Phalangerida

Abstract: *To whom correspondence should be addressed ABSTRACT--The approximately 330 living species of marsupials are currently divided into three American (Didelphimorphia, Microbiotheria, and Paucituberculata) and four Australasian (Dasyuromorphia, Diprotodontia, Notoryctemorphia, and Peramelemorphia) orders. Studies of interordinal relationships generally support the monophyly of Australidelphia, which includes the four Australian orders and the South American Microbiotheria. Within Australidelphia, monophyly of the Australasian orders (Eomarsupialia), relationships between the Australasian orders, and diprotodontian interfamilial relationships are still disputed. We analyzed protein-coding portions of five nuclear genes (ApoB, BRCA1, IRBP, Rag1, and vWF) from representatives of all extant marsupial families using maximum parsimony, maximum likelihood, and Bayesian methods. Two relaxed molecular clock methods (Multidivtime, IRDIVTIME) were employed to estimate divergence times. Likelihood and Bayesian analyses favored rooting the tree between Didelphimorphia and all other marsupials, but alternate positions for the root (Paucituberculata versus other marsupials, Ameridelphia versus Australidelphia) could not be rejected. Australidelphia was supported in all analyses, but interordinal relationships within this clade were not strongly supported. Diprotodontian monophyly was recovered in all analyses. Within this order there was a basal split between Vombatiformes (koalas, wombats) and Phalangerida (kangaroos, possums). Within Phalangerida, Macropodiformes grouped with Phalangeroidea to the exclusion of Petauroidea. Within Petauroidea, there was a basal split between Acrobatidae and all other petauroids. Among the remaining petauroids, Pseudocheiridae grouped with Petauridae to the exclusion of Tarsipedidae. Multidivtime divergence time estimates suggest a Late Cretaceous common ancestor for Marsupialia (80.4-78.1 Ma), interordinal divergences that range into the early Paleocene (60.7-59.5 Ma for Dasyuromorphia to Peramelemorphia), and mostly Paleogene interfamilial diversification. IRDIVTIME analyses resulted in slightly older dates for the most recent common ancestor of Marsupialia (83.9-80.6 Ma), but also showed increased stemminess (i.e., proportion of overall tree length comprised of internal branches) and a longer time window (~ 36 million years) for interordinal cladogenesis than Multidivtime analyses. Multidivtime dates for the last common ancestor of Australidelphia (65.0-64.8 Ma) allow for overland dispersal to Australia prior to the submergence of the South Tasman Rise at 64 Ma (Woodburne and Case, 1996). By contrast, IRDIVTIME dates for the last common ancestor of Australidelphia (62.2-58.2 Ma) are slightly younger than dates for the submergence of the South Tasman Rise and imply over water dispersal.

Abstract: Australidelphia is the cohort, originally named by Szalay, of all Australian marsupials and the South American Dromiciops. A lot of mitochondria and nuclear genome studies support the hypothesis of a monophyly of Australidelphia, but some familial relationships in Australidelphia are still unclear. In particular, the familial relationships among the order Diprotodontia (koala, wombat, kangaroos and possums) are ambiguous. These Diprotodontian families are largely grouped into two suborders, Vombatiformes, which contains Phascolarctidae (koala) and Vombatidae (wombat), and Phalangerida, which contains Macropodidae, Potoroidae, Phalangeridae, Petauridae, Pseudocheiridae, Acrobatidae, Tarsipedidae and Burramyidae. Morphological evidence and some molecular analyses strongly support monophyly of the two families in Vombatiformes. The monophyly of Phalangerida as well as the phylogenetic relationships of families in Phalangerida remains uncertain, however, despite searches for morphological synapomorphy and mitochondrial DNA sequence analyses. Moreover, phylogenetic relationships among possum families (Phalangeridae, Petauridae, Pseudocheiridae, Acrobatidae, Tarsipedidae and Burramyidae) as well as a sister group of Macropodoidea (Macropodidae and Potoroidae) remain unclear. To evaluate familial relationships among Dromiciops and Australian marsupials as well as the familial relationships in Diprotodontia, we determined the complete mitochondrial sequence of six Diprotodontian species. We used Maximum Likelihood analyses with concatenated amino acid and codon sequences of 12 mitochondrial protein genomes. Our analysis of mitochondria amino acid sequence supports monophyly of Australian marsupials+Dromiciops and monophyly of Phalangerida. The close relatedness between Macropodidae and Phalangeridae is also weakly supported by our analysis.