Neutral and quantitative genetic differentiation among Trollius europaeus populations within a fragmented landscape

In a fragmented landscape, evolutionary processes are expected to differ among small and large remnants of formerly abundant plant species. Genetic drift and/or divergent selection result in population genetic differentiation, while gene flow and/or unifying selection foster genetic similarities. Management strategies for conservation need to consider the (dis)similarities of populations to avoid negative effects of interventions. Quantitative (QST) and neutral (FST) genetic differentiation was investigated in montane populations of Trollius europaeus, a plant of wet meadows that has undergone recent habitat loss. We studied plant performance in a greenhouse experiment and estimated genetic variation with AFLPs. By comparing QST and FST, we assessed the importance of selection versus genetic drift among four small, four large and all eight populations. Population genetic variation indicated no loss of diversity in small compared with large populations. Population size classes did not explain the variation of the six measured plant traits. Among the small populations, similar QST and FST estimates in four of the six traits suggested that population differentiation is mainly driven by genetic drift. Among the large populations and across all populations QST values were greater than FST values in four and five of the six traits, respectively, suggesting diversifying selection. Excluding the single high elevation population, however, resulted in QST–FST patterns similar to the small populations. This implies that exchange of genetic material among populations from similar elevations would be a suitable management strategy for maintaining genetic diversity of T. europaeus in habitat remnants.