Nosil Patrik, Vines Timothy H, Funk Daniel J
Department of Biosciences, Behavioural Ecology Research Group, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
Evolution. 2005 Apr;59(4):705-19.
The classification of reproductive isolating barriers laid out by Dobzhansky and Mayr has motivated and structured decades of research on speciation. We argue, however, that this classification is incomplete and that the unique contributions of a major source of reproductive isolation have often been overlooked. Here, we describe reproductive barriers that derive from the reduced survival of immigrants upon reaching foreign habitats that are ecologically divergent from their native habitat. This selection against immigrants reduces encounters and thus mating opportunities between individuals from divergently adapted populations. It also reduces the likelihood that successfully mated immigrant females will survive long enough to produce their hybrid offspring. Thus, natural selection against immigrants results in distinctive elements of premating and postmating reproductive isolation that we hereby dub "immigrant inviability." We quantify the contributions of immigrant inviability to total reproductive isolation by examining study systems where multiple components of reproductive isolation have been measured and demonstrate that these contributions are frequently greater than those of traditionally recognized reproductive barriers. The relevance of immigrant inviability is further illustrated by a consideration of population-genetic theory, a review of selection against immigrant alleles in hybrid zone studies, and an examination of its participation in feedback loops that influence the evolution of additional reproductive barriers. Because some degree of immigrant inviability will commonly exist between populations that exhibit adaptive ecological divergence, we emphasize that these barriers play critical roles in ecological modes of speciation. We hope that the formal recognition of immigrant inviability and our demonstration of its evolutionary importance will stimulate more explicit empirical studies of its contributions to speciation.
由多布赞斯基（Dobzhansky）和迈尔（Mayr）提出的生殖隔离屏障分类法，推动并构建了数十年来关于物种形成的研究。然而，我们认为这种分类并不完整，而且生殖隔离一个主要来源的独特贡献常常被忽视。在此，我们描述了这样一种生殖屏障，它源自移民到达与其原生栖息地生态不同的异域栖息地后存活率的降低。这种对移民的选择减少了相遇机会，从而减少了适应不同环境的种群个体之间的交配机会。它还降低了成功交配的移民雌性存活足够长时间以产生杂交后代的可能性。因此，针对移民的自然选择导致了交配前和交配后生殖隔离的独特因素，我们在此将其称为“移民不存活”。我们通过研究那些测量了生殖隔离多个组成部分的系统，来量化移民不存活对总生殖隔离的贡献，并证明这些贡献常常大于传统上认可的生殖屏障的贡献。通过对群体遗传学理论的思考、对杂交区研究中针对移民等位基因选择的综述，以及对其在影响其他生殖屏障进化的反馈回路中的参与情况的考察，进一步说明了移民不存活的相关性。由于在表现出适应性生态差异的种群之间通常会存在某种程度的移民不存活，我们强调这些屏障在物种形成的生态模式中起着关键作用。我们希望对移民不存活的正式认可以及我们对其进化重要性的证明，将激发更多关于其对物种形成贡献的明确实证研究。
