Constraints on evolution and postcopulatory sexual selection: trade-offs among ejaculate characteristics

Area of Science:

• Evolutionary biology
• Quantitative genetics
• Reproductive biology

Background:

• Ejaculates function as integrated units crucial for male fertility and paternity.
• Studies often focus on sperm traits and testes size in male-male competition.
• Understanding genetic variation and covariation is key to ejaculate evolution.

Purpose of the Study:

• Investigate the quantitative genetics of ejaculate components in the cockroach *Nauphoeta cinerea*.
• Examine genetic variation and covariation to infer evolutionary constraints on ejaculate structure and function.
• Assess the functional integration of ejaculate characters under sexual selection.

Main Methods:

• Quantitative genetic study of *Nauphoeta cinerea* ejaculate components.
• Analysis of additive genetic variance and evolvability of ejaculate traits.
• Examination of phenotypic and genetic correlations among ejaculate characters.

Main Results:

• Ejaculate components exhibited high variability, significant additive genetic variance, and moderate to high evolvability.
• Despite strong selection, substantial genetic variation persists, possibly due to integrated selection episodes.
• Few significant phenotypic correlations were found, but all genetic correlations were significant, indicating trade-offs.

Conclusions:

• Genetic covariation among ejaculate traits suggests significant trade-offs, constraining unhindered evolution.
• Functional integration of ejaculate components shapes its evolutionary trajectory.
• Understanding genetic relationships is vital for comprehending ejaculate evolution and functional integration.