|Boa constrictor imperator, Belize. JCM
The Boa constrictor species complex has the widest distribution of any boid, with a latitudinal range from Mexico (30° N) to Argentina (35° S), and inhabiting a variety of environments Some geographically delimited populations have been recognized as subspecies, which exhibit extensive variation in morphological and ecological traits. Despite their popularity in the pet trade and relatively high abundance, no comprehensively detailed phylogeographical studies exist for this species. The only published work, based mostly on boas from captive breeders, describes two clades (based upon cytochrome b): one from Mexico and Central America, and the other encompassing localities from South America. The Central American clade coincides with the recognized subspecies Boa constrictor imperator Daudin, 1803.
Suárez‐Atilano and colleagues sampled throughout the range of B. c. imperator in Neotropical Mexico and continental Central America and used nuclear and mitochondrial molecular markers to infer the biogeographical processes that determine population structure in a coalescent framework, an approach that allows patterns at different spatial and temporal scales to be examined. The workers characterize the boa’s genetic diversity and phylogeographical structure to test: (1) whether it demonstrates key spatial patterns observed in other vertebrates in this region, such as a Pacific–Atlantic divergence; (2) whether times of divergence of lineages were related to historical and dispersal events occurring in Mexico and Central America; and (3) whether biogeographical boundaries in the region, like the Mexican Transition Zone delimit the current genetic groups.
Cytochrome b results revealed two main reciprocally monophyletic lineages, one along the Mexican Pacific coast and another along the Gulf of Mexico, Yucatan Peninsula and Central America, diverging about 5.2 million years ago. Both lineages are subdivided into haplogroups and show steady historical growth and a more recent population expansion. High genetic diversity was observed for both cytochrome b and microsatellites
. The authors demonstrate a deep phylogeographical structure with two reciprocally monophyletic lineages and five genetic clusters in Mexico and Central America. And, the results suggest that several geographical barriers (including the Trans-Mexican Volcanic Belt and the Motagua–Polochic–Jocoan faults) and ecological features generated this genetic structure, and suggest that the two lineages may be considered distinct species.
Suárez‐Atilano, Marco, Frank Burbrink, and Ella Vázquez‐Domínguez. “Phylogeographical structure within Boa constrictor imperator across the lowlands and mountains of Central America and Mexico.” Journal of Biogeography (2014).