Original paper

Coregonids of Russia: Evolutionary genetic approach in assessment of the current state of biodiversity

Politov, Dmitry V.

Fundamental and Applied Limnology Volume 189 Nr. 3 (2017), p. 181 - 192

published: Feb 1, 2017

DOI: 10.1127/fal/2017/0814

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Abstract

Coregonid fishes (Teleostei: Salmoniformes: Coregonidae) are important components of subarctic and subalpine water ecosystems in the Palearctic. Watersheds of the northern part of European Russia, Siberia and the Russian Far East harbor many species and forms of uncertain status, some of which are endemic, and some that can be considered as basal for major evolutionary clades within the genus Coregonus, which is the most diverse in the sense of species richness in the family Coregonidae. Due to increasing human pressure and the negative effects of global warming, coregonid populations and associated ecosystems are currently considered as threatened or at least vulnerable. Both gene pool conservation of coregonids and the sustainable use of their resources require knowledge on a number of conservation units and the state of genetic diversity at different levels of taxonomic and ecological hierarchies. General morphoecological plasticity, blurring of species edges due to hybridization and gene introgres- sion, reticulate evolution, and the existence of multiple sympatric forms make the task of coregonid biodiversity inventory challenging if based exclusively on fish morphology. Two contrasting approaches in traditional coregonid systematics, 'splitting' and 'lumping' that have dominated during the last decades have led to an appearance of quite different regional species checklists worldwide, especially for the most disputed genus Coregonus. For Russia, a uniting approach may generate a modest list of a minimum of 11 species (Prosopium cylindraceum, P. coulteri, Stenodus leucichthys, Coregonus albula, C. peled, C. lavaretus, C. muksun, C. nasus, C. autumnalis, C. tugun, C. ussuriensis). Alternatively, up to hundreds if not thousands of 'morphospecies' can be recognized in Russia according to a 'splitting' approach, which has already created dozens of species for relatively small territories and within recently diverged lineages. Combined use of multiple nuclear and mitochondrial molecular genetic markers usually brings an order to the chaos of taxonomy since DNA structure is generally less sensitive to convergence and is able to date speciation events and disclose reticulate evolutionary patterns. Instead of generating ad hoc plain alphabeti- cally ordered checklists, the evolutionary genetic approach based on molecular markers, coupled with a thorough analysis of fish morphology and anatomy, results in the construction of a structured hierarchical system of evolutionary lineages. Within the genus Coregonus, the major lineages are: 1) Arctic ciscoes C. autumnalis + C. laurettae; 2) European whitefish ' C. lavaretus complex' + northern Siberian whitefish C. pidschian complex + C. muksun ; 2a) southern Siberian whitefish C. pidschian (riverine and lacustrine populations in mid- and upper streams of Siberian rivers) + C. smitti + C. pravdinellus; 3) Amur river whitefishes C. ussuriensis + C. chadary; 4) Lake Baikal and mid- stream Yenisey river complex C. migratorius + C. fluviatilis; 5) Broad whitefish C. nasus; 6) Least cisco complex C. albula – C. sardinella – C. peled – C. subautumnalis, 7) tugun C. tugun. Additional well diverged clades traced by mtDNA are represented by ancient haplogroups found in the Anadyr river whitefishes C. pidschian + C. anaulorum and within the 'Lake Baunt cisco'. Biomolecules (DNA and proteins) provide information on conservation issues based on the quantification of genetic variability, and divergence is usually tree-shaped. However, taking into account reticulate scenarios, a more realistic representation of phylogenetic relationships is as a network. Molecular reconstructions are often topologically different from traditional purely morphological taxonomic schemes, but are getting increased support from studies when phenotypic classification traits other than mouth position and gill raker counts are being used.

Keywords

prosopiumevolutionary genetic approachcoregonusstenoduscoregonid fishesbiodiversity