Patterns of Genetic Diversity in Platanthera bifolia (Orchidaceae) with Respect to Life History Traits and Recent Range Expansion

摘要

For evolutionary and ecological analyses, genetic diversity at different scales needs to be studied in terms of biological properties, habitat, population size and population history. We surveyed Platanthera bifolia populations from six regions in northeastern Poland to determine the impact of the mating system and population history on genetic diversity. Based on variation at allozyme markers, genetic variation was relatively moderate (P = 22.3%, A = 1.48, H O = 0.083, F IS = −0.015) and similar to other Platanthera species. These parameters varied between populations (P = 13.3%–26.6%, A = 1.26–1.66, H O = 0.055–0.111, F IS = −0.262–0.147). The genetic diversity patterns were shaped by different proportions of facilitated selfing and/or outcrossing, resulting in positive and negative F IS values, respectively. No relationship between inbreeding coefficient and population size, however, and no impact of apomixis on the level of genetic diversity of P. bifolia were found. The relatively low level of genetic differentiation among the investigated regions (F CT = 0.002, P > 0.05) and among populations (F ST = 0.048, P < 0.001), and the lack of a significant relationship between genetic and geographical distance, are discussed in the context of possible scenaria of postglacial expansion.