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. Yet, our understanding of these barriers for large mammals in the context of genetic connectivity within urbanising landscapes is limited. Objective: We investigated the effects of landscape structures 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 = 48) to quantify the strength of the relationship between observed genetic distances and landscape structures. 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: Genetic differentiation was explained primarily by vegetation structures, major waterways, roads and built infrastructure. Changes in biophysical variables related to vegetation health and moisture explained gene flow unilaterally in fine-scale scenarios, while built infrastructure best explained broad-scale genetic differences. Influence of landscape structures 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. The findings of this study can inform spatially-guided management decisions and long-term conservation strategies for large mammals under growing urban pressures worldwide.