ABSTRACT
Closely related mammalian species often have differences in chromosome number and morphology, but there is still a debate about how these differences relate to reproductive isolation. To study the role of chromosome rearrangements in speciation, we used the gray voles in the Alexandromys genus as a model. These voles have a high level of chromosome polymorphism and substantial karyotypic divergence. We investigated testis histology and meiotic chromosome behavior in the captive-bred colonies of Alexandromys maximowiczii, Alexandromys mujanensis, two chromosome races of Alexandromys evoronensis, and their interracial and interspecies hybrids, to explore the relationship between karyotypic differences and male hybrid sterility. We found that the seminiferous tubules of the males of the parental species and the interracial hybrids, which were simple heterozygotes for one or more chromosome rearrangements, contained germ cells at all stages of spermatogenesis, indicating their potential fertility. Their meiotic cells displayed orderly chromosome synapsis and recombination. In contrast, all interspecies male hybrids, which were complex heterozygotes for a series of chromosome rearrangements, showed signs of complete sterility. Their spermatogenesis was mainly arrested at the zygotene- or pachytene-like stages due to the formation of complex multivalent chains, which caused extended chromosome asynapsis. The asynapsis led to the silencing of unsynapsed chromatin. We suggest that chromosome asynapsis is the main cause of meiotic arrest and male sterility in the interspecies hybrids of East Asian voles.
Subject(s)
Arvicolinae , Infertility, Male , Animals , Male , Arvicolinae/genetics , Chromosomes/genetics , Infertility, Male/geneticsABSTRACT
BACKGROUND: Tandem repeats in mitochondrial DNA control region are known to different animal taxa, including bat species of the family Vespertilionidae. The long R1-repeats in the bat ETAS-domain are often presented in a variable copy number and may exhibit both inter-individual and intra-individual sequence diversity. The function of repeats in the control region is still unclear, but it has been shown that repetitive sequences in some animal groups (shrews, cats and sheep) may include parts of ETAS1 and ETAS2 conservative blocks of mitochondrial DNA. METHODS AND RESULTS: Analysis of the control region sequences for 31 Myotis petax specimens allowed the identification of the inter-individual variability and clarification of the composition of the R1-repeats. The copy number of the R1-repeats varies from 4 to 7 in individuals. The specimens examined do not exhibit a size heteroplasmy previously described for Myotis species. The unusual short 30 bp R1-repeats have been detected in M. petax for the first time. The ten specimens from Amur Region and Primorsky Territory have one or two copies of these additional repeats. CONCLUSIONS: It was determined that the R1-repeats in M. petax control region consist of parts of the ETAS1 and ETAS2 blocks. The origin of the additional repeats seems to be related to the 51 bp deletion in the central part of the R1-repeat unit and subsequent duplication. Comparison of repetitive sequences in the control region of closely-related Myotis species identified the occurrence of incomplete repeats also resulting from the short deletions, but distinct from additional repeats of M. petax.
Subject(s)
Chiroptera , Animals , Sheep/genetics , Chiroptera/genetics , Repetitive Sequences, Nucleic Acid/genetics , Mitochondria/genetics , DNA, Mitochondrial/genetics , Tandem Repeat Sequences/geneticsABSTRACT
The vole Alexandromysevoronensis (Kovalskaya et Sokolov, 1980) with its two chromosomal races, "Evoron" (2n = 38-41, NF = 54-59) and "Argi" (2n = 34, 36, 37, NF = 51-56) is the endemic vole found in the Russian Far East. For the "Argi" chromosomal race, individuals from two isolated populations in mountain regions were investigated here for the first time using GTG-, GTC-, NOR methods. In the area under study, 8 new karyotype variants have been registered. The karyotype with 2n = 34 has a rare tandem fusion of three autosomes: two biarmed (Mev6 and Mev7) and one acrocentric (Mev14) to form a large biarmed chromosome (Mev6/7/14), all of which reveal a heterozygous state. For A.evoronensis, the variation in the number of chromosomes exceeded the known estimate of 2n = 34, 36 and amounted to 2n = 34, 36, 38-41. The combination of all the variations of chromosomes for the species made it possible to describe 20 variants of the A.evoronensis karyotype, with 11 chromosomes being involved in multiple structural rearrangements. In the "Evoron" chromosomal race 4 chromosomes (Mev1, Mev4, Mev17, and Mev18) and in the "Argi" chromosomal race 9 chromosomes (Mev6, Mev7, Mev14, Mev13, Mev11, Mev15, Mev17, Mev18, and Mev19) were observed. Tandem and Robertsonian rearrangements (Mev17/18 and Mev17.18) were revealed in both chromosomal races "Evoron" and "Argi".
ABSTRACT
The DNA-barcoding and chromosomal study of the eastern water bat, Myotis petax Hollister, 1912, from the earlier unexplored localities in the Russian Far East are carried out. The COI barcoding obtained for 18 from a total of 19 individuals captured in five localities in the Russian Far East showed the low nucleotide variability with the prevalence of the central, the most abundant haplotype. The chromosomal characteristics of eight M. petax specimens (2n = 44, NFa = 52) in the Russian Far East are clarified. The number and localization of NOR in karyotype of M. petax is described at the first time and differ from distributional patterns of NOR in the sibling species M. daubentonii Kuhl, 1819 that can be used as diagnostic feature. The considerable intraspecific variability in the distribution of heterochromatin material revealed is not typical of the genus Myotis, but it has been found in other species of the family Vespertilionidae.
ABSTRACT
Population dispersal and migration often indicate an expanded habitat and reduced inbreeding probability, and to some extend reflects improvement in the condition of the population. The Amur tiger population in the northern region of the Changbai mountain in China mostly distributes along the Sino-Russian border, next to the population in southwest Primorye in Russia. The successful dispersal westward and transboundary movement are crucial for the persistence of the Amur tiger in this area. This study explored the spatial dispersal of the population, transboundary migration, and the genetic condition of the Amur tiger population within the northern Changbai mountain in China, using occurrence data and fecal samples. Our results from 2003 to 2016 showed that the Amur tiger population in this area was spreading westward at a speed of 12.83 ± 4.41 km every three years. Genetic diversity of the Amur tiger populations in southwest Primorye was slightly different than the population in our study area, and the potential individual migration rate between these two populations was shown to be about 13.04%. Furthermore, the relationships between genetic distances and spatial distances indicated the existence of serious limitations to the dispersal of the Amur tiger in China. This study provided important information about spatial dispersal, transboundary migration, and the genetic diversity of Amur tigers in China, showed the urgent need for Amur tiger habitat restoration, and suggested some important conservation measures, such as corridor construction to eliminate dispersal barriers and joint international conservation to promote trans-boundary movement.
ABSTRACT
The Muya Valley vole (Microtus mujanensis) has a constant diploid chromosome number of 2n = 38, but an unstable karyotype with polymorphic chromosome pairs. Here, we describe 4 karyotypic variants involving 2 polymorphic chromosome pairs, MMUJ8 and MMUJ14, in 6 animals from Buryatia using a combination of GTG-banding and chromosome painting with M. agrestis probes. We suggest that the polymorphic pairs MMUJ8 and MMUJ14 were formed through pericentric inversions that played a major role during karyotype evolution of the species. We also propose that the stable diploid number with some ongoing polymorphism in the number of chromosome arms indicates that this evolutionarily young endemic species of Russian Far East is on the way to karyotype and likely species stabilization.
