Brachysira (Naviculales, Bacillariophyceae) in lowland waters from Colombia

This study focuses on the genus Brachysira Kutzing from lowland waters as part of the diatom flora investigation of Colombia. Periphyton samples were collected in lentic and lotic waterbodies from different Amazonian basins and the Ayapel swamp system in the northern Atlantic plain of Colombia. Diatoms were analysed with light and scanning electron microscopy. Two new taxa, B. guarrerai and B. huitotarum, are described. These species were differentiated from their allied taxa based on the combination of: the shape of the central area; the shape and number of the areolae that delimit the central area; stria position; presence or absence of papillae on the interstriae; and degree of silicification of the ribs that delimit the raphe. In addition, five other taxa are reported and described: B. microcephala (Grunow) Compere and B. subrostrata Lange-Bertalot are recorded for the first time from Colombia, while B. manfredii Lange-Bertalot was previously found in the Sierra Nevada. The other two taxa were identified as B. aff. brebissonii Ross and B. aff. microcephala because the Colombian specimens differ slightly from the type material of these cosmopolitan species.