The Relative Importance of Intra- and Interspecific Competition in Scorpionfly Mating Systems

Abstract

Little research has examined whether interspecific competition for resources may influence the evolution of resource-based social systems in animals. An experimental field study of adults of two species of co-occurring Panorpa scorpionflies determined the relative importance of intra- and interspecific interactions at food (dead arthropods) on the fecundity, weight changes, and mating system of each species. Panorpa species exhibit resource-defense polygyny that includes not only male-male competition for dead arthropods, which are offered to females in exchange for mating, but also female mate choice and condition-dependent alternative male mating tactics. The three mating tactics used by males are arthropod defense, salivary-mass defense, and forced copulation. P. latipennis and P. mirabilis were studied because their similar ecological requirements (diet, seasonal occurrence, etc.) result in a high degree of interspecific interaction in nature and because the latter species is strongly dominant over th...