Within-population variability in a moth sex pheromone blend, part 2: selection towards fixation

Area of Science:

• Evolutionary genetics
• Animal behavior
• Chemical ecology

Background:

• Sexual communication systems are crucial for mate recognition in many animals.
• Coevolution of signals and preferences is challenging when genes controlling them assort independently, as seen in moths.
• Previous work suggested a complex genetic model for pheromone variation in *Heliothis virescens*.

Purpose of the Study:

• To identify the genetic basis of variation in female sex pheromone signals in the moth *Heliothis virescens*.
• To investigate the evolutionary implications of signal and response genetic control.

Main Methods:

• Selection experiments on moth populations to isolate extreme phenotypes.
• Genetic mapping and sequencing to identify causative mutations.
• Analysis of mutation effects on male response, growth, and fertility.

Main Results:

• A single point mutation, a premature stop codon in the delta-11-desaturase gene, was identified as the cause of phenotypic variation.
• This mutation was traced to its laboratory origin.
• The identified mutation had no discernible pleiotropic effects on male response, growth, or fertility.

Conclusions:

• A single point mutation can underlie significant phenotypic variation in moth sex pheromones.
• This finding supports independent genetic control of signals and responses in Lepidoptera, contrasting with other insects like *Drosophila melanogaster*.
• This study provides the first identification of a single mutation responsible for pheromone signal variation in moths.