Components of variance in male lifetime copulatory and reproductive success in a seed bug

Abstract

Males and females of the seed bug, Neacoryphus bicrucis Say, were individually numbered in the field in southeastern Georgia (USA) and census taken daily for 6 weeks. Variation in male mating efficiency (ME = no. copulations/no. sightings) exceeded that in females and was significantly greater than that generated by a null model. Lifetime copulatory success, estimated as the product of ME and longevity, ranged from 0 to 41, with ME accounting for over 88% of the variation. Lifetime reproductive success (LRS), estimated as the product of ME, longevity, and clutch size, ranged from 0 to 898. Among males copulating at least once, ME accounted for over 40% of the variation in LRS, while longevity alone or in combination with clutch size accounted for 21% and 46%, respectively, of the variation in LRS. Failure of some males (26%) to copulate contributed 38% of the total variation in LRS. Thus, among males surviving to adulthood, sexual selection pressure arising from variation in ME is approximately as strong a “force” for phenotypic change as is natural selection pressure arising from variation in longevity.