PARENT SESSION
Poster Session #4: Herbivory.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Grubs, grass and shrubs: a clearer view of selective root herbivory.

Brumbaugh, Shawn^*,1, Jackson, Robert², Fowler, Norma¹, ¹ The University of Texas at Austin, Austin, TX² Duke University, Durham, NC

ABSTRACT- In semi-arid grasslands, such as those in central Texas, selective grazing by ungulates and insects has been shown to regulate community composition and often contributes to the invasion of woody plants and exotic species. However, relatively little is known about selective root herbivory and its ability to structure plant communities. We investigated the feeding preference of June beetle larvae (Phyllophaga crinita) in a two-choice feeding experiment pairing little bluestem (Schizachyrium scoparium), a dominant native grass, with either mesquite (Prosopis glandulosa) or juniper (Juniperus ashei) seedlings, both native invasive woody species, or with King Ranch bluestem (Bothriochloa ischaemum), a co-dominant exotic grass. In a greenhouse, we grew plants separately in thin (.32-cm thick) plexiglass pots (30-cm x 30-cm). After four weeks we combined each pot of little bluestem with a pot of one of the comparison plants; a single beetle larva was then placed equidistantly from the two plants. We mapped larval location daily for nine weeks. In little bluestem-juniper pairings, larvae spent significantly more time (>70%) feeding on little bluestem, whereas larvae showed no preference in the pairings with mesquite or King Ranch bluestem. Furthermore, little bluestem had significantly lower (>65%) final dry biomass when paired with juniper than with mesquite or King Ranch bluestem. These results indicate the presence of selective root herbivory that may have important consequences for community structure.

KEY WORDS: root herbivory, feeding preference, grasslands, shrub invasion