Data from: Mixed population genomics support for the central marginal hypothesis across the invasive range of the cane toad (Rhinella marina) in Australia

Understanding factors that cause species’ geographic range limits is a major focus in ecology and evolution. The central marginal hypothesis (CMH) predicts that species cannot adapt to conditions beyond current geographic range edges because genetic diversity decreases from core to edge due to smaller, more isolated edge populations. We employed a population genomics framework using 24,235-33,112 SNP loci to test major predictions of the CMH in the ongoing invasion of the cane toad (Rhinella marina) in Australia. Cane toad tissue samples were collected along broad-scale, core-to-edge transects across their invasive range. Geographic and ecological core areas were identified using GIS and habitat suitability indices from ecological niche modeling. Bayesian clustering analyses revealed three genetic clusters, in the northwest invasion-front region, northeast precipitation-limited region, and southeast cold temperature-limited region. Core-to-edge patterns of genetic diversity and differentiation were consistent with the CMH in the southeast, but were not supported in the northeast and showed mixed support in the northwest. Results suggest cold temperatures are a likely contributor to southeastern range limits, consistent with CMH predictions. In the northeast and northwest, ecological processes consisting of a steep physiological barrier and ongoing invasion dynamics, respectively, are more likely explanations for population genomic patterns than the CMH.探究物种地理分布范围限制的成因，是生态学与进化生物学领域的核心研究议题之一。中心边缘假说（Central Marginal Hypothesis，CMH）提出，物种无法适应当前地理分布范围边界以外的环境条件，其内在机制为：边缘种群规模更小且隔离程度更高，致使遗传多样性从分布核心区向边缘区逐步降低。本研究采用包含24235至33112个单核苷酸多态性（Single Nucleotide Polymorphism，SNP）位点的群体基因组学分析框架，针对甘蔗蟾蜍（Rhinella marina）在澳大利亚的持续入侵过程，对CMH的核心预测展开验证。研究人员沿该物种入侵分布区的大尺度核心-边缘样带采集组织样本；借助地理信息系统（Geographic Information System，GIS）及生态位模型生成的生境适宜性指数，确定了该物种的地理与生态核心区。贝叶斯聚类分析结果显示，该物种存在三个遗传簇，分别分布于西北入侵前沿区域、东北部降水限制区域以及东南部低温限制区域。在东南部区域，遗传多样性与遗传分化的核心-边缘分布模式与CMH的预测相符；但在东北部区域，该模式并不支持CMH，而在西北部区域则呈现出混合支持的结果。研究结果表明，低温可能是制约该物种东南部分布范围的关键因素，这与CMH的预测相一致。而在东北部与西北部区域，分别由陡峭生理屏障与持续入侵动态构成的生态过程，相较CMH而言，更能解释观测到的群体基因组学模式。