Collaborative Research: From cooperation to exploitation: context-dependent effects of nectar microbes on pollination mutualisms

Cooperation is ubiquitous across ecological systems; yet how it continues to persist, even in the face of cheating, remains an enigma. This project will explore if and how microbes affect cooperation using plants and the microbes that reside in floral nectar as a model system. Across different systems, mutualistic species have been observed to steal floral resources without providing pollination services in return. This project uses a combination of field experiments across a community of wildflowers, floral visitors, and associated microbes in the Rocky Mountains. The main goals are to characterize (1) drivers of nectar microbial community structure; (2) how nectar microbes influence behaviors displayed by floral visitors; and (3) how microbes and the visitor behaviors affect plant reproduction. Broader impacts include student training, public outreach, and improved understanding of a major ecosystem service: pollination. The project will train undergraduate students, a graduate student, and a postdoctoral researcher. Public outreach is planned through a partnership with a non-profit museum, as well as through work with middle schools and summer science camps.Interactions among plants, pollinators, and nectar robbers have long served as an important model system for exploring ecological shifts between states of cooperation and conflict. Yet, despite their extensive study, the mechanisms that underlie shifts between these states, and constancy within, remain surprisingly unclear. Nectar microbes represent understudied but potentially significant interactors that may shape the foraging conditions under which floral visitors may decide to cooperate or cheat. This project will (1) employ the use of culture-dependent and culture-independent approaches to characterize the nectar microbiome of five montane wildflowers after legitimate vs. nectar robber floral visits; (2) assess how nectar microbes influence floral odor, nectar chemistry, and visitor behaviors; and (3) measure feedbacks of the microbes and floral visitor community on components of plant reproduction. By studying nectar microbes, their impact on floral phenotype, and whether they reinforce or facilitate the breakdown of pollination, we will gain a broader understanding of the factors that shape plant reproduction and pollination mutualisms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.