Epilithic diatoms (Bacillariophyta) from cloud forest and alpine streams in Bolivia, South America 3: diatoms from Sehuencas, Carrasco National Park, Department of Cochabamba

Studies on Bolivian diatoms are scarce and they do not represent the great geographic variability of the country. One of the regions with the highest biological diversity in Bolivia is the Yungas (cloud forest), a 90.500 km(2) strip located between the Andean Puna and the Amazonian lowlands. The Carrasco National Park is the park with the largest extension of Yungas within its boundaries. This park is located east from Cochabamba, the third largest city in Bolivia, and has an area of ca 6.226 km(2), serving as a refuge to 5.000 recorded species of plants and more than 300 species of vertebrates. Very little is known about the aquatic biota in the zone and there are no studies on diatoms. One of the preferred tourist spots within the park is Sehuencas, located 17 degrees 31'42" S and 65 degrees 16'17" W and characterized by numerous lotic waterbodies. The present work was carried on 5 epilithic samples from which 118 species, varieties and forms were identified using light (LM) and scanning electron microscopy (SEM). Forty-two (36%) of these taxa were not found in the literature for South America or other regions of the world. This high percentage of unknown taxa suggests a high potential for the contribution of new organisms to science, many of which are possibly endemic to the region, thus justifying an additional effort to preserve the aquatic habitats in the park. Two new species are described herein (Fragilaria cochabambina Morales sp. nov. and Achnanthidium sehuencoensis Morales sp. nov.) and comparisons with published morphologically similar taxa are presented. Unknowns remain undescribed until larger populations that allow detailed LM and SEM studies are found.