The Relationship Between Carpenter Bees and Pyne’s Ground-plum (Astragalus bibullatus)

Abstract

Astragalus bibullatus is a federally endangered species, endemic to the limestone cedar glades of Middle Tennessee. Cedar glades are an endangered ecosystem, and the plant is found in only a few naturally occurring populations, all within Rutherford County, Tennessee. Insects in the genus Xylocopa, known as carpenter bees, perform a phenomenon referred to as nectar robbing on A. bibullatus. This method of nectar collection bypasses pollination and thus poses a threat to the reproductive fitness of the plant. Scant data on nectar rubbing by carpenter bees exists, especially regarding A. bibullatus.The goal of this research project has been to determine the level of interference that carpenter bees have on the pollination and reproduction of A. bibullatus. Carpenter bees started to visit plants of A. bibullatus 4 weeks after flowering started in the species. The bees remained constant to A. bibullatus and did not move to the co-flowering Pediomelum subacuale. No other insect species visited the holes made by carpenter bees to collect nectar, in contrast to other researcher’s observations in previous years. While no fruit production was observed on plants visited by carpenter bees, additional studies are needed to determine the degree that carpenter bees impact the reproduction of A. bibullatus.