Landscape discontinuities influence gene flow and genetic structure in a large, vagile Australian mammal,Macropus fuliginosus

Abstract

Large vagile mammals typically exhibit little genetic structuring across their range, particularly when their habitat is essentially continuous. We investigated the population genetic structure of a large vagile Australian macropodid, Macropus fuliginosus, which is continuously distributed across most of southern Australia, using nine highly polymorphic nuclear microsatellite loci. Five distinct genetic units were identified across the range, four on the mainland and one on Kangaroo Island. In addition to the predicted historic Nullarbor Plain Barrier, two unexpected mainland barriers to gene flow were identified. Both were associated with landscape discontinuities (Swan River, Flinders Ranges), which appear within the dispersal capabilities of M. fuliginosus. Typical of large vagile mammals, M. fuliginosus displays high genetic diversity (with the exception of an insular population) and weak genetic structuring (within genetic units). However, the expansion of M. fuliginosus from southwestern Australia during the Pleistocene has resulted in significantly reduced genetic diversity in eastern populations. No significant sex-biased dispersal was detected, although differences in habitat, densities and climatic conditions between the eastern and western regions of the range appear to influence dispersal with the effects of isolation by distance only evident in the west. These results suggest that the biogeography of southern Australia is more complex than previously thought and reveal that seemingly minor landscape features can significantly impact genetic structuring in large vagile mammals.

Spatial Genetic Structure and Mitochondrial DNA Phylogeography of Argentinean Populations of the Grasshopper Dichroplus elongatus

“…Even though, Pleistocene climatic changes affect patterns of intraspecific diversity [80], recent approaches have demonstrated that other causes, such as behavioural and morphological adaptations, may also influence dispersal and differentiation [81], [82]. Competition among males for local resources or mating chances (intrasexual selection) envisages a male-biased dispersal in polygynous species.…”

Extensive genetic differentiation detected within a model marsupial, the tammar wallaby (Notamacropus eugenii)

“…These high levels of diversity may be a consequence of Kangaroo Island’s large size (Table 1), which has enabled the tammar wallabies to retain a large Ne since isolation from the mainland population and so reduce the impact of genetic drift [94,97]. Some macropodid populations on other large Australian islands, for example King and Flinders Islands, also show high diversity [98,99], although not the sympatric western grey kangaroo population on Kangaroo Island [78,100]. The now extinct SA mainland tammar wallaby population is therefore likely to have also been highly diverse, maybe even more so than surviving mainland populations in WA.…”

“…Reduced diversity in WA populations is hypothesised from biogeography, since tammar wallabies are thought to have spread from eastern to western Australia across the arid Nullabor Barrier [77]. Similarly, in the western grey kangaroo, an expansion across southern Australia (although in the opposite direction) resulted in reduced genetic diversity in the more recently colonised population [78,95,100]. However, determining the original levels of diversity in SA and WA mainland tammar wallaby populations prior to their recent decline, and in SA extinction, is now almost impossible due to poor historic sampling.…”

Holocene vertebrate fossils aid the management and restoration of Australian ecosystems

“…Similarly, postsettlement land clearing has proven beneficial to Western Grey Kangaroo ( Macropus fuliginosus ), causing range expansion and increased population density (Neaves et al . ). What then should we conserve: the pre‐European extirpated species, the invasive native species or some other species that performs a vital ecological function?…”