In terms of categories, there's actually more than just the Mexican and temperate ones.
Generally, there's ~4 or so categories: Mexican, tropical, warm-temperate, and cold-temperate.
Cold-temperate species like P. vulgaris
and P. grandiflora
actually form a winter resting bud (hibernaculum) and need colder winters than the warm-temperate species.
Warm-temperate species are basically all the SE USA native species, e.g. P. primuliflora
, P. caerulea
, P. planifolia
and so on. These also go dormant during the winter but generally slow down and maybe die back a bit rather than form a real resting bud.
Mexican species are the ones most people are familiar with: P. moranensis
x 'Aphrodite', P. gypsicola
and that sort of stuff. These are the ones with a dry "dormancy" and have carnivorous leaves in active growth, and succulent leaves during the resting period.
The tropical species don't really have a resting period as far as I know (I think one or two might have some weird heterophyllous growth pattern). Some of them may be fairly short lived. Barely anyone grows them, but they are available some places and the requirements are really quite different from the others. This group consists of P. chuquisacensis
, P. filifolia
, P. cubensis
and the like.
There are a few weirdo species that don't really fit in with the others either, and "exceptions to the rule". A couple homophyllous Mexican species (P. emarginata
is the only one off the top of my head, P. moctezumae
might also be in practice) don't like to dry out during the winter and grow year-round. This is probably the important exception, as both of these are fairly commonly grown.
Then there's a couple annual species like P. lusitanica
, which are pretty self explanatory.
Finally there's the whole P. crystallina
complex which is just... weird. They're definitely temperate and live in places you'd expect cold-temperate species to be, but they don't form hibernacula. Species in this complex are generally found on rocky cliffs that are kept permanently wet by a film of water, which might explain some of their oddities.
EDIT: Lol I didn't see this was from 2009