Speciation and the evolution of sex pheromone blends

We have discovered a single gene mutation in the cabbage looper moth thatresults in a dramatic change in the pheromonal blend released by the female.These females are more attractive to the distantly related black cutwormmoth, than they are to their own males. After laboratory selection, maleswill respond to the abnormal pheromone phenotype. We are currently investigatingthe impact of this single gene mutation on speciation. Currently thesestudies involve a collaboration with Dr.Allen J. Moore (Entomology, Manchester, England).

Physiological control of pheromone release.

In addition to genetically based variation in the pheromone blend, we foundthat the pheromone blend emitted by cabbage looper shows periodical changesover the course of the day/night cycle. A male moth responding early inthe female's calling period will be faced with a substantially differentpheromone blend than a male that responds later in this period. Our studyindicates that pheromone biosynthesis is continuous, but transport of pheromoneto the gland's surface only occurs during the period of time when femaleswould normally call. This latter finding has not been documented beforefor any species. Recent results suggest that this mobilization of pheromonereserves may be controlled by the same brain factor that controls pheromonebiosynthesis in other species.

Sensory and behavioral responses.

The sensory and behavioral responses of the cabbage looper male moth topheromones appear to be well protected from background chemical "noise"that may originate from other species that share pheromone components.One potent behavioral antagonist of the response of males to their ownpheromone is (Z)-7-dodecenol. This compound, which is a pheromone componentof other species, if released from the same source as the pheromone blend,shuts down the attraction of males in the wind tunnel and field. However,if there is spatial separation (e.g. 5 cm) between the pheromone sourceand the source of the behavioral antagonist, then the behavioral responseoccurs normally. This pattern suggests that individual uncontaminated filamentsof pheromone can maintain normal upwind progress, thus the signal is protectedfrom background noise. Rapid sensory adaptation and central nervous systemhabituation may protect the signal from background noise.

Origins of chemical communication

The female southern masked chafer (a scarabaeid beetle) releases a sexpheromone that attracts conspecific males. The presence of the same chemicals in the larval stage of this insect suggests that pheromone signals mayhave originated from larval odors. This work currently involves a collaborationwith Dr. Daniel A. Potter (Entomology, U.K.), Dr. Jerold Meinwald (Chemistry,Cornell), Dr. Athula Attygalle (Chemistry, Cornell), and Dr. Walter Leal(Japan).

Exploitation of chemical communication by a spider predator

Bolasspiders attract their prey by mimicking the sex pheromone releasedby a small number of species of lepidopterous prey. We have worked towardsthe identification of the pheromones involved in the communication systemsof the moths. Recently, we have begun to test the hypothesis that the spiderreleases the same compounds. This work has involved a collaboration withDr. Kenneth V. Yeargan (Entomology, U.K.).