Post-glacial colonisation, latitude, isolation-by-distance, and local fragmentation have shaped the genetic diversity of common toads (Bufo bufo) across Britain_Datasets_Scripts_Figs

The evolutionary history of many species found in Britain has been shaped by a combination of postglacial colonisation dynamics and more recent anthropogenic activity. Documenting genetic diversity is important for informing the overall conservation status of given species, and to aid in developing suitable conservation management strategies. In this study we present the first island-wide population genetic study of the toad Bufo bufo in Britain, using two mitochondrial and eight nuclear microsatellite markers which generated data for 823 animals. We found low genetic diversity and low levels of geographic structuring, and possible evidence of a two wave-colonisation to Britain from mainland Europe in the mitochondrial loci. Our microsatellite data recovered moderate genetic structuring, with evidence of recent admixture in most sampled sites. Assigned genetic clusters were only loosely associated with geography, suggesting that genetic differentiation is primarily driven by the observed isolation-by-distance rather than discrete barriers to gene flow. Levels of allelic richness decreased significantly with higher latitude and correlated positively with census size based on counts. Other genetic diversity indices and estimates of genetic effective population sizes did not correlate with population census size proxies. Our study identified sites with high genetic distinctiveness or signs of genetic erosion, and will inform the future conservation management of B. bufo across the UK.英国境内诸多物种的演化历史，均由冰期后定殖动态与近代人类活动共同塑造。厘清物种的遗传多样性，对于明确目标物种的整体保护现状、制定适宜的保护管理策略均具有关键意义。本研究首次针对英国境内的普通蟾蜍（Bufo bufo）开展全岛范围的种群遗传学研究，采用2个线粒体（mitochondrial）标记与8个核微卫星（nuclear microsatellite）标记，对823个个体进行基因分型并获取了遗传数据。研究发现，该物种的遗传多样性水平与地理种群结构程度均较低；在线粒体基因座中，存在英国种群源自欧洲大陆的两次定殖事件的潜在证据。核微卫星数据则揭示了中等程度的种群遗传结构，多数采样位点均呈现近期遗传混合的特征。所划分的遗传聚类与地理分布仅呈现松散关联，表明遗传分化主要由观测到的距离隔离（isolation-by-distance）效应驱动，而非由基因流的离散障碍所导致。等位基因丰富度随纬度升高呈显著下降趋势，且与基于种群计数得到的种群普查规模呈正相关；但其余遗传多样性指标与有效种群大小的估计值，均未与种群普查规模代理变量呈现显著相关性。本研究识别出若干遗传特异性较高或存在遗传侵蚀迹象的采样位点，可为未来英国境内普通蟾蜍的保护管理工作提供科学依据。