Female genital mutilation and monandry in an orb-web spider

Area of Science:

• Evolutionary biology
• Animal behavior
• Arachnology

Background:

• Monandry, or a single mating partner, is contrasted with ubiquitous polyandry in many species.
• Sexual conflict arises when males attempt to monopolize mating opportunities, and females evolve countermeasures.
• Previous research suggests male interference can lead to monandry, but female counter-strategies are common.

Purpose of the Study:

• To investigate the mechanism behind monandry in the orb-web spider Cyclosa argenteoalba.
• To determine if female genital injury plays a role in limiting mating frequency.
• To assess the evolutionary implications of female genital mutilation (FGM) in spiders.

Main Methods:

• Observation of mating behavior in female Cyclosa argenteoalba.
• Examination of female genitalia post-mating to identify injuries.
• Analysis of the functional consequences of genital injury on subsequent mating attempts.

Main Results:

• The genital appendage (scape) of female Cyclosa argenteoalba is injured after the first mating.
• This injury, termed female genital mutilation (FGM), permanently prevents further copulation.
• Females appear to lack countermeasures against this male-induced injury.

Conclusions:

• Female genital mutilation (FGM) in Cyclosa argenteoalba confers a significant advantage to males in sexual conflict.
• This mechanism may explain the prevalence of monandry in spiders and potentially other taxa.
• FGM represents a novel evolutionary strategy in the context of mating system evolution.