PARENT SESSION
Oral Session #71: Animal Population Ecology. Presiding: J. Dooley.
Thursday, August 9, 2001. 1:00 PM to 4:15 PM. Hall of Ideas J.
Evidence of rapid evolution in the biological control weevil, Rhinocyllus conicus?
Arnett, Amy1, Louda, Svata2, 1 2
ABSTRACT- In this study we investigated the recent host range expansion of the biological control weevil, Rhinocyllus conicus, from Musk thistle (Carduus spp.) onto native Platte thistle (Cirsium spp.). The question addressed is: Is there evidence that R. conicus is in the process of adapting to a new, native host plant. In 1999, we conducted a combined laboratory/ reciprocal-transplant experiment to test for a relationship between oviposition preference and offspring performance of weevils on the two potential hosts. In the laboratory, mated pairs of weevils taken from either Platte or Musk thistle populations were placed in a cage to allow females to choose between hosts for oviposition. These same weevils were transferred into the field and allowed to oviposit on both hosts. Egg number and larval weight were quantified for each female. Our results show that female weevils collected from Platte preferred to lay their eggs on Platte, relative to weevils from Musk (F1,58 = 4.25; p = 0.04). Weevils from Platte laid more eggs than weevils from Musk overall (F1,34 = 4.99; p = 0.03). There was no difference in larval weights among weevils raised on the different hosts. These results suggest that R. conicus may be adapting to its new host. Because few studies follow biocontrol agents after release these findings have important implications for the assessment of environmental risks associated with introducing exotic organisms for biological control.
KEY WORDS: host range expansion, biological control, rapid evolution, Rhinocyllus conicus