Rapid chromosomal evolution in enigmatic mammal with XX in both sexes, the Alay mole vole Ellobiusalaicus Vorontsov et al., 1969 (Mammalia, Rodentia).

Irina Bakloushinskaya,Sergey N Matveevsky,Patricia C.M O’Brien,Aleksey S Bogdanov,Elena A Lyapunova,Natalia A Serdyukova,Malcolm A Ferguson-Smith,Abdusattor S Saidov,Svetlana A Romanenko

doi:10.3897/compcytogen.v13i2.34224

Irina Bakloushinskaya, Sergey N Matveevsky + Show 7 more

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https://doi.org/10.3897/compcytogen.v13i2.34224

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Abstract

Evolutionary history and taxonomic position for cryptic species may be clarified by using molecular and cytogenetic methods. The subterranean rodent, the Alay mole vole Ellobiusalaicus Vorontsov et al., 1969 is one of three sibling species constituting the subgenus Ellobius Fischer, 1814, all of which lost the Y chromosome and obtained isomorphic XX sex chromosomes in both males and females. E.alaicus is evaluated by IUCN as a data deficient species because their distribution, biology, and genetics are almost unknown. We revealed specific karyotypic variability (2n = 52–48) in E.alaicus due to different Robertsonian translocations (Rbs). Two variants of hybrids (2n = 53, different Rbs) with E.tancrei Blasius, 1884 were found at the Northern slopes of the Alay Ridge and in the Naryn district, Kyrgyzstan. We described the sudden change in chromosome numbers from 2n = 50 to 48 and specific karyotype structure for mole voles, which inhabit the entrance to the Alay Valley (Tajikistan), and revealed their affiliation as E.alaicus by cytochrome b and fragments of nuclear XIST and Rspo1 genes sequencing. To date, it is possible to expand the range of E.alaicus from the Alay Valley (South Kyrgyzstan) up to the Ferghana Ridge and the Naryn Basin, Tien Shan at the north-east and to the Pamir-Alay Mountains (Tajikistan) at the west. The closeness of E.tancrei and E.alaicus is supported, whereas specific chromosome and molecular changes, as well as geographic distribution, verified the species status for E.alaicus. The case of Ellobius species accented an unevenness in rates of chromosome and nucleotide changes along with morphological similarity, which is emblematic for cryptic species.

Highlights

An origin of species due to chromosome changes is still debatable (King 1993, Castiglia 2014, Dobigny et al 2017)
To bring a phylogenetic framework to the delimiting species, we examined the phylogeny of the subgenus Ellobius using the mitochondrial DNA marker, complete cytochrome b gene, cytb, and two nuclear DNA markers, fragments of the XIST (X-inactive specific transcript) and Rspo1 (R-spondin 1) genes
The main result was a discovery of specific chromosome variability in E. alaicus, with 2n varying from 52 to 48 chromosomes

Summary

Introduction

An origin of species due to chromosome changes is still debatable (King 1993, Castiglia 2014, Dobigny et al 2017). Species of the subgenus Ellobius (E. talpinus Pallas, 1770, E. tancrei Blasius, 1884, and E. alaicus Vorontsov et al 1969) are cryptic ones, indistinguishable by morphological features (Yakimenko and Vorontsov 1982), the main diagnostic features are distant karyotypes. The species lost the Y chromosome, the Sry gene, and obtained isomorphic XX chromosomes in both males and females (Lyapunova and Vorontsov 1978, Vorontsov et al 1980, Kolomiets et al 1991, Just et al 1995, Romanenko et al 2007, Bakloushinskaya et al 2012, Bakloushinskaya and Matveevsky 2018). The first signs of sex chromosomes heteromorphism in E. talpinus and E. tancrei were observed in the meiotic behaviour of XX chromosomes in males (Kolomiets et al 1991 2010, Matveevsky et al 2016 2017)

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