Abstract
We document the diversity of diatom taxa from the G. acuminatum and truncatum-capitatum species complexes in Lake Baikal using light and scanning electron microscopy. This investigation revealed four species new to Science, namely G. pseudacuminatum sp. nov., G. microlaticollum sp. nov., G. paracapitatum sp. nov., and G. microcapitatum sp. nov. In addition, we consider seven previously described species that are part of these ‘typical Gomphonema’ complexes. Some of the taxa treated here were previously observed from other regions, especially from Mongolia. These data show a wide distribution of species from these complexes in waterbodies of Central Asia, and confirm the presence of some cosmopolitan taxa within Lake Baikal.