How Hot Are Drosophila Hotspots? Examining Recombination Rate Variation and Associations with Nucleotide Diversity, Divergence, and Maternal Age in Drosophila pseudoobscura

Fine scale meiotic recombination maps have uncovered a large amount of variation in crossover rate across the genomes of many species, and such variation in mammalian and yeast genomes is concentrated to <5 kb regions of highly elevated recombination rates (10-100x the background rate) called "hotspots." Drosophila exhibit substantial recombination rate heterogeneity across their genome, but evidence for these highly-localized hotspots is lacking. We assayed recombination across a 40 Kb region of Drosophila pseudoobscura chromosome 2, with one 20 Kb interval assayed every 5 Kb and the adjacent 20 Kb interval bisected into 10 Kb pieces. We found that recombination events across the 40 Kb stretch were relatively evenly distributed across each of the 5 Kb and 10 Kb intervals, rather than concentrated in a single 5 Kb region. This, in combination with other recent work, indicates that the recombination landscape of Drosophila may differ from the punctate recombination pattern observed in many mammals and yeast. Additionally, we found no correlation of average pairwise nucleotide diversity and divergence with recombination rate across the 20 Kb intervals, nor any effect of maternal age in weeks on recombination rate in our sample.