Do certain species of pokemon mate for life like some animals do? Or is it up to each individual’s own preferences?

Well, some part of it is up to the individual’s preference. While divorce is not a concept that exists among pokémon, capriciousness is.

On a serious note, absolutely, there are plenty of pokémon that mate for life. Many of the human-shaped ones do. The ralts line, for example, is well-known for it, although there are plenty of others, including the gothorita line, the mr. mime line, the machop line, the abra line (despite being fox-like as well), and so forth. Some dog-like pokémon such as the riolu line also do. Bird-like pokémon are also known for it, with some—such as swanna and members of the murkrow line—being symbols of monogomy for this exact reason. And of course, there are a few non-avian pokémon that are also monogamous, such as members of the deerling line, durant, finneon and lumineon, many rodent pokémon, and—of course—luvdisc.

Honestly, just about the only kinds of pokémon that are consistently not monogamous are the more “inanimate-like” pokémon, such as rock-like pokémon, genderless pokémon that can still mate, and a number of plant-like pokémon.