Three new species of the diatom genus Epithemia Brébisson ex Kützing (Bacillariophyceae, Rhopalodiales) from Yunnan Province, China

Light and scanning electron observation results are presented for three new species of the genus Epithemia Brébisson ex Kützing collected from Yunnan Province, China. They are the first species of the genus ever reported from Yunnan, and comprise 3 of the 4 species ever described from the country. The three species belong to three different morphological groups within Epithemia. Epithemia cistulina sp. nov. is similar to Epithemia cistula and its allies by virtue of the placement of the raphe, having a segment-like frustule and primarily simple, c-shaped areolar openings. Epithemia sinensis sp. nov. is morphologically similar to species assigned to the Epithemia sorex group, due to its strongly biarcuate raphe that terminates near the dorsal margin. Epithemia yunnaniana sp. nov. has features that assign it to the Epithemia adnata group, including the raphe being positioned mostly on the ventral mantle, extending barely onto the valve face in the middle of the valve. The small number of Epithemia species described from Asia in general, and from China, as well as these new reports of the genus in the biodiverse rich province of Yunnan, suggest that additional work on the diversity of this genus across Asia is needed.