Data from: The coalescent in boundary-limited range expansions

Habitat ranges of most species shift over time, for instance due to climate change, human intervention, or adaptation. These demographic changes often have drastic population genetic effects, such as a stochastic resampling of the gene pool through the "surfing" phenomenon. Most models assume that the speed of range expansions is only limited by the dispersal ability of the colonizing species and its reproductive potential. While such models of "phenotype-limited" expansions apply to species invasions, it is clear that many range expansions are limited rather by the slow motion of habitat boundaries, as driven for instance by global warming. Here, we develop a coalescent model to study the genetic impact of such "boundary-limited" range expansions. Our simulations and analysis show that the resulting loss of genetic diversity is markedly lower than in species invasions if large carrying capacities can be maintained up to the habitat frontier. Counterintuitively, we find that the total loss of diversity does not depend on the speed of the range expansion: Slower expansions have a smaller rate of loss, but also last longer. Boundary-limited range expansions exhibit a characteristic genetic footprint and should therefore be distinguished from range expansions limited only by intrinsic characteristics of the species.

多数物种的栖息地分布范围会随时间发生变迁，其驱动因素包括气候变化、人类干预或物种自身的适应性演化等。这类种群动态变化往往会对群体遗传产生显著影响，例如通过“冲浪现象（surfing phenomenon）”实现基因库的随机重采样。现有多数模型假设，物种分布范围扩张的速率仅受定植物种的扩散能力与繁殖潜力限制。尽管这类“表型受限型（phenotype-limited）”扩张模型适用于物种入侵场景，但显然许多物种的分布范围扩张实则受限于栖息地边界的缓慢移动——例如由全球变暖驱动的边界移动。本研究构建了溯祖模型（coalescent model），以此探究这类“边界受限型（boundary-limited）”分布范围扩张所带来的遗传效应。模拟与分析结果表明，若能在栖息地前沿维持较高的环境容纳量，该扩张模式下的遗传多样性损失程度将显著低于物种入侵场景。与直觉相悖的是，研究发现遗传多样性的总损失量并不取决于分布范围扩张的速率：扩张速率越慢，多样性损失的速率越低，但扩张持续的时间也越长。边界受限型分布范围扩张具有独特的遗传足迹（genetic footprint），因此需将其与仅受物种内在特性限制的分布范围扩张模式区分开来。