Centre for Biological Diversity, School of Biology, University of St Andrews, Fife, UK.
School of Science and Health, Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia.
J Evol Biol. 2020 Jul;33(7):990-1005. doi: 10.1111/jeb.13631. Epub 2020 Apr 27.
A major challenge for studying the role of sexual selection in divergence and speciation is understanding the relative influence of different sexually selected signals on those processes in both intra- and interspecific contexts. Different signals may be more or less susceptible to co-option for species identification depending on the balance of sexual and ecological selection acting upon them. To examine this, we tested three predictions to explain geographic variation in long- versus short-range sexual signals across a 3,500 + km transect of two related Australian field cricket species (Teleogryllus spp.): (a) selection for species recognition, (b) environmental adaptation and (c) stochastic divergence. We measured male calling song and male and female cuticular hydrocarbons (CHCs) in offspring derived from wild populations, reared under common garden conditions. Song clearly differentiated the species, and no hybrids were observed suggesting that hybridization is rare or absent. Spatial variation in song was not predicted by geography, genetics or climatic factors in either species. In contrast, CHC divergence was strongly associated with an environmental gradient supporting the idea that the climatic environment selects more directly upon these chemical signals. In light of recently advocated models of diversification via ecological selection on secondary sexual traits, the different environmental associations we found for song and CHCs suggest that the impact of ecological selection on population divergence, and how that influences speciation, might be different for acoustic versus chemical signals.
研究性选择在分歧和物种形成中的作用所面临的一个主要挑战是，要理解不同的性选择信号在种内和种间背景下对这些过程的相对影响。不同的信号可能更容易或更不容易被用于物种识别，这取决于作用于它们的性选择和生态选择之间的平衡。为了检验这一点，我们提出了三个预测来解释两种澳大利亚蟋蟀物种（Teleogryllus spp.）在 3500 多公里长的横截面上长程与短程性信号地理变异的原因：（a）物种识别选择，（b）环境适应，和（c）随机分歧。我们在野外种群中测量了后代雄性的鸣叫和雄性和雌性的表皮碳氢化合物（CHC），并在共同的花园条件下进行饲养。鸣叫清楚地区分了物种，并且没有观察到杂种，这表明杂交是罕见的或不存在的。在这两个物种中，鸣声的空间变异都不能由地理、遗传或气候因素来预测。相比之下，CHC 的分化与支持这样一种观点的环境梯度密切相关，即气候环境更直接地选择这些化学信号。鉴于最近提倡的通过对次生性特征的生态选择来促进多样化的模型，我们发现鸣叫声和 CHC 之间存在不同的环境关联，这表明生态选择对种群分歧的影响，以及这种影响如何影响物种形成，对于声学信号和化学信号可能是不同的。
