Data from: The role of immigration and local adaptation on fine-scale genotypic and phenotypic population divergence in a less mobile passerine

Dispersal and local patterns of adaptation play a major role on the
ecological and evolutionary trajectory of natural populations. In this
study, we employ a combination of genetic (25 microsatellite markers) and
field-based information (seven study years) to analyse the impact of
immigration and local patterns of adaptation in two nearby (< 7 km)
blue tit (Cyanistes caeruleus) populations. We used genetic assignment
analyses to identify immigrant individuals and found that dispersal rate
is female-biased (72%). Data on lifetime reproductive success indicated
that immigrant females produced fewer local recruits than their
philopatric counterparts whereas immigrant males recruited more offspring
than those that remained in their natal location. In spite of the
considerably higher immigration rates of females, our results indicate
that, in absolute terms, their demographic and genetic impact in the
receiving populations is lower than that in immigrant males. Immigrants
often brought novel alleles into the studied populations and a high
proportion of them were transmitted to their recruits, indicating that the
genetic impact of immigrants is not ephemeral. Although only a few
kilometres apart, the two study populations were genetically
differentiated and showed strong divergence in different phenotypic and
life-history traits. An almost absent inter-population dispersal, together
with the fact that both populations receive immigrants from different
source populations, is probably the main cause of the observed pattern of
genetic differentiation. However, phenotypic differentiation (PST) for all
the studied traits greatly exceeded neutral genetic differentiation (FST),
indicating that divergent natural selection is the prevailing factor
determining the evolutionary trajectory of these populations. Our study
highlights the importance of integrating individual- and population-based
approaches to obtain a comprehensive view about the role of dispersal and
natural selection on structuring the genotypic and phenotypic
characteristics of natural populations.