Males missing their sexually selected weapon have decreased fighting ability and mating success in a competitive environment

摘要

Intraspecific competition over access to females has led to a large diversity of animal weapons. Generally, the relative size (and presence) of these weapons is positively correlated with mating success, as individuals with the largest weapons often obtain most of the mates. Despite their importance, individuals in some species can lose their weapons. For example, a crab's claw can be dropped to escape life-threatening situations and a beetle's horn can break if it exceeds its mechanical limit. Previous research has shown that individuals missing their weapons are less successful at male-male competition, but few studies have investigated how weapon loss translates to changes in mating behavior and mating success. Here, we investigated how weapon loss affected fighting ability and mating success in the leaf-footed cactus bug Narnia femorata Stal (Hemiptera: Coreidae). In this study, males who lost their sexually selected weapons fought in the same manner as intact males, but were five times less likely to establish dominance. Despite this decrease in dominance, 34% of the weaponless males were still able to access females, and the lack of weaponry did not affect a female's willingness to mate. Still, weapon loss ultimately decreased mating success by 37% in a competitive environment.