Influence of co-evolution with a parasite, Nosema whitei, and population size on recombination rates and fitness in the red flour beetle, Tribolium castaneum.

The high prevalence of meiotic recombination-an important element of sexual reproduction-represents one of the greatest puzzles in biology. The influence of either selection by a co-evolving parasite alone or in combination with genetic drift on recombination rates was tested in the host-parasite system Tribolium castaneum and Nosema whitei. After eight generations, populations with smaller genetic drift had a lower recombination rate than those with high drift whereas parasites had no effect. Interestingly, changes in recombination rate at one site of the chromosome negatively correlated with changes at the adjacent site on the same chromosome indicating an occurrence of crossover interference. The occurrence of spontaneous or plastic changes in recombination rates could be excluded with a separate experiment.