Correspondence of male-to-male aggression to spatial distribution of individuals in field populations of a subsocial spider mite

Abstract

The intensity of male-to-male aggression, when evaluated in the laboratory, varies geographically in a subsocial spider mite, Schizotetranychus miscanthi Saito. This species includes two types of populations showing different clinal trends in aggression. We examined the relationships between the intensity of male aggression and the distribution patterns of individuals within nests for 22 field populations of the "low-aggression group." The intensity of male aggression was negatively correlated with the index of male aggregation across nests, which strongly suggests that aggression measured under experimental conditions is actually reflected in the interaction between males within nests in the field. The intensity of male aggression was also negatively correlated with the mean number of males per nest, suggesting that mortal fight between males, observed in the laboratory, actually occurs in the field.