As I understand it, a population with high variation is something sought after, since it makes the population better equipped to face a dynamic environment.
Then, I guess features in an individual which causes it's population's variation to be high, should be selected for (high mutation rate, other features.. ?).
If so, does this manifest itself partly as individuals preferring to mate with individuals from another population? (With genetic difference within reason, perhaps a norm for a proffered genetic difference between individuals)