Perhaps you didn't look hard enough...
... Aldrovanda is scattered all over the Old World, but these are the most commonly grown strains:
Poland - Temperate, goes dormant
Japan - Subtropical, I believe that if it is warm enough, it will not go dormant
Botswana - Tropical, but will go dormant if it's cold enough
Australia - Tropical, but will go dormant if it's cold enough
European strains need to go dormant, African strains can but don't require it, same with Aldrovanda from Japan and Australia, as a general rule. All Aldrovanda can go dormant, but not all need it.