Santos Josiane, Pascual Marta, Simões Pedro, Fragata Inês, Rose Michael R, Matos Margarida
Centro de Biologia Ambiental, Departamento de Biologia Animal, Campo Grande, 1749-016 Lisboa, Portugal.
J Genet. 2013;92(2):183-94. doi: 10.1007/s12041-013-0239-x.
Founder effects during colonization of a novel environment are expected to change the genetic composition of populations, leading to differentiation between the colonizer population and its source population. Another expected outcome is differentiation among populations derived from repeated independent colonizations starting from the same source. We have previously detected significant founder effects affecting rate of laboratory adaptation among Drosophila subobscura laboratory populations derived from the wild. We also showed that during the first generations in the laboratory, considerable genetic differentiation occurs between foundations. The present study deepens that analysis, taking into account the natural sampling hierarchy of six foundations, derived from different locations, different years and from two samples in one of the years. We show that striking stochastic effects occur in the first two generations of laboratory culture, effects that produce immediate differentiation between foundations, independent of the source of origin and despite similarity among all founders. This divergence is probably due to powerful genetic sampling effects during the first few generations of culture in the novel laboratory environment, as a result of a significant drop in Ne. Changes in demography as well as high variance in reproductive success in the novel environment may contribute to the low values of Ne. This study shows that estimates of genetic differentiation between natural populations may be accurate when based on the initial samples collected in the wild, though considerable genetic differentiation may occur in the very first generations of evolution in a new, confined environment. Rapid and significant evolutionary changes can thus occur during the early generations of a founding event, both in the wild and under domestication, effects of interest for both scientific and conservation purposes.
在新环境定殖过程中的奠基者效应预计会改变种群的基因组成，导致定殖种群与其源种群之间产生分化。另一个预期结果是，源自同一源种群的多次独立定殖所产生的种群之间也会出现分化。我们之前已经检测到显著的奠基者效应，影响了源自野生型的果蝇实验室种群的实验室适应率。我们还表明，在实验室的最初几代中，不同奠基群体之间会发生相当程度的遗传分化。本研究深化了这一分析，考虑了六个奠基群体的自然抽样层次结构，这些群体来自不同地点、不同年份，且其中一年有两个样本。我们表明，在实验室培养的前两代中会出现显著的随机效应，这些效应会立即导致不同奠基群体之间产生分化，与起源无关，尽管所有奠基者之间存在相似性。这种差异可能是由于在新的实验室环境中培养的最初几代中强大的基因抽样效应，这是有效种群大小（Ne）显著下降的结果。人口统计学的变化以及新环境中繁殖成功率的高方差可能导致Ne值较低。这项研究表明，基于在野外收集的初始样本，对自然种群之间遗传分化的估计可能是准确的，尽管在新的受限环境中进化的最初几代中可能会发生相当程度的遗传分化。因此，在奠基事件的早期几代中，无论是在野外还是在驯化过程中，都可能发生快速而显著的进化变化，这对科学和保护目的都具有重要意义。
