Genomic comparisons reveal biogeographic and anthropogenic impacts in the koala (Phascolarctos cinereus): a dietary-specialist species distributed across heterogeneous environments

The Australian koala is an iconic marsupial with highly specific dietary requirements distributed across heterogeneous environments, over a large geographic range. The distribution and genetic structure of koala populations has been heavily influenced by human actions, specifically habitat modification, hunting and translocation of koalas. There is currently limited information on population diversity and gene flow at a species-wide scale, or with consideration to the potential impacts of local adaptation. Using species-wide sampling across heterogeneous environments, and high-density genome-wide markers (SNPs and PAVs), we show that most koala populations display levels of diversity comparable to other outbred species, except for those populations impacted by population reductions. Genetic clustering analysis and phylogenetic reconstruction reveals a lack of support for current taxonomic classification of three koala subspecies, with only a single evolutionary significant unit supported. Furthermore, similar to 70% of genetic variance is accounted for at the individual level. The Sydney Basin region is highlighted as a unique reservoir of genetic diversity, having higher diversity levels (i.e., Blue Mountains region; AvHe(corr)-0.20, PL% = 68.6). Broad-scale population differentiation is primarily driven by an isolation by distance genetic structure model (49% of genetic variance), with clinal local adaptation corresponding to habitat bioregions. Signatures of selection were detected between bioregions, with no single region returning evidence of strong selection. The results of this study show that although the koala is widely considered to be a dietary-specialist species, this apparent specialisation has not limited the koala's ability to maintain gene flow and adapt across divergent environments as long as the required food source is available

Landscape, koalas and people: A historical account of koala populations and their environment in South Gippsland

We present an ecological history of the koala (Phascolarctos cinereus) population and its environment in South Gippsland, Victoria, both pre- and post-European settlement. We consider the role that the region's history may have had on the genetic structure of the current koala population in South Gippsland, which is the only known koala population in Victoria that does not originate from animals re-introduced as part of the Victorian translocation program. Following European colonisation of Australia, a range of anthropogenic factors, including hunting for the fur trade, resulted in widespread population declines for the koala. In Victoria, the situation was extreme. Currently, many koala populations in Victoria are derived from only a few individuals which existed less than 120 years ago. These populations therefore have comparatively low genetic diversity, a factor that plays a key role in long term population viability. In Victoria, the koala is not listed as a threatened species. Despite the low genetic diversity of most populations, the species is widely distributed across the state, and relatively common. Indeed, some populations are considered overabundant. However, many koala populations are not abundant, and population data are lacking for most. The South Gippsland koala population is of high conservation significance as it has greater genetic diversity compared to other Victorian populations, though there is little additional data to inform its conservation. An improved understanding of genetic diversity and gene flow between populations across the koala's range is required to guide the conservation of genetic diversity in this species. Monitoring population size, health and genetic relationships both within and between koala populations will enable better conservation outcomes.Associated Grant:This research project was supported and funded by Grand Ridge Plantations Pty. Ltd. (HVP Plantations) and the Holsworth Wildlife Research Endowment - Equity Trustees Charitable Foundatio

Landscape, koalas and people: A historical account of koala populations and their environment in South Gippsland

We present an ecological history of the koala (Phascolarctos cinereus) population and its environment in South Gippsland, Victoria, both pre- and post-European settlement. We consider the role that the region's history may have had on the genetic structure of the current koala population in South Gippsland, which is the only known koala population in Victoria that does not originate from animals re-introduced as part of the Victorian translocation program. Following European colonisation of Australia, a range of anthropogenic factors, including hunting for the fur trade, resulted in widespread population declines for the koala. In Victoria, the situation was extreme. Currently, many koala populations in Victoria are derived from only a few individuals which existed less than 120 years ago. These populations therefore have comparatively low genetic diversity, a factor that plays a key role in long term population viability. In Victoria, the koala is not listed as a threatened species. Despite the low genetic diversity of most populations, the species is widely distributed across the state, and relatively common. Indeed, some populations are considered overabundant. However, many koala populations are not abundant, and population data are lacking for most. The South Gippsland koala population is of high conservation significance as it has greater genetic diversity compared to other Victorian populations, though there is little additional data to inform its conservation. An improved understanding of genetic diversity and gene flow between populations across the koala's range is required to guide the conservation of genetic diversity in this species. Monitoring population size, health and genetic relationships both within and between koala populations will enable better conservation outcomes