This research will involve two interrelated projects, (1) calculating nestmate relatedness and (2) assessing the extent of sperm precedence in a communal, ground-nesting bee, Perdita portalis. These two goals can be achieved most effectively using methods of DNA fingerprinting. Estimating average relatedness among nestmates is of interest because female P. portalis nest communally, with from 3 to 29 adult females per nest. Communal nesting, the sharing of a single nest by more than one reproductively active female, is an evolutionary stable form of social interaction which is widespread in bees, but which has received little attention by students of social evolution. While many relatedness estimates exist for eusocial species, few data exist for communal species. All behavioral evidence suggests that nestmates in P. portalis are closely related, both because nests are re-used for generations and because flightless males mate with their female nestmates. In order to understand the role of kin selection, and other factors, in shaping communal societies, it is essential to accurately assess within nest relatedness. Part two of the project focuses on the selective factors underlying the origin of maintenance of dimorphic males in P. portalis. Males in this species occur in two non- overlapping morphs: a large-headed, flightless morph and a small- headed, flight capable morph. Large-headed males mate with their female nestmates immediately prior to oviposition and engage in male-male battles which often lead to death of one combatant. These observations suggest that the large-headed morph has arisen as a result of sperm precedence that confers a last male mating advantage. In order to test this hypotheses it will be necessary to assess paternity of eggs produced in observation nests. The two projects are related in that the female social behavior establishes selective pressures on male mating behavior, and intra-nest mating should lead to elevated levels to nestmate relatedness.
