Tropical diatoms of South America

This treatise on tropical diatoms from South America may serve as a pilot study introducing a representative selection of neotropical diatoms. The neotropical diatom flora is completely different from the flora of other continents and also different from the diatom flora of the temperate climatic zones of the subcontinent. About 700 taxe are documented here by 2515 micrographs. Most of them have been found exclusively in the tropical zone of South America where 202 are described as new taxa. Moreover, about 130 „morphotypes“ are documented and taxonomically indeterminated (new) species. The extent of real endemic elements has still to be determined since identity and distribution of tropical diatoms are still poorly investigated. Nevertheless, it can be shown that many of these species are indicative characteristic elements of oligotrophic or oligodystrophic so-called clearwater- and blackwater rivers. Many established taxa so far recorded as a single specimen only or considered to be rare, have now been found to be widespread in different parts of Brazil, Guyana and Venezuela, where waters have not been under the negative influence of human activities.