Are the Lake Baikal diatoms endemic?

An electron-microscopy study of Aulacoseira baicalensis, A. islandica (A. skvortzowii), Cyclotella baicalensis, C. minuta, and Stephanodiscus meyerii in phytoplankton samples from some mountain lakes of Zabaikalye (an area north and east of Lake Baikal) shows that these algae possess morphological similarities with the algae inhabiting Lake Baikal, including some elements of their ultra-structure. We hypothesise that they were more widespread in the past and persist today in mountain lakes along the Baikal rift zone owing to certain features of their biology. We conclude that these baikalian diatom algae, previously regarded as endemic, should be re-assigned to relict status.