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animal personality; candidate gene; dopamine receptor; DRD4; genetic association; exploratory behaviour; gene by environment interaction; great tit Parus major; novelty seeking; replication study; wild populations
Abstract:
Polymorphisms in the dopamine receptor D4 gene (DRD4) have been related to
individual variation in novelty-seeking or exploratory behaviour in a variety of animals,
including humans. Recently, the human DRD4 orthologue was sequenced in a wild bird,
the great tit (Parus major) and a single nucleotide polymorphism in exon 3 of this gene
(SNP830) was shown to be associated with variation in exploratory behaviour of labraised
individuals originating from a single wild population. Here we test the generality
of this finding in a large sample of free-living individuals from four European great tit
populations, including the originally sampled population. We demonstrate that the
association between SNP830 genotype and exploratory behaviour also exists in freeliving
birds from the original population. However, in the other three populations we
found only limited evidence for an association: in two populations the association
appeared absent; while in one there was a nonsignificant tendency. We could not confirm
a previously demonstrated interaction with another DRD4 polymorphism, a 15 bp indel
in the promoter region (ID15). As yet unknown differences in genetic or environmental
background could explain why the same genetic polymorphism (SNP830) has a
substantial effect on exploratory behaviour in one population, explaining 4.5–5.8% of
the total variance—a large effect for a single gene influencing a complex behavioural
trait—but not in three others. The confirmation of an association between SNP830
genotype and personality-related behaviour in a wild bird population warrants further
research into potential fitness effects of the polymorphism, while also the population
differences in the strength of the association deserve further investigation. Another
important future challenge is the identification of additional loci influencing avian
personality traits in the wild.
