Phylogeny, phylogeography and conservation genetics of the brachyotis group of rock-wallabies.

Abstract

This thesis explores phylogenetic relationships amongst rock-wallabies, genus Petrogale, throughout Australia and in particular the phylogeographic relationships of three species (brachyotis taxonomic group) from north-west Australia. A combination of nuclear and mitochondrial DNA markers have been utilised to assess evolutionary history at several spatial scales. The first data chapter assesses broad scale relationships amongst rock-wallaby species with subsequent chapters examining the impacts of biogeographic processes on genetic diversification within the brachyotis group and conservation implications. These studies have increased our understanding of rock-wallaby evolution and provide valuable data to support the recognition of multiple species within Petrogale brachyotis (short-eared rock-wallaby). It has also established new hypotheses about the relationships of P. burbidgei (monjon) and P. concinna (nabarlek) to P. brachyotis within the brachyotis group. Although P. brachyotis is widespread, we have found this species is highly divergent across its range, with future management needing to ensure the survival of multiple highly diverse genetic lineages. The phylogenetic analysis (chapter two) identified four distinct clades within Petrogale, with three comprising taxa with the ancestral karyotype (2n=22). The brachyotis group was the first to diverge and phylogenetic relationships within this lineage suggest the need for a focused phylogeographic study of this group and the likelihood of taxonomic revisions. There was support for P. purpureicollis being reinstated as a full species and P. concinna being classified within Petrogale rather than the monotypic genus Peradorcas. Ancestral habitat reconstructions suggested ancestral Petrogale were originally widespread across Australia and have undergone vicariance as a result of isolation caused by environmental/climatic changes during the Plio-Pleistocene. The third chapter concentrated on north-west Australia, the main focus of this thesis, and its numerous proposed biogeographic barriers which have remained largely untested by phylogeographic studies. This thesis provides the first evidence of how these barriers have profoundly influenced the genetic differentiation of mammals within north-west Australia. Rock-wallabies, with their habitat specificity and naturally low gene flow are a good indicator species for biogeographic barriers and provide good evidence of how past climatic cycles during the Plio-Pleistocene have influenced genetic differentiation across northern Australia. The fourth chapter was more localised and focused on the genetic diversity of P. brachyotis within the Kimberley. This study provided evidence of greater connectivity of populations than previously recorded for any other rock-wallaby, highlighting how suitably connected habitat can allow dispersal of rock-wallabies across large distances. Large genetic differentiation was detected between the East and West Kimberley P. brachyotis, supporting the need for a reassessment of taxonomic classifications and conservation units within P. brachyotis. The final data chapter examined the conservation status of the brachyotis group of rock-wallabies and outlined taxonomic reclassifications of P. brachyotis. This analysis provided evidence for division of P. brachyotis into two species. It is likely that additional taxonomic changes will be necessary in the future as further sampling and analyses are undertaken. Although this thesis has significantly advanced our understanding of the relationships within the brachyotis group, it also highlights the need for future work on this group of rock-wallabies.