Differing impact of a major biogeographic barrier on genetic structure in two large kangaroos from the monsoon tropics of Northern Australia

Authors

  • Mark D. B. Eldridge,

    Corresponding author
    1. Australian Museum Research Institute, Australian Museum, Sydney, New South Wales, Australia
    • Correspondence

      Mark D. B. Eldridge, Australian Museum Research Institute, Australian Museum, 6 College St, Sydney, NSW 2010, Australia. Tel: 61 2 9320 6320; Fax: 61 2 9320 6059; E-mail: mark.eldridge@austmus.gov.au

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  • Sally Potter,

    1. Australian Museum Research Institute, Australian Museum, Sydney, New South Wales, Australia
    2. Research School of Biology, Australian National University, Acton, Australian Capital Territory, Australia
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  • Christopher N. Johnson,

    1. School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia
    Current affiliation:
    1. School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
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  • Euan G. Ritchie

    1. School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia
    2. Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria, Australia
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Abstract

Tropical savannas cover 20–30% of the world's land surface and exhibit high levels of regional endemism, but the evolutionary histories of their biota remain poorly studied. The most extensive and unmodified tropical savannas occur in Northern Australia, and recent studies suggest this region supports high levels of previously undetected genetic diversity. To examine the importance of barriers to gene flow and the environmental history of Northern Australia in influencing patterns of diversity, we investigated the phylogeography of two closely related, large, vagile macropodid marsupials, the antilopine wallaroo (Macropus antilopinus; n = 78), and the common wallaroo (Macropus robustus; n = 21). Both species are widespread across the tropical savannas of Australia except across the Carpentarian Barrier (CB) where there is a break in the distribution of M. antilopinus. We determined sequence variation in the hypervariable Domain I of the mitochondrial DNA control region and genotyped individuals at 12 polymorphic microsatellite loci to assess the historical and contemporary influence of the CB on these species. Surprisingly, we detected only limited differentiation between the disjunct Northern Territory and Queensland M. antilopinus populations. In contrast, the continuously distributed M. robustus was highly divergent across the CB. Although unexpected, these contrasting responses appear related to minor differences in species biology. Our results suggest that vicariance may not explain well the phylogeographic patterns in Australia's dynamic monsoonal environments. This is because Quaternary environmental changes in this region have been complex, and diverse individual species’ biologies have resulted in less predictable and idiosyncratic responses.

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