Paleobiogeography of trilophodont gomphotheres (Mammalia: Proboscidea). A reconstruction applying DIVA (Dispersion-Vicariance Analysis)
Keywords: sea-level changes, dispersal, event-based biogeography method, DIVA, Cenozoic
AbstractThe objective of our paper was to analyze the distributional patterns of trilophodont gomphotheres, applying an event-based biogeographic method. We have attempted to interpret the biogeographical history of trilophodont gomphotheres in the context of the geological evolution of the continents they inhabited during the Cenozoic. To reconstruct this biogeographic history we used DIVA 1.1. This application resulted in an exact solution requiring three vicariant events, and 15 dispersal events, most of them (i.e., 14) occurring at terminal taxa. The single dispersal event at an internal node affected the common ancestor to Sinomastodon plus the clade Cuvieronius – Stegomastodon. A vicariant event took place which resulted in two isolated groups: (1) Amebelodontinae (Africa – Europe – Asia) and (2) Gomphotheriinae (North America). The Amebelodontinae clade was split by a second vicariant event into Archaeobelodon (Africa and Europe), and the ancestors of the remaining genera of the clade (Asia). In contrast, the Gomphotheriinae clade evolved mainly in North America. A dispersal event expanded the range of the common ancestor to Sinomastodon plus the clade Cuvieronius - Stegomastodon to include Asia again. A new vicariant event split North America and Asia resulting in the isolation of Sinomastodon in the latter, and the ancestor of the clade Cuvieronius - Stegomastodon in the former. Finally, these two genera reached South America in two independent dispersal events. This biogeographic history has been driven by sea-level changes. During the low sea-level episodes, trilophodont gomphotheres expanded its geographical distribution by means of dispersion events, and during high sea-level episodes suffered vicariant events.