PHYLOGENETIC RELATIONSHIPS OF DIDELPHID MARSUPIALS: A FRAMEWORK FOR TAXONOMIC, BIOGEOGRAPHIC, AND EVOLUTIONARY RESEARCH

JANSA, S.; VOSS, R.; FLORES, D.

Mendoza

Congreso; 10th International Mammalogical Congress; 2009

International Federation of Mammalogists

New World marsupials include three major clades, two of which (caenolestids and microbiotheriids) contain just a few species restricted to wet-temperate and montane-forest habitats of South America. By contrast, didelphids (opossums) consist of at least 100 living species that occupy many terrestrial biomes from Patagonia to Canada. Recent research based on morphology and nuclear gene sequences from 44 exemplar species in 18 didelphid genera has produced an almost completely resolved opossum phylogeny with strong support at most nodes. Optimizations of habitat on geography on this topology suggest that the early radiation of didelphids was confined to South American rain forests, from which several lineages subsequently invaded nonforest and dry-forest habitats. Diversification analyses provide compelling evidence for a mid-Tertiary extinction event that was preceded and followed by intervals of approximately linear lineage accumulation. Because rainforest faunas are poorlyrepresented in the fossil record, opossum phylogenies provide a useful window from which hitherto obscure aspects of South America’s «splendid isolation» may be glimpsed. However, extending our preliminary results to test relevant hypotheses about the impact of tectonic and climatic events on the rainforest biota will require much more densely taxon-sampled trees. Obtaining a complete species-level opossum phylogeny is a daunting goal because many didelphid genera remain unrevised and because new species are still being discovered. Happily, much important revisionary work is now underway, as evidenced by other talks and posters in this symposium.