Family-level relationships among the Australasian marsupial ‘‘herbivores’’ (Diprotodontia: Koala, wombats, kangaroos and possums)
Phillips, MJ & Pratt, RC 2008, Molecular Phylogenetics and Evolution, vol. 46, pp. 594-605.
This study attempts to determine the phylogenetic relationships between families in Diprotodontia, a diverse order of marsupials occupying a range of niches across Australasia, including koalas, wombats, kangaroos and possums. Using mitochondrial and nuclear sequences, phylogenetic analysis serves to resolve relationships that were previously inconclusive, specifically between Vombatiformes and Phalangerida groupings.
Phylogeny of diprotodontians has remained unresolved as previous studies provided conflicting results regarding relationships, basing inferences on two little mitochondrial and nuclear data. The combination of multiple mitochondrial and nuclear sequences, in addition to nuclear loci and partition models used in this study, provide a phylogenetic tree that results in an almost complete resolution of diprotodontial relationships of different familial groups, with the exception of a few possible alternative trees. The analysis resulted in a phylogeny that groups together macropodoids, phalangerids and burramyids with a sister relationship to a separate clade containing petauroidea, all of which are divergent from the clade of vombatiformes which includes wombats and koalas. Phylogeny based on mitochondrial and nuclear data provided a high level of support for a tree in which resolution of Diprotodontia was achieved, with groups comprising possums and kangaroos divergent to sister groups of wombats and koalas. Alternative hypotheses to the taxonomic groupings presented here, which grouped families differently, were confidently rejected.
Closer association between macropodoids and phalangerids over petauroids is supported by this analysis and an increased sampling of nuclear sequences. Morphological analysis that supported the possibility of phalangeriformes as a divergent clade was refuted. In the past limited sampling across families led to conclusions about artificial relationships based on limited data showing that increased taxon sampling is necessary for confident phylogenetic inference. To be able to consistently resolve relationships between taxa, robust support from data and genomic sequences is needed.
Niche differentiation between groups within the diprotodontian tree is evident, and using both mitochondrial and nuclear data is useful in resolving taxonomic relationships. This procedure can also lead to an exploration of both morphological and ecological questions surrounding maintenance of niche diversification and divergence of groups.
Summarised by Meredith Kraina
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