Data from: The genetics of adaptation to discrete heterogeneous environments: frequent mutation or large-effect alleles can allow range expansion

Range expansions are complex evolutionary and ecological processes. From an evolutionary standpoint, a populations' adaptive capacity can determine the success or failure of expansion. Using individual-based simulations, we model range expansion over a two-dimensional, approximately continuous landscape. We investigate the ability of populations to adapt across patchy environmental gradients and examine how the effect sizes of mutations influence the ability to adapt to novel environments during range expansion. We find that genetic architecture and landscape patchiness both have the ability to change the outcome of adaptation and expansion over the landscape. Adaptation to new environments succeeds via many mutations of small effect or few of large effect, but not via the intermediate between these cases. Higher genetic variance contributes to increased ability to adapt, but an alternative route of successful adaptation can proceed from low genetic variance scenarios with alleles of sufficiently large effect. Steeper environmental gradients can prevent adaptation and range expansion on both linear and patchy landscapes. When the landscape is partitioned into local patches with sharp changes in phenotypic optimum, the local magnitude of change between subsequent patches in the environment determines the success of adaptation to new patches during expansion.

物种分布范围扩张是一类兼具复杂性的进化与生态过程。从进化视角来看，种群的适应能力决定了分布扩张的成败。本研究采用基于个体的模拟（individual-based simulations）方法，在近似连续的二维景观中构建物种分布范围扩张模型。本研究探究了种群在异质性环境梯度下的适应能力，并分析了在分布扩张过程中，突变效应量如何影响种群适应新环境的能力。研究结果表明，遗传架构（genetic architecture）与景观异质性均可改变种群在景观中适应与扩张的结果。种群对新环境的适应可通过两类路径实现：携带大量小效应突变，或携带少量大效应突变，但介于二者之间的中间路径无法达成有效适应。较高的遗传方差（genetic variance）可提升种群适应能力，但也存在另一类成功适应的路径：在低遗传方差的情境下，携带效应足够强的等位基因（alleles）即可实现适应。更陡峭的环境梯度会阻碍种群在线性与异质性景观中的适应与分布扩张。当景观被划分为多个表型最适值（phenotypic optimum）存在剧烈变化的局地斑块时，相邻斑块间环境变化的局地幅度，决定了扩张过程中种群对新斑块的适应成败。