Vicariance and marine migration in continental island populations of a frog endemic to the Atlantic Coastal forest.

The theory of island biogeography is most often studied in the context of oceanic islands where all island inhabitants are descendants from founding events involving migration from mainland source populations. Far fewer studies have considered predictions of island biogeography in the case of continental islands, where island formation typically splits continuous populations and thus vicariance also contributes to the diversity of island populations. We examined one such case on continental islands in southeastern Brazil, to determine how classic island biogeography predictions and past vicariance explain the population genetic diversity of Thoropa taophora, a frog endemic to the Atlantic Coastal Forest. We used nuclear microsatellite markers to examine the genetic diversity of coastal and island populations of this species. We found that island isolation has a role in shaping the genetic diversity of continental island species, with island populations being significantly less diverse than coastal populations. However, area of the island and distance from coast had no significant effect on genetic diversity. We also found no significant differences between migration among coastal populations and migration to and from islands. We discuss how vicariance and the effects of continued migration between coastal and island populations interact to shape evolutionary patterns on continental islands.

Characterization of microsatellite markers for Thoropa taophora (Anura, Cycloramphidae), a frog endemic to the Brazilian Atlantic Rain Forest.

Here we characterize nine microsatellite loci for Thoropa taophora collected from a coastal and an island population in southeastern Brazil. The number of alleles per locus ranged from three to 11 for the coastal population and from two to eight for the island population. Observed heterozygosities ranged from 0.308 to 0.778 for the coastal population and from zero to 0.737 for the island population. One locus did not conform to Hardy-Weinberg expectations on the coast, while two were in disequilibrium on the island. These markers are currently being used to examine genetic differentiation and patterns of dispersal in T. taophora.