Data from: A range-wide genetic bottleneck overwhelms landscape heterogeneity and local abundance in shaping genetic patterns of an alpine butterfly (Lepidoptera: Pieridae: Colias behrii)

Spatial and environmental heterogeneity are major factors in structuring species distributions in alpine landscapes. These landscapes have also been affected by glacial advances and retreats, causing alpine taxa to undergo range shifts and demographic changes. These non-equilibrium population dynamics have the potential to obscure the effects of environmental factors on the distribution of genetic variation. Here we investigate how demographic change and environmental factors influence genetic variation in the alpine butterfly Colias behrii. Data from 14 microsatellite loci provide evidence of bottlenecks in all population samples. We test several alternative models of demography using approximate Bayesian computation (ABC), with the results favoring a model in which a recent bottleneck precedes rapid population growth. Applying independent calibrations to microsatellite loci and a nuclear gene, we estimate that this bottleneck affected both northern and southern populations 531 to 281 years ago, coinciding with a period of global cooling. Using regression approaches, we attempt to separate the effects of population structure, geographical distance and landscape on patterns of population genetic differentiation. Only 40% of the variation in F_ST is explained by these models, with geographical distance and least cost distance among meadow patches selected as the best predictors. Various measures of genetic diversity within populations are also decoupled from estimates of local abundance and habitat patch characteristics. Our results demonstrate that demographic change can have a disproportionate influence on genetic diversity in alpine species, contrasting with other studies that suggest landscape features control contemporary demographic processes in high elevation environments.

空间与环境异质性是塑造高山景观中物种分布格局的核心驱动因素。此类高山景观同时受到冰川进退作用的影响，致使高山类群发生分布范围变迁与种群动态改变。这类非平衡种群动态（non-equilibrium population dynamics）可能会掩盖环境因子对遗传变异分布的调控效应。本研究以高山蝴蝶Colias behrii为对象，探究种群动态变化与环境因子如何调控其遗传变异格局。基于14个微卫星位点（microsatellite loci）的检测数据显示，所有种群样本均存在瓶颈效应（bottleneck）信号。本研究采用近似贝叶斯计算（approximate Bayesian computation, ABC）方法对多种种群动态备选模型开展检验，结果支持“近期瓶颈效应后伴随种群快速扩张”的模型。通过对微卫星位点与核基因分别进行独立校准，我们估算出该瓶颈效应发生于531至281年前，同时波及南北两侧种群，这一时间窗口与全球变冷时期高度重合。本研究采用回归分析方法，尝试拆分种群结构、地理距离与景观因子对种群遗传分化格局的影响效应。上述模型仅能解释F_ST（群体分化系数）40%的变异，其中地理距离与草甸斑块间的最小成本距离被筛选为最优预测因子。种群内多项遗传多样性指标同样与当地种群丰度估算值及栖息地斑块特征脱耦联。本研究结果表明，种群动态变化对高山物种遗传多样性的影响可能远超预期，这与此前认为“景观特征调控高海拔环境中当代种群动态”的相关研究结论形成鲜明对比。