Exaggeration through sexual selection may impact the thermal biology of arthropods.

Abstract

Sexual selection is often invoked to explain the evolution of extravagant morphologies, such as antlers and horns. While the focus is typically on the process of exaggeration of these traits, the functional impact of exaggeration remains a topic of debate. One aspect that has been largely overlooked is how exaggerated structures might impact thermal biology. For example, as a hollow (i.e., non-vascularized or non-perfused) structure increases in size, its surface area and volume change, potentially impacting its ability to obtain and dissipate heat passively. However, if the exaggerated structure is vascularized, or in the case of arthropods, has hemolymph perfusion, then it may be actively used as a thermal radiator to avoid overheating in instances of thermal stress. Based on these and additional examples, we propose that morphological exaggeration may influence how arthropods manage heat exchange with the environment. Ultimately, individuals that bear exaggerated structures may develop ecological innovations that, due to selection or as a corollary effect, maximize effectiveness of thermoregulation. Our essay is divided into four sections. First, we delve on how exaggerated structures, particularly animal weapons, may impact how organisms exchange heat with the environment, and the implications for whole-organism thermoregulation. Second, we use beetles and fiddler crabs to provide experimental evidence of how structural exaggeration may influence thermal biology. Third, we examine macroecological data from arthropods to explore how the size of sexually-selected morphologies varies with changes in environmental temperature. Finally, we synthesize these pieces of evidence to identify significant ecological implications and gaps in knowledge. Through this essay, we aim to ignite discussion on how morphological changes driven by sexual selection can lead to innovations not only in the functional role of morphologies but also in the thermal biology of individuals.