Extended Parental Care in Communal Social Groups

Recent developments in social insect research have challenged the need for close kinship as a prerequisite for the evolution of stable group living. In a model communal bee species, Lasioglossum (Chilalictus) hemichalceum, previous allozyme work indicated that groups of cooperating adult females are not relatives. Yet at any given time, not all group members perform the risky task of foraging. We previously hypothesized that tolerance for non-foragers was a component of extended parental care, previously known only for kin based social systems. DNA microsatellites were used to study colony genetic structure in order to test this hypothesis. Microsatellite polymorphism was substantial (He = 0.775). Overall intracolony relatedness, mainly of immatures, was low but significant in nine, late season nests (r = 0.136 +/- 0.023), indicating that broods contain five to six unrelated sib ships. Detailed analyses of kinship between pairs of individuals revealed that most pairs were unrelated and most related pairs were siblings. Mothers are absent for 89-91% of the developing immature females, and 97% of developing males. Alternatively, 46% of adult females had neither sibs nor offspring in their nests. These findings indicate that the extended parental care model applies broadly to both kin based and nonkin based social systems in the Hymenoptera.