Two focal populations and three regional populations of Sobralia chrysostoma

The dispersal and colonization of plant populations allow species to occupy novel habitats, migrate, and undergo range shifts in response to changing environmental factors and, as such, are fundamental ecological processes for ensuring the long-term persistence of species. Natural landscape disturbance often generates habitats available for colonization. Patterns of colonization and population expansion can be inferred from the levels and partitioning of genetic variation of plant populations with known disturbance histories, such as recent volcanic eruptions. We sampled and mapped 496 individuals from two populations of the colonizing terrestrial orchid, Sobralia chrysostoma, on the 1992 lava flow of Volcán Arenal in central Costa Rica. We used neutral co-dominant markers to genotype individuals and estimate population genetic statistics.  Both populations had high mean levels of genetic diversity (P = 100%; AP = 3.31; He = 0.259) suggesting that the lava flow was colonized by numerous...