GENETIC RELATEDNESS AND INCIPIENT EUSOCIALITY IN STENOGASTRINE WASPS

Social wasps of the subfamily Stenogastrinae represent an incipient stage of eusociality characterized by slight behavioural and morphological differences between egg-layers and non-egglayers, and the preservation of several reproductive options in all adult females. Females may remain as helpers on the colony where they emerge, join a non-relative on another nest as egg-layer or helper, or begin a new nest. To explore eusociality in this group, a sample was collected from colonies of two of the best-studied species, Liostenogaster flavolineata and Parischnogaster alternata. Because females move between nests, and mother/daughter overlap in generations is slight, relatedness by pedigree is difficult to assess. Therefore, inbreeding and relatedness among colony members was estimated from allozyme variation. Inbreeding or population viscosity might elevate relatedness between colony members from the same cluster of colonies, but there was no evidence for this in either species. Among 57 female colony members from 22 colonies of P. alternata relatedness was 0.56 (SE=0.19) and among 95 female colony members from 38 colonies of L. flavolinenta relatedness was 0.22 (SE=0.10), the lowest reported thus far for any primitively eusocial insect. Although a minority of females actually become egg-layers on their own colonies (a key factor in assessing the eusocial status of the group), females exhibit continual efforts to maximize their direct reproductive success in ways more reminiscent of vertebrate communal groups than of eusocial insects.