The Cenozoic American Tapirs: Phylogeny and Biogegraphy

HOLANDA CELESTINO ELIZETE; FERRERO BRENDA SOLEDAD

San Juan

Congreso; IV Congreso Latinoamericano de Paleontología de Vertebrados; 2011

Universidad Nacional de San Juan

The earliest records of genus Tapirus Brisson 1762 in North American are late Miocene (late Clarendonian) (Hulbert, 2005). The genus appeared in South America from the faunistic events the Great American Biotic Interchange (GABI), as a immigrant of Holarctic origin. A phylogenetic analysis was performed in order to elucidate the relationships of American fossil species and extant species. This analysis comprises a total of 51 characters and 18 terminal taxa including the outgroups. Outgroups include five species of Tapiridae: Colodon occidentalis, Nexuotapirus marslandensis , Miotapirus harrisonensis, Plesiotapirus yagii, and Paratapirus helveticus. We consider as terminal taxa the living species of the genus Tapirus (T. bairdii, T. terrestris, T. pinchaque, and T. indicus); three Miocene species from North America (T. johnsoni, T. webbi and T. polkensis); three Pliocene - Pleistocene species from North America (T. lundeliusi, T. haysii, and T. veroensis); and three South American fossil taxa, T. mesopotamicus, T. rondoniensis and T. cristatellus. The criterion of maximum parsimony was followed using the TNT program. The multistate characters were codified as unordered. A single most parsimonious tree (MPT) was obtained by exhaustive searching, with 110 steps under equal weights, consistency index (CI) of 0.47 and a retention index (RI) of 0.67. T. webbi (late Miocene) shown a close relationship with the extant tapirs and derived fossil from South and North American. T. pinchaque is group sister of Neotropical fossil, extant tapirs and derived North American species. The clade composed by (T. mesopotamicus (T. terrestris, T. rondoniensis)) diverge from clade composed by (T. cristatellus (T. indicus (T. bairdii ( T. polkensis (T. lundeliusi (T. veroensis, T. haysii)))))). This cladogram differs from the previous phylogeny of the New World Tapirus proposed by Hulbert and Wallace (2005) and Hulbert (2010) in the fact that the South American tapirs, T. pinchaque and T. terrestris, appeared as a monophyletic group in these analysis. Our result is consistent with a paraphyletic hypothesis for South American tapirs, since T. pinchaque, T. terrestris, T. mesopotamicus, T. rondoniensis and T. cristatellus do not form a monophyletic group. According to our phylogenetic hypothesis T. bairdii and T. indicus would be the living tapirs with more derivated morphological characters. The result from phylogenetic analysis suggests a close relatioship between the South American tapirs and T. webbi, which supports the hypothesis of a dispersal event from North America to South America during the Miocene. Moreover, our data indicate a second dispersal event from South America to North America, possibly from a form closely related to T. cristatellus, which would have resulted to the derived forms os southeast North America.