Impact of Pleistocene aridity oscillations on the population history of a widespread, vagile Australian mammal, Macropus fuliginosus

Contents

Abstract

Aim: Climatic fluctuations during the Pleistocene have shaped the population structure of many extant taxa. However, few studies have examined widespread species inhabiting the Australian continent, where periods of increased aridity characterised the Pleistocene. Here we investigate the phylogeography and population history of a widespread and vagile southern Australian marsupial, the western grey kangaroo (Macropus fuliginosus).
Location: Southern Australia.
Methods: We examined mitochondrial DNA (mtDNA) control region variation from 511 M. fuliginosus sampled throughout their trans-continental distribution. Maximum likelihood and Bayesian analyses were used to investigate the phylogeography and coalescence analyses where then used to test hypothesised biogeographical scenarios.
Results: The combined results of the phyogeographical and coalescence analyses revealed a complex evolutionary history. M. fuliginosus originated in the south-west of the continent, with north- and south-western populations subsequently diverging as a result of vicariance events during the mid-Pleistocene. Subsequent arid phases impacted these populations differently. In the north-west, the expansion and contraction of the arid zone resulted in repeated vicariance events and multiple divergent north-western mtDNA sub-clades. In contrast, the south-western population was less impacted by climatic oscillations but gave rise to a major transcontinental eastward expansion.
Main conclusions: Macropus fuliginosus exhibits the genetic signature of divergence due to unidentified barriers in south-western Western Australia, while previously identified barriers across southern Australia appear to have had little impact despite evidence of a broad scale range expansion prior to the Last Glacial Maximum. This pattern of localised expansion and contraction is comparable to unglaciated regions, in both the Northern and Southern Hemispheres. Furthermore, this study indicates that despite the potential similarities between Northern Hemisphere glaciation and the activation of dune systems in the Australian arid zone, both of which rendered large areas inhospitable, the biotic responses and resultant phylogeographic signatures are dissimilar: while a limited number of major geographically concordant refugia are observed in glaciated areas, the Southern Hemisphere arid zone appears associated with multiple species specific idiosyncratic refugia.