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      https://www.ias.ac.in/article/fulltext/jgen/092/02/0183-0194

    • Keywords

       

      founding event; genetic drift; colonization; captive populations; genetic differentiation; Drosophila subobscura.

    • Abstract

       

      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 $N_{\text{e}}$. Changes in demography as well as high variance in reproductive success in the novel environment may contribute to the low values of $N_{\text{e}}$. 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.

    • Author Affiliations

       

      Josiane Santos1 Marta Pascual2 Pedro Simões1 Inês Fragata1 Michael R. Rose2 Margarida Matos1

      1. Faculdade de Ciências da Universidade de Lisboa, Centro de Biologia Ambiental, Departamento de Biologia Animal, Campo Grande, 1749-016 Lisboa, Portugal
      2. Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, 08028 Barcelona, España
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