Population divergence in co-distributed Caribbean landfrogs (Eleutherodactylidae: Eleutherodactylus) along the Soufrière volcanic slope of Guadeloupe Island, Lesser Antilles

Local adaptation to environmental heterogeneity across a landscape can result in population divergence and formation of lineages. On Guadeloupe Island, the active volcano, La Grande Soufrière, peaks at 1460 m a.s.l., with rainforest at low elevations transitioning to humid savannahs at high elevations. Two endemic sister species of Eleutherodactylus frogs are co-distributed across this habitat gradient, and previous studies have reported phenotypic differences between lowland and high-elevation populations in each species, in addition to potential ongoing hybridization between the species at high-elevation sites. Here we generate mitochondrial DNA and nuclear DNA genomic data along the elevational transect to quantify population genetic structure, provide historical context for the diversification of these island endemics, and identify potential bottlenecks attributable to the eruptive history of the volcano. We find that both taxa exhibit population clusters that correspond to low- and high-elevation localities; however, genetic divergence is not associated with climate variables or geographical distance. The timing of divergence between the species is estimated at ~3.75 Mya; demographic models indicate low levels of migration between the species after divergence, and we find that ongoing hybridization is likely to be limited. Finally, we find moderate heterozygosity across populations, suggesting that they were minimally impacted by recent volcanic activity. A version of this abstract translated to French can be found in the Supplementary Data. Une version de ce résumé traduite en français est disponible dans les Données Supplémentaires.