It is not so much related to the fat being liquid but rather to it being stable. The nuts in warm climates have evolved to have oils that are more stable in warm climates, this leads to high saturated content and low polyunsaturated content (since in stability saturated > monounsaturated > polyunsaturated). The nuts in colder climates have not had this evolutionary pressure so you don't see high saturated content in most of those nuts.
cold blooded animals have higher PUFA. warm blooded animals have higher saturated fat. Even within an animal, fat towards the center of the animal tends to be higher in saturated fat and fat towards the extremity higher in PUFA.