Inra, UMR 1062 CBGP, Montpellier, France.
J Evol Biol. 2013 Aug;26(8):1691-9. doi: 10.1111/jeb.12167. Epub 2013 May 31.
High propagule pressure is arguably the only consistent predictor of colonization success. More individuals enhance colonization success because they aid in overcoming demographic consequences of small population size (e.g. stochasticity and Allee effects). The number of founders can also have direct genetic effects: with fewer individuals, more inbreeding and thus inbreeding depression will occur, whereas more individuals typically harbour greater genetic variation. Thus, the demographic and genetic components of propagule pressure are interrelated, making it difficult to understand which mechanisms are most important in determining colonization success. We experimentally disentangled the demographic and genetic components of propagule pressure by manipulating the number of founders (fewer or more), and genetic background (inbred or outbred) of individuals released in a series of three complementary experiments. We used Bemisia whiteflies and released them onto either their natal host (benign) or a novel host (challenging). Our experiments revealed that having more founding individuals and those individuals being outbred both increased the number of adults produced, but that only genetic background consistently shaped net reproductive rate of experimental populations. Environment was also important and interacted with propagule size to determine the number of adults produced. Quality of the environment interacted also with genetic background to determine establishment success, with a more pronounced effect of inbreeding depression in harsh environments. This interaction did not hold for the net reproductive rate. These data show that the positive effect of propagule pressure on founding success can be driven as much by underlying genetic processes as by demographics. Genetic effects can be immediate and have sizable effects on fitness.
高繁殖体压力可以说是殖民成功的唯一一致预测因子。更多的个体可以提高殖民成功率，因为它们有助于克服小种群数量带来的人口统计学后果（例如随机性和阿利效应）。 创始人的数量也可能具有直接的遗传效应：个体越少，近交程度越高，从而发生近交衰退的可能性越大，而更多的个体通常具有更大的遗传变异。 因此，繁殖体压力的人口统计学和遗传成分是相互关联的，这使得很难理解哪些机制对确定殖民成功率最重要。 通过在一系列三个互补实验中操纵释放个体的创始人数量（更少或更多）和遗传背景（近交或远交），我们实验性地分离了繁殖体压力的人口统计学和遗传成分。 我们使用烟粉虱并将它们释放到它们的出生地（良性）或新宿主（具有挑战性）上。 我们的实验表明，拥有更多的创始个体和那些远交的个体都可以增加产生的成虫数量，但只有遗传背景始终塑造了实验种群的净生殖率。 环境也很重要，并与繁殖体大小相互作用来确定产生的成虫数量。 环境质量还与遗传背景相互作用，以确定建立成功率，在恶劣环境中近交衰退的影响更为明显。 这种相互作用不适用于净生殖率。 这些数据表明，繁殖体压力对建立成功率的积极影响既可以通过潜在的遗传过程驱动，也可以通过人口统计学来驱动。 遗传效应可以是即时的，并对适应性产生相当大的影响。
