Monday, January 7, 2013

Treeboa Phylogeny


Treeboas of the genus Corallus (subfamily Boinae), had a Gondwanan origin. As noted in the previous post there are eight species  recognized based on morphology and some have been confirmed with molecular data: C. annulatus, C. batesii, C. caninus, C. cookii, C. cropanii, C. grenadensis, C. hortulanus, and C. ruschenbergerii. Four of these species are endemic to South America, including the rare and very poorly known C. cropanii, which is known from four specimens (three existing) and whose taxonomic placement has been of great interest. Two species are distributed in both Central and South America (C. annulatus and C. ruschenbergerii), and two species are endemic to the Lesser Antilles (C. cookii and C. grenadensis). Phylogenetic relationships have been explored using morphology and molecular phylogeographic analyses have been conducted on 115 individuals. However, a time-calibrated phylogeny for all species has not been available.

In a forthcoming paper, Colston et al. (2013) use DNA sequence data from two mitochondrial and three nuclear genes from all species of Corallus to infer their phylogenetic relationships and reconstruct their biogeographic history. The authors find Corallus diversified within mainland South America, and disperse over-water to the Lesser Antilles and Central America, and they used the traditionally recognized Panamanian land bridge. Divergence time estimates reject the South American Caribbean-Track as a general biogeographic model for Corallus and suggest Oligocene and Miocene played a role diversification. These events include marine incursions and the uplift of the Andes. The results also suggest that recognition of the island endemic species, C. grenadensis and C. cookii, is questionable as they are nested within the widely distributed species, C. hortulanus.

The research suggests that Ruschenberg's treeboa C. ruschenbergerii dispersed from South America to Central America during the Pleistocene via the traditionally recognized Panamanian land bridge, although the results also allow for the possibility that C. ruschenbergerii may have arrived in Central America prior to the closure of the Panamanian Isthmus in the middle Miocene.

Citation

Colston, T.J., et al. (2013) Molecular systematics and historical biogeography of tree boas (Corallus spp.). Mol. Phylogenet. Evol., http://dx.doi.org/10.1016/j.ympev.2012.11.027