Reproductive skew and split sex ratios in social Hymenoptera

I present a model demonstrating that, in social Hymenoptera, split sex allo cation can influence the evolution of reproductive partitioning (skew). In a facultatively polygynous population (with one to several queens per colon y), workers vary in their relative relatedness to females (relatedness asym metry). Split sex-ratio theory predicts that workers in monogynous (single- queen) colonies should concentrate on female production, as their relatedne ss asymmetry is relatively high, whereas workers in the polygynous colonies should concentrate on male production, as their relatedness asymmetry is r elatively low. By contrast, queens in all colonies value males more highly per capita than they value females, because the worker-controlled populatio n sex ratio is too female-biased from the queens' standpoint. Consider a po lygynous colony in a facultatively polygynous population of perennial, soci al Hymenoptera with split sex ratios. A mutant queen achieving reproductive monopoly would gain from increasing her share of offspring but, because th e workers would assess her colony as monogynous, would lose from the worker s rearing a greater proportion of less-valuable females from the colony's b rood. This sets an upper limit on skew. Therefore, in social Hymenoptera, s kew evolution is potentially affected by queen-worker conflict over sex all ocation.