How does female-specific selection affect male fertility?

Understanding how male and female fitness evolve requires an
understanding of how they are linked. Males and females share
most of their genome, so selection on one sex is likely to have
consequences for the other. If selection acts upon sexually
dimorphic traits with a shared developmental/genetic basis (e.g.
gonadal function), these consequences may be substantial both
at the genotypic and phenotypic level (Rogers et al. 2020).
In birds, selection for egg production induces large changes to
the oviduct. Male and female gonads differentiate from the
same tissue, so correlated responses in the testes are likely.
Pick et al. (2017) recently demonstrated that artificial selection
for female reproductive investment affects reproductive success
in males . It is not yet known whether sex-specific selection
influences ejaculate traits (e.g. sperm function), or how this is
linked to testis morphology.