Munoz Nicole E, Zink Andrew G
Department of Biology, San Francisco State University, CA 94132, USA.
Ethology. 2012 Oct;118(10):943-954. doi: 10.1111/j.1439-0310.2012.02086.x.
Extreme asymmetric morphologies are hypothesized to serve an adaptive function that counteracts sexual selection for symmetry. However direct tests of function for asymmetries are lacking, particularly in the context of animal weapons. The weapon of the maritime earwig, Anisolabis maritima, exhibits sizeable variation in the extent of directional asymmetry within and across body sizes, making it an ideal candidate for investigating the function of asymmetry. In this study, we characterized the extent of weapon asymmetry, characterized the manner in which asymmetric weapons are used in contests, staged dyadic contests between males of different size classes and analyzed the correlates of fighting success. In contests between large males, larger individuals won more fights and emerged as the dominant male. In contests between small males, however, weapon asymmetry was more influential in predicting overall fighting success than body size. This result reveals an advantage of asymmetric weaponry among males that are below the mean size in the population. A forceps manipulation experiment suggests that asymmetry may be an indirect, correlate of a morphologically independent factor that affects fighting ability.
极端不对称形态被认为具有一种适应性功能，可抵消对对称性的性选择。然而，目前缺乏对不对称性的功能进行直接测试，特别是在动物武器的背景下。海蠼螋（Anisolabis maritima）的武器在不同体型个体内部和之间的方向不对称程度上表现出相当大的差异，这使其成为研究不对称性功能的理想候选对象。在本研究中，我们描述了武器不对称的程度，刻画了不对称武器在争斗中使用的方式，对不同体型类别的雄性进行了二元争斗实验，并分析了争斗成功的相关因素。在大型雄性之间的争斗中，体型较大的个体赢得了更多争斗并成为优势雄性。然而，在小型雄性之间的争斗中，武器不对称性在预测总体争斗成功方面比体型更具影响力。这一结果揭示了在种群中低于平均体型的雄性中不对称武器的优势。一项钳子操纵实验表明，不对称可能是影响战斗能力的形态学独立因素的间接关联因素。
