Like many species in the mint family, common thyme (Thymus vulgaris L.), produces volatile chemicals called monoterpenes in tiny sacs located on leaves and flowering parts. Plants use these chemicals for a variety of functions, including: suppressing plant competitors, repelling herbivores, and attracting pollinators. Due to simple genetic differences, individual thyme plants will be one of six different chemical types, called chemotypes. Plants of a particular chemotype produce one monoterpene that dominates their chemical composition. This means that individuals of the same species can have very different smells, tastes, and interactions with other organisms. For instance, one chemotype may repel herbivores or attract pollinators better than another chemotype. How a single species maintains these chemical differences is the focus of this work. In particular, are certain chemotypes better at attracting pollinators than others, thereby affording them better reproductive success? To determine whether the volatile chemicals from different thyme chemotypes influence pollinators differentially, a series of experiments has been planned. First, the volatiles from different thyme chemotypes will be collected and characterized to show how much and which chemicals are actually emitted. Next, observations of thyme pollinators will be conducted to determine if they behave differently toward the various chemotypes, using whole plants, plant extracts and pure monoterpenes from different chemotypes. Finally, plants of specific chemotypes will be grown in populations of other chemotypes and their reproduction assessed by measuring seed production, which is directly proportional to pollinator visitation.
