Field distribution and effects of Bt-expressing corn anthers on survival, development, and behavior of the monarch butterfly, Danaus plexippus (L)

dc.contributor.advisor Richard L. Hellmich
dc.contributor.advisor Leslie C. Lewis Anderson, Patricia
dc.contributor.department Entomology 2018-08-24T19:28:11.000 2020-06-30T07:12:46Z 2020-06-30T07:12:46Z Thu Jan 01 00:00:00 UTC 2004 2004-01-01
dc.description.abstract <p>Previous studies suggest that exposure to anthers from corn, Zea mays L., expressing Bacillus thuringiensis (Bt)-derived protein may have adverse effects on larvae of the monarch butterfly, Danaus plexippus (L.). The objectives of this research were to: (1) measure the effects of short-term and long-term exposure to anthers in the laboratory, (2) examine anther distribution in space and time, (3) measure the effects of long-term exposure to anthers in the field, (4) examine how exposure to Bt anthers and pollen affects larval fitness and behavior, and (5) investigate how larvae were affected by Bt anthers without detectable ingestion of Bt anther tissue. Laboratory studies revealed that monarch butterfly larvae will feed on anthers on milkweed leaves and showed that Bt anthers are a potential hazard to monarch butterflies. However, toxic anther densities are rare on milkweeds in and near corn fields. Field-cage studies detected no adverse effects on development or survival after larvae were exposed to five Bt anthers per leaf for 11 days. Based on a low probability of exposure to toxic densities, Bt anthers alone are not likely to pose a significant risk to monarch butterflies in Iowa. Data from petri dish and cage studies supported the hypothesis that exposure to Bt anthers and pollen have additive effects on larvae and a possible behavior mechanism for additive effects was revealed. A video-tracking system was used to investigate effects seen on larval feeding and weight after 4 days of exposure to Bt with little detectable anther-tissue feeding. A possible hypothesis to explain these effects is that exposure to Bt anthers results in increased searching behavior which in turn results in less feeding and reduced weight. Larvae did not exhibit increased searching behavior when exposed to Bt anthers, but they did exhibit some degree of avoiDance; Although the behavioral changes seen in this study are not likely to occur in the field because the anther density tested is rare and natural feeding behaviors already mitigate exposure to Bt anthers, this study shows that direct toxicity is not the only means by which a toxin like Bt can affect non-target insects.</p>
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dc.identifier archive/
dc.identifier.articleid 2141
dc.identifier.contextkey 6090576
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath rtd/1142
dc.language.iso en
dc.source.bitstream archive/|||Fri Jan 14 18:49:56 UTC 2022
dc.subject.disciplines Entomology
dc.subject.keywords Entomology
dc.title Field distribution and effects of Bt-expressing corn anthers on survival, development, and behavior of the monarch butterfly, Danaus plexippus (L)
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication f47c8cad-50be-4fb0-8870-902ff536748c dissertation Doctor of Philosophy
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