Tree squirrels: A key to understand the historic biogeography of Mesoamerica?

A multi-taxon historical biogeography approach (Brooks Parsimony Analysis) was used to estimate relationships among the Mesoamerican lowland and highland areas and the particular biogeographic history of Mesoamerican squirrels (Sciurus, Microsciurus and Syntheosciurus species). A total of 15 lowland areas and 12 highland areas plus 41 clades comprising 240 species (45,135 records) were employed to obtain Taxon-Area Cladograms and Area Cladograms. A single most parsimonious General Area Cladogram indicated a strong vicariant relationship between Southern Mexico and the remainder of Mesoamerica, and identified several vicariant nodes (Modern Chiapanencan Volcanic Arc, Honduras’ Great Central Depression, and Nicaraguan Depression) as well as historically independent highland areas. A secondary BPA in relation with Sciurus species showed several instances of post speciation dispersal or range expansion, lack of response to vicariant events, and, possibly, lineage duplication. The results obtained suggest that Mesoamerican biotas have been subjected to several major vicariant events, but the reticulated nature of some of its areas also indicates that dispersal (post-speciation dispersal and range expansion) had been important in the diversification of the Mesoamerican biota. This trend was also observed in the particular biogeographic history of Mesoamerican tree squirrels.