Three divergent lineages within an Australian marsupial (Petrogale penicillata) suggest multiple major refugia for mesic taxa in southeast Australia

Abstract

Mesic southeastern Australia represents the continent's ancestral biome and is highly biodiverse, yet its phylogeographic history remains poorly understood. Here, we examine mitochondrial DNA (mtDNA) control region and microsatellite diversity in the brush-tailed rock-wallaby (Petrogale penicillata;n = 279 from 31 sites), to assess historic evolutionary and biogeographic processes in southeastern Australia. Our results (mtDNA, microsatellites) confirmed three geographically discrete and genetically divergent lineages within brush-tailed rock-wallabies, whose divergence appears to date to the mid-Pleistocene. These three lineages had been hypothesized previously but data were limited. While the Northern and Central lineages were separated by a known biogeographic barrier (Hunter Valley), the boundary between the Central and Southern lineages was not. We propose that during particularly cool glacial cycles, the high peaks of the Great Dividing Range and the narrow adjacent coastal plain resulted in a more significant north–south barrier for mesic taxa in southeastern Australia than has been previously appreciated. Similarly, located phylogeographic breaks in codistributed species highlight the importance of these regions in shaping the distribution of biodiversity in southeastern Australia and suggest the existence of three major refuge areas during the Pleistocene. Substructuring within the northern lineage also suggests the occurrence of multiple local refugia during some glacial cycles. Within the three major lineages, most brush-tailed rock-wallaby populations were locally highly structured, indicating limited dispersal by both sexes. The three identified lineages represent evolutionarily significant units and should be managed to maximize the retention of genetic diversity within this threatened species.

Evolutionary and contemporary responses to habitat fragmentation detected in a mesic zone marsupial, the long‐nosed potoroo (Potorous tridactylus) in south‐eastern Australia

“…This suggests extensive connectivity across the region in evolutionary time. While a similar pattern was also identified in the Brush‐tailed rock‐wallaby (Hazlitt et al ., ), these results are not reflected in studies of the regions herpetofauna, in which multiple lineages are often identified within Victoria (Symula et al ., ; Chapple et al ., ; Ng et al ., ). These have been attributed to habitat breaks, such as the volcanic basalt plains of western Victoria (Ng et al ., ).…”

“…Samples distributed either side of the Clarence River valley formed two distinct sub‐lineages, estimated to have diverged around 1.2 Ma during the Pleistocene. The Brush‐tailed rock‐wallaby ( Petrogale penicillata ) and the Hastings River mouse ( Pseudomys oralis ) also appear to have distinct lineages across this region (Jerry et al ., ; Rowe et al ., ; Hazlitt et al ., ). Our estimates of early Pleistocene divergence is older than that observed in Petrogale penicillata (Hazlitt et al ., ) and Pseudomys oralis (Rowe et al ., ) but similar in timing to divergences in some reptiles across this region (Colgan et al ., ).…”

“…As no robust estimate of marsupial mtDNA mutation rate exists, a mid-range mammalian CR rate of 7.5% per million years (Birungi & Arctander, 2000) was used to estimate divergence times (Neaves et al, 2012;Hazlitt et al, 2014).…”

“…South-eastern Australia is one of the most topographically complex regions of the continent, perhaps resulting in species-specific idiosyncratic phylogeographical breaks occurring in the absence of biogeographical barriers (e.g. Hazlitt et al, 2014;Pepper et al, 2014).…”

“…A potential candidate is the Hunter Valley, a major river valley denoting a major shift in east coast Australian habitat, located around 120 km north of Sydney in central NSW (Cracraft, 1991). This region has impacted a variety of taxa (Short et al, 1983;Ford, 1987;Donnellan et al, 1999;Moussalli et al, 2005;Joseph et al, 2008Chapple et al, 2011bHazlitt et al, 2014). The identification of a northern mainland lineage individual, from south of the Hunter Valley at Mangrove Mountain in Poproan National Park [7], demonstrates that the Hunter is currently not the location of the phylogeographical break between the northern and southern mainland lineages.…”