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

Abstract

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.

Role of colonization history and species‐specific traits on contemporary genetic variation of two salamander species in a Holocene island‐mainland system

“…Our ABC framework also supports a scenario of vicariance for both species, corroborating other studies highlighting its influence on contemporary genetic variation in amphibian land bridge populations (e.g. Bell et al., ; Bessa‐Silva et al., ; Duryea, Zamudio, & Brasileiro, ; Wang et al., ). Interestingly, the mean date of divergence of insular populations from the mainland deme (10.9 kya for insular populations of S. salamandra ; 8.0 kya for L. boscai on Ons) coincides with the estimated period in which coastal lowlands flooded due to increasing seawater levels (ca.…”

Origins and Genetic Diversity of Introduced Populations of the Puerto Rican Red-Eyed Coquí,Eleutherodactylus antillensis, in Saint Croix (U.S. Virgin Islands) and Panamá

“…The nearly ubiquitous presence of E. antillensis in residential gardens and plant nurseries in Puerto Rico (Joglar, 1998), frequent transport of horticultural and landscaping materials across the Puerto Rican Bank and Saint Croix, and a long history of species introductions in Saint Croix (Platenberg, 2007) point to accidental or intentional transport of individuals and/or eggs of E. antillensis to this island. Nevertheless, genetic evidence suggests that some anuran species have crossed salt-water barriers via rafting (Vences et al, 2003; Heinicke et al, 2007; Bell et al, 2015; Duryea et al, 2015), and therefore we cannot entirely discount the possibility that E. antillensis dispersed to Saint Croix naturally.…”

Long-Term Habitat Fragmentation Is Associated With Reduced MHC IIB Diversity and Increased Infections in Amphibian Hosts

“…The best-studied of these is Thoropa taophora, a Cycloramphid frog that inhabits wet rocks and is widespread along the São Paulo coast (Sazima, 1971;Bokermann, 1974;Giaretta and Facure, 2004). The island T. taophora populations were recently shown to possess reduced genetic diversity relative to mainland populations (evaluated with microsatellite loci), with estimated divergence times approximately consistent with island age estimates (ranging from 4,000 to 28,000 years for most island populations), little significant migration among populations, and no effect of island size or distance from mainland on migration or population genetic diversity (Duryea et al, 2015).…”

“…Segregating sites (S) and nucleotide diversity (π) were calculated in DnaSP (Version 5;Librado and Rozas, 2009). T-tests were used to evaluate differences in S and π among populations, and simple linear regression was used to compare MHC N A and heterozygosity with microsatellite N A and heterozygosity (extracted from Duryea et al, 2015) in R (Version 3.3.0; Lighten et al, 2014).…”

“…These islands are essentially forest patches that were naturally isolated by marine incursions 12,000-20,000 years ago; thus they represent very old habitat fragments. Remaining frog populations were once part of contiguous mainland populations, and are now isolated to the islands (Bell et al, 2012;Duryea et al, 2015).…”