Pheromone diversification and age-dependent behavioural plasticity decrease interspecific mating costs in Nasonia

Area of Science:

• Evolutionary Biology
• Behavioral Ecology
• Chemical Ecology

Background:

• Interspecific mating between closely related species can lead to significant fitness costs due to hybrid inviability or reduced fitness.
• Theory predicts selection for traits that minimize reproductive interactions between sympatric species.
• The parasitic wasp Nasonia vitripennis possesses a unique sex pheromone component compared to other Nasonia species, but the evolutionary drivers are unclear.

Purpose of the Study:

• To investigate the role of costly interspecific sexual interactions with Nasonia giraulti in the evolution of sex pheromones and courtship behaviors in Nasonia vitripennis.
• To understand the selective pressures driving pheromone diversification in Nasonia species.

Main Methods:

• Laboratory experiments were conducted to assess mating behaviors and preferences.
• Microcosm experiments were used to evaluate fitness costs under simulated natural conditions.
• Analysis of pheromone composition and courtship interactions between Nasonia vitripennis and Nasonia giraulti.

Main Results:

• Nasonia giraulti males invest in costly sex pheromones and do not discriminate between N. vitripennis and conspecific females during courtship.
• N. vitripennis females face risks of producing all-male broods due to Wolbachia-induced cytoplasmic incompatibility when mating with N. giraulti.
• Young N. vitripennis females actively reject N. giraulti males using their more complex conspecific sex pheromone, but older females are less discriminating.

Conclusions:

• Costly interspecific sexual interactions and communication interference between Nasonia vitripennis and Nasonia giraulti likely drove the evolution of N. vitripennis's complex sex pheromone and courtship adaptations.
• These adaptations facilitate reproductive isolation and divergence between the closely related sympatric species.
• Despite counter-adaptations, some fitness costs associated with heterospecific mating may persist under natural conditions.