Maternal age alters recombination rate in Drosophila pseudoobscura

As individuals senesce, factors correlated with fitness, such as fecundity and longevity, decline. Increased age also alters recombination rates in a variety of taxa. Changes in individual recombination rate, or recombination rate plasticity, can increase meiotic errors. In Drosophila melanogaster, multiple studies on maternal age and recombination rate have found a characteristic pattern where rates initially increase, then decrease, then increase again relative to controls. Here, this phenomenon was investigated in D. pseudoobscura. First, fecundity and survivorship were investigated to guide the choice of treatment age. Then, a large-scale recombination analysis (N=23,559) was set up using three X-linked phenotypic markers. Recombination rate differences in two genomic intervals were measured in females aged to 7 days (control) and 35 days (selected treatment age) prior to mating, with progeny collection continuing for 12 days post-mating in 72 hour timepoints. Results revealed a 3.39% increase in recombination rate due to maternal age (p=0.025), for the first 72 hour time point in one of the two marker intervals. For both genomic intervals, recombination rates were higher in the age treatment for the first time point and lower in later time points of the experiment. Next, these data were used to investigate crossover interference, which decreased with maternal age in the first time point and increased in the last time point. Overall, these results suggest that the mechanisms responsible for recombination rate plasticity may differ between maternal age and stressors, such as temperature.