PARENT SESSION
Oral Session #78: Insect Population and Community Ecology. Presiding: R. Denno.
Friday, August 10, 2001. 8:00 AM to 11:45 AM. Hall of Ideas I.

Effects of vegetation structure on ground beetle diversity and species occurrence on tallgrass prairie.

Cook, William¹, Holt, Robert¹, ¹

ABSTRACT- Vegetation structure is an important variable that affects the occurrence of animal species within tallgrass prairie. Previous work from our study of carabid beetle communities at the Konza Prairie LTER has shown striking contrasts between prairie tracts under different fire regimes, indicating that fire frequency and associated microhabitat changes can affect occurrence of individual beetle species. We predicted that some species found rarely on open prairie would be common in restricted habitats such as gallery forests and shrub islands, and that communities in these habitats would be distinct. Pitfall sampling in 2000 from gallery forests, large and small shrubby islands, and nearby prairie gleaned 859 beetles of 21 morphospecies. While fewer carabids were trapped in gallery forests than in other microhabitats, forests had the highest species richness, diversity, and evenness, and the most unique species. Most common species in these samples were among the common species collected in previous years on open prairie, though several were found in higher densities in areas of structure. Differences in composition among habitats was dependent on the occurrence of uncommon species, but our results give support to the idea that gallery forests maintain species not found in the general prairie habitat. However, species spillover appears to occur from the prairie into the gallery forest rather than the reverse, and the occurrence of rare species found in open prairie samples was not explained.

KEY WORDS: tallgrass prairie, community ecology, vegetation structure, Carabidae