Multivariate intralocus sexual conflict in seed beetles

Area of Science:

• Evolutionary biology
• Sexual conflict research
• Quantitative genetics

Background:

• Intralocus sexual conflict (IaSC) arises from differing male and female selection pressures on shared genes.
• Multivariate IaSC, particularly concerning integrated life-history traits, remains underexplored.
• Previous work demonstrated opposing fitness effects in males and females under artificial selection on male lifespan.

Purpose of the Study:

• To investigate the sex-specific evolutionary responses of four integrated traits (metabolic rate, locomotor activity, body mass, lifespan) to artificial selection.
• To determine if genetic integration of these traits underlies multivariate IaSC.
• To examine the consequences of correlated evolution for sexual dimorphism and fitness.

Main Methods:

• Utilized established artificial selection lines in the seed beetle Callosobruchus maculatus.
• Applied male-limited artificial selection for increased and decreased lifespan.
• Measured correlated evolutionary changes in metabolic rate, locomotor activity, body mass, and lifespan in both sexes.

Main Results:

• Selection for short male lifespan caused females to evolve a more male-like multivariate phenotype.
• Selection for long male lifespan resulted in males evolving a more female-like multivariate phenotype.
• Lifespan, metabolism, and body mass showed correlated evolution between sexes, but locomotor activity evolved only in females, leading to monomorphism and negative fitness effects in short-life lines.

Conclusions:

• Genetic integration of life-history traits facilitates intralocus sexual conflict.
• Widespread pleiotropy can generate IaSC, even with sex-specific genetic architectures.
• Correlated evolution can lead to unexpected outcomes, such as sexual monomorphism and fitness costs in one sex.