Successive range expansion promotes diversity and accelerates evolution in spatially structured microbial populations
Successive range expansion promotes diversity and accelerates evolution in spatially structured microbial populations
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DOI：
10.1038/ismej.2017.76
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发表时间：
2017-09-01
期刊：
影响因子：
11
通讯作者：
Johnson, David R.
中科院分区：
文献类型：
--
作者：
Goldschmidt, Felix;Regoes, Roland R.;Johnson, David R.
连续的范围扩张发生在所有的生活领域，其中一个种群首先扩张（初级扩张），然后是一个或多个次级种群（次级扩张）。一般来说，遗传漂变在分布区扩展过程中减少了多样性。然而，不清楚在连续的分布区扩张中是否也有同样的效果，主要是因为次级种群必须扩张到初级种群所占据的空间。在这里，我们使用了一个实验微生物模型系统，以表明，与主要的范围扩张，连续的范围扩张促进当地人口的多样性。由于机械约束的存在下的主要人口，二次人口形成分形状的树枝状结构。这将前进的次级种群分成许多小的亚种群，并促进初级种群和次级种群之间的混合。我们进一步发展了一个数学模型来模拟演替过程中次生种群中树枝状结构的形成。通过在初级或树突状次级群体中引入突变，我们发现突变更可能在树突状次级群体中积累。因此，我们的研究结果表明，连续的范围扩大可以促进混合在短期内和增加遗传多样性的长期。因此，我们的研究结果具有潜在的重要意义，预测生态过程和微生物群落的进化轨迹。
Successive range expansions occur within all domains of life, where one population expands first (primary expansion) and one or more secondary populations then follow (secondary expansion). In general, genetic drift reduces diversity during range expansion. However, it is not clear whether the same effect applies during successive range expansion, mainly because the secondary population must expand into space occupied by the primary population. Here we used an experimental microbial model system to show that, in contrast to primary range expansion, successive range expansion promotes local population diversity. Because of mechanical constraints imposed by the presence of the primary population, the secondary population forms fractal-like dendritic structures. This divides the advancing secondary population into many small sub-populations and promotes intermixing between the primary and secondary populations. We further developed a mathematical model to simulate the formation of dendritic structures in the secondary population during succession. By introducing mutations in the primary or dendritic secondary populations, we found that mutations are more likely to accumulate in the dendritic secondary populations. Our results thus show that successive range expansion can promote intermixing over the short term and increase genetic diversity over the long term. Our results therefore have potentially important implications for predicting the ecological processes and evolutionary trajectories of microbial communities.