PARENT SESSION
Thursday, August 10, 8:00-11:30 am
COS 75 - Invasive species V: detection and prediction
Ballroom A, Ballroom Level, Cook Convention Center
Presiders: G Ervin
Insect community composition in ecological resistance to invasiveness of bull thistle in Nebraska.
Takahashi, Masaru 1, Louda, Svata1, 1 University of Nebraska, Lincoln, Lincoln, NE
ABSTRACT- Negative ecological and economic impacts associated with plant invasions are growing concerns today. Impact exerted by indigenous herbivore assemblages on invading plants has been hypothesized as a potential mechanism for suppression of invasiveness of the exotic plant species, such as by the exotic bull thistle, Cirsium vulgare (Savi) Tenore in western tallgrass prairies of eastern Nebraska. Some evidence suggests that the thistle-feeding, local insect community from the native tall thistle, Cirsium altissimum (L.) Spreng also feeds on the non-native bull thistle, potentially providing biological resistance to the invasiveness of bull thistle. However, the identity of insect species and the guild structure of herbivores on bull thistle remains imprecisely known. Consequently, we examined: 1) species accumulation curves and species richness as well as 2) composition and abundance of thistle specialists vs. generalist insect herbivores on the native tall thistle and the exotic bull thistle. In two years of intensive observations, we found species accumulated on bull thistle occurred as rapidly as on tall thistle over each season. The floral guild formed a large proportion of the entire insect community on both thistle species. Abundance of leaf feeding guilds, mainly composed of more generalized herbivores, such as grasshoppers, tended to be higher on the exotic bull thistle. Both thistle species shared the most of the numerically abundant and thistle-related insects, yet relative proportions of each guild varied through each season. These results contribute to our understanding of inherent ecosystem resistance to invasion, and the dynamic interactions between indigenous insect communities and native vs. related non-native plants.
Key words: Biotic resistance, Insect guild structure, Tall grass prairie