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Bagley JC, Hickerson MJ, Johnson JB.2018. Testing hypotheses of diversification in Panamanian frogs and freshwater fishes using hierarchical approximate Bayesian computation with model averaging. PeerJ Preprints6:e26623v1https://doi.org/10.7287/peerj.preprints.26623v1
Most Neotropical frog and freshwater fish species sampled to date show phylogeographic breaks along the Pacific coast of the Isthmus of Panama, with lineages in Costa Rica and western Panama isolated from central Panama. We examine temporal patterns of diversification of taxa across this ‘western Panama isthmus’ (WPI) break to test hypotheses about the origin of species geographical distributions and genetic structuring in this region. We tested for synchronous diversification of four codistributed frog taxon-pairs and three fish taxon-pairs sharing the WPI break using hierarchical approximate Bayesian computation with model averaging based on mitochondrial DNA sequences. We also estimated lineage divergence times using full-Bayesian models. Several of our results supported synchronous divergences within the frog and freshwater fish assemblages; however, Bayes factor support was equivocal for or against synchronous or asynchronous diversification. Nevertheless, we infer that frog populations were likely isolated by one or multiple Pliocene–Pleistocene events more recently than predicted by previous models, while fish genetic diversity was structured by Pleistocene events. By integrating our results with external information from geology and elevational sea level modeling, we discuss the implications of our findings for understanding the biogeographical scenario of the diversification of Panamanian frogs and fishes. Consistent with the ‘Bermingham/Martin model’ (Mol. Ecol. 1998, 7: 499-517), we conclude that the regional fish assemblage was fractured by processes shaping isthmian landscapes during the Pleistocene glaciations, including drainage basin isolation during lowered sea levels.
BEAST MCC time trees for all seven focal species/lineages
Gray bars represent the upper and lower 95% highest posterior density (HPD) estimates of divergence times at each node and correspond to x-axis scale bars in units of millions of years ago (Ma). Yellow portions of node bars extend beyond x-axis limits and thus represent scale-less, truncated estimates; for upper 95% HPD ends of the truncated bars, and for nodes corresponding to the WPI break, geometric mean divergence time estimate values are given. Tip labels are colored green (west of the WPI break) or purple (east of the WPI break) consistent with the colors of sampling locations in Fig. 2.
This map is based on a 250 m Digital Elevation Model (DEM) and shows predicted eustatic sea levels in the study area potentially resulting from highstands of +50 m (light blue), +100 m (blue), and +250 m (dark blue) above present sea level (relative to current elevation).