TY - JOUR A1 - Fischer, Markus A1 - Galeuchet, D. A1 - Perret, C. T1 - Microsatellite variation and structure of 28 populations of the common wetland plant Lychnis flos-cuculi L. in a fragemented landscape N2 - Habitat fragmentation is known to cause genetic differentiation between small populations of rare species and decrease genetic variation within such populations. However, common species with recently fragmented populations have rarely been studied in this context. We investigated genetic variation and its relationship to population size and geographical isolation of populations of the common plant species, Lychnis flos-cuculi L., in fragmented fen grasslands. We analysed 467 plants from 28 L. flos-cuculi populations of different sizes (60 000-54 000 flowering individuals) in northeastern Switzerland using seven polymorphic microsatellite loci. Genetic differentiation between populations is small (F-ST = 0.022; AMOVA; P < 0.001), suggesting that gene flow among populations is still high or that habitat fragmentation is too recent to result in pronounced differentiation. Observed heterozygosity (H-O = 0.44) significantly deviates from Hardy-Weinberg equilibrium, and within-population inbreeding coefficient F-IS is high (0.30-0.59), indicating a mixed mating breeding system with substantial inbreeding in L. flos-cuculi. Gene diversity is the only measure of genetic variation which decreased with decreasing population size (R = 0.42; P < 0.05). While our results do not indicate pronounced effects of habitat fragmentation on genetic variation in the still common L. flos-cuculi, the lower gene diversity of smaller populations suggests that the species is not entirely unaffected Y1 - 2005 SN - 0962-1083 ER - TY - JOUR A1 - Fischer, Markus A1 - Perret, Catherine A1 - Galeuchet, David J. T1 - Performance of Lychnis flos-cuculi from fragmented populations under experimental competition and pathogen infection, Ecology Y1 - 2005 SN - 0012-9658 ER - TY - JOUR A1 - Fischer, Markus A1 - Wipf, S. A1 - Rixen, C. A1 - Stöckli, V. T1 - Effects of ski piste preparation on alpine vegetation N2 - 1. Ski resorts increasingly affect alpine ecosystems through enlargement of ski pistes, machine-grading of ski piste areas and increasing use of artificial snow. 2. In 12 Swiss alpine ski resorts, we investigated the effects of ski piste management on vegetation structure and composition using a pairwise design of 38 plots on ski pistes and 38 adjacent plots off-piste. 3. Plots on ski pistes had lower species richness and productivity, and lower abundance and cover of woody plants and early flowering species, than reference plots. Plots on machine-graded pistes had higher indicator values for nutrients and light, and lower vegetation cover, productivity, species diversity and abundance of early flowering and woody plants. Time since machine-grading did not mitigate the impacts of machine-grading, even for those plots where revegetation had been attempted by sowing. 4. The longer artificial snow had been used on ski pistes (2-15 years), the higher the moisture and nutrient indicator values. Longer use also affected species composition by increasing the abundance of woody plants, snowbed species and late-flowering species, and decreasing wind-edge species. 5. Synthesis and applications. All types of ski piste management cause deviations from the natural structure and composition of alpine vegetation, and lead to lower plant species diversity. Machine-grading causes particularly severe and lasting impacts on alpine vegetation, which are mitigated neither by time nor by revegetation measures. The impacts of artificial snow increase with the period of time since it was first applied to ski piste vegetation. Extensive machine-grading and snow production should be avoided, especially in areas where nutrient and water input are a concern. Ski pistes should not be established in areas where the alpine vegetation has a high conservation value Y1 - 2005 SN - 0021-8901 ER - TY - JOUR A1 - Maurer, Katrin A1 - Gautschi, B A1 - Weyand, Anne A1 - Stocklin, J A1 - Fischer, Markus T1 - Isolation and characterization of microsatellite DNA markers in the grass Poa alpina L. N2 - The important fodder grass Poa alpina L. occurs at several ploidy levels with common aneuploidy. We isolated and characterized five polymorphic microsatellite markers for the study of molecular genetic variation of this species. As first examples of the value of the developed markers for population genetic analyses, we show that plants with more chromosomes have more microsatellite bands and that isolation by distance plays a small role in shaping microsatellite diversity of P. alpina in the Swiss Alps Y1 - 2005 ER - TY - JOUR A1 - van Kleunen, Mark A1 - Fischer, Markus T1 - Constraints on the evolution of adaptive phenotypic plasticity in plants N2 - The high potential fitness benefit of phenotypic plasticity tempts us to expect phenotypic plasticity as a frequent adaptation to environmental heterogeneity. Examples of proven adaptive plasticity in plants, however, are scarce and most plastic responses actually may be 'passive' rather than adaptive. This suggests that frequently requirements for the evolution of adaptive plasticity are not met or that such evolution is impeded by constraints. Here we outline requirements and potential constraints for the evolution of adaptive phenotypic plasticity, identify open questions, and propose new research approaches. Important open questions concern the genetic background of plasticity, genetic variation in plasticity, selection for plasticity in natural habitats, and the nature and occurrence of costs and limits of plasticity. Especially promising tools to address these questions are selection gradient analysis, meta-analysis of studies on genotype-by-environment interactions, QTL analysis, cDNA-microarray scanning and quantitative PCR to quantify gene expression, and two-dimensional gel electrophoresis to quantify protein expression. Studying plasticity along the pathway from gene expression to the phenotype and its relationship with fitness will help us to better understand why adaptive plasticity is not more universal, and to more realistically predict the evolution of plastic responses to environmental change Y1 - 2005 ER - TY - JOUR A1 - van Kleunen, Mark A1 - Fischer, Markus A1 - Schmid, Bernhard T1 - Three generations under low versus high neighborhood density affect the life history of a clonal plant through differential selection and genetic drift N2 - We tested whether neighborhood density affects the clonal life history of the stoloniferous plant Ranunculus reptans through selection and genetic drift. After three generations of sexual reproduction of 16 low- and 16 high- density lines, we studied traits related to growth form and reproduction in a common competition free environment. A 7.7% lower branching frequency and slightly longer internodes indicated an evolutionary shift towards a less compact growth form under high neighborhood density, but because stolons grew also more vertically, horizontal spread per ramet was slightly decreased. Neighborhood density had no directional effects on the evolution of allocation to sexual and vegetative reproduction in R. reptans. Variation among replicated high-density lines was significantly lower than among replicated low-density lines in both growth form and reproductive characteristics, indicating less pronounced genetic drift under high neighborhood density. This study demonstrates that a clonal plant can respond to selection imposed by neighborhood density. Moreover, it shows that the effect of random genetic drift increases with decreasing neighborhood density. In a declining species, such as R. reptans in central Europe, this may lower the potential for adaptive evolutionary change and increase extinction risk Y1 - 2005 ER - TY - JOUR A1 - Willi, Yvonne A1 - Fischer, Markus T1 - Genetic rescue effect in interconnected populations of small and large size of the self-incompatible Ranunculus reptans Y1 - 2005 ER - TY - JOUR A1 - Willi, Yvonne A1 - van Buskirk, J. A1 - Fischer, Markus T1 - A threefold genetic allee effect : Population size affects cross-compatibility, inbreeding depression and drift load in the self-incompatible Ranunculus reptans Y1 - 2005 SN - 0016-6731 ER -