Male choice and costly sexual signals in moths

Event date: Thursday, May 29, 2014, at 12:00 PM
Location: UTSc: AA112

Speaker: Dr. Ally Harari, Department of Entomology, The Volcani Center, Israel

Host: Dr. Maydianne Andrade

NOTES: grad student lunch to follow

Abstract: In all moth species sperm is limited and ejaculates are costly,
thus males are expected to be choosy. My hypothesis is that males use the
female-produced sex pheromone to select females with higher reproductive
potential. The sex pheromone, a secondary sexual character, may act as an
honest signal of the quality of the individual if the trait bears a cost
and if its expression is phenotypically condition dependent. The cost of
increasing the trait should be tolerable for individuals in good condition
but not for those in a poor condition. The trait thus provides an honest
signal of quality that enables the receiver to choose higher quality
mates. Evidence for sex pheromones, which play a major role in shaping
sexual evolution, inflicting a signaling cost is scarce. I show that the
amount of the major component of the pheromone in glands of Lobesia
botrana
(Lepidoptera) females at signaling time is greater in large than
in small females, that male moths prefer larger females as mates when
responding to volatile signals, and small virgin females, but not large
ones, exposed to conspecific pheromone, produced, when mated,
significantly fewer eggs than non-exposed females. The latter indicates a
condition-dependent cost of signaling. These results are in accordance
with the predictions of condition-dependent honest signals. I therefore
suggest that females signaling for males using sex pheromones bear a cost
and thus calling may serve as honest advertisement for female quality.