Roo-tine Obstacles: Uncovering the spatio-genetic barriers for Eastern Grey Kangaroos (Macropus giganteus) in an urbanising landscape

Abstract

Context Urban landscapes present a diverse matrix of structures and habitats containing significant physical and behavioural barriers to terrestrial wildlife dispersal. As a result, large mammals, with large home ranges, may be negatively impacted as behavioural and physical barriers are created. However, our understanding of these barriers in the context of genetic connectivity within urbanising landscapes is limited, particularly so for herbivores occupying these spaces. Objective We investigated the effects of landscape composition on the genetic differentiation of a large herbivorous macropodid, the Eastern grey kangaroo (Macropus giganteus), within the Sunshine Coast region of Australia. We tested whether genetic differentiation and gene flow in this rapidly urbanising environment was best explained by landscape structures (Isolation-by-Resistance) or geographical distances (Isolation-by-Distance) at multiple spatial scales. Methods We simulated ecological succession from genetic (n =130), and spatial datasets (n =56) to determine the magnitude of relationships between observed genetic distances and landscape composition. A multiscale design was used to assess spatio-genetic impacts at different spatial scales. Circuit theory methods were used to simulate ecological successions and subsequently infer landscape effects on observed genetic differentiations. Results Both Isolation-by-Distance and Isolation-by-Resistance explained the interpopulation genetic differentiation of our 12 surveyed populations. Genetic differentiation was explained primarily by vegetation structures, major waterways, roads and built infrastructure. Variables were scale-dependent, with biophysical and built infrastructures exhibiting the most variability across scales. Conclusion Our results suggest that gene flow between M. giganteus populations is highly dependent on the structure of the landscape, and influenced by anthropogenic structures. As such, emphasis on gene flow pathways of M. giganteus, and other large mammals, is required in conservation planning to preserve populations under urban pressures. The findings of this study can inform spatially-guided management decisions and long-term conservation strategies for large mammals under growing urban pressures worldwide.