A new metazoan recombination rate record and consistently high recombination rates in the honey bee genus apis accompanied by frequent inversions but not translocations

Abstract

Western honey bees (Apis mellifera) far exceed the commonly observed 1-2 meiotic recombination events per chromosome and exhibit the highest Metazoan recombination rate (20 cM/Mb) described thus far. However, the reasons for this exceptional rate of recombination are not sufficiently understood. In a comparative study, wereport on the newly constructed genomic linkagemaps of Apis florea and Apis dorsata that represent the two honey bee lineages without recombination rate estimates so far. Each linkage mapwas generated de novo,basedonSNP genotypes of haploidmale offspringof a single female. The A. floreamapspans 4,782 cM with 1,279 markers in 16 linkage groups. The A. dorsata map is 5,762cM long and contains 1,189 markers in 16 linkage groups. Respectively, these map sizes result in average recombination rate estimates of 20.8 and 25.1cM/Mb. Synteny analyses indicate that frequent intra-chromosomal rearrangements but no translocations among chromosomes accompany the high rates of recombination during the independent evolution of the threemajor honey bee lineages. Our results imply a common cause for the evolution of very high recombination rates in Apis. Our findings also suggest that frequent homologous recombination during meiosis might increase ectopic recombination and rearrangements within but not between chromosomes. It remains to be investigated whether the resulting inversions may have been important in the evolutionary differentiation between honey bee species.