Abstract
Karyotype studies of common shrews in the vicinity of Lake Baikal (Irkutsk Region, Eastern Siberia) resulted in the description of two new chromosomal races of Sorex araneus Linnaeus, 1758 (Lypotyphla, Mammalia), additional to 5 races formerly found in Siberia. In the karyotypes of 12 specimens from 3 locations, the polymorphism of metacentric and acrocentric chromosomes of the Robertsonian type was recorded and two distinct groups of karyotypes interpreted as the chromosomal races were revealed. They are geographically distant and described under the racial names Irkutsk (Ir) and Zima (Zi). Karyotypes of both races were characterized by species-specific (the same for all 74 races known so far) metacentric autosomes af, bc, tu and jl, and the typical sex chromosome system – XX/XY1Y2. The race-specific arm chromosome combinations include three metacentrics and four acrocentrics in the Irkutsk race (gk, hi, nq, m, o, p, r) and four metacentrics and two acrocentrics in the Zima race (gm, hi, ko, nq, p, r). Within the races, individuals with polymorphic chromosomes were detected (g/m, k/o, n/q, p/r). The presence of the specific metacentric gk allowed us to include the Irkutsk race into the Siberian Karyotypic Group (SKG), distributed in surrounding regions. The Zima race karyotype contained two metacentrics, gm and ko, which have been never found in the Siberian part of the species range, but appear as the common feature of chromosomal races belonging to the West European Karyotypic Group (WEKG). Moreover, the metacentrics of that karyotype are almost identical to the Åkarp race (except the heterozygous pair p/r) locally found in the southern Sweden. One of two Siberian races described here for the first time, the Zima race, occurs in an area considerably distant from Europe and shares the common metacentrics (gm, hi, ko) with races included in WEKG. This fact may support a hypothesis of independent formation of identical arm chromosome combinations due to occurrence of the same centric fusions in different parts of the species range.
Highlights
The common shrew Sorex araneus Linnaeus, 1758 (Soricidae, Lypotyphla, Mammalia) is a small insectivore mammal and one of large-sized species of the genus
In this paper we present data on karyotypic variation of shrews collected from a so far unstudied area in Eastern Siberia (Russia), and discuss a hypothesis whether chromosomal translocations result in the appearing of the same arm combinations in geographically remote races independently
Following the rules of the standard nomenclature for S. araneus karyotype proposed by Hausser et al (1994), we give the description of two new chromosomal races of the common shrew (Sorex araneus): Zima race (Zi)
Summary
The common shrew Sorex araneus Linnaeus, 1758 (Soricidae, Lypotyphla, Mammalia) is a small insectivore mammal and one of large-sized species of the genus. Afterwards, 49 known races have been combined into four main karyotypic groups: the West (WEKG), East (EEKG) and North (NEKG) European, and Siberian (SKG) (Searle and Wójcik 1998). It is very important to note that all 10 race-specific chromosomes were used for the cladistic analysis, the combinations including only three large arms – g, h, and i were responsible for the separation of races into individual karyotypic groups (Searle and Wójcik 1998). Despite less karyotypic data being available from the “European” race-specific metacentrics in East Siberian common shrews (Sorex araneus)... In this paper we present data on karyotypic variation of shrews collected from a so far unstudied area in Eastern Siberia (Russia), and discuss a hypothesis whether chromosomal translocations result in the appearing of the same arm combinations in geographically remote races independently
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