Sexual selection has resulted in some of the most exaggerated and diverse traits in the animal kingdom. Examples include sexually selected weapons, which are used by members of the same sex to compete over access to mates, resources, and high-quality territories. Typically, conspecifics with larger/more invested weapons win more fights and have higher mating success when compared to smaller rivals. However, using and maintaining highly exaggerated weapons often comes with drawbacks. This can include substantial material and metabolic costs, alongside tradeoffs with other fitness-enhancing traits. Thus, variation in weaponry can have large implications for individual reproductive success. This dissertation examines variation in weapon size and form within populations, and how this variation can influence individual behavior and the outcomes of male-male competitions. Using a combination of morphological and behavioral analyses in the giant mesquite bug (Pachylis neocalifornicus). Chapter 1 investigates the mechanisms of sexual selection on a unique weapon polymorphism. Chapter 2 uses an ecological stoichiometric approach to examine how the maintenance of sexually selected weapons can influence local distribution and adult nutritional acquisition of key elements (C,N,P) within populations. Chapter 3 complements the previous study by examining how juvenile nutrition within insects can influence the weapon size and integrity of adults. Because weapons can accumulate damage through repeated use in rigorous physical contests, diet quality may play a crucial role in maintaining cuticle integrity and influencing fighting outcomes. However, this remains to be tested empirically.
Isaac McEvoy
Dr. Zachary Emberts, Advisor
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