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

Local adaptation to environmental heterogeneity across a landscape can result in population divergence and lineage formation. On Guadeloupe island, the active volcano La Soufriere peaks at 1,460 meters above sea level with rainforest at low elevations 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, as well as potential on-going hybridization between the species at high elevation sites. Here we generate mtDNA and nuDNA 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 due to the volcanos eruptive history. 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 geographic distance. The timing of divergence between the species is estimated at 3.75 Mya, demographic models indicate low levels of migration between the species post divergence, and we find that ongoing hybridization is likely limited. Finally, we find moderate heterozygosity across populations suggesting they were minimally impacted by recent volcanic activity.