Male choice and costly sexual signals in moths

Event Details

May 29, 2014
12:00 pm
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.