Tomkins Joseph L, Kotiaho Janne S, LeBas Natasha R
Division of Environmental and Evolutionary Biology, Sir Harold Mitchell Building, University of St. Andrews, St. Andrews, Fife KY16 9TH, United Kingdom.
Am Nat. 2005 Mar;165(3):389-402. doi: 10.1086/427732. Epub 2005 Jan 20.
The developmental independence of alternative phenotypes is key to evolutionary theories of phenotypic plasticity and the origins of diversity. Male dimorphisms associated with alternative reproductive tactics are widely cited examples of such facultative expression of divergent fitness optima. Current models for the evolution of male dimorphisms invoke a size-dependent threshold at which the phenotype is reprogrammed. We use predictions derived from allometric modeling to test for the existence of reprogramming thresholds in two species of beetle, Onthophagus taurus and Onthophagus binodis, and the European earwig Forficula auricularia. We also compare the allometry of a number of morphological traits to determine whether minor males suppress their secondary sexual traits. The intercept of the horn allometry was suppressed, but there was no evidence of reprogramming of horn growth in either beetle species. There was reprogramming in the earwig. In the beetles, the horn length in all males can be explained largely in terms of exponential horn growth following an extraordinarily steep power function. The asymptote in O. taurus can be explained by exponential growth meeting the constraint of resource exhaustion. These findings question the currently held view that beetle horn dimorphisms showcase the importance of developmental independence in the evolution of diversity.
替代表型的发育独立性是表型可塑性进化理论和多样性起源的关键。与替代生殖策略相关的雄性二态性是这种不同适应度最优值的兼性表达的广泛引用例子。当前关于雄性二态性进化的模型引入了一个大小依赖性阈值，在该阈值下表型会被重新编程。我们使用从异速生长模型得出的预测来测试两种甲虫，即金牛座嗡蜣螂和双瘤嗡蜣螂，以及欧洲蠼螋耳夹子虫中是否存在重新编程阈值。我们还比较了一些形态特征的异速生长情况，以确定小型雄性是否抑制其第二性征。角的异速生长截距被抑制，但在这两种甲虫物种中均没有角生长重新编程的证据。蠼螋中存在重新编程。在甲虫中，所有雄性的角长度在很大程度上可以用遵循极其陡峭幂函数的指数角生长来解释。金牛座嗡蜣螂中的渐近线可以用指数生长遇到资源耗尽的限制来解释。这些发现质疑了目前所持的观点，即甲虫角的二态性展示了发育独立性在多样性进化中的重要性。
