Abstracts

Genetic Bases of Biodiversity

Lake Baikal is inhabited by about 3600 species of animals and plants (Timoshkin, 1997). To explain this biodiversity, we proposed a mechanism of speciation (1998, 1999, 2001a,b; Kamaltynov, 1999a, b) under the conditions of climate oscillation, specified here.

Lake Baikal formation occurred under climate changes in Cenozoic, and warmings were alternated with coolings (Logachev, 1974; Yasamanov, 1985; Mats et al., 1987; Vorobyova et al., 1995; Sherstyankin et al., 1995; Shimaraev et al., 1995; Klige et al., 1998; Karabanov, 1999). Recent species appeared in Pleistocene, when water temperature and productivity decrease, and water turbidity (Bezrukova et al., 1991; Sharstyankin et al., 1995; Shimaraev et al., 1997; Grachev et al., 1998; Karabanov et al., 2000b) caused ecological crises (Kamaltynov, 1998). Probably, benthos biomass at deep areas decreased up to zero. The biota was suppressed and transferred to shallow waters of bays, where plants could vegetate. Geographic isolation of populations in those areas resulted in genetic isolation and subsequent formation of races, subspecies and species. Many phytophagous amphipods move easily from stony grounds to higher water vegetation up to now, e.g. Pallasea cancellus. In winter they inhabit plants, and in the beginning of winter – stony grounds. A diatomic-ciliates cryophilic community forms on the lower ice surface of Lake Baikal (Obolkina et al., 2000). The underwater video recording showed the presence of P. cancellus (and of other species) among this periphyton community (see also: Bondarenko et al., 2001). The complete cycle of seasonal migrations of such species appears as follows: vegetation – stones covered with plants – lower ice surface with algae (pagon) – vegetation. Pre-adaptations to adaptation of this species (and of other ones) to ice conditions (behaviour evolution) are: inhabiting a solid substrate and phytophagous diet. Absence of common shallow water species Eulimnogammarus vittatus at Ushkanyi Islands allows to suppose that these uplifts survived a underwater phase after which they were colonized by species of shallow water fauna. They could cross the strait between the islands and Svyatoy Nos Peninsula using the ice cover as a substrate. There is an opinion (Mats et al., 2000) that water level in Lake Baikal decreased during glaciations. It can be confirmed by the presence of some shallow water species only in Maloye More and Chivyrkuy Bay. Their distribution can be explained by migration along Akademichesky Ridge which was shallower during low water level. Species inhabiting shallows near Selenga delta penetrate opposite Anga Bay via Buguldeiskaya Saddle which also became shallower. Some representatives of the Baikalian fauna was rather widespread (Kozhov, 1962). Probably, their areal is mainly post-glacial one, and the pre-glacial one was mainly eliminated due to ice accumulation on the rivers during glaciations.

This work was supported by SB RAS Integration grant No. 66 of 2000 and by RFBR grants No. 01-04-48970 and 01-04-97214.

Note. Abstracts are published in author's edition

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