UC Santa Barbara

Environmental disturbances and biodiversity turnover in the Anthropocene increasingly threaten species interactions – the scaffolding of ecosystems. Plant and pollinator communities and their interactions provide ecosystem functions and services (i.e., pollination) that are biologically and economically critical. Species interactions are particularly vulnerable to environmental disturbances because each interacting group can be individually impacted with a resulting loss of the interaction. Importantly, environmental disturbances that threaten biodiversity rarely occur in isolation and, rather, occur in combination with regional and local scale effects. To protect ecosystem functions and services, and thus, the interactions between species, we must first collect a realistic understanding of the multiple stressors that can affect species, interactions, and ecosystem structure.

This dissertation takes an empirical approach to understanding plant and pollinator communities, investigating: (1) the relative effects of multiple environmental attributes on plant-pollinator network structure, (2) the relative effects of regional climate and species introduction across ecosystem boundaries on plant community diversity, and (3) the bottom-up or top-down effects of regional and local stressors on plant reproduction.

Through these studies, we find that the amount of available habitat and the quality of habitat is vital for the diversity of both plant and pollinator communities and the resulting complexity and frequency of their interactions. Importantly, habitat quality could be especially influential where resources are limited. These findings support the integration of habitat quality into conservation planning in order to mitigate the effects of multiple stressors on species interactions across landscapes. This work confirms conservation goals such as prioritizing habitat size in reserve planning, but also encourages a more comprehensive examination of the impacts of introduced species.