Viviparity and Speciation: Testing the Alternatives

当种群分化到繁殖隔离的程度时，新物种就出现了。这种隔离是由交配和受精障碍引起的，还是由受精后的遗传不相容引起的？最近的理论表明，生殖模式可能是一个关键因素，活产（胎生）物种的亲密母胎关系特征使它们比产卵的物种更容易受到受精后遗传不相容的影响。本研究将利用典型胎生无脊椎动物Cordylochernes scorpioides独特的生殖特征，探讨生殖模式在物种形成中的作用。利用跨越一系列遗传差异的种群对，研究将包括种群间杂交、行为实验和分子分析，旨在将生殖隔离划分为交配、配子和受精后的组成部分，以确定各种形式的生殖隔离进化的精确顺序。这项研究将首次全面研究胎生动物的物种形成机制，并将阐明物种形成中最引人注目但鲜为人知的模式之一，即谱系在受精前和受精后隔离进化的相对速度上存在巨大差异。加深对活生育物种生殖隔离的进化和机制原因的了解，不仅有助于物种形成理论，而且有助于旨在确定和保护生物多样性的研究。

New species arise when populations diverge sufficiently to become reproductively isolated. Is this isolation initiated by barriers to mating and fertilization or by post-fertilization genetic incompatibility? Recent theory suggests that reproductive mode may be a critical factor, with the intimate mother/fetus relationship characteristic of live-bearing (viviparous) species making them far more vulnerable to post-fertilization genetic incompatibility than species that lay eggs. This study will exploit unique reproductive features of a model viviparous invertebrate, the false scorpion Cordylochernes scorpioides, to investigate the role of reproductive mode in speciation. Using population pairs spanning a range of genetic divergence, the research will encompass interpopulation crosses, behavioral experiments, and molecular analyses designed to partition reproductive isolation into mating, gametic, and post-fertilization components to determine the precise sequence through which the various forms of reproductive isolation evolve. This research will represent the first comprehensive study of speciation mechanisms in a viviparous animal and will shed light on one of the most striking but poorly understood patterns in speciation, namely that lineages differ profoundly in the relative rates at which pre- and post-fertilization isolation evolve. An increased understanding of the evolutionary and mechanistic causes of reproductive isolation in live-bearing species promises to contribute not only to speciation theory but also to studies aimed at identifying and preserving biological diversity.