Avian genome evolution: insights from a linkage map of the blue tit (Cyanistes caeruleus).

We provide a first-generation linkage map of the blue tit (Cyanistes caeruleus), a passerine within the previously genetically uncharacterized family Paridae, which includes 91 orthologous loci with a single anchored position in the chicken (Gallus gallus) sequence assembly. The map consists of 18 linkage groups and covers 935 cM. There was highly conserved synteny between blue tit and chicken with the exception of a split on chromosome 1, potential splits on chromosome 4 and the translocation of two markers from chromosome 2 and 3, respectively, to chromosome 5. Gene order was very well conserved for the majority of chromosomes, an exception being chromosome 1 where multiple rearrangements were detected. Similar results were obtained in a comparison to the zebra finch (Taeniopygia guttata) genome assembly. The recombination rate in females was slightly higher than in males, implying a moderate degree of heterochiasmy in the blue tit. The map distance of the blue tit was approximately 78% of that of the Wageningen chicken broiler population, and very similar to the Uppsala chicken mapping population, over homologous genome regions. Apart from providing insights into avian recombination and genome evolution, our blue tit linkage map forms a valuable genetic resource for ecological and evolutionary research in Paridae.