Kartavtseva I.V., Stepanova A.I.
В журнале Biology Bulletin
Год: 2025 Том: 52 Номер: 4
Previously, only Alexandromys fortis had been found to occur in the northeastern part of the Middle Amur Lowland. Karyotype studies on voles at the northernmost locality of the lowland, near the village of Elban, reveal a second species, A. maximowiczii, shifting its eastern range limit 200 km east of the nearest known one. Four karyotype variants found in individuals from the Middle Amur Lowland are described for the first time for Maximowicz’s vole, which shows multiple chromosomal polymorphism. Two karyotype variants are found to predominate: 2n = 40, NF = 58 and 2n = 41a, NF = 60, and two that are rare: 2n = 41b, NF = 59 and 2n = 41c, NF = 59. According to the 2n and NF numbers, these variants correspond to the chromosomal form “C.” The variability of the chromosome number in this species is due to the tandem fusion of metacentric chromosomes no. 3 and no. 4 to form a large metacentric no. 3/4. Centric fusion of acrocentric chromosomes no. 11 and no. 20 to form a medium-sized metacentric chromosome no. 11.20 is generally stabilized, with the exception of one individual of 54 examined. A sharp decrease in heterozygotes for tandem fusion is noted for individuals in the middle part of the lowland, compared to the northeastern part where it was high. The number of chromosomes being 39 is excluded from the chromosomal form “C” as unsubstantiated. Rare variants have one pair of autosomes in the heterozygous state (SM/A). Such variability seems to be associated with a shift in the centromere in chromosome no. 10 in variant 41b and a pericentric inversion in chromosome no. 16 in variant 41c. Based on the previously published data of genetic, allozyme, chromosomal, and molecular–genetic analyses for both species involved, A. maximowiczii and A. fortis, the chromosomal characteristics and their habitats, including syntopic ones, are presented.
