Understanding how urbanization alters functional interactions among pollinators and plants is critically important given increasing anthropogenic land use. Students from the University of San Francisco’s Pollination Biology class have been collecting longitudinal data on short-term specialization of pollinators in urban and natural environments. Short-term specialization occurs when pollinators visit plants of the same species during one foraging bout. This facilitates plant receipt of conspecific pollen, defined as pollen on a pollinator that is the same species as the plant on which the pollinator was visiting. Conspecific pollen receipt facilitates plant reproductive success, and is thus important to plant and pollinator persistence. We tested the hypothesis that urbanization decreases short term specialization, by comparing the proportion of conspecific pollen on pollinators in urban fragments and natural areas. The urban sites had been restored with native plants or contained remnant native plant communities. We also explored how urbanization affects plant-pollinator network specialization.
Results/Conclusions
Surprisingly, we found a higher proportion of conspecific pollen on pollinators in urban fragments relative to natural areas. This was not explained by differences in plant species diversity, or network specialization, between site types. We discuss how differences in the spatial distribution of plant species may drive higher short-term specialization in urban areas.