A POSSIBLE CYTOGENETIC ANALOGY TO GENOMIC «SPECIATION ISLANDS» AS REVEALED BY CHROMOSOME STUDY OF A NATURAL HYBRID VOLE.

Chromosome analysis in mammals over the last half century has largely focused on species identification. A growing number of hybrid zones of karyotypically differentiated cryptic taxa have been described. A good example is provided by two karyoforms of the 46-chromosome common vole (long known as «arvalis» and «obscurus») that make contact longitudinally from the north to the south of European Russia. The hybrid F1 karyotype displays genomic markers which distinguish arvalis and obscurus and which are cytogenetically detectable as minor variants. The apparent insignificance of the genomic region of heterozygosity associated with these markers perhaps does not prevent hybrid chromosome pair formation at meiosis but may reflect a site resistant to gene flow. A cytogenetic analogy with so-called «speciation islands», based, for example, on the study of the corvine hybrid zone and represented by a small number of limited genomic sites (occupying less than 1 % of the genome) (Poelstra et al., 2014), may be relevant.