Intraspecific variation in ant sex ratios and the Trivers-Hare hypothesis
Boomsma JJ., Grafen A.
Examines worker-controlled sex investments in eusocial Hymenoptera and assume that relatedness asymmetry is variable among colonies and that workers are able to assess the relatedness asymmetry in their own colony. Such "assessing' workers should maximize their inclusive fitness by specializing in the production of the sex to which they are relatively most related, ie colonies whose workers have a relatedness asymmetry below the population average should specialize in males, whereas colonies whose workers have a higher than average relatedness asymmetry should specialize in making females. This yields the expectation that colony sex ratios will be bimodally distributed in ant populations where relatedness asymmetry is variable owing to multiple mating, worker reproduction, and/or polygyny. No such bimodality is expected, however, in ant species where relatedness asymmetry is known to be constant, or in cases where relatedness asymmetry is supposed to be irrelevant due to allospecific brood rearing under queen control, as in the slave-making ants. Data partly support these contentions. -from Authors