Résumé
The genetic variance–covariance matrix (G-matrix) summarizes the genetic
architecture of multiple traits. It has a central role in the
understanding of phenotypic divergence and the quantification of the
evolutionary potential of populations. Laboratory experiments have shown
that G-matrices can vary rapidly under divergent selective pressures.
However, because of the demanding nature of G-matrix estimation and
comparison in wild populations, the extent of its spatial variability
remains largely unknown. In this study, we investigate spatial variation
in G-matrices for morphological and life-history traits using long-term
data sets from one continental and three island populations of blue tit
(Cyanistes caeruleus) that have experienced contrasting population history
and selective environment. We found no evidence for differences in
G-matrices among populations. Interestingly, the phenotypic
variance–covariance matrices (P) were divergent across populations,
suggesting that using P as a substitute for G may be inadequate. These
analyses also provide the first evidence in wild populations for additive
genetic variation in the incubation period (that is, the period between
last egg laid and hatching) in all four populations. Altogether, our
results suggest that G-matrices may be stable across populations
inhabiting contrasted environments, therefore challenging the results of
previous simulation studies and laboratory experiments.