Background/Question/Methods
Ipomoea pandurata and Hibiscus moscheutos are southern Illinois wildflowers that are the preferred pollen hosts of the solitary specialist bees Melitoma taurea and Ptilothrix bombiformis (Apoidea: Emphorini), respectively.  Although each bee has a strong preference for only one of these taxa, each occasionally collects pollen from the others’ host plant.  Moreover, phylogenetic analyses indicate that multiple independent switches between convolvulaceous and malvaceous hosts have occurred in emphorine bees.  These patterns suggest that the plants may share morphological or chemical characteristics involved in host selection and the evolution of host choice in these bees.  

Results/Conclusions

Here we present preliminary qualitative data on the floral odor constituents of both plant species.  We collected scent from flowers at two sites using dynamic headspace sampling.  GC/MS analysis yielded a total of 32 volatile compounds detected in the floral samples but absent from ambient controls.  Preliminary data indicate that a group of seven unidentified, naphthalene-derived compounds are shared in both species.  Future studies will further explore the role of these compounds in attracting M. taurea and P. bombiformis.  Very few studies have addressed the role of floral chemistry in specialist bee host choice.