9509563 Morris That ecologists have paid little attention to mutualisms relative to other kinds of species interactions may reflect the attitude that mutualisms are fragile constructs subject to invasion by "non-cooperators" that profit from another species without providing compensating benefits. However, few studies have explored the full range of possible benefits and detriments in mutualistic systems, even those in which apparently non-cooperative behavior is common. The proposed study will address the balance between benefit and detriment in the mutualistic interaction between panicled bluebells and nectar-robbing bumble bees. Contrary to preconceived notions, nectar-robbers, especially those that also pay legitimate visits to flowers, may provide benefits to the plant that equal or outweigh the negative effects they inflict while nectar-robbing. A full exploration of the balance between positive and negative effects in the bluebell and nectar-robber interaction requires three new approaches. First, it is necessary to measure the impact of nectar-robbery on both the male and female success of the plant. Second, the plant's reproductive success must be measured at an appropriate scale. Third, it is necessary to determine if the production of a reward that is obtained by a non-cooperative behavior is actually necessary to assure that the plant receives a mutualistic benefit from facultative nectar-robbers. The experiments in this study will be the first to assess the effects of nectar-robbery on both male and female fitness measured at the scale of entire clones. Additional experiments will manipulate the nectar-producing flowers to elucidate the role of floral rewards in eliciting beneficial behavior from nectar-robbing pollinators. These experiments will examine whether mutualisms in general, and the archetypal mutualism between plants and their pollinators in particular, contain elements of both benefit and detriment.
