Environmental heterogeneity can tip the population genetics of range expansions
Environmental heterogeneity can tip the population genetics of range expansions
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DOI：
10.7554/elife.44359
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发表时间：
2019-04-12
期刊：
影响因子：
7.7
通讯作者：
Hallatschek, Oskar
中科院分区：
文献类型：
--
作者：
Gralka, Matti;Hallatschek, Oskar
大多数分布区扩展的群体遗传学被认为是由达尔文选择和分布区边缘的随机遗传漂变之间的竞争形成的。在这里，我们表明，在范围扩张的进化动力学是高度敏感的环境异质性引起的额外的波动。在随机图案表面上生长的细菌菌落中跟踪具有可调适应性效应的突变克隆，我们发现环境异质性可以显着降低选择的功效。延时显微镜和计算机模拟表明，这种效应一般产生于局部“钉扎”的扩张前，从而拉伸的前面放慢了长度尺度，这取决于环境异质性的结构。这种牵制将范围扩张集中到少数“幸运”的个体中，这些个体可以进入扩张路径，改变了中性的进化动力学，并增加了机会相对于选择的重要性。
The population genetics of most range expansions is thought to be shaped by the competition between Darwinian selection and random genetic drift at the range margins. Here, we show that the evolutionary dynamics during range expansions is highly sensitive to additional fluctuations induced by environmental heterogeneities. Tracking mutant clones with a tunable fitness effect in bacterial colonies grown on randomly patterned surfaces we found that environmental heterogeneity can dramatically reduce the efficacy of selection. Time-lapse microscopy and computer simulations suggest that this effect arises generically from a local 'pinning' of the expansion front, whereby stretches of the front are slowed down on a length scale that depends on the structure of the environmental heterogeneity. This pinning focuses the range expansion into a small number of 'lucky' individuals with access to expansion paths, altering the neutral evolutionary dynamics and increasing the importance of chance relative to selection.