PARENT SESSION
Poster Session #32: Plant-Animal Interactions I.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
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Keeping your mutualists at bay: do extrinsic factors balance the yucca-yucca moth mutualism?
Segraves, Kari*,1, 1 Vanderbilt University, Nashville, TN
ABSTRACT- Mutualistic interactions form an integral part of many communities, and may be the most important interactions involved in maintaining and promoting biodiversity. The inherent conflict of interest between mutualists suggests that partners should defect whenever possible. As a result, defensive mechanisms may evolve to prevent exploitation by both partners. Evolved defenses intrinsic to the interaction may be unnecessary, however, when particular ecological conditions serve to maintain stability in a mutualism. The yucca-yucca moth interaction is one of the classic examples of mutualism and provides the opportunity to examine the relative contributions of intrinsic and extrinsic mechanisms in the maintenance of mutualisms. I examined the interaction between the pollinating yucca moth Tegeticula cassandra and its host plant Yucca filamentosa to determine whether extrinsic factors are important in promoting stability in this mutualism. Yuccas can selectively abscise fruit with high moth egg loads for moth species that damage ovules during oviposition. Tegeticula cassandra, however, oviposits superficially so that plants are unable to regulate egg loads. Despite this, only 10% of T. cassandra eggs survive to exit the fruit as mature larvae. I tested the hypothesis that T. cassandra survivorship is regulated by an abiotic factor: exposure to dehydration. Moth eggs in flowers with experimentally increased relative humidity and lowered temperatures had significantly greater survivorship whereas survivorship was unaffected in a closely related locule-ovipositing moth species. The results suggest that the factors regulating the stability of mutualisms can depend at least in part on environmental conditions.
KEY WORDS: yucca-yucca moth interaction, mutualism, coevolution, exploitation