摘要：This study analyses the geographical variations in the floristic composition and in the species richness of diatoms taken from 85 water bodies along a transect included in the southern Santa Cruz province, south of Tierra del Fuego province and maritime Antarctica (South Shetland Islands and Antarctic Peninsula). Endemic and cosmopolitan species were found. The data provided will contribute to answer some of the basic questions related to the origin of the Antarctic diatom species. Two hundred and sixty nine taxa were identified, with only 19 (7.1%) present simultaneously in Santa Cruz, Tierra del Fuego and Antarctica, with an evident decrease on the species richness with increasing latitudes. The high number of common species found between Patagonia and Antarctica, would support the hypothesis that most diatoms found in the studied Antarctic area would have been dispersed from the southernmost area of South America. This enhances the importance of this region as a propagule source for the Antarctica
