Data from: Reed frog diversification in the Gulf of Guinea: overseas dispersal, the progression rule, and in situ speciation

Oceanic islands accumulate endemic species when new colonists diverge from
source populations or by in situ diversification of resident island
endemics. The relative importance of dispersal versus in situ speciation
in generating diversity on islands varies with a number of archipelago
characteristics including island size, age, and remoteness. Here we
characterize inter-island dispersal and in situ speciation in frogs
endemic to the Gulf of Guinea islands. Using mitochondrial sequence and
genome-wide SNP data we demonstrate that dispersal proceeded from the
younger island (São Tomé) to the older island (Príncipe) indicating that
for organisms that disperse overseas on rafts, dispersal between islands
may be determined by ocean currents and not island age. We find that
dispersal between the islands is not ongoing, resulting in genotypically
distinct but phenotypically similar lineages on the two islands. Finally,
we demonstrate that in situ diversification on São Tomé Island likely
proceeded in allopatry due to the geographic separation of breeding sites,
resulting in phenotypically distinct species. We find evidence of
hybridization between the species where their ranges are sympatric and the
hybrid zone coincides with a transition from agricultural land to primary
forest, indicating that anthropogenic development may have facilitated
secondary contact between previously allopatric species.