Abundance of and Floral Herbivory on Exotic Bull Thistle versus Native Tall Thistle in Western Tallgrass Prairie

摘要: An important, yet poorly quantified mechanism to explain the failure of some exotic species increase and spread is that indigenous natural enemies provide ecosystem resistance invasiveness. To evaluate this idea, we hypothesized spillover native thistle-feeding floral insect herbivores onto Eurasian bull thistle (Cirsium vulgare) from prairie tall (C. altissimum) helps limit population growth throughout western tallgrass region in Nebraska. test hypothesis, both occurrence thistle, a known invasive worldwide, herbivory on it by relation across region. We plant recording presence/absence each 1600 m x 30 (0.1 mile ~100 ft) quadrats along four radiating 16 km (10 mile) transects at nine sites stratified three longitudes latitudes span range eastern For flowering plants, recorded distance nearest with size, reproductive effort, damage for thistles. Bull occurred 20%. Although varied significantly among sites, no strong patterns longitude or latitude either thistle. These results suggest are not controlled geographic variation large-scale physical climatic variables. Floral was high, tendency be lower north. The proportion flower heads damaged as sometimes higher, (68 – 83%) (64 78%). Herbivory increased proximity adult study support hypothesis important limiting abundance potentially Proceedings North American Prairie Conference 20:33-50