Variation in mate recognition specificities among fourCallosobruchusseed beetles

Abstract

AbstractDifferentiation of mate recognition systems is one of the important steps for speciation in animals. For some insects, a contact sex pheromone present on the cuticular surface is indispensable in discriminating reproductive partners. InCallosobruchusspecies (Coleoptera: Chrysomelidae: Bruchinae), contact sex pheromones have been found in two species,Callosobruchus chinensis(L.) andCallosobruchus maculatus(Fabricius). It was suggested, however, that these two species lacked the ability to discriminate their conspecific and/or heterosexual partners. To elucidate this inconsistency, we verified the existence of contact sex pheromones from two other species,Callosobruchus rhodesianus(Pic) andCallosobruchus analis(Fabricius). As a result, unlikeC. chinensisandC. maculatus, the males ofC. rhodesianusandC. analiswere able to discriminate their heterosexual partners. Comparing cross‐copulation behavior, i.e., copulation behavior between two species, against these four species indicated that the mate recognition specificities were quite different. Males ofC. rhodesianusandC. analishad highly species‐specific mating behavior, whereas males ofC. chinensisandC. maculatuswere much less specific. These results indicate that variation in mate recognition can arise even among congeneric species living in a sympatric environment, and this variation might have arisen during species differentiation. Based on our results in combination with previous reports on interspecific competition, we suggest that the observed asymmetric cross‐copulation behavior might be, at least partially, an adaptation for surviving interspecific competition.