University of Vienna, Department of Mathematics, 1180 Wien, Austria.
Philos Trans R Soc Lond B Biol Sci. 2022 Apr 11;377(1848):20210011. doi: 10.1098/rstb.2021.0011. Epub 2022 Feb 21.
Dispersal has three major effects on adaptation. First, gene flow mixes alleles adapted to different environments, potentially hindering (swamping) adaptation. Second, it brings in other variants and inflates genetic variance: this aids adaptation to spatially (and temporally) varying environments but if selection is hard, it lowers the mean fitness of the population. Third, neighbourhood size, which determines how weak genetic drift is, increases with dispersal-when genetic drift is strong, increase of the neighbourhood size with dispersal aids adaptation. In this note, I focus on the role of dispersal in environments that change gradually across space, and when local populations are quite small such that genetic drift has a significant effect. Using individual-based simulations, I show that in small populations, even leptokurtic dispersal benefits adaptation by reducing the power of genetic drift. This has implications for management of fragmented or marginal populations: the beneficial effect of increased dispersal into small populations is stronger than swamping of adaption under a broad range of conditions, including a mixture of local and long-distance dispersal. However, when environmental gradient is steep, heavily fat-tailed dispersal will swamp continuous adaptation so that only patches of locally adapted subpopulations remain. This article is part of the theme issue 'Species' ranges in the face of changing environments (Part II)'.
扩散对适应有三个主要影响。首先，基因流混合了适应不同环境的等位基因，可能会阻碍（淹没）适应。其次，它带来了其他变体并增加了遗传方差：这有助于适应空间（和时间）变化的环境，但如果选择很困难，它会降低种群的平均适应性。第三，邻域大小决定了遗传漂变的强度，随着扩散的增加而增加——当遗传漂变较强时，随着扩散增加邻域大小有助于适应。在本说明中，我专注于扩散在空间上逐渐变化的环境中的作用，以及当地种群非常小以至于遗传漂变有重大影响的情况。使用基于个体的模拟，我表明在小种群中，即使是长尾分布也可以通过减少遗传漂变的影响来促进适应。这对碎片化或边缘种群的管理具有重要意义：在包括局部和远距离扩散混合在内的广泛条件下，增加向小种群的扩散比适应淹没具有更强的有益效果。然而，当环境梯度陡峭时，长尾分布会淹没连续的适应，只留下局部适应的亚种群斑块。本文是主题为“面对不断变化的环境的物种范围（第二部分）”的一部分。
