The roles of nicotine and natural enemies in determining larval feeding site distributions of Manduca sexta L. and Manduca quinquemaculata (Haworth) on tobacco |
| |
Authors: | Karen M Kester Steven C Peterson Frank Hanson D Michael Jackson R F Severson |
| |
Institution: | (1) Department of Biology, Virginia Commonwealth University, 1000 W. Cary St., Richmond, VA 23284-2012, USA, US;(2) Department of Biological Sciences, University of Maryland, Baltimore, Maryland 21228, USA, US;(3) USDA-ARS, U.S. Vegetable Laboratory, 2875 Savannah Hwy, Charleston, SC 29414, USA, US;(4) USDA-ARS, Tobacco Safety Research Unit, Athens, Georgia 30604, USA, US |
| |
Abstract: | Summary. Field observations indicated that hornworms select feeding sites non-randomly on tobacco. We tested the hypotheses that differences
in feeding site locations of larvae of Manduca
sexta L. and Manduca
quinquemaculata (Haworth) (Lepidoptera: Sphingidae) on tobacco could be explained by differential nicotine concentrations within plants and
leaves, species-specific responses to nicotine, or pressure exerted by natural enemies. Results showed that third-instar larvae
of M. sexta fed more proximally and centrally on the leaf, whereas M. quinquemaculata fed more distally. Within-plant selection of leaves did not differ; both species selected leaves in the middle region of
the plant. Nicotine concentrations in a high nicotine genotype, NC95, varied within each leaf, increasing 2—3 fold from the
basal to apical portion of the leaf, and within each plant, increasing 7—10 fold from the first fully expanded leaf to the
twelfth (lowest) leaf. In laboratory bioassays, both Manduca species responded to nicotine as a feeding deterrent. Electrophysiological studies demonstrated that gustatory organs of
both species responded to nicotine at concentrations found in tobacco leaves and that M. quinquemaculata generally showed a less vigorous response to nicotine than M. sexta. Field mortality of M. sexta due to parasitism by Cotesia
congregata (Say) and to parasitism and predation combined differed among feeding sites; predation alone did not. Results suggest that
although nicotine concentration and species specific responses to nicotine play a role in determining feeding site locations,
pressure exerted by natural enemies, especially parasitism by C. congregata, is more important.
Received 22 February 2000; accepted 20 July 2001. |
| |
Keywords: | , Feeding behavior —, tritrophic interactions —, chemoreception —, electrophysiology —, nicotine —, tobacco —, Lepidoptera:,,,,,Sphingidae —,Manduca—,Manduca sexta—,Cotesia congregata |
本文献已被 SpringerLink 等数据库收录! |
|