SPECIES-DIVERSITY IN AQUATIC ANGIOSPERMS - LATITUDINAL PATTERNS

Preliminary studies of aquatic plants in numerous tropical aquatic habitats in Costa Rica indicate a low level of diversity, and such a level of species richness appears to be in direct conflict with the general viewpoint that tropical ecosystems are exceedingly diverse. Furthermore, there is a strong tendency for dominance of particular plant species within tropical aquatic ecosystems, whereas in tropical forest ecosystems, individuals of a species tend to be scattered rather than to express dominance. A comparison of aquatic plant diversity on a latitudinal basis reveals a higher level of diversity at warm temperate latitudes and a surprisingly high, if not highest, level at cool temperate latitudes. This appears to be true when comparing representative aquatic families as well as aquatic habitats. Standardized data on biodiversity in aquatic ecosystems are needed for further comparative purposes. Additionally, aquatics are poorly known for tropical regions; thus, there is a great need for field work to be conducted in aquatic habitats of the tropics.