Behavioural Ecology Lab, School of Molecular and Life Sciences, Curtin University, Bentley, Western Australia, Australia.
School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia.
PLoS One. 2021 Oct 29;16(10):e0259124. doi: 10.1371/journal.pone.0259124. eCollection 2021.
Urbanisation alters landscapes, introduces wildlife to novel stressors, and fragments habitats into remnant 'islands'. Within these islands, isolated wildlife populations can experience genetic drift and subsequently suffer from inbreeding depression and reduced adaptive potential. The Western tiger snake (Notechis scutatus occidentalis) is a predator of wetlands in the Swan Coastal Plain, a unique bioregion that has suffered substantial degradation through the development of the city of Perth, Western Australia. Within the urban matrix, tiger snakes now only persist in a handful of wetlands where they are known to bioaccumulate a suite of contaminants, and have recently been suggested as a relevant bioindicator of ecosystem health. Here, we used genome-wide single nucleotide polymorphism (SNP) data to explore the contemporary population genomics of seven tiger snake populations across the urban matrix. Specifically, we used population genomic structure and diversity, effective population sizes (Ne), and heterozygosity-fitness correlations to assess fitness of each population with respect to urbanisation. We found that population genomic structure was strongest across the northern and southern sides of a major river system, with the northern cluster of populations exhibiting lower heterozygosities than the southern cluster, likely due to a lack of historical gene flow. We also observed an increasing signal of inbreeding and genetic drift with increasing geographic isolation due to urbanisation. Effective population sizes (Ne) at most sites were small (< 100), with Ne appearing to reflect the area of available habitat rather than the degree of adjacent urbanisation. This suggests that ecosystem management and restoration may be the best method to buffer the further loss of genetic diversity in urban wetlands. If tiger snake populations continue to decline in urban areas, our results provide a baseline measure of genomic diversity, as well as highlighting which 'islands' of habitat are most in need of management and protection.
城市化改变了景观，将野生动物引入新的压力源，并将栖息地分割成残余的“岛屿”。在这些岛屿中，孤立的野生动物种群可能会经历遗传漂变，随后遭受近交衰退和适应能力降低的影响。西部虎蛇（Notechis scutatus occidentalis）是斯旺海岸平原（Swan Coastal Plain）湿地的一种捕食者，该地区是一个独特的生物区系，由于西澳大利亚珀斯市的发展，已经遭受了巨大的退化。在城市基质中，虎蛇现在只存在于少数几个湿地中，这些湿地已知会生物积累一系列污染物，最近被认为是生态系统健康的一个相关生物指标。在这里，我们使用全基因组单核苷酸多态性（SNP）数据来探索七个虎蛇种群在城市基质中的当代种群基因组学。具体来说，我们使用种群基因组结构和多样性、有效种群大小（Ne）和杂合度-适合度相关性来评估每个种群在城市化方面的适应性。我们发现，种群基因组结构在主要河流系统的北部和南部两侧最强，北部种群聚类的杂合度低于南部种群聚类，这可能是由于历史上缺乏基因流。我们还观察到，由于城市化导致的地理隔离增加，近交和遗传漂变的信号也在增加。大多数地点的有效种群大小（Ne）都很小（<100），Ne 似乎反映了可用栖息地的面积，而不是相邻城市化的程度。这表明，生态系统管理和恢复可能是缓冲城市湿地进一步丧失遗传多样性的最佳方法。如果虎蛇种群在城市地区继续减少，我们的结果提供了基因组多样性的基线衡量标准，并突出了哪些“岛屿”的栖息地最需要管理和保护。
