Meeting Abstract

P1.24  Friday, Jan. 4  Plant Competition in a Greek Island Ecosystem: A Perturbation Experiment BARTHELL, J. F.*; HRANITZ, J. M.; REDD, J. R.; BREWSTER, T. N.; CHICAS-MOSIER, A. M.; DINGES, C. W.; HAYES, C. A.; RIVERA-VEGA, K. M.; WILLIAMS, M. I.; PETANIDOU, T.; WELLS, H.; University of Central Oklahoma; Bloomsburg University of Pennsylvania ; University of Central Oklahoma; Clarkson University; Oklahoma State University; Oklahoma State University; Bowdoin College; Fordham University; College of New Jersey; University of the Aegean; University of Tulsa jbarthell@uco.edu

Flowering plants use nectar and other rewards to compete for pollinators. It is known, for example, that the ability to consistently attract large-bodied and strong-flying bees can be mediated by nectar standing crop levels within and between species. Yellow star-thistle, Centaurea solstitialis, is an effective competitor for pollinators in the western USA where it has realized an extensive range expansion during the last century. However, in its native range, C. solstitialis occurs in relatively low densities and fails on average to attract large-bodied bee species like honey bees. Using a perturbation experiment to explore this phenomenon, visitation rates by flying Hymenoptera (bees, wasps, etc.) were observed in plots of C. solstitialis within an island ecosystem on Lesvos, Greece, after introducing flowers of the sympatric competitor, Vitex agnus-castus. The results indicate that even a short-term introduction of the competing V. agnus-castus (with its relatively high standing crop nectar volumes) can disrupt visitation patterns within pollinator guilds of C. solstitialis. Although mediated by densities of C. solstitialis in the study plots, this effect suggests that the range expansion of newly introduced flowering plant species, especially those requiring outcrossing, may be directly related to the competitive landscape these species encounter upon arriving in new environments.