Boreskov

PP‐28MICROEVOLUTIONARY PROCESSES AND SPECIATION IN EXTREME BIOTOPESDEPEND ON SPECIALIZATION TO THE BIOTOPES: STUDIES OF HYDROTHERMALVENT SHRIMPSLunina A.A., Vereshcaka A.L.P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Nakhimov Prospekt 36,Moscow, 117997, RussiaHydrothermal vents may be considered as model ecosystem reflecting biologicalprocesses on earlier Earth. Cairns‐Smith et al. (1992), Russell et al. (1988; 1994) and Russelland Hall (1997), and other researchers proposed that life emerged in submarine hot springsin a Fe‐rich ocean in Hadean Earth 4.4–3.85 billion years ago. Recent hydrothermal ventcommunities are interesting objects for studies of patterns of evolutionary processes. Ventbiotopes are extreme ones from biological viewpoint and we can reveal a row of taxa thatdemontrates increasing specialization to the biotope. One of the best objects to studyspecialization to such extreme biotopes are vent shrimps of the superfamily Bresilioidea.Bresiliid shrimps represent the key elements of hydrothermal communities of the Mid‐Atlantic Ridge and they are members of the hydrothermal communities in other areas of theoceans. The present COI nucleotide divergence estimates reveal that recent species of vent‐and seep‐endemic shrimp constitute a natural (i.e., monophyletic) group that most likelyradiated in the Miocene, 6.7 to 11.7 MYA (Shank et al., 1999). Vent shrimps give examples ofalmost unspecialized genus (the genus Alvinocaris), extremely specialized genus (the genusRimicaris), and intermediate forms (the genera Chorocaris, Mirocaris, and Opaepele). Weanalyzed how degree of specialization determines speciation, biogeographic patterns, lifecycles, and microevolutionary processes. All known species of vent shrimps were involvedinto analysis.Phylogenetic analysis of the vent shrimps revealed two main clades and 26 species ofvent shrimps. Species within each of these clades are randomly distributed throughout theWorld Ocean, thus making impossible to show the area where the group originated. Lessspecialized genus (Alvinocaris) was found to be much more divergent than more specialized.The most specialized Rimicaris is nearly monotypic.Each species within less specialized genera inhabits 1‐2 vent fields. Each species of themost specialized species occurs in numerous vent sites. Genera with intermediatespecialization demonstrate intermediate pattern of geographic distribution.181