PATTERNS OF PATERNITY SKEW IN FORMICA ANTS

Reproductive skew among cooperatively breeding animals has recently at tracted considerable interest. In social insects reproductive skew has been studied in females but not in males. However, cooperative breedi ng of males occurs when two males mate with the same queen and father offspring. Here we present the first analysis of comparative data on p aternity skew in ants. We show that, across seven species of Formica a nts, the average skew in paternity among worker offspring of doubly ma ted queens is negatively correlated with the population-wide frequency of multiple (mostly double) mating. We also demonstrate that this tre nd is relatively robust in additional analyses taking phylogenetic rel ationships between species into account. The observed trend is opposit e to the one normally found in non-social insects with second-male pre cedence through sperm displacement, but agrees with predictions based on queen-male conflict over sperm allocation as a consequence of facul tative, worker controlled, sex allocation an interpretation which assu mes first-male precedence. However, alternative (but not mutually excl usive) explanations are possible and further studies will be needed to discriminate between these alternatives.