What's about disliking trespass on your property in general? (edit: and use of your property) Now that definitely has evolved in animals long before serious pair bonding, and can serve the function just fine.

edit: The crux of the issue is that saying 'jealousy is evolved' is a fake explanation like phlogiston, that stops further inquiry (when further enquiry is still well warranted via the 'difficulty to evolve' based prior that is not unlike occam's razor).

edit: ahh, by the way, consider female jealousy, and the jealousy for the sake of not losing the partner.