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

了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。特别是配偶选择和男性竞争，是男性形态演变的有力推动力，并产生了一系列吸引女性的华丽装饰品，以及有助于男性与男性战斗的放大武器武器库。尽管以前的研究广泛关注女性选择的过程和男性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工作很少，而且被选来与男性交战和吸引女性的武器的多样性仍然知之甚少。这项研究采取了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：犀牛甲壳虫的角。具体地说，该项目研究了如何1)选择以最大限度地减少角的生理成本，以及2)选择以最大限度地提高角在战斗中的性能，这可能有助于解释犀牛甲虫在武器形式上的差异模式。这项研究已经给出了一个令人兴奋和意想不到的解释，解释了为什么甲虫的角如此之大和多样：角的制造或携带成本并不是特别高，因此在进化上可能特别不稳定。这里概述的实验通过结合包括微CT扫描和有限元分析在内的几项新技术来扩展这项研究，以明确测试角形态的变化如何影响战斗中的表现。因此，本论文项目涵盖了生物学的许多领域，包括进化论、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身体形态的变化。总而言之，这项研究有望对生物形态、功能和多样性之间的相互作用提供新的见解。角的表面重建将发布在http://dbs.umt.edu/emlenlab/上

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/