Strong gene flow explains lack of mating system variation in the perennial herb, Vincetoxicum hirundinaria , in a fragmented landscape

Fragmented landscapes may have implications for the genetic structure of populations and microevolution plant species. In particular, landscape fragmentation and/or population isolation might affect evolution mating systems. Here, we study consequences on a perennial herb, Vincetoxicum hirundinaria with mixed system. Our area, south-western Finnish archipelago, was formed after glacial ice sheet started to retreat 12 000 years ago. Due isostatic land uplift following retreat, suitable habitats been gradually, as consequence, V. differ in age, size their degree area. We hypothesized that mixed-mating system has selected these due advantage self-fertilization newly colonized areas outcrossing adaptation heterogeneous environments. To test this hypothesis, collected seeds open-pollinated flowers from 13 differing size, age isolation, used 15 microsatellite markers perform progeny-array analysis estimate population-level rates, indices structure. found is almost completely area no signs past among relatives. The overall low inbreeding coefficients indicate even small relatives rare. High allelic richness both maternal offspring genotypes well limited differentiation studied strong gene flow them. findings suggest successful seed pollen dispersal allowed colonization new fragmented led genetically well-mixed group at scale study.