4 - Sexual selection in resource defense polygyny: lessons from territorial grasshoppers

Summary

ABSTRACT

Sexual selection in resource defense polygyny systems is characterized by male–male competition for valuable resource patches, female settlement among patches based on both resource quality and male quality, and positive correlations between resource quality and male quality. These correlations confound the processes of sexual selection and pose special challenges for their study. Ligurotettix, an unusual genus of gomphocerine grasshoppers in which males defend individual host shrubs as mating territories, have proved to be useful species for investigating these issues.

Female Ligurotettix generally settle on certain host shrubs whose foliage represents high–quality food, which may promote egg development. Males are usually found on the same set of host shrubs that harbor females. The settlement of adult males, which occurs prior to the seasonal appearance of adult females, is based on the expected value of a shrub as both a female encounter site and a food resource whose consumption could increase male competitive abilities. Males compete for exclusive residence at valuable shrubs by means of early adult maturation, searching mechanisms for finding the shrubs, and aggression. Loud acoustic signaling by the males attracts females and influences their initial settlement among these shrubs.

Despite high levels of aggression, Ligurotettix males congregate on the most valuable host shrubs. Females may prefer congregated males per se, possibly as a means of reducing the costs of selecting males and locating resources. Some findings suggest that males display mutual attraction and exploit this possible female preference.