Phylogenetic position of Porthidium hespere (Viperidae: Crotalinae) and phylogeography of arid-adapted hognosed pitvipers based on mitochondrial DNA

Gaps in recent studies of hognosed pit vipers in the genus Porthidium have left researchers with an incomplete estimate of the evolutionary history of this group. Mitochondrial DNA sequence data from the poorly known A hespere and additional Porthidium sequences obtained from GenBank were used to re-analyze the phylogenetic relationships of Porthidium. Using sequence data from the South American Porthidium, we also updated a previous molecular clock calibration based on the uplift of the Isthmus of Panama, and utilized this updated calibration to evaluate the phylogeography of arid-adapted Porthidium. Results from Bayesian Markov chain Monte Carlo phylogenetic methods underscore the historical pattern of bi-directional dispersal into and out of South America within Porthidium, and place A hespere as the sister species to A dunni. The three species of arid-adapted Porthidium distributed across the Pacific coast of southern Mexico and northern Central America may have diverged in the late Miocene after the enlargement of the Rio Balsas drainage following the formation of the Mexican Transvolcanic Belt and the volcanic uplifting across the Chiapan-Guatemalan highlands.