First combined cladistic analysis of marsupial mammal interrelationships
Robert J. Ashera,*, Inés Horovitzb, Marcelo R. Sánchez-Villagrac
a Institut ür Spezielle Zoologie, Museum für Naturkunde, Invalidenstr. 43, 10115 Berlin, Germany
b Department of Organismic Biology, Ecology, and Evolution, University of California, 621 Young Drive, S., Los Angeles, CA 90095-1606, USA
c Lehrstuhl für Spezielle Zoologie, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
We combine osteological, dental, and soft tissue data with sequences from three nuclear and five mitochondrial genes, sampling all major living clades of marsupials plus several extinct taxa, to perform a simultaneous analysis of marsupial interrelationships. These data were analyzed using direct optimization and sensitivity analysis on a parallel supercomputing cluster, and compared with trees produced with conventional parsimony and likelihood algorithms using a static alignment. A major issue in marsupial phylogeny is the relationships among australidelphians. Optimal analyses using direct optimization and those based on the static alignment support the basal positions of peramelians (bandicoots) and Dromiciops (monito del monte) within Australidelphia, and in all but one case these analyses support a monophyletic Eometatheria, a group consisting of all australidelphians excluding peramelians. Dromiciops is basal within Eometatheria in analyses that maximize congruence across partitions, including the equally weighted parameter set. The topologies resulting from direct optimization under all parameter sets show some differences, but all show a high degree of resolution. Direct optimization supports high-level clades supported by analyses of partitioned molecular (e.g., Notoryctes as sister group of Dasyuromorphia) and morphological (e.g., Diprotodontia) data.