with high levels of anthropogenic nitrogen deposition. The aim was to investigate if this peatland currently acts as a sink for atmospheric carbon. Peat cores were sampled from the top peat layer in five different vegetation types. Small pines were used to date the cores. The cores bulk density and carbon and nitrogen content were determined. A vegetation-classified satellite image was used to estimate the areal extent of the vegetation types and to scale up these results to bog level. The rate of current carbon input into the upper oxic acrotelm was 290 g m(-2) yr(-1), and there were no significant differences in accumulation rates among the vegetation types. This organic matter input to the acrotelm was almost completely decomposed before it was deposited for storage in the deeper peat layers (the catotelm) and only a small fraction (< , 1%) or 0.012 g m(-2) yr(-1) of the carbon would be left, assuming a residence time of 100 years in the acrotelm. Nitrogen accumulation rates differed between the vegetation classes, and the average input via primary production varied from 5.33 to 16.8 g m(-2) yr(-1). Current nitrogen input rates into the catotelm are much lower, 0-0.059 g m(-2) yr(-1), with the highest accumulation rates in lawn-dominated communities. We suggest that one of the main causes of the low carbon input rates is the high level of nitrogen deposition, which enhances decomposition and changes the vegetation from peat-forming Sphagnum-dominance to dominance by dwarf shrubs and graminoids.

  • 74.
    Gunnarsson, Urban
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Flodin, Lars-Åke
    Vegetation shifts towards wetter site conditions on oceanic ombrotrophic bogs in south-west Sweden2007In: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 18, no 4, p. 595-604Article in journal (Refereed)
    Abstract [en]

    Question: Is ombrotrophic bog vegetation in an oceanic region of southwestern Sweden changing in the same direction over a five year period (1999 - 2004) as northwest European bogs in the last 50 years, i.e. towards drier and more eutrophic vegetation?

    Location: The province of Halland, southwestern Sweden.

    Methods: Changes in species composition were monitored in 750 permanently marked plots in 25 ombrotrophic bogs from 1999 to 2004. Changes in species occurrences and richness were analysed and a multivariate statistical method (DCA) was used to analyse vegetation changes.

    Results: The species composition changed towards wetter rather than drier conditions, which is unlike the general pattern of vegetation change on bogs in northwestern Europe. Species typical of wetter site conditions including most Sphagnum species increased in abundance on the bogs until 2004. The total number of species per plot increased, mostly due to the increased species richness of Sphagnum species. Nitrogen-demanding (eutrophic) species increased in occurrence.

    Conclusions: Ombrotrophic bog vegetation in an oceanic region in Sweden became wetter and was resilient to short-term climatic shifts, after three years of below normal precipitation followed by several years with normal precipitation levels. Shifts towards more nitrogen demanding species were rapid in this region where the deposition levels have been high for several decades.

  • 75.
    Gunnarsson, Urban
    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.
    Granberg, G
    Nilsson, M
    Growth, production and interspecific competition in Sphagnum: effects of temperature, nitrogen and sulphur treatments on a boreal mire2004In: New Phytologist, Vol. 163, p. 349-359Article in journal (Refereed)
  • 76.
    Gunnarsson, Urban
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Löfroth, Michael
    Våtmarksinventeringen: resultat från 25 års inventeringar : nationell slutrapport för våtmarksinventeringen (VMI) i Sverige2009Report (Other academic)
  • 77.
    Gunnarsson, Urban
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Shaw, A.J.
    Lönn, Mikael
    Local-scale genetic structure in the peatmoss Sphagnum fuscum2007In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 16, no 2, p. 305-312Article in journal (Refereed)
    Abstract [en]

    Sphagnum (peatmoss) dominates huge areas of the Northern Hemisphere and acts as a significant carbon sink on a global scale, yet little is known about the genetic structure of Sphagnum populations. We investigated genetic structure within a population of the common peatmoss Sphagnum fuscum, to assess local patterns of genetic diversity and the spatial extent of clones. One hundred seventeen shoots were sampled from five transects in Fuglmyra, central Norway, and sequenced for three anonymous DNA regions. Five neighbourhood patches were marked along each transect, and from each patch, five stems were sampled for molecular analyses. Seventeen haplotypes could be distinguished and two major groups of haplotypes differed by 12 mutational steps. The two major haplotype groups differed significantly in microhabitat association along the distance to groundwater table and the pH gradients, indicating microhabitat differentiation. The haplotypes within these groups were all genetically similar, differing by one or two mutations. The most common haplotype occurred in four transects separated by 250-m distance. Most of the molecular variation in the population was found among transects, and within patches. Large dominating clones within each transect resulted in low variation explained by the among-patch-within-transect component of spatial structure. Mutation appears to account for a larger proportion of the population variation than recombination. Within the population, vegetative growth and asexual reproduction from gametophyte fragments dominate as the main reproductive mode.

  • 78.
    Gunnarsson, Urban
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Söderström, Lars
    Can artificial introductions of diaspore fragments work as a conservation tool for maintaining populations of the rare peatmoss Sphagnum angermanicum?2007In: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 135, no 3, p. 450-458Article in journal (Refereed)
    Abstract [en]

    Species can become regionally rare when limited by the availability of suitable habitats or by limited dispersal ability. We tested if the presence of a rare bryophyte species (Sphagnum angermanicum) was dispersal or habitat limited and at the same time investigated the possibility of establishing new populations of this rare species. Further, we tested how propagule (fragment) size and small scale disturbances affected establishment success. All field experiments were performed by artificially transporting propagules (of various sizes) to new and old sites for the species in Sweden.

    We show that S. angermanicum is dispersal limited on a regional scale, as no significant differences in establishment success were found between new suitable sites and old occupied sites. The larger the propagule the better was the establishment success; the best establishment success was found when transplanting whole shoots. Disturbances did not increase establishment success, in contrary, when compared to controls success was reduced by the more intensive disturbance treatments. We suggest that disturbance maybe more important for increasing direct dispersal than for making the microhabitat more advantageous for establishment. However, an intermediate disturbance, which slightly reduces the Sphagnum-community length increment, might also be beneficial for the establishment success of S. angermanicum propagules.

    The reasonably high establishment success of S. angermanicum propagules in new suitable sites suggests that artificial introductions of fragments could be considered as an active management regime for the species if the number of localities continues to decrease.

  • 79.
    Gustafsson, C. and Ehrlén, J.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. PLANT ECOLGY.
    Effects of intraspecific and interspecific density on the demography of a perennial herb, Sanicula europaea2003In: Oikos, Vol. 100, p. 317-324Article in journal (Refereed)
  • 80.
    Gustafsson, Christel
    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 timing and amount of leaf removal on survival, growth and reproduction in the perennial herb Sanicula europaea L.2004In: Plant Ecology, Vol. 170, p. 29-34Article in journal (Refereed)
  • 81. Görs, Solvig
    et al.
    Schumann, Rhena
    Häubner, Norbert
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Karsten, Ulf
    Fungal and algal biomass in biofilms on artificial surfaces quantified by ergosterol and chlorophyll a as biomarkers2007In: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 60, no 1, p. 50-59Article in journal (Refereed)
    Abstract [en]

    The occurrence of microbial colonisation on artificial surfaces in urban areas (building facades, roof tiles) and interiors (damp rooms: silicone sealings, wallpaper) causes not only an aesthetically unacceptable discolouration of the surface, it also represents a conspicuous problem in terms of biodeterioration, accelerated weathering and a potential health risk for humans by fungal mycotoxines. The most conspicuous organisms responsible for biofouling terrestrial surfaces are fungi and green microalgae as well as cyanobacteria. Microorganisms are often estimated by cultivating, but the biomass can be Misjudged because of contaminations or the existence of nonculturable cells and spores. By using ergosterol as a specific biomarker for living fungi and yeasts in combination with chlorophyll a for aeroterrestrial microalgae it is possible to quantify fungal and algal infection independent from cultivation and undisturbed by surface (dis)colouration. Using HPLC and photometric methods, conversion factors for microbial biomass were determined in representative fungal and algal species: 5 mg ergosterol g(-1) fungal dry biomass and 23 mg chlorophyll a g(-1) algal dry biomass. The applied wipe technique allowed a non-invasive sampling and evaluating of infections per square meter. Very low detection limits for ergosterol and chlorophyll a permitted determining fungi and algae before they become macro scopically visible. Up to 36 mg ergosterol m(-2) and 180 mg chlorophyll a m(-2) were detected on outdoor artificial surfaces, equivalent to approximately 7 g m(-2) fungal dry biomass and 8 g m(-2) algal dry biomass. The distribution and the composition of the microbial communities varied strongly between the sampling locations. Fungi were observed above windows of damp rooms or at more sun-exposed locations, whereas algae covered more wet and shadowed surfaces. The established methods are well suited for the precise joint determination of fungal and algal biomass in microbial communities of natural biofilms on artificial surfaces as a pre-condition for the development of prevention strategies against microbial colonisation.

  • 82. Hagenah, Nicole
    et al.
    Munkert, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Gerhardt, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Olff, Han
    Interacting effects of grass height and herbivores on the establishment of an encroaching savanna shrub2009In: Plant Ecology, ISSN 1385-0237, E-ISSN 1573-5052, Vol. 201, no 2, p. 553-566Article in journal (Refereed)
    Abstract [en]

    Shrub encroachment is a widely observed problem in Southern African savannas. Although the effects of herbivory and grass height on woody species recruitment have been studied individually, little information exists about how these factors interact. In this study seeds and seedlings of the encroaching shrub Dichrostachys cinerea were planted in clipped and unclipped grass plots, with and without large herbivores present. Seed germination, seedling survival and seedling predation were monitored for 8 months. Germination started earlier in plots where herbivores were excluded. Overall, the earlier the seeds germinated, the longer the seedlings survived. Clipping positively affected the number of germinated seeds, seedling growth and survival but effects varied among herbivore exclusion treatments and sites. Invertebrates caused the majority of the seedling damage. We conclude the recruitment of D. cinerea is influenced by the interplay of grass height and herbivory. In this study, the presence of large herbivores early in the wet season, and the absence of simulated grazing later on, affected the regeneration of D. cinerea negatively. However, differences in effects among sites suggest that the mechanisms found here may work differently in other habitats.

  • 83. 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)
  • 84.
    Hofgaard, Annika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Dalen, Linda
    Hytteborn, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Tree recruitment above the treeline and potential for climate-driven treeline change2009In: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 20, no 6, p. 1133-1144Article in journal (Refereed)
    Abstract [en]

    Questions   How do population structure and recruitment characteristics of Betula   saplings beyond the treeline vary among climatic regions, and what is   the potential for development into tree-sized individuals with   interacting grazing pressure?   Location   Scandes Mountains.   Methods   Sapling characteristics of Betula pubescens subsp. tortuosa, their   topographic position above the treeline, growth habitat and evidence of   recent grazing was investigated in three areas with a long continuous   grazing history, along a latitudinal gradient (62-69 degrees N).   Results   Saplings were common up to 100 m above the treeline in all areas. The   northern areas were characterised by small (< 30 cm) and young (mean 14   years old) saplings in exposed micro-topographic locations unfavourable   to long-term survival. In the southern area, broad height (2-183 cm)   and age (4-95 years; mean 32 years) distributions were found in   sheltered locations. Age declined with altitude in all areas. Sapling   growth rate varied within and between areas, and the age x height   interaction was significant only in the southern area. Growth rates   decreased from south to north and indicated a considerable time   required to reach tree size under prevailing conditions.   Conclusions   Regional differences can be attributed to climatic differences,   however, interacting biotic and abiotic factors such as   micro-topography, climate and herbivory, mutually affect the   characteristics of birch saplings. In view of the long time needed to   reach tree size, the generally expected evident and fast treeline   advance in response to climate warming may not be a likely short-term   scenario. The sapling pool in the southern region possesses strongest   potential for treeline advance.

  • 85.
    Holeton, Clare
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Lindell, Kristin
    Holmborn, Towe
    Högfors, Hedvig
    Gorokhova, Elena
    Decreased astaxanthin at high feeding rates in the calanoid copepod Acartia bifilosa2009In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 31, no 6, p. 661-668Article in journal (Refereed)
    Abstract [en]

    In marine food webs, copepods are the major producers of a carotenoid  pigment astaxanthin, which is an important antioxidant. The availability of astaxanthin for higher trophic levels can be affected by changes in phytoplankton stocks and copepod feeding; however, the functional relationship between food availability and astaxanthin production is poorly understood. We hypothesized that with a given food  type and quality, astaxanthin content in copepods is positively related  to feeding and egg production rates. The hypothesis was tested by  measuring astaxanthin accumulation in concert with ingestion and egg production rates in the copepod Acartia bifilosa exposed to different algal concentrations (Tetraselmis suecica; 0 to 1200 mu g C L-1). Egg production and ingestion rates increased with increasing food availability and reached a plateau at >= 400-600 mu g C L-1. In contrast, increasing accumulation of astaxanthin with increasing food availability was observed only at concentrations <= 150 mu g C L-1. Contrary to our hypothesis, at 600-1200 mu g C L-1 copepods had maximal ingestion and egg production rates, but low astaxanthin contents. It is suggested that this low accumulation of astaxanthin at high food concentrations results from a food-dependant decrease in assimilation efficiency. These findings are important for the understanding of astaxanthin dynamics within marine food webs, where increases in phytoplankton biomass may translate to a trade-off between zooplankton quantity and its nutritional quality for zooplanktivores.

  • 86. Holmborn, Towe
    et al.
    Dahlgren, Kristin
    Holeton, Claire
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Hogfors, Hedvig
    Gorokhova, Elena
    Biochemical proxies for growth and metabolism in Acartia bifilosa (Copepoda, Calanoida)2009In: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, Vol. 7, p. 785-794Article in journal (Refereed)
    Abstract [en]

    Biochemical proxies are becoming increasingly common for growth assessment in zooplankton. Their suitability is often unknown, however, and proper calibration is lacking. We investigated correlations between physiological variables (ingestion, egg production, and respiration rates) and biochemical indices related to protein synthesis (RNA content, RNA: DNA ratio, RNA: protein ratio, and protein specific aminoacyl-tRNA synthetases [spAARS] activity) in copepods Acartia bifilosa exposed to different algal concentrations (0-1200 mu g C L-1). All variables assayed increased with increasing food concentration either linearly (spAARS) or nonlinearly (all other variables). Egg production and ingestion rates were significantly and positively correlated with RNA content and RNA: protein ratio, whereas correlations with spAARS and RNA: DNA ratio were weaker or nonsignificant. However, when RNA: DNA ratio and spAARS activity were used as predictors of ingestion, together they had higher explanatory value than did either variable separately. As there were substantial differences in saturating food concentrations among the assayed variables, applicability of biomarkers as proxies of physiological rates will be more reliable if restricted to the nonsaturated phase of the functional response of either variable, unless both variables saturate simultaneously. These findings contribute to methodology of zooplankton growth assessment and to our understanding of biochemical processes underlying growth and metabolism in copepods.

  • 87.
    Huber, Renate
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    van der Maarel, Eddy
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Plant species turnover in an alvar grassland under different environmental conditions and at different scales2008In: Acta Phytogeographica Suecica, ISSN 0084-5914, Vol. 88, p. 43-54Article in journal (Refereed)
    Abstract [en]

    Nutrient and water supply, light availability and removal of biomass were manipulated in a limestone grassland community on the Swedish island of Öland from 1990 to 1993 in order to investigate how these factors influence species richness and year-to-year turnover at fine scales. Turnover, broken down into disappearance (‘extinction’) and appearance (‘immigration’) of vascular plant species, was measured at different spatial scales in plots ranging from 4 cm2 to 0.25 m2.

    For most treatments, turnover was highest at the finest scale, both measured as absolute and relative numbers. Turnover rate increased at all scales when the treatment implied such a change in the environment, where application of fertilizer was combined with shading. In these cases, disappearance of species largely exceeded appearance in a predictable manner, and resulted in species-poor assemblages at all scales. In plots treated with either fertilizer or shade, there were large differences in the direction of the turnover (i.e. whether immigration or extinction dominated) between years, apparently depending on the weather conditions in the respective year. After drought spells total turnover was also high for such treatments, whereas plots regularly receiving additional water supplies had rather similar turnover rates during the whole experiment.

  • 88.
    Jakobsson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Lázaro, Amparo
    Totland, Ørjan
    Relationships between the floral neighborhood and individual pollen limitation in two self-incompatible herbs2009In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 160, no 4, p. 707-719Article in journal (Refereed)
    Abstract [en]

    Local flower density can affect pollen limitation and plant reproductive success through changes in pollinator visitation and availability of compatible pollen. Many studies have investigated the relationship between conspecific density and pollen limitation among populations, but less is known about within-population relationships and the effect of heterospecific flower density. In addition, few studies have explicitly assessed how the spatial scales at which flowers are monitored affect relationships. We investigated the effect of floral neighborhood on pollen limitation at four spatial scales in the self-incompatible herbs Armeria maritima spp. maritima and Ranunculus acris spp. acris. Moreover, we measured pollen deposition in Armeria and pollinator visits to Ranunculus. There was substantial variation in pollen limitation among Armeria individuals, and 25% of this variation was explained by the density of compatible and heterospecific flowers within a 3 m circle. Deposition of compatible pollen was affected by the density of compatible and incompatible inflorescences within a 0.5 m circle, and deposition of heterospecific pollen was affected by the density of heterospecific flowers within a 2 m circle. In Ranunculus, the number of pollinator visits was affected by both conspecific and heterospecific flower densities. This did not, however, result in effects of the floral neighborhood on pollen limitation, probably due to an absence of pollen limitation at the population level. Our study shows that considerable variation in pollen limitation may occur among individuals of a population, and that this variation is partly explained by floral neighborhood density. Such individual-based measures provide an important link between pollen limitation theory, which predicts ecological and evolutionary causes and consequences for individual plants, and studies of the effects of landscape fragmentation on plant species persistence. Our study also highlights the importance of considering multiple spatial scales to understand the spatial extent of pollination processes within a population.

  • 89.
    Jakobsson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Padron, Benigno
    Traveset, Anna
    Competition for pollinators between invasive and native plants: Effects of spatial scale of investigation (note)2009In: Ecoscience, ISSN 1195-6860, Vol. 16, no 1, p. 138-141Article in journal (Refereed)
    Abstract [en]

    In this study we show that spatial scale of investigation affects the estimated strength of competition for pollinators between an invasive and a native plant species. The effect of the invasive herb Oxalis pes-caprae on pollinator visits to the native herb Diplotaxis erucoides was studied when the invader was (1) totally present, (2) present on a large scale (of hectares) but absent on a small scale (of square metres), and (3) totally absent. No difference in number of pollinator visits to D. erucoides was found between treatment 1 and 3, i.e., between total presence and total absence of the invader. However, when the invader was removed in the small scale while still remaining in the large scale, a higher number of visits to the native was recorded. Our study thus shows the importance of incorporating multiple spatial scales to allow for investigation of hierarchical effects on competition for pollinators, and it suggests that small-scale studies of effects of invasive plants on pollinator visitation might risk overstating negative effects of the invader.

  • 90.
    Jakobsson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Padrón, Benigno
    Traveset, Anna
    Pollen transfer from invasive Carpobrotus spp. to natives - a study of pollinator behaviour and reproduction success2008In: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 141, no 1, p. 136-145Article in journal (Refereed)
    Abstract [en]

    The influence of invasive plant species on native community composition is well-documented, but less is known about underlying mechanisms. Especially scarce is knowledge about effects on biotic interactions such as relationships between native plants and their pollinators. In this study we investigate if pollen transfer from the invasive and highly pollen productive Carpobrotus spp. affects seed production and/or seed quality in three native species. We monitored pollinator movements and pollen loads on pollinators and native stigmas, and in a field pollination experiment we investigated the effect of invasive pollen on reproduction. Invasive pollen adhered to pollinators, pollinators switched from Carpobrotus spp. to natives, invasive pollen was transferred to native stigmas, and it affected seed production in one species. Although all possible steps for interference with seed production were found to be qualitatively taken, invasive pollen has probably little impact on the native community because the frequency of invasive pollen transfer to natives was low. However, pollination interactions may change with plant abundance and our study provides evidence that pollen transfer from Carpobrotus spp. to natives does occur and have the potential to affect seed production. We found the species identity of shared pollinators to be of importance, higher flower constancy and lower capacity of pollen adherence are likely to result in less invasive pollen transfer.

  • 91.
    Johansson, G. and Snoeijs, P.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. PLANT ECOLGY.
    Genetic variability and level of differentiation in North Sea and Baltic Sea populations of the green alga Cladophora rupestris2003In: Marine Biology, Vol. 142, p. 1019-1027Article in journal (Refereed)
  • 92.
    Johansson, Johanna
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Snoeijs, Pauli
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Charasomer i svenska kransalger2002In: Svensk Botanisk Tidskrift, Vol. 96, p. 256-259Article in journal (Refereed)
  • 93. Johansson, L
    et al.
    Gerhardt, Karin
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Urban impact in the history of water quality in the Stockholm Archipelago2001In: Ambio, Vol. 30, p. 277-281Article in journal (Refereed)
  • 94. Johansson, Per
    et al.
    Rydin, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Thor, Göran
    Tree age relationships with epiphytic lichen diversity and lichen life history traits on ash in southern Sweden2007In: Ecoscience, ISSN 1195-6860, Vol. 14, no 1, p. 81-91Article in journal (Refereed)
    Abstract [en]

    We examined the influence of tree- and stand-level conditions on lichen diversity on 143 ash trees, varying in age from 11 to 140+ y, in 5 deciduous stands in southern Sweden. The number of lichen species per tree varied from 2 to 30 and was primarily explained by tree trunk diameter and to a lesser extent by tree age, crown cover, lichen cover, and stand identity. The positive relationship between species richness and lichen cover seems compatible with a random placement of species and suggests that similar factors affect both lichen growth and establishment. Species richness did not increase on trees above 65 y of age, while species composition changed with tree age. Together with the positive linear effect of trunk diameter, these results suggest a slight overall positive effect of area, but that species richness over time depends more on species turnover. In addition, we examined if lichens occurring on trees of different ages differed in life history traits, e.g., spore size, thallus height, and pH preference. The results indicate that lichens that most frequently occurred on old trees had larger spores and thicker thalli than other species, suggesting that lichen species' response to tree age can be understood to some extent from their life history traits. However, in this respect lichen ecology is still in its infancy.

  • 95.
    Johnson, S. D., Alexandersson, R. and Linder, H. P.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. PLANT ECOLGY.
    Experimental and phylogenetic evidence for floral mimicry in a guild of fly-pollinated plants2003In: Biological Journal of the Linnaean Society, Vol. 80, p. 289-304Article in journal (Refereed)
  • 96. 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)
  • 97. 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)
  • 98. 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.

  • 99. 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.

  • 100.
    Karlsson, P. S. and Weih, M.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. PLANT ECOLGY.
    Long-term patterns of leaf, shoot and wood production after insect herbivory in the Mountain Birch2003In: Functional Ecology, Vol. 17, p. 841-850Article in journal (Refereed)
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