Heritability of size, a sexually selected character, and the response to sexual selection in a natural population of the southern green stink bug, nezara viridula (Hemiptera: Pentatomidae)

Abstract

Using half-sib analysis and two dietary regimens, the heritability of size was estimated for the first generation offspring of field-collected southern green stink bugs, Nezara viridula, from a population in the southeastern U.S. Heritability estimates and actual size were larger under the condition of higher quality diet. A response to sexual selection was estimated using: (a) the estimate of heritability obtained from rearing under low quality diet (since this diet yields individuals of the same size as field bugs), and (b) the selection differential for size derived from random collections of mating and nonmating males in the natural population. Phenotypic evolution may occur in the study population if natural selection for size does not oppose sexual selection and if environmental conditions, such as food availability, do not mask genetic variation for size. Sampling of marked individuals revealed that a significant intensity of sexual selection is maintained during the season of adult activity. Correlations of size with longevity or number of parasites suggest natural selection also favours larger size. The results suggest that directional sexual selection and environmental heterogeneity may promote population differentiation as a consequence of differences in the exposure to selection of genetic variation for sexually selected traits. © The Genetical Society of Great Britain.