Local mate competition, variable fecundity and information use in a parasitoid

Area of Science:

• Behavioral ecology
• Evolutionary biology
• Insect behavior

Background:

• Sex allocation theory predicts female-biased sex ratios in patchily distributed populations.
• Individual females may adjust their offspring sex ratio based on clutch size and knowledge of competitors.

Purpose of the Study:

• To test theoretical models of sex allocation in parasitic wasps (Nasonia vitripennis).
• To investigate how females use information about their own and other females' clutch sizes to adjust offspring sex ratios.

Main Methods:

• Simultaneous oviposition experiments with two Nasonia vitripennis females on a patch.
• Analysis of offspring sex ratio in relation to female's clutch size and the body size of the competitor female.

Main Results:

• Offspring sex ratio was negatively correlated with a female's own clutch size.
• Offspring sex ratio was positively correlated with the body size of the competitor female.
• Larger females laid more offspring, suggesting females assess competitor's clutch size via body size.

Conclusions:

• Nasonia vitripennis females adjust sex allocation based on perceived total clutch size on a patch.
• Females appear to possess 'complete knowledge' of competitors' clutch sizes, using body size as an indicator.
• This behavior supports theoretical models where females adjust sex ratios based on relative contribution to the patch's offspring.