AbstractsBiology & Animal Science

The short-tailed opossums of the genus Monodelphis Burnett, 1830 are small-bodied semifossorial marsupials which inhabit almost all major biomes of South America up to 2200 m. Even though it is one of the most speciose genera of neotropical marsupials with over 30 species proposed, most taxonomic reviews of the genus have been limited to few species, and even the latest most conprehensive molecular revision enabled only an estimate to phylogenetic species groups. The present research is a fine scale search for intra and interspecifically basicranial variation, expanded from the first character list in Vidigal (2004), across 8 species groups and 21 species to provide detailed comparative characterizations and an insight into the philogeographical history of the genus. A pelage pattern and geographic classification into six groups was described for the identification of specimens. With over 165 specimens coded and 102 characters, the basicranial anatomy proved to be a stable, diverse and numerous source of phylogenetic information. I described 17 characters of the basisphenoid, 4 of the pterygoid, 7 of the orbitosphenoid, 2 of the basioccipital, 25 of the alisphenoid, 11 of the ectotympanic, 20 of the petrosal, 2 of the exoccipital, 4 of the stapes, 5 of the squamosal, and 5 of the contact among the petrosal, the exoccipital and the basioccipital. The cladistic analysis yielded a final 275 steps tree, where Marmosa comes out as the sister group to a three synapomorphies based monophyletic Monodelphis. To minimize missing data, as a post-coding data treatment, specimens were aggregated into ecoregion populations. Within Monodelphis, the supported monophyletic clades were: (M. emiliae (M. americana from NT0170 – Tocantins-Araguaia-Maranhão moist forests, M. rubida (M. umbristriata, M. americana from NT0104 – Bahia Interior Forests))), (M. henseli (brevicaudata species group, M. domestica (M. kunsi, M. adusta), and (M. touan, M. brevicaudata from NT0143 – Negro-Branco moist forests, M. brevicaudata from eastern Venezuela). An additional analysis recovered M. scalops as sister to a clade containing the americana s.l. group and M. emiliae. The phylogeographic patterns recovered from the plotted cladogram are much similar to those obtained by the pelage and basicranial analysis in Vidigal (2004), though with better resolution. According to the present analisis, Monodelphis provides three examples of the overlaping multiple evolutionary species diversity models proposed by Costa (2003) and Patton and Costa (2003) for South America. The (M. kunsi, M. adusta) sister group indicates a relationship among the Andean and the Atlantic forests, enabling a scenario of dispersion events via Central Brasil or of exploitation of corridors of more homogeneous dispersal habitats (Costa 2003), like that of the Paraná River basin “pathway”. The close relationship among the brevicaudata group, with Amazonian distribution, and M. domestica, with Cerrado and Caatinga distribution, to the kunsi-adusta pair, points to a common history among…