X's Fast and Slow

Sex chromosomes have long been suggested to undergo distinct evolutionary dynamics to the rest of the genome. Their distinct ploidy and transmission genetics may result in differing strengths of selection, magnitude of drift, and mutation rates to the autosomes, particularly if there are sex differences. Consequently, a body of theory and empirical work has developed investigating such differences, and how they might manifest in the rates of change between populations, and the diversity observed within populations. I will briefly review the theoretical basis of these comparisons, how we can infer rates of evolutionary change from genetic data, and what we can learn from non-model systems, particularly focusing on fungus gnats and pea aphids.