DISSERTATION RESEARCH: Animal weapon diversity: Insights from the form and function of rhinoceros beetle horns

理解驱动形态多样性的选择压力是进化生物学家面临的最令人兴奋的挑战之一。尤其是配偶选择和雄性之间的竞争，是雄性形态进化的有力驱动力，并产生了一系列吸引雌性的华丽装饰，以及一系列有助于雄性之间战斗的放大武器。尽管以前的研究广泛关注女性选择的过程以及男性装饰品的进化和多样化，但令人惊讶的是，关于男性武器的进化的研究却很少，而且人们对选择武器吸引男性和吸引女性的多样性仍然知之甚少。这项研究采用多学科和综合的方法来探索一类特别奢侈的雄性武器：犀牛甲虫角的进化和多样化。具体来说，该项目研究了如何1)选择最小化角的生理成本，以及2)选择最大化角在战斗中的性能，这可能有助于解释犀牛甲虫在武器形式上的差异模式。对于甲虫的角为何如此巨大和多样，一个令人兴奋和意想不到的解释已经从这项研究中出现了：角的生产和携带成本并不高，因此在进化上可能特别不稳定。本文概述的实验通过结合几种新技术（包括微型ct扫描和有限元分析）扩展了该研究，以明确测试角形态的变化如何影响战斗中的性能。因此，本论文项目涵盖了生物学的许多领域，包括进化、行为生态学、生理学和生物力学，并应用新的工程工具来分析和解释动物形体的变化。结合起来，这项研究有望对生物形式、功能和多样性之间的相互作用提供新的见解。牛角的表面重建将在http://dbs.umt.edu/emlenlab/上发布

Understanding the selective pressures that drive morphological diversity is one of the most exciting challenges facing evolutionary biologists. Mate Choice and male-male competition, in particular, are potent drivers in the evolution of male morphology and has given rise to an array of flashy ornaments that are attractive to females, and an arsenal of enlarged weapons that aid in male-male combat. Although previous studies have focused extensively on the process of female choice and the evolution and diversification of male ornaments, surprisingly little work has been done on the evolution of male weapons, and the diversity of selected weapons to engage males and attract females is still poorly understood. The research takes a multidisciplinary and integrative approach to explore the evolution and diversification of a class of particularly extravagant male weapons: rhinoceros beetle horns. Specifically, the project examines how 1) selection to minimize the physiological costs of horns, and 2) selection to maximize the performance of horns during combat may help explain the patterns of divergence in weapon form among rhinoceros beetles. One exciting and unexpected explanation for why beetle horns are so large and diverse is already emerging from this research: horns are not especially costly to produce or carry, and therefore may be particularly evolutionarily labile. The experiments outlined here expand on this research by incorporating several novel techniques, including micro-CT scanning and finite element analysis, to explicitly test how variation in horn morphology affects performance during combat. This dissertation project therefore encompasses many fields of biology, including evolution, behavioral ecology, physiology, and biomechanics, and applies new engineering tools for analyzing and interpreting variation in animal body form. Combined, the research promises new insight into the interplay between organismal form, function, and diversity.Surface reconstructions of the horns will be posted at http://dbs.umt.edu/emlenlab/