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。特别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品，以及一个扩大的武器库，有助于雄性之间的战斗。虽然以前的研究已经广泛地集中在女性选择的过程和男性装饰品的演变和多样化，但令人惊讶的是，很少有人对男性武器的演变做过研究，并且对吸引男性和吸引女性的所选武器的多样性仍然知之甚少。该研究采用多学科和综合的方法来探索一类特别奢侈的男性武器的进化和多样化：犀牛甲虫角。具体来说，该项目研究了如何1）选择，以尽量减少角的生理成本，2）选择，以最大限度地提高角在战斗中的性能可能有助于解释犀牛甲虫之间的武器形式的分歧模式。对于甲虫角为何如此巨大和多样化，一个令人兴奋和意想不到的解释已经从这项研究中出现：角的生产或携带成本并不特别高，因此可能在进化上特别不稳定。这里概述的实验通过结合几种新技术（包括微CT扫描和有限元分析）扩展了这项研究，以明确测试角形态的变化如何影响战斗期间的性能。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体形的变化。结合起来，这项研究有望对有机体的形态、功能和多样性之间的相互作用有新的认识。http://dbs.umt.edu/emlenlab/

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/