Resource Patchiness and Variation in the Intensity of Sexual Selection in a Resource Defending Polygynous Insect Species

Abstract

Mark-recapture experiments demonstrated that the intensity of sexual selection among males of the ragwort seed bug, Neacoryphus bicrucis Say (Hemiptera: Lygaeidae), varies with resource patchiness. In large patches of host plants, Senecio smallii, the intensity of sexual selection is less than one-third as great as in small patches of host plants. Oviposition and the proportion of males copulating are greater in large patches. Field data indicate that most of the variance in male reproductive success is attributable to variance in the number of mates per male and not to differences in female fertility. The greater variance in male copulatory success in small patches of S. smallii is probably attributable to greater variation in the attractiveness of these patches as sites for oviposition. Consequently, males in small patches encounter fewer receptive females than males in large patches.