Pedigree and phenotypic variables used for estimation of heritability of sand lizard badge size and condition

Sexual selection on fitness-determining traits should theoretically erode
genetic variance and lead to low heritability. However, many sexually
selected traits maintain significant phenotypic and additive genetic
variance, with explanations for this “lek paradox” including genic capture
due to condition-dependence, and breaks on directional selection due to
environmental sources of variance including maternal effects. Here we
investigate genetic and environmental sources of variance in the
intrasexually selected green badge of the sand lizard (Lacerta agilis).
The badge functions as a cue to male fighting ability in this species, and
male-male interactions determine mate acquisition. Using animal models on
a pedigree including three generations of males measured over an extensive
nine year field study, we partition phenotypic variance in both badge size
and body condition into additive genetic, maternal, and permanent
environmental effects experienced by an individual over its lifespan.
Heritability of badge size was 0.33 with a significant estimate of
underlying additive genetic variance. Body condition was strongly
environmentally determined in this species and does not show either
significant additive genetic variance or heritability. Neither badge size
nor body condition were responsive to maternal effects. We propose that
the lack of additive genetic variance and heritability of body condition
makes it unlikely that genic capture mechanisms maintains additive genetic
variance for badge size. That said, genic capture was originally proposed
for male traits under female choice, not agonistic selection. If
developmental pathways generating variance in body condition, and/or the
covarying secondary sex trait, differ between inter- and intrasexual
selection, or the rate at which their additive genetic variance or
covariance is depleted, future work may show whether genic capture is
largely restricted to intersexual selection processes.