They can go together, and what matters is the size of the district magnitude. If you have a small district—Spain has three-to-five, Ireland has five—then essentially the individual voter can find, in particular, not just an MP but a couple of MPs, perhaps from different parties, to represent their constituency concerns or to lobby for them or to do any other sort of service work.
If you get a large district, however, that dilutes. Many countries will have districts of, say, 16-20, and there is no constituency service when you get to a very, very large constituency. The classic cases are in Israel, where you have the whole country as one constituency, and in the Netherlands. In those countries, there are very weak links indeed between the members of the Knesset in Israel and individual voters. At that stage it's broken.
It really depends on how you draw your boundaries as to how you actually create an incentive to have constituency service. It's not about an either/or system, PR versus single member.