McGaughran Angela, Morgan Katy, Sommer Ralf J
Department for Evolutionary Biology, Max Planck Institute for Developmental Biology, Tübingen, Germany.
PLoS One. 2014 Jan 31;9(1):e87317. doi: 10.1371/journal.pone.0087317. eCollection 2014.
The distribution of a species is a complex expression of its ecological and evolutionary history and integrating population genetic, environmental, and ecological data can provide new insights into the effects of the environment on the population structure of species. Previous work demonstrated strong patterns of genetic differentiation in natural populations of the hermaphroditic nematode Pristionchus pacificus in its La Réunion Island habitat, but gave no clear understanding of the role of the environment in structuring this variation. Here, we present what is to our knowledge the first study to statistically evaluate the role of the environment in shaping the structure and distribution of nematode populations. We test the hypothesis that genetic structure in P. pacificus is influenced by environmental variables, by combining population genetic analyses of microsatellite data from 18 populations and 370 strains, with multivariate statistics on environmental data, and species distribution modelling. We assess and quantify the relative importance of environmental factors (geographic distance, altitude, temperature, precipitation, and beetle host) on genetic variation among populations. Despite the fact that geographic populations of P. pacificus comprise vast genetic diversity sourced from multiple ancestral lineages, we find strong evidence for local associations between environment and genetic variation. Further, we show that significantly more genetic variation in P. pacificus populations is explained by environmental variation than by geographic distances. This supports a strong role for environmental heterogeneity vs. genetic drift in the divergence of populations, which we suggest may be influenced by adaptive forces.
一个物种的分布是其生态和进化历史的复杂表现，整合种群遗传学、环境和生态数据能够为环境对物种种群结构的影响提供新的见解。先前的研究表明，雌雄同体的太平洋普氏线虫在留尼汪岛栖息地的自然种群中存在强烈的遗传分化模式，但对于环境在构建这种变异中所起的作用却没有清晰的认识。在此，据我们所知，我们开展了首项统计评估环境在塑造线虫种群结构和分布中作用的研究。我们通过结合对来自18个种群和370个菌株的微卫星数据进行种群遗传分析、对环境数据进行多变量统计以及物种分布建模，来检验太平洋普氏线虫的遗传结构受环境变量影响这一假设。我们评估并量化环境因素（地理距离、海拔、温度、降水和甲虫宿主）对种群间遗传变异的相对重要性。尽管太平洋普氏线虫的地理种群包含源自多个祖先谱系的巨大遗传多样性，但我们发现了环境与遗传变异之间存在局部关联的有力证据。此外，我们表明，太平洋普氏线虫种群中由环境变异解释的遗传变异显著多于由地理距离解释的遗传变异。这支持了环境异质性相对于遗传漂变在种群分化中所起的重要作用，我们认为这可能受到适应性力量的影响。
