Abstract:
Conventional wisdom is that selection decreases genetic variation in populations, variation that is essential for population persistence in an ever-changing world. Basically, I find the opposite. Response to selection on biting in the pitcher-plant mosquito, Wyeomyia smithii, increases from 20-80%, but reverts back to the original 20% after seven generations of relaxed (not reversed) selection. At the same time, biting in the control line remains at the original 20% through 30 generations without blood feeding. Imposition of selection on biting in both lines elicits a rapid response in the previously selected line, but, importantly, not in the control line. Hence genetic variation for biting has increased, not decreased as a consequence of long-term directional selection, contrary to expectations. In short, history matters.