Gilbert K J, Whitlock M C
Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
J Evol Biol. 2017 Mar;30(3):591-602. doi: 10.1111/jeb.13029. Epub 2017 Jan 5.
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.
范围扩张是复杂的进化和生态过程。从进化的角度来看，一个种群的适应能力可以决定扩张的成败。我们使用基于个体的模拟方法，对二维近似连续景观上的范围扩张进行建模。我们研究了种群在斑驳环境梯度中适应的能力，并考察突变效应大小如何影响范围扩张过程中适应新环境的能力。我们发现，遗传结构和景观斑驳性都有能力改变景观上适应和扩张的结果。适应新环境可通过许多小效应突变或少数大效应突变成功实现，但不是通过这两种情况之间的中间状态。较高的遗传方差有助于提高适应能力，但成功适应的另一条途径可以从具有足够大效应等位基因的低遗传方差情景出发。更陡峭的环境梯度会阻碍线性和斑驳景观上的适应和范围扩张。当景观被划分为具有表型最优值急剧变化的局部斑块时，环境中后续斑块之间的局部变化幅度决定了扩张过程中适应新斑块的成功与否。
