Population Genetic Structure and Social Evolution in the Sphecid Wasp Microstigmus comes

Abstract

Genetic structure and sex allocation were studied in a natural population of the primitively eusocial sphecid wasp Microstigmus comes. No higher-level genetic structure was discernible at the level of the subpopulation, and microgeographic structure at the level of the local deme or individual host palm was, at most, modest. In contrast, genetic structure at the level of the individual nest was striking, with the average genetic relatedness among female nest mates estimated to be 0.62-0.67. This high relatedness results from the fact that colonies comprise relatively simple families, which are, in many instances, matrifilial monogynous societies. High relatedness among female nest mates and the absence of conspicuous higher-level structure, in conjunction with the observed female-biased sexinvestment ratios, are compatible with the interpretation that kin selection has played a major role in the origin of eusocial behavior in the recent ancestors of this wasp. The inferred colony composition and social organization further suggest that this social evolution may have occurred via a subsocial route, with simple matrifilial families rather than polygynous groups serving as the principal setting for the development of worker altruism.