PARENT SESSION
Contributed Oral Session 168: Invertebrate Ecology: Food Webs, Physiology, and Communities
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 524 B, Level 5, Palais des congrès de Montréal

Interaction across three trophic levels: Cynomys ludovicianus colonies increase floral resources and insect visitation on the shortgrass steppe.

Hardwicke, Kelly^{*,1, 2}, Detling, James^{1, 2}, ¹ Colorado State University, Fort Collins, CO² Shortgrass Steppe LTER Program, Fort Collins, CO

ABSTRACT- Black-tailed prairie dogs (Cynomys ludovicianus) change vegetation structure and composition on the mixed grass prairie and shortgrass steppe, with active colonies showing higher herbaceous dicot coverage, reduced canopy height, and an increase in bare ground. Extensive C. ludovicianus colonies create large landscape patches within the prairie matrix, to which pollinating insects should react favorably if floral resources increase with herbaceous dicot abundance. In early summer 2003, and again throughout the entire growing season in 2004, floral resources were measured on a total of 6 colony sites on the SGS-LTER in Northeastern Colorado. Diurnal insect floral visitation was also measured at these sites. 2003 and 2004 differed extensively in terms of weather and temperature patterns, and the most commonly utilized floral resources, as well as the most common insect taxa, differed between years. However, total abundance of inflorescences from all zoophilic species was higher on colony sites in both years, and total frequency of insect visitation also was higher on colony sites in both years. The functional, high-level diversity of the community of diurnal insect floral visitors tracks the species diversity of the floral resources present in a given year and area. Trophic web structure also appears to differ between these two community types. Pollinating insects utilize colonies as an attractive and resource-rich alternate foraging habitat. These findings show a clear link between three trophic levels, with conservation and possible management implications for optimizing suitable habitat for a thriving native pollinator community and the host plants they service on the shortgrass steppe.

Key words: community-wide floral resources, zoophilic plants, trophic webs, Cynomys ludovicianus