Effects of historical forest contraction on the phylogeographic structure of Australo-Papuan populations of the red-legged pademelon (Macropodidae: Thylogale stigmatica)

Abstract

Geographic patterns of genetic variation are strongly influenced by historical changes in species habitats. Whether such patterns are common to co-distributed taxa may depend on the extent to which species vary in ecology and vagility. We investigated whether broad-scale phylogeographic patterns common to a number of small-bodied vertebrate and invertebrate species in eastern Australian forests were reflected in the population genetic structure of an Australo-Papuan forest marsupial, the red-legged pademelon (Macropodidae: Thylogale stigmatica). Strong genetic structuring of mtDNA haplotypes indicated the persistence of T. stigmatica populations across eastern Australia and southern New Guinea in Pleistocene refugial areas consistent with those inferred from studies of smaller, poorly dispersing species. However, there was limited divergence of haplotypes across two known historical barriers in the northeastern Wet Tropics (Black Mountain Barrier) and coastal mideastern Queensland (Burdekin Gap) regions. Lack of divergence across these barriers may reflect post-glacial recolonization of forests from a large, central refugium in the Wet Tropics. Additionally, genetic structure is not consistent with the present delimitation of subspecies T. s. wilcoxi and T. s. stigmatica across the Burdekin Gap. Instead, the genetic division occurs further to the south in mideastern Queensland. Thus, while larger-bodied marsupials such as T. stigmatica did persist in Pleistocene refugia common to a number of other forest-restricted species, species-specific local extinction and recolonization events have resulted in cryptic patterns of genetic variation. Our study demonstrates the importance of understanding individualistic responses to historical climate change in order to adequately conserve genetic diversity and the evolutionary potential of species.