The genetic consequences of rarity in the western prairie fringed orchid (Platanthera praeclara)

摘要

Habitat loss is a major driver of species extinction globally. The tallgrass prairie habitat of the Western Prairie Fringed Orchid (Platanthera praeclara) has been almost entirely converted to cropland; greatly reducing and fragmenting P. praeclara populations. As a result P. praeclara now occurs in small populations that are often separated by tens of kilometers, that may be vulnerable to genetic isolation, loss of genetic diversity and inbreeding. To investigate the genetic diversity and genetic isolation of P. praeclara we used six microsatellite loci in eight populations located in Minnesota and North Dakota. Evidence of genetic divergence among the populations was found; the overall G(ST) was 0.081. A Principal component analysis of six of the populations showed two centrally located populations were more divergent from each other than the other populations. Two populations located a greater distance from each other than to other populations were the most genetically similar. A structure analysis showed an optimal K of 5 populations, with the two central populations genetically distinct from each other and all other populations. Significant inbreeding was shown to occur in these populations. The average F-IS value (0.230) indicated a level of inbreeding comparable with other self-compatible plants. The populations of P. praeclara are not significantly isolated but may suffer inbreeding depression as a result of small population size.