Phylogeny and phylogeography of the pademelons (Macropodidae: Thylogale) in Australia and New Guinea

Peggy Ellen Macqueen (2011). Phylogeny and phylogeography of the pademelons (Macropodidae: Thylogale) in Australia and New Guinea PhD Thesis, School of Biological Sciences, The University of Queensland.

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Author Peggy Ellen Macqueen
Thesis Title Phylogeny and phylogeography of the pademelons (Macropodidae: Thylogale) in Australia and New Guinea
School, Centre or Institute School of Biological Sciences
Institution The University of Queensland
Publication date 2011-02
Thesis type PhD Thesis
Supervisor Anne W. Goldizen
Jennifer M. Seddon
Total pages 229
Total colour pages 4
Total black and white pages 225
Subjects 06 Biological Sciences
Abstract/Summary Throughout the late Tertiary, global climatic change caused the decline of wet forests across Australia and continental drift resulted in the uplift of much of the New Guinean landmass. Glacial cycles of the Quaternary caused severe contraction and fragmentation of the New Guinean and remaining Australian forests. The current diversity of forest fauna in this region is, therefore, a result of long-term changes in habitat distribution. Through consideration of genetic relationships within and among species and the distribution of genetic lineages in the context of geography and palaeoenvironmental data, we can attempt to understand how historical events have influenced the distribution of biological diversity in Australo-Papuan forests. This thesis examines the evolutionary history of the wet-forest restricted pademelons (Macropodidae: Thylogale). The broad geographic distribution of this genus provides an excellent system for studying the effects of historical changes in habitat on Australo-Papuan forest marsupials. Due to the impact of increased hunting on the abundance of the New Guinean pademelons and the fragmented nature of forest habitat for Australian pademelons, understanding the geographic distribution of genetic lineages within this genus is also critical for conservation and taxonomic purposes. The first research chapter of this thesis investigates phylogenetic relationships among Thylogale species using mitochondrial and nuclear DNA sequence data. Australian Thylogale species are resolved as monophyletic clades. New Guinean Thylogale species, however, do not form phylogroups consistent with current morphological taxonomy. Radiation of the genus in Australia is estimated to have occurred in the mid to late Miocene and the persistence of pademelons across eastern Australia is likely a result of their adaptation to both browsing and grazing. Genetic divergence of the endemic New Guinean lineage suggests the presence of a partially forested landbridge connecting Australia and New Guinea during the Miocene. Divergence between Australian and New Guinean populations of T. stigmatica is consistent with gene flow during Pleistocene glacial periods. In the second research chapter, the biogeographic history of the endemic New Guinean Thylogale species is further explored using more comprehensive geographic sampling and mitochondrial DNA. Phylogenetic analyses indicate subdivision of pademelons into ‘eastern’ and ‘western’ regional clades and genetic divergence among populations within and among species is consistent with the influence of forest habitat redistribution during the Pleistocene. Populations of T. brunii from the southern Aru Islands appear to have diverged during the mid-Pleistocene from northern mainland T. browni populations, rather than from southern lowland T. brunii populations. Genetic divergence between presently isolated subalpine and lowland to mid-montane populations indicates gene flow during the mid to late Pleistocene due to the lowering of treelines. Populations of T. browni sampled from islands of the Bismarck Archipelago show low genetic differentiation from northeastern mainland T. browni populations, consistent with human-mediated translocations. In the third research chapter, I test the hypothesis that populations of T. stigmatica were restricted to Pleistocene forest refugia across eastern Australia and southern New Guinea. Mitochondrial genealogies infer two major clades, with both clades including populations from central Queensland. Genetic divergence between these clades may reflect the extinction of pademelons in central Queensland forests during the Pliocene with subsequent recolonisation from the north and south during the Pleistocene. Strong genetic structuring of populations in southeastern Queensland and vicariance across the Torres Strait, and dry habitat Normanby and St Lawrence Gaps, is consistent with the persistence of populations in multiple Pleistocene forest refugia. However, phylogeographic structuring suggests extinction of populations to the north of the Black Mountain Barrier in the Wet Tropics with recolonisation during the late Pleistocene. Additionally, the current subspecies delimitation for T. s. wilcoxi and T. s. stigmatica across the dry habitat ‘Burdekin Gap’ is not supported by genetic data. In the final research chapter of this thesis, I investigate the effect of forest fragmentation on population genetic structuring of the Tasmanian pademelon (T. billardierii) using mitochondrial and microsatellite DNA. High genetic diversity suggests the maintenance of large historical population sizes and weak phylogeographic structuring of haplotypes suggests that pademelons persisted throughout Tasmania during the Pleistocene. A single divergent clade implies the mid-Pleistocene isolation of a far northwestern population. Tasmanian populations appear divided into eastern and western regions, consistent with a dry habitat barrier in the ‘midlands’ region during glacial periods and also with a contemporary barrier resulting from anthropogenic forest loss in that region. Gene flow among western populations appears to have been relatively unrestricted during glacial maxima, while in the east there is evidence for expansion from at least one glacial refuge.
Keyword glacial cycles
New Guinea
Torres Strait
Additional Notes Colour pages: 1, 122, 123, 189. Landscape: 68-69, 72-75, 81, 116, 118, 151, 155-156, 218-227.

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Created: Mon, 14 Mar 2011, 14:36:50 EST by Miss Peggy Macqueen on behalf of Library - Information Access Service