Centre for Evolutionary Biology, School of Animal Biology (M092), The University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia, Australia
Department of Biological Sciences (E8C 209), Macquarie University, 6 Wally's Walk, Sydney 2109, New South Wales, Australia.
Proc Biol Sci. 2018 May 30;285(1879). doi: 10.1098/rspb.2018.0335.
Theory predicts that the evolution of polyphenic variation is facilitated where morphs are genetically uncoupled and free to evolve towards their phenotypic optima. However, the assumption that developmentally plastic morphs can evolve independently has not been tested directly. Using morph-specific artificial selection, we investigated correlated evolution between the sexes and male morphs of the bulb mite Large 'fighter' males have a thick and sharply terminating pair of legs used to kill rival males, while small 'scrambler' males have unmodified legs, and search for unguarded females, avoiding fights. We selected on the relative leg width of only the fighter male morph, tracked the evolutionary responses in fighters and the correlated evolutionary responses in scramblers and females that were untouched by direct selection. Fighters diverged in relative leg thickness after six generations; assaying scramblers and females at the ninth generation we observed correlated responses in relative leg width in both. Our results represent strong evidence for the evolution of intraspecific phenotypic diversity despite correlated evolution between morphs and sexes, challenging the idea that male morphs are genetically uncoupled and free to independently respond to selection. We therefore question the perceived necessity for genetic independence in traits with extreme phenotypic plasticity.
理论预测，在形态在遗传上不相关且可以自由进化到表型最优状态的情况下，多态性变异的进化会得到促进。然而，形态发育可塑性形态可以独立进化的假设尚未得到直接检验。使用形态特异性人工选择，我们研究了性别的相关进化和雄性形态。大型“斗士”雄性有一对粗壮而急剧终止的腿，用于杀死竞争对手雄性，而小型“ scrambling ”雄性腿没有经过修饰，它们会寻找没有守卫的雌性，避免战斗。我们仅在斗士雄性形态上选择相对腿宽，跟踪斗士的进化反应以及未直接选择的 scrambler 和雌性的相关进化反应。经过六代，斗士在相对腿厚方面出现分歧；在第九代检测 scrambler 和雌性时，我们观察到两者的相对腿宽都出现了相关的进化反应。我们的结果代表了尽管形态和性别之间存在相关进化，但仍然存在种内表型多样性进化的有力证据，这挑战了雄性形态在遗传上不相关且可以自由独立响应选择的观点。因此，我们对具有极端表型可塑性的特征所需的遗传独立性提出质疑。
