PARENT SESSION
Oral Session #72: Herbivory: Herbivore Response to Plants.
Presiding: C. Mitchell
Wednesday, August 7. 1:00 PM to 4:45 PM. Mesquite Room, Radisson.
Fecundity of a specialist herbivore on its native and exotic host plants.
Marko, Michelle*,1, Krueger, Julie1,2, Newman, Raymond1, 1 Department of Fisheries, Wildlife and Conservation Biology, St. Paul, MN2 Department of Biology, Williamsburg, VA
ABSTRACT- The native milfoil weevil Euhrychiopsis lecontei (Curculionidae) is a submersed specialist on watermilfoils. Its native host plant, Northern watermilfoil, Myriophyllum sibiricum (Haloragaceae) has been displaced in many waterways by the exotic, Eurasian watermilfoil, Myriophyllum spicatum. The weevil has expanded its host range to the chemically and morphologically similar Eurasian watermilfoil. In fact, the weevil preferred the exotic to its native host plant in both host attraction and oviposition studies. In this experiment, we measured the cumulative (two-week) fecundity of the weevil in both no-choice and choice oviposition experiments. Exotic-reared weevils had significantly higher fecundity on the exotic host plant than on the native host plant (repeated measures ANCOVA, F=1.89, p=0.0004). The number of eggs oviposited was greatest for exotic-reared weevils on the exotic plant (mean ± SE; 4.6 ± 0.27 eggs/female/day) and least for native-reared weevils on the native host plant (2.2 ± 0.23). In choice tests, both weevil types preferred to oviposit on the exotic rather than the native host plant (chi-square, p<0.0001). Previous one-day oviposition studies have shown that native-reared weevils have no preference between the exotic and native plants. By extending this study over a two-week period we have shown that there is in fact a strong preference by native-reared weevils for the exotic host plant. Despite the greater fecundity and preference for the exotic plant, a complete shift is unlikely due to the continued oviposition by nearly all weevils on both host plants.
KEY WORDS: fecundity, host preference, Euhrychiopsis lecontei, Myriophyllum sibiricum