Understanding changes in a plant-pollinator network over a century of global change

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Understanding human impacts on biodiversity is hindered by a lack of long-term studies spanning decades and documenting these changes. Such studies are so rare because they are difficult to maintain and because they often take decades to yield insights about global changes that occur over long time spans. Historical datasets from studies documenting past ecological conditions can be repeated to better understand human impacts on biodiversity. Mutualisms like pollination support a great deal of biodiversity and are thought to be particularly susceptible to disruption in the face of environmental change. We depend on pollinators for the ecosystem services they provide. This project will evaluate the long-term change in a diverse plant-pollinator network by re-sampling data from a century-old classic study on community-wide plant-pollinator interactions conducted by Clements and Long (1923). The influential ecologist, Frederic E. Clements, and his protégée, Frances L. Long, carefully documented interactions between a diverse assemblage of plants and pollinators in the region of Pikes Peak, CO, USA, starting in 1910. Clements and Long’s study is special due to the richness of its detailed data which go beyond species occurrences and include observations of plant-pollinator interactions, phenology (dates), and pollinator visitation rates. The habitat of the Clements and Long study has been preserved, allowing researchers in this project to assess the roles of global changes with uncertain impacts such as potential insect declines and climate-induced phenological mismatches (compared to impacts like extensive habitat loss and fragmentation which have large, well-documented impacts). The project will provide opportunities to train and engage students. Findings from this work will be disseminated to broad audiences in various ways which include local K-12 interpretive outdoor programs, museum exhibits, presentations to the general public and managers, and web video to disseminate this work widely. This project will advance knowledge of biodiversity change and ecological networks by providing a rare opportunity to understand of how interaction networks change over the temporal scale of a century. This work will determine how the composition and structure of the plant-pollinator network has changed and whether there is evidence for changes in phenology and pollinator declines, which could in turn explain changes in interactions. The research questions in this project are: (1) How has the abundance and richness of flower visitors changed between historical and contemporary datasets? (2a) How has the timing (phenology) of plants, pollinators and their interactions changed between historical and contemporary datasets; (2b) and do shifts in phenological overlap of plants and pollinators predict interaction loss? (3) How have the structure and composition plant-pollinator networks on Pikes Peak changed between historical and contemporary times? Only one other study examined long-term changes in plant-pollinator networks at comparable time scales and it has done so in highly modified, human-dominated landscapes. It recorded declines in pollinator species and disassembly of networks indicating increased susceptibility to further species loss. However, the long-term changes and their consequences in habitats that have not been destroyed and fragmented remains uncertain. This uncertainty has led to debate about whether wholesale insect declines have occurred in natural ecosystems. This work will inform that debate and explain the causes and consequences of biodiversity change. Additionally, it will examine spatiotemporal dimensions of ecological networks, a burgeoning topic in the field.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.