Durkee Lily F, Olazcuaga Laure, Melbourne Brett A, Hufbauer Ruth A
Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, United States.
Department of Agricultural Biology, Colorado State University, Fort Collins, CO, United States.
J Evol Biol. 2024 Jun 28;37(6):665-676. doi: 10.1093/jeb/voae031.
In today's rapidly changing world, it is critical to examine how animal populations will respond to severe environmental change. Following events such as pollution or deforestation that cause populations to decline, extinction will occur unless populations can adapt in response to natural selection, a process called evolutionary rescue. Theory predicts that immigration can delay extinction and provide novel genetic material that can prevent inbreeding depression and facilitate adaptation. However, when potential source populations have not experienced the new environment before (i.e., are naive), immigration can counteract selection and constrain adaptation. This study evaluated the effects of immigration of naive individuals on evolutionary rescue using the red flour beetle, Tribolium castaneum, as a model system. Small populations were exposed to a challenging environment, and 3 immigration rates (0, 1, or 5 migrants per generation) were implemented with migrants from a benign environment. Following an initial decline in population size across all treatments, populations receiving no immigration gained a higher growth rate one generation earlier than those with immigration, illustrating the constraining effects of immigration on adaptation. After 7 generations, a reciprocal transplant experiment found evidence for adaptation regardless of immigration rate. Thus, while the immigration of naive individuals briefly delayed adaptation, it did not increase extinction risk or prevent adaptation following environmental change.
在当今瞬息万变的世界中，研究动物种群将如何应对严峻的环境变化至关重要。在诸如污染或森林砍伐等导致种群数量下降的事件之后，除非种群能够通过自然选择进行适应（这一过程称为进化拯救），否则将会发生灭绝。理论预测，迁入可以延缓灭绝，并提供新的遗传物质，从而防止近亲繁殖衰退并促进适应。然而，当潜在的源种群之前没有经历过新环境（即缺乏经验）时，迁入可能会抵消选择作用并限制适应。本研究以赤拟谷盗（Tribolium castaneum）作为模型系统，评估了缺乏经验的个体迁入对进化拯救的影响。将小种群置于具有挑战性的环境中，并以来自良性环境的个体实施3种迁入率（每代0、1或5个迁入个体）。在所有处理中种群数量最初下降之后，未接受迁入的种群比接受迁入的种群提前一代获得了更高的增长率，这说明了迁入对适应的限制作用。7代之后，一项 reciprocal transplant experiment 发现无论迁入率如何，都有适应的证据。因此，虽然缺乏经验的个体迁入短暂地延迟了适应，但它并没有增加灭绝风险，也没有阻止环境变化后的适应。
