Sex Ratios, Parent-Offspring Conflict, and Local Competition for Mates in the Social Wasps Polistes metricus and Polistes variatus

Abstract

Fisher's prediction of a 1:1 ratio of parental investment for a population is in excellent agreement with the observed values. For both Polistes metricus and P. variatus, each with different degrees of sexual dimorphism and hence parental investment per individual, less cost in the smaller females is offset by their greater number to bring the ratio of PI to nearly 1:1. P. metricus has an identifiable subpopulation that produces only male reproductives, i.e., nests where the foundress has died and the workers have become egg-layers. The prediction implicit in Fisher's theory that the remaining population will exhibit a female-biased PI ratio bringing the population investment ratio to 1:1 is met. No local competition for mates is inferred to have occurred based on the observation of no inbreeding and viscosity of the female portion of the population. As predicted by Hamilton (1967) a 1:1 ratio of PI is observed in the absence of local competition for mates. Parents prevent offspring from either laying male-destined eggs or skewing PI toward females.