Nectar Robbers, Pollinators, and Plants: The Importance of Direct and Indirect Effects on Individuals and Communities

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9806501 Alison Brody A fundamental goal of evolutionary ecologists is to understand how interactions among species govern their abundance and design. The interactions among plants and their pollinators have received considerable attention over the years and these studies have yielded much insight into the ecology and evolution of species interactions. However, some floral visitors do not pollinate their host plants and, in fact, can do significant harm. One such group of animals is nectar robbers -- animals that rob flowers of nectar without effecting pollination. The focus of this study is to examine how a nectar robbing bumblebee, Bombus occidentalis, affects the success of its sub-alpine host plant, scarlet gilia (Ipomopsis aggregata), and indirectly affects other members of the flowering plant community. The research combines manipulative experiments with observations to test three overarching hypotheses: (1) nectar robbers affect realized male and female fitness of the hummingbird-pollinated plant, scarlet gilia, (2) floral traits known to be important in attracting pollinators also attract nectar robbers which may thus mediate floral evolution, and (3) nectar robbing indirectly affects the success of co-occurring plant species by changing the behavior of hummingbird pollinators toward robbed and unrobbed plants. The work is timely in that it addresses a question of long-standing interest to ecologists and evolutionary biologists, i.e., the importance of multiple species interactions and their direct and indirect effects on each other. The work also has applied significance in understanding how multiple species interactions combine to affect the seed production of animal pollinated plants, their floral evolution, and community-level dynamics.