Biogeography and ecology of freshwater diatoms in Subantarctica: a review

Subantarctica is situated between the Antarctic and the Subtropical Converg ence and consists of the islands in the southern Atlantic, Indian and Pacif ic Oceans. Diatoms are an important component of all Subantarctic aquatic, moss and soil habitats. Taxonomic studies reveal a high diversity and speci es richness in both the present-day and the fossil diatom flora. Planktonic diatoms are almost completely absent. A similarity analysis of the diatom composition from different localities in the southern zone (below 40 degree s S) resulted in a biogeographical zonation, Three regions could be formed, based on their diatom composition: Subantarctica, Maritime Antarctica and the Antarctic Continent. The diatom communities in the different regions ar e all characterized by a high proportion of cosmopolitan species. A second feature of the southern diatom floras is the decreasing diversity when movi ng southwards.