Molecular phylogenetics of the glass frog Hyalinobatrachium orientale (Anura: Centrolenidae): evidence for Pliocene connections between mainland Venezuela and the island of Tobago.

The presence of Hyalinobatrachium orientale in Tobago and in northeastern Venezuela is puzzling as this species is unknown from the island of Trinidad, an island often hypothesized to be a stepping-stone for the mainland fauna to colonize Tobago. A period of extended isolation on Tobago could result in the Hyalinobatrachium population becoming distinct from the mainland H. orientale. Here, we use 12S and 16S rDNA gene fragments from nine H. orientale specimens from Tobago and the mainland to assess their relationship and taxonomy, as well as the tempo and mode of speciation. The results suggest H. orientale from Venezuela and Tobago are monophyletic and the two populations diverged about 3 million years ago. This estimate corresponds with the drier climate and lower sea levels of the Pliocene glaciation periods. We hypothesize that lower sea levels resulted in land-bridge formations connecting the mainland and Tobago, with a corridor of habitat allowing H. orientale to colonize Tobago to the west of Trinidad.