Exploring the genetics of nestling personality traits in a wild passerine bird: testing the phenotypic gambit

When several personality traits covary, they form a behavioral syndrome.
Understanding the evolutionary dynamics of a behavioral syndrome requires
knowledge of its genetic underpinning. At present, our understanding of the
genetic basis of behavioral syndromes is largely restricted to domestic and laboratory
animals. Wild behavioral syndromes are mostly inferred on the basis of
phenotypic correlations, and thus make the “phenotypic gambit” of assuming
that these phenotypic correlations capture the underlying genetic correlations.
On the basis of 3 years of reciprocal cross-fostering of 2896 nestlings of 271
families within a pedigreed population, we show that the nestling personality
traits handling aggression, breathing rate, and docility are heritable (h2 = 16–29%),
and often have a pronounced “nest-of-rearing” variance component (10–15%),
but a relatively small “nest-of-origin” variance component (0–7%). The three
nestling personality traits form a behavioral syndrome on the phenotypic and
genetic level. Overall, the phenotypic correlations provide a satisfactory description
of the genetic ones, but significantly underestimate the magnitude of one
of the pairwise genetic correlations, which mirrors the conclusion based on
domestic and laboratory studies.