Section of Integrative Biology, University of Texas at Austin, 1 University Station, C0930, Austin, Texas 78712, USA.
Evolution. 2011 Sep;65(9):2481-91. doi: 10.1111/j.1558-5646.2011.01307.x. Epub 2011 May 2.
Population genetic theory predicts that adaptation in novel environments is enhanced by genetic variation for fitness. However, theory also predicts that under strong selection, demographic stochasticity can drive populations to extinction before they can adapt. We exposed wheat-adapted populations of the flour beetle (Tribolium castaneum) to a novel suboptimal corn resource, to test the effects of founding genetic variation on population decline and subsequent extinction or adaptation. As previously reported, genetically diverse populations were less likely to go extinct. Here, we show that among surviving populations, genetically diverse groups recovered faster after the initial population decline. Within two years, surviving populations significantly increased their fitness on corn via increased fecundity, increased egg survival, faster larval development, and higher rate of egg cannibalism. However, founding genetic variation only enhanced the increase in fecundity, despite existing genetic variation-and apparent lack of trade-offs-for egg survival and larval development time. Thus, during adaptation to novel habitats the positive impact of genetic variation may be restricted to only a few traits, although change in many life-history traits may be necessary to avoid extinction. Despite severe initial maladaptation and low population size, genetic diversity can thus overcome the predicted high extinction risk in new habitats.
种群遗传理论预测，适应新环境的能力会因适应度的遗传变异性而增强。然而，理论也预测，在强烈的选择压力下，种群在适应之前可能会因人口随机波动而灭绝。我们将适应小麦的粉斑螟（Tribolium castaneum）种群暴露在一种新的次优玉米资源中，以检验创始遗传变异对种群减少和随后的灭绝或适应的影响。如前所述，遗传多样性的种群不太可能灭绝。在这里，我们表明，在幸存的种群中，遗传多样性较高的群体在最初的种群减少后恢复得更快。在两年内，幸存的种群通过增加繁殖力、提高卵存活率、更快的幼虫发育和更高的卵食率，显著提高了在玉米上的适应性。然而，尽管存在遗传变异——并且明显没有权衡——用于卵存活率和幼虫发育时间，但创始遗传变异仅增强了繁殖力的增加。因此，在适应新栖息地的过程中，遗传变异的积极影响可能仅限于少数几个特征，尽管许多生活史特征的改变可能是避免灭绝所必需的。尽管最初严重的适应不良和种群规模较小，但遗传多样性可以克服新栖息地中预测的高灭绝风险。
