Forsman Anders, Berggren Hanna
Ecology and Evolution in Microbial Model Systems EEMiS Department of Biology and Environmental Science Linnaeus University Kalmar Sweden.
Ecol Evol. 2016 Dec 25;7(2):751-761. doi: 10.1002/ece3.2671. eCollection 2017 Jan.
Spatial sorting is a process that can contribute to microevolutionary change by assembling phenotypes through space, owing to nonrandom dispersal. Here we first build upon and develop the "neutral" version of the spatial sorting hypothesis by arguing that in systems that are not characterized by repeated range expansions, the evolutionary effects of variation in dispersal capacity and assortative mating might not be independent of but interact with natural selection. In addition to generating assortative mating, variation in dispersal capacity together with spatial and temporal variation in quality of spawning area is likely to influence both reproductive success and survival of spawning migrating individuals, and this will contribute to the evolution of dispersal-enhancing traits. Next, we use a comparative approach to examine whether differences in spawning migration distance among 18 species of freshwater eels have evolved in tandem with two dispersal-favoring traits. In our analyses, we use information on spawning migration distance, body length, and vertebral number that was obtained from the literature, and a published whole mitochondrial DNA-based phylogeny. Results from comparative analysis of independent contrasts showed that macroevolutionary shifts in body length throughout the phylogeny have been associated with concomitant shifts in spawning migration. Shifts in migration distance were not associated with shifts in number of vertebrae. These findings are consistent with the hypothesis that spatial sorting has contributed to the evolution of more elongated bodies in species with longer spawning migration distances, or resulted in evolution of longer migration distances in species with larger body size. This novel demonstration is important in that it expands the list of ecological settings and hierarchical levels of biological organization for which the spatial sorting hypothesis seems to have predictive power.
空间分选是一个过程，由于非随机扩散，它可以通过在空间上聚集表型来促进微进化变化。在这里，我们首先在空间分选假说的“中性”版本基础上进行拓展和发展，认为在没有反复范围扩张特征的系统中，扩散能力和选型交配的变化所产生的进化效应可能并非独立于自然选择，而是与自然选择相互作用。除了产生选型交配外，扩散能力的变化以及产卵区域质量的时空变化可能会影响产卵洄游个体的繁殖成功率和存活率，这将有助于促进扩散的性状的进化。接下来，我们采用比较方法来研究18种淡水鳗鱼的产卵洄游距离差异是否与两种有利于扩散的性状协同进化。在我们的分析中，我们使用了从文献中获得的关于产卵洄游距离、体长和脊椎数量的信息，以及已发表的基于全线粒体DNA的系统发育树。独立对比的比较分析结果表明，整个系统发育过程中体长的宏观进化变化与产卵洄游的相应变化相关。洄游距离的变化与脊椎数量的变化无关。这些发现与以下假设一致：空间分选促成了产卵洄游距离较长的物种中身体更细长的进化，或者导致了体型较大的物种中洄游距离更长的进化。这一新的论证很重要，因为它扩展了空间分选假说似乎具有预测能力的生态环境和生物组织层次水平的列表。
