Social groups are built around cooperation, in which individuals work together to benefit the group. Human success as a social species is built around this mutual benefit, but we know little about its evolution and maintenance. Cooperative groups risk being vulnerable to cheating, if a group member takes advantage of the effort of others to secure a disproportionate amount of resources. In groups of relatives, these effects can be offset by kinship. However, the costs and benefits of cooperation among non-relatives are more difficult to assess and explain. The California harvester ant provides a rare opportunity to examine the costs and benefits of cooperation among non-relatives. In this species, some queens practice primary polygyny, in which unrelated queens cooperatively build a new nest and rear offspring together, forming what is essentially a multi-family colony. The proposed work will investigate what ecological conditions favor the evolution of cooperation in this species, and how these cooperative societies deal with the possibility of cheating by some group members. The proposed research will be combined with undergraduate training, in which students participate in field and laboratory research. This builds on a record of mentoring excellence by the principal investigator and graduate student. The researchers will also work in conjunction with the local parks department to provide educational materials highlighting this unusual ant population. This research is fundamental to our understanding of social evolution, and may provide insight into the issues of cooperation and conflict in human societies.
Prior work has shown that colonies in the polygynous population have lower reproductive output than those in a nearby population without polygyny. This suggests polygyny may be a functional response to local environmental constraints. Polygynous colonies also face issues of cheating, if reproduction is non-equitably distributed among queens. Interpretation of these findings is limited, because the polygynous and single-queen populations investigated so far are in different environments. The researchers will quantify the reproductive output of single- versus multi-queen colonies within a single population, to determine whether variation in reproduction is environmentally driven, or an intrinsic colony attribute. This analysis will be combined with a food supplement experiment, to determine whether reproduction in polygynous colonies is resource limited. Finally, relative queen contributions to reproduction versus worker production within polygynous colonies will be analyzed via microsatellites, to determine whether queens share in reproduction equitably. If not, this suggests that subtle cheating may be taking place within these cooperative associations. Data will be stored locally and on ASU server space for a minimum of 5 years, with the expectation of permanently archiving them. Data will be indexed and made available to an open source data depository after publication.
