Effects of Urban Horticulture on Insect Pollinator Community Structure: Sites

Insects that pollinate flowering plants are often considered
"keystone species," animals that play extremely important roles in ecosystem
functioning such that their absence would have more widespread and far-reaching
effects than their abundance alone would indicate. For example, the absence of
pollinating insects would translate to a severe reduction in plant reproduction,
which would in turn affect not only the plants but also seed-eating animals,
herbivorous animals, predators of the herbivores, and so on in a trophic
cascade. Such a scenario would impact not only wildlife but also human
populations because insects pollinate the majority of human food-plants. While
the importance of these relationships is acknowledged, surprisingly, little is
known about how insect pollinator communities are affected by environmental
changes, such as global climate change or urban development. There has recently
been a call for research on insect pollinator communities, citing a pressing
need to obtain baseline information in the face of probable future environmental
changes. The Sonoran Desert has one of the most diverse insect communities in
the world (particularly for members of the Order Hymenoptera [bees, wasps, and
ants], which perform the lion's share of pollination duties for both native and
crop plants). This community may be threatened from the presence of the exotic
honeybee and from habitat alteration in the form of urban development. We
propose to conduct a pilot study to examine how the pollinator community differs
under different forms of urban land use in the Phoenix metropolitan
area. We have three research questions: (1) How does the ratio of native
species to the exotic honeybee differ among natural desert, urban desert
remnants, and residential areas that also have flowering plants? (2) How does
insect pollinator community structure (richness and abundance) differ among
natural desert, urban desert remnants, and residential areas? and (3) How does
insect pollinator community structure differ with different residential
horticultural practices (xeriscaping with native plants vs. watered lawns with
exotic species)?