Résumé
Understanding the causes and consequences of population phenotypic
divergence is a central goal in ecology and evolution. Phenotypic
divergence among populations can result from genetic divergence,
phenotypic plasticity or a combination of the two. However, few studies
have deciphered these mechanisms for populations geographically close and
connected by gene flow, especially in the case of personality traits. In
this study, we used a common garden experiment to explore the genetic
basis of the phenotypic divergence observed between two blue tit
(Cyanistes caeruleus) populations inhabiting contrasting habitats
separated by 25 km, for two personality traits (exploration speed and
handling aggression), one physiological trait (heart rate during
restraint) and two morphological traits (tarsus length and body mass).
Blue tit nestlings were removed from their population and raised in a
common garden for up to five years. We then compared adult phenotypes
between the two populations, as well as trait-specific Qst and Fst . Our
results revealed differences between populations similar to those found in
the wild, suggesting a genetic divergence for all traits. Qst - Fst
comparisons revealed that the traits divergences likely result from
dissimilar selection patterns rather than from genetic drift. Our study is
one of the first to report a Qst - Fst comparison for personality traits
and adds to the growing body of evidence that population genetic
divergence is possible at a small scale for a variety of traits including
behavioural traits.