Intraclonal Resource Sharing and Functional Specialization of Ramets in Response to Resource Heterogeneity in Three Stoloniferous Herbs

Environments with reciprocal patchiness of resources, in which the availability of two resources such as light and soil nutrients are patchily distributed in horizontal space and negatively correlated in each patch, are common in many ecosystems. The strategies by which clonal plants adapt to this type of heterogeneous environment were examined in three stoloniferous herbs,Potentilla reptans L. var. sericophylla Franch., P. anserina L. and Halerpestes ruthenica (Jacq.) Qvcz., commonly inhabiting forest understories, grasslands and low saline meadows, respectively. As pairs of connected ramets were subjected to reciprocal patchiness of light and nutrients, stolon connection between the two ramets significantly enhanced biomass of both ramet growing in low light intensity but high soil nutrient condition (LH ramet) and ramet growing in high light intensity but low soil nutrient condition (HL ramet) as well as whole ramet pairs (consisting of LH ramets and HL ramets). Additionally, stolon connection greatly increased root/shoot ratio of LH ramet while significantly decreased that of HL ramet. The results indicate that a reciprocal transportation of resources between interconnected ramets and a functional specialization of ramets in uptake of abundant resources occurred. By resource sharing and functional specialization, clonal plants can efficiently acquire locally abundant resources and buffer the stress caused by reciprocal patchiness of resources.

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.

Genetic composition,genetic diversity and small-scale environmental variation matter for the experimental reintroduction of a rare plant

Aims Reintroduction has become an important tool for the management of endangered plant species.We tested the little-explored effects of small-scale environmental variation,genotypic composition(i.e.identity of genotypes)and genotypic diversity on the population survival of the regionally rare clonal plant Ranunculus reptans.For this species of periodically inundated lakeshores,genetic differentiation had been reported between populations and between short-flooded and long-flooded microsites within populations.Methods We established 306 experimental test populations at a previously unoccupied lakeshore,comprising either monocultures of 32 genotypes,mixtures of genotypes within populations or mixtures of genotypes between populations.In 2000,three years after planting out at the experimental site,a long-lasting flood caused the death of half of the experimental populations.In 2003,an extreme drought resulted in the lowest summer water levels ever measured.Important Findings Despite these climatic extremes,27%of the established populations survived in December 2003.The success of experimental populations largely differed between microsites.Moreover,the success of genotype monocultures depended on genotype and source population.Genetic differentiation between microsites played a minor role for the success of reintroduction.After the flood,populations planted with genotypes from different source populations increased in abundance,whereas populations with genotypes from single source populations and genotype monocultures decreased.In 2014,several small patches of Ranunculus clones were still present,but plants were strongly intermingled,which precluded their assignment to the original treatments.We conclude that sources for reintroductions need to be selected carefully.Moreover,mixtures of plants from different populations appear to be the best choice for successful reintroduction,at least in unpredictably varying environments.