Spatial genetic structure and gene flow of the eastern grey kangaroo (Macropus giganteus), in a rapidly urbanising landscape

Abstract

Urban landscapes contain many barriers to wildlife movement and gene flow, particularly for large terrestrial mammals with extensive natural home ranges. Eastern grey kangaroos (Macropus giganteus) are a large macropodid, whose biological range partially coincides with areas subjected to high rates of urban expansion, including the Southeast Queensland (SEQ) bioregion of Australia. Within this region, M. giganteus populations have had recent, rapid declines in numbers with ongoing urbanisation posing a significant threat due to the isolation of populations. Therefore, we investigated the genetic profile of kangaroos in a rapidly urbanising SEQ region (Sunshine Coast) by comparing them to other SEQ kangaroos (Greater Brisbane) and to higher density kangaroo populations in a landscape matrix with greater levels of connectivity (Australian Capital Territory; ACT). We utilised a targeted genetic probe of genome-wide SNPs to obtain baseline genetic profiles of M. giganteus using scat samples collected from 24 sites in the Sunshine Coast (n = 103) and compared these to Greater Brisbane (n = 20) and ACT (n = 29) scat samples. Genetic diversity was similar when comparing the ACT, Sunshine Coast and Greater Brisbane regions (HE: 0.224–0.238), yet effective population size was markedly higher for the ACT region (Ne = 3453) than for both the Sunshine Coast and Greater Brisbane (Ne = 43.3 and 25.0, respectively), with clear genetic differentiation on a regional scale. We also identified six genetic groups within our SEQ study area, with significant differences in genetic diversity (HE: 0.188 – 0.289). The presence of high numbers of private alleles in all regions and within some SEQ populations highlights the conservation significance of preserving local populations. We also identified natural and anthropogenic barriers, which may have impacted genetic processes such as gene flow in the region. Therefore, this research highlights the need for localised management of kangaroo populations to preserve genetic diversity and structure in the SEQ region, by maintaining and improving landscape connectivity. We emphasise that for the conservation of local and global biodiversity, it is imperative to assess baseline genetic status of both common and threatened species, particularly when declines and extirpations are occurring across these species’ ranges.