Population isolation shapes plant genetics, phenotype and germination in naturally patchy ecosystems

Aims Habitat connectivity is important in conservation since isolation can diminish the potential of a population for adaptation and increase its risk of extinction.However,conservation of naturally patchy ecosystems such as peatlands has mainly focused on preserving specific sites with exceptional characteristics,neglecting the poten-tial interconnectivity between patches.In order to better under-stand plant dynamics within a peatland network,we assessed the effect of population isolation on genetic distinctiveness,phenotypic variations and germination rates using the peatland-obligate white-fringed orchid(Platanthera blephariglottis).Methods Fifteen phenotypic traits were measured for 24 individuals per pop-ulation(20 distinct populations,Quebec,Canada)and germination rates of nearly 20000 seeds were assessed.Genetic distinctiveness was quantified for 26 populations using single nucleotide polymor-phism markers obtained via a pooled genotyping-by-sequencing approach.Geographic isolation was measured as the distance to the nearest population and as the number of populations occurring in concentric buffer zones(within a radius of 2,5 and 10 km)around the studied populations.Important Findings All phenotypic traits showed significant differences among popu-lations.Genetic results also indicated a pattern of isolation-by-distance,which suggests that seed and/or pollen exchange is restricted geographically.Finally,all phenotypic traits,as well as a reduced germination rate,were correlated with either geographic isolation or genetic distance.We conclude that geographic iso-lation likely restricts gene flow,which in turn may affect germi-nation.Consequently,it is imperative that conservation programs take into account the patchy nature of such ecosystems,rather than targeting a few specific sites with exceptional character for preservation.