Investigating the effects of tallgrass prairie habitat restoration and forb diversity on the diversity and composition of pollinator communities

Almost 90% of flowering plants rely on animal-mediated pollination, yet pollinators worldwide are vulnerable to numerous anthropogenic threats.  Historically, tallgrass prairies throughout the Midwestern U.S. supported diverse pollinator communities, but less than 4% of native tallgrass prairies remain.  Despite significant effort to restore prairies, little is known about the effects of habitat restoration on pollinator communities.  In 2013, we surveyed pollinators across northeast Kansas prairie remnants (n = 5) and reconstructions (habitat restorations; n = 5).  We assessed whether site-scale forb diversity is positively associated with pollinator diversity, and we compared forb and pollinator diversity and composition between prairie remnants and reconstructions.

Prairie remnants and reconstructions were distinct in forb species composition (P = 0.035), and remnants had greater forb richness (P = 0.044) and diversity (P = 0.036).  Additionally, forb richness was significantly positively associated with bee richness (P = 0.0020) and bee diversity (P = 0.0023) but not with the richness or diversity of the entire pollinator community. Furthermore, prairie reconstructions had 37% lower bee diversity than remnants, although this difference was only marginally statistically significant (P = 0.073).  These preliminary results are consistent with the hypothesis that local-scale floral resources play a role in driving the diversity of bees, an important group of pollinators worldwide.  Lower bee diversity at prairie reconstructions may suggest that attempts to restore tallgrass prairie plant communities might not consistently reinstate bee communities. However, factors such as management regime and landscape-scale resource availability likely also strongly regulate pollinator diversity and composition in prairies.