GENETIC RELATEDNESS AND INCIPIENT EUSOCIALITY IN STENOGASTRINE WASPS

Social wasps of the subfamily Stenogastrinae represent an incipient st age of eusociality characterized by slight behavioural and morphologic al differences between egg-layers and non-egglayers, and the preservat ion 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 explo re eusociality in this group, a sample was collected from colonies of two of the best-studied species, Liostenogaster flavolineata and Paris chnogaster alternata. Because females move between nests, and mother/d aughter overlap in generations is slight, relatedness by pedigree is d ifficult to assess. Therefore, inbreeding and relatedness among colony members was estimated from allozyme variation. Inbreeding or populati on viscosity might elevate relatedness between colony members from the same cluster of colonies, but there was no evidence for this in eithe r species. Among 57 female colony members from 22 colonies of P. alter nata 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), t he lowest reported thus far for any primitively eusocial insect. Altho ugh a minority of females actually become egg-layers on their own colo nies (a key factor in assessing the eusocial status of the group), fem ales exhibit continual efforts to maximize their direct reproductive s uccess in ways more reminiscent of vertebrate communal groups than of eusocial insects.