Population genetics and conservation of the small white orchid, pseudorchis albida, in Ireland

Genetic diversity can play a key role in the survival of endangered species. Both the number and size of populations of a species can affect genetic diversity and may be reduced by fragmentation of natural habitats. Here we examine the effects of a low number of populations and small population sizes on the population genetics of the nationally endangered and red-listed orchid Pseudorchis albida. To determine genetic variability within and among populations of P. albida, we employed AFLP and four plastid microsatellite (SSR) markers. In addition, we compared the SSR data from Irish P. albida to the closely related P. straminea. AFLP markers showed that P. albida has a high level of polymorphism and that significant differentiation occurred both within and among populations, with increasing population genetic isolation through distance. However, SSR markers revealed no variation, but did show that all Irish individuals had the same alleles as P. straminea rather than P. albida. Further work is required to assess the taxonomic status of P. albida/straminea in Western Europe. Irish populations of P. albida s.l. require immediate conservation attention due to their decreasing number and low numbers of individuals within populations.