Pollen abundance predicts attractiveness of desert plants to bees

Background/Question/Methods   It has long been noted that different plant species attract different guilds of pollinators, but there has been far less attention paid to differential attraction within pollinator guilds. In many plant communities, especially those in xeric areas, bees are the dominant pollinator group and they visit a diverse array of plant species with widely divergent phenotypes. While there is rampant specialization in these systems, there is substantial generalization as well with a convergence of bee species on super attractive host plants. In most cases, it is far from clear to the human eye what makes these species so attractive and makes them potentially very important in supporting a large fauna of pollinators that may spill over onto less attractive hosts as well.

Results/Conclusions   Working in the San Bernardino Valley of Sonora, Mexico, we examined the interactions between a very rich bee fauna (>300 local species) and a diverse flora over a four year period. We considered floral complexity, nectar abundance, and pollen abundance, both at the flower and the plant level, as potential drivers for overall bee visitation patterns. The most important, and only statistically significant factor at the community level, was pollen production per plant.