Experimental evidence for interspecific directional selection on moth pheromone communication

Area of Science:

• Evolutionary Biology
• Chemical Ecology
• Animal Behavior

Background:

• Moth pheromone blends are typically under stabilizing selection, limiting diversity.
• Intraspecific selection cannot fully explain the wide variety of pheromone signals observed in nature.

Purpose of the Study:

• To investigate if interspecific communication interference can drive the evolution of moth pheromone signals.
• To determine the role of directional selection from closely related species in pheromone evolution.

Main Methods:

• Field experiments comparing mating success of Heliothis subflexa (Hs) females with normal (norm-OAc) versus reduced (low-OAc) acetate pheromone production.
• Mate-choice assays in controlled cage environments.
• Quantitative estimation of interspecific selection pressures based on field data and existing reproductive biology data.

Main Results:

• Males of a closely related species (Heliothis virescens - Hv) were 10 times more attracted to low-OAc Hs females than norm-OAc Hs females.
• Interspecific mating resulted in hybrids with near-zero fitness in the field.
• Estimated directional selection pressure from Hv males on Hs females to produce high acetate levels ( >5%) ranged from 0.135 to 0.231.

Conclusions:

• Intense interspecific selection can counteract stabilizing selection, driving the evolution of moth pheromone blends.
• Communication interference from related species is a significant factor promoting sexual signal diversification in moths.