The importance of ecological interactions, such as those between parasitic plants and their hosts, are often overlooked in conservation efforts and are extremely important for threatened or endangered parasitic plants. For these species, basic background and natural history data must be available so that the best management and reintroduction techniques can be implemented to assure their persistence. In a greenhouse study, we examined the parasitic relationship of the Illinois threatened plant Agalinis auriculata (Michx.) Blake (eared false-foxglove, Scrophulariaceae), an annual hemiparasitic plant, with potential host species. This study had two main objectives: 1) determine host preference (i.e., presence/absence of haustoria) and 2) determine percent seed germination and percent seedling survivorship in the presence of different potential host species. Overall, seed germination and seedling survivorship were very low. Agalinis auriculata had the highest seed germination percent and seedling survivorship, but no haustoria when paired with Sporobolus heterolepis. Haustoria development was found when A. auriculata was associated with Helianthus occidentalis, Silphium terebinthinaceum, and Solidago rigida. Flower and fruit development in A. auriculata was not only associated with these three species but also in control pots (i.e., no host plant). This suggests that A. auriculata is a facultative hemiparasitic species. Our results suggest that one group of plants may provide better germination conditions while another group may serve as hosts for A. auriculata. A second part of our study includes assessing the levels and patterns of genetic variation in A. auriculata using isozymes. Preliminary results show low levels of isozyme variation in five wild populations. We will also employ RAPD makers as a tool to detect additional genetic variation. This information will be valuable to land managers and assist them in the proper reintroduction of A. auriculata into suitable sites.

Key words: Agalinis auriculata, hemiparasite, population gentics, seed germination