Changes in reproductive investment with altitude in an alpine plant

Aims In perennial species,the allocation of resources to reproduction results in a reduction of allocation to vegetative growth and,therefore,impacts future reproductive success.As a consequence,variation in this trade-off is among the most important driving forces in the life-history evolution of perennial plants and can lead to locally adapted genotypes.In addition to genetic variation,phenotypic plasticity might also contribute to local adaptation of plants to local conditions by mediating changes in reproductive allocation.Knowledge on the importance of genetic and environmental effects on the tradeoff between reproduction and vegetative growth is therefore essential to understand how plants may respond to environmental changes.Methods We conducted a transplant experiment along an altitudinal gradient from 425to1921 min the frontrange of the Western Alps of Switzerland to assess the influence of both altitudinal origin of populations and altitude of growing site on growth,reproductive investment and local adaptation in Poa alpina.Important findings In our study,the investment in reproduction increased with plant size.Plant growth and the relative importance of reproductive investment decreased in populations originating from higher altitudes compared to populations originating from lower altitudes.The changes in reproductive investment were mainly explained by differences in plant size.In contrast to genetic effects,phenotypic plasticity of all traits measured was low and not related to altitude.As a result,the population from the lowest altitude of origin performed best at all sites.Our results indicate that in P.alpina genetic differences in growth and reproductive investment are related to local conditions affecting growth,i.e.interspecific competition and soil moisture content.

Spatial isolation and genetic differentiation in naturally fragmented plant populations of the Swiss Alps

The effect of anthropogenic landscape fragmentation on the genetic diversity and adaptive potential of plant populations is a major issue in conservation biology.However,little is known about the partitioning of genetic diversity in alpine species,which occur in naturally fragmented habitats.Here,we investigate molecular patterns of three alpine plants(Epilobium fleischeri,Geum reptans and Campanula thyrsoides)across Switzerland and ask whether spatial isolation has led to high levels of population differentiation,increasing over distance,and a decrease of within-population variability.We further hypothesize that the contrasting potential for long-distance dispersal(LDD)of seed in these species will considerably influence and explain diversity partitioning.Methods For each study species,we sampled 20–23 individuals from each of 20–32 populations across entire Switzerland.We applied Random Amplified Polymorphic Dimorphism markers to assess genetic diversity within(Nei’s expected heterozygosity,He;percentage of polymorphic bands,Pp)and among(analysis of molecular variance,Ust)populations and correlated population size and altitude with within-population diversity.Spatial patterns of genetic relatedness were investigated using Mantel tests and standardized major axis regression as well as unweighted pair group method with arithmetic mean cluster analyses and Monmonier’s algorithm.To avoid known biases,we standardized the numbers of populations,individuals and markers using multiple random reductions.We modelled LDD with a high alpine wind data set using the terminal velocity and height of seed release as key parameters.Additionally,we assessed a number of important life-history traits and factors that potentially influence genetic diversity partitioning(e.g.breeding system,longevity and population size).Important findings For all three species,we found a significant isolation-by-distance relationship but only a moderately high differentiation among populations(Ust:22.7,14.8 and 16.8%,for E.fleischeri,G.reptans and C.thyrsoides,respectively).Within-population diversity(He:0.19–0.21,Pp:62–75%)was not reduced in comparison to known results from lowland species and even small populations with<50 reproductive individuals contained high levels of genetic diversity.We further found no indication that a high long-distance seed dispersal potential enhances genetic connectivity among populations.Gene flow seems to have a strong stochastic component causing large dissimilarity between population pairs irrespective of the spatial distance.Our results suggest that other life-history traits,especially the breeding system,may play an important role in genetic diversity partitioning.We conclude that spatial isolation in the alpine environment has a strong influence on population relatedness but that a number of factors can considerably influence the strength of this relationship.