Historical recombination maps diverge between Eurasian blackcap
populations with distinct migratory strategies
Abstract
Recombination generates new combination of alleles, whereby it maintains
haplotype diversity and enhances the efficacy of selection. Despite the
apparent stasis in positioning recombination events in birds,
recombination rates differ widely across the genome and within species.
The causes of recombination rate variation and its evolutionary impact
on natural populations remain poorly understood. We used whole-genome
resequencing data of 167 individuals of the Eurasian blackcap (Sylvia
atricapilla) to characterise the historical recombination landscape
variation at broad and fine scales among populations with distinct
migratory phenotypes. We additionally evaluated the interplay between
recombination rates with patterns of genetic diversity, population
divergence (based on Fst and dxy), and potential signs of selection. Our
comparative analyses revealed: i) Lower divergence of recombination maps
at the broad scale and higher variability at fine scales. Resident
island populations showed higher variability in recombination patterns
among them and with continental populations. Recombination rates were
more conserved in continental populations regardless of the migratory
phenotype. ii) The degree of divergence between recombination maps
correlated with population differentiation. It could also recapitulate
population-specific demographic history and genetic structure. iii)
Recombination rates correlated negatively with Fst and positively with
nucleotide diversity and dxy, suggesting that recombination may reduce
the effect of linked selection over the loss of neutral diversity. We
identified chromosomal regions with potential signs of linked selection.
This study evidences that recombination is a variable trait that shapes
the diversity and evolution of population differentiation in the
blackcap.