School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland.
School of Science and Health, Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales, Australia.
J Evol Biol. 2019 Mar;32(3):243-258. doi: 10.1111/jeb.13408. Epub 2018 Dec 21.
Speciation research dissects the genetics and evolution of reproductive barriers between parental species. Hybrids are the "gatekeepers" of gene flow, so it is also important to understand the behavioural mechanisms and genetics of any potential isolation from their parental species. We tested the role of multiple behavioural barriers in reproductive isolation among closely related field crickets and their hybrids (Teleogryllus oceanicus and Teleogryllus commodus). These species hybridize in the laboratory, but the behaviour of hybrids is unusual and there is little evidence for gene flow in the wild. We found that heterospecific pairs exhibited reduced rates of courtship behaviour due to discrimination by both sexes, and that this behavioural isolation was symmetrical. However, hybrids were not sexually selected against and exhibited high rates of courtship behaviour even though hybrid females are sterile. Using reciprocal hybrid crosses, we characterized patterns of interspecific divergence and inheritance in key sexual traits that might underlie the mating patterns we found: calling song, courtship song and cuticular hydrocarbons (CHCs). Song traits exhibited both sex linkage and transgressive segregation, whereas CHCs exhibited only the latter. Calculations of the strength of isolation exerted by these sexual traits suggest that close-range signals are as important as long-distance signals in contributing to interspecific sexual isolation. The surprisingly weak mating barriers observed between hybrids and parental species highlight the need to examine reproductive isolating mechanisms and their genetic bases across different potential stages of introgressive hybridization.
物种形成研究剖析了亲种间生殖隔离的遗传和进化。杂种是基因流动的“守门员”，因此了解与其亲种隔离的任何潜在行为机制和遗传基础也很重要。我们测试了近缘蟋蟀及其杂种（Teleogryllus oceanicus 和 Teleogryllus commodus）之间生殖隔离的多种行为障碍的作用。这些物种在实验室中杂交，但杂种的行为异常，并且在野外几乎没有证据表明存在基因流动。我们发现，由于两性的歧视，异种对表现出较低的求偶行为率，并且这种行为隔离是对称的。然而，杂种并没有受到性选择的抵制，即使杂种雌性不育，它们也表现出很高的求偶行为率。通过正反杂交实验，我们描述了关键的性特征的种间差异和遗传模式，这些特征可能是我们发现的交配模式的基础：鸣叫、求偶鸣唱和表皮碳氢化合物（CHC）。鸣唱特征既表现出性别连锁，也表现出超越分离，而 CHC 只表现出后者。这些性特征产生的隔离强度的计算表明，近距离信号与远距离信号一样，对种间性隔离有重要贡献。在杂种和亲种之间观察到的惊人弱的交配障碍强调了需要检查不同潜在渐渗杂交阶段的生殖隔离机制及其遗传基础。
