(NSF-funded collaborative research, Judie Bronstein and Becky Irwin, Dartmouth College)
Why cooperation is so common and how it can persist in the face of cheating is one of the great enigmas in biology. Empirical understanding, however, currently lags far behind theoretical exploration. Ecological conditions under which organisms will and will not choose to cooperate are barely known, nor are the relative payoffs of these behaviors or the rules that regulate behavioral switches. Pollination mutualisms are ideal model systems in which these questions can be addressed empirically. They are prone to exploitation when “cheaters” scrounge floral rewards without pollinating (Irwin et al. 2010). For example, primary nectar robbers steal nectar through holes they bite in flowers, often without transferring pollen, whereas secondary nectar robbers steal additional nectar through the holes made by primary robbers. The goal of our collaboration is to understand the ecological and energetic conditions that encourage pollinators to switch from beneficial to cheating behaviors and the consequences of these behavioral shifts for the reproduction of both the animals and the plants. Using three plant species and two bee species that switch between pollinating and cheating behaviors, this project (being carried out at the Rocky Mountain Biology Lab in Colorado) combines field observations, manipulative experiments, and a model to determine (1) when and why bees cheat the plants they visit; (2) the reproductive consequences of beneficial vs. cheating visits for the bees and how they vary depending on the ecological community; and (3) the relative effects of primary and secondary robbing on male (pollen donation) and female (seed production) components of plant reproduction. Sarah Richman’s dissertation is providing a great base on which our project is building. For training opportunities for undergraduate students and postdocs linked to this project, see under Teaching.