Examining potential multi-scale drivers of flower visitor communities and plant-pollinator interactions in the context of tallgrass prairie habitat reconstruction

Abstract

The processes governing community assembly, whereby species from a regional species pool colonize local sites, occur over a wide range of spatial and temporal scales. Studies of community assembly are fundamental to the fields of ecology and conservation, as developing our understanding of the drivers of species distributions and abundances will help advance ecological theory and will aid in the conservation and restoration of Earth’s biodiversity. Insect pollinators are ideal systems for studies of community assembly, as they have been shown to be influenced both by fine-scale factors (e.g. the local provisioning of floral resources) and by the broader landscape context (e.g. the extent of natural lands surrounding focal sites). Moreover, our need to understand the drivers of pollinator community structure continues to increase, as pollinators worldwide have been shown to be declining due to numerous human-induced threats. In this dissertation, I evaluated multiple drivers of insect flower visitor community structure and plant-pollinator network architecture in the context of habitat reconstruction in the tallgrass prairie. In Chapter 1, I assessed the effects of tallgrass prairie reconstruction on the structure of both forb and flower visiting insect communities. I found substantial differences in forb communities between these two types of prairie, but these differences largely did not extend to flower visitor communities, which were similar across remnant and reconstructed prairies. In Chapter 2, I assessed the extent to which flower visitor community structure was influenced by site-scale forb richness, abundance and composition, as well as the composition and configuration of the landscapes within which these sites were situated. My results indicate that flower visitors are largely not associated with site-scale forb -diversity but may be strongly structured both by site-scale forb composition and landscape context. In Chapter 3, I used a network approach to assess the efficacy of prairie reconstruction on plant-pollinator interactions. Plant-pollinator networks allow researchers to visualize community-wide interactions between forbs and flower visitors, and their structural properties can shed insight on the status and stability of plant-pollinator interactions at a given site. I found that network structure was very similar across remnant and reconstructed prairies, and that the particular features of these networks (i.e. modularity, robustness to species loss) suggest that plant-pollinator interactions have been reinstated. Taken together, my results suggest that habitat reconstruction has successfully re-established functioning communities of flower visitors in this system. In addition, my work indicates that landscape context likely plays a central role in structuring flower visitor communities in the highly modified and fragmented tallgrass prairie ecosystem.