D. Yu. Sherbakov

Molecular phylogenetic studies on the origin of biodiversity in Lake Baikal

Lake Baikal is host to some 2500 metazoan species, maybe more, the majority of which are endemic. When studies of the lake shifted from purely descriptive work to a more analytical approach in the second half of this century, the question of the origin of its fauna became central and is still one of the main challenges to researchers of Baikalian biodiversity. Current research is investigating whether biodiversity can be explained by a few adaptive radiations since the Miocene, whether it results from the accumulation of diversity throughout the whole history of the Baikalian rift zone (about 70 million years) or whether it stems from even older events.

Population Structure of the Baikalian Amphipod Gmelinoides fasciatus (Stebbing)

Using the data on 71 individual sequences of the gene for the mitochondrial cytochrome-c-oxidase subunit one, molecular and phylogenetic characterization of the Baikalian amphipod, Gmelinoides fasciatus (Crustacea, Amphipoda), was performed. Interspecific polymorphism was demonstrated. Four main amphipod populations, Southeastern, Southwestern, Northern, and Central, were distinguished. A low level of genetic diversity typical of Southwestern population was revealed. For its explanation, the bottleneck hypothesis was proposed.

Molecular evidence reveals a polyphyletic origin and chromosomal speciation of Lake Baikal's endemic asellid isopods

The six endemic isopod species of Lake Baikal have been regarded as a small species flock with uncertain affinities to related asellids. We provide evidence from 16S rRNA sequences for polyphyletic origins of Baikalian Asellidae. One clade of two species is related to the Eurasian genus Asellus. The other clade, Baicalasellus, shows affinities to North American asellids and may have a long evolutionary history within the lake basin. Some speciation events within Baicalasellus clearly have a chromosomal basis. In contrast with numerous taxa exhibiting monophyletic radiations in ancient lakes, the endemic Baikalian isopods arose by multiple invasions and chromosomal mechanisms.

Genetic differentiation of the endemic Baikalian mollusk Baicalia carinata (Mollusca: Caenogastropoda)

In gastropod mollusk Baicalia carinata Dybowski, 1875, sampled in different sites of the Lake Baikal, comparison of 81 sequences of internal transcribed spacer 1 (ITS1) located between the genes for 18S rRNA and 5.8S rRNA, and of 100 sequences of the fragment of mitochondrial DNA cytochrome-c-oxidase subunit 1 gene (CO1) was performed. Molecular phylogenetic analysis showed that the endemic mollusk species studied formed at least two distinct populations, Southwestern and Eastern. Statistical significance of the species subdivision into two populations was evaluated using the Mann-Whitney rank test.

Molecular phylogenetic study of the systematic position of Baikalian oligochaetes in Clitellata

Phylogenetic relationships within the class Clitellata were examined using partial nucleotide sequences of the nuclear 18S ribosomal RNA gene. In the analysis, the already determined sequences for the individual species representing the class members Hirudinea, Acanthobdellida, Branchiobdellida, and Oligochaeta were included. Furthermore, newly determined sequences of the thirteen representatives of the family Lumbriculidae, including 12 Baikalian endemic species, were analyzed. The hypothesis on the close relatedness of these four groups of Clitellata was supported. Leeches, branchiobdellids, and lumbriculids form three independent parallel branches of evolution. These results were consistent with the hypothesis on the role of the family Lumbriculidae as a connecting link, or the transition form between the parasitic and free-living groups of Clitellata. At the same time, these data refute the suggestion that Lumbriculidae could be the ancestral lineage of other Oligochaeta. Moreover, polymorphic group of Baikalian lumbriculids clustered independently from the other representatives of the family, pointing to the uniqueness of the Baikalian fauna of oligochaetes, which was formed within relatively closed system of this ancient lake.

The formation of a fouling community on artificial substrate in Lake Baikal

The development of a fouling community at the surface of an artificial substrate in the littoral zone of Lake Baikal was studied. This epibenthic community was composed of 23 diatom species and 57 invertebrate species. The core community consisted of molluscs and caddisflies feeding mostly on diatoms. In Lake Baikal a fouling community develops in a sequence similar to marine environments.

Genetic and morphological diversification in gastropods of the Baicaliidae family

The combined (“total evidence”) phylogenetic inference was based on the comparison of the intronic nucleotide sequences of the ATP synthase α-subunit gene of 11 gastropod species belonging to the rapidly evolving Baikalian endemic family Baicaliidae, the morphological description of these species, and the previously published sequences of the mitochondrial gene coding the first subunit of cytochrome c oxidase. The phylogeny based on the intron sequences agrees well with the morphology. It is shown that sister species usually have similar substrate preferences. Certain discrepancy in the phylogenetic tree topology and the taxonomy based on morphological traits is probably due to the rapid morphological evolution of mollusks of the family Baicaliidae.

Evolution of a phosphofructokinase gene intron in gastropods of the family Baicaliidae

One of the introns of the phosphofructokinase gene was sequenced and analyzed in seven species of endemic Baikalian gastropods of the family Baicaliidae. The intron length differed even between sister species. Along with relatively few single nucleotide substitutions, extended deletions and insertions accumulated during the evolution of the intron. The number of deletions/insertions did not correlate with the genetic distance estimated for the species by comparing the sequences of a mitochondrial DNA fragment. The deduced secondary structure markedly differed even between sister species, although a consensus motif was detectable. Since long RNA stems that appeared and disappeared in the course of evolution may contain regulatory elements, the evolution of the intron may be nonneutral.

Speciation in status nascendi in Siberian Crabapple Malus baccata (L.) Borkh

Molecular genetic and morphometric studies of the tall and dwarf forms of the Siberian crabapple, which grow on the territory of Buryatia, were carried out. A phylogenetic analysis based on six highly polymorphic microsatellite loci showed that the dwarf form descends from the tall forms of Malus baccata and both studied forms belong to the same species of Siberian crabapple. Based on the obtained data, we propose that the dwarf form is an ecological form of the Siberian crabapple and possibly represents an initial stage of parapatric speciation.

Identification of filamentous green algae from an area of local biogenic pollution of Lake Baikal (Listvennichnyi Bay) using SSU 18S rDNA

A local eutrophication process is noted for the first time in Listvennichnyi Bay in Lake Baikal. Using morphological and molecular-genetic methods, species of filamentous green algae that form mats at site of the lake subjected to anthropogenic impact are identified. The presence of species of the genus Spirogyra Link., atypical for this part of the lake, as well as their distribution, together with species Ulothrix zonata (Web. et Mohr) Kürz. in an atypically large depth, indicates the serious disturbance of the structure of plant community of the studied site of Baikal.