The utility of DNA Barcoding for species identification and discovery has catalyzed a concerted effort to build the global reference library; however, many animal groups of economical or conservational importance remain poorly represented. This study aims to contribute DNA barcode records for all ground squirrel species (Xerinae, Sciuridae, Rodentia) inhabiting Eurasia and to test efficiency of this approach for species discrimination. Cytochrome c oxidase subunit 1 (COI) gene sequences were obtained for 97 individuals representing 16 ground squirrel species of which 12 were correctly identified. Taxonomic allocation of some specimens within four species was complicated by geographically restricted mtDNA introgression. Exclusion of individuals with introgressed mtDNA allowed reaching a 91.6% identification success rate. Significant COI divergence (3.5–4.4%) was observed within the most widespread ground squirrel species (Spermophilus erythrogenys, S. pygmaeus, S. suslicus, Urocitellus undulatus), suggesting the presence of cryptic species. A single putative NUMT (nuclear mitochondrial pseudogene) sequence was recovered during molecular analysis; mitochondrial COI from this sample was amplified following re-extraction of DNA. Our data show high discrimination ability of 100 bp COI fragments for Eurasian ground squirrels (84.3%) with no incorrect assessments, underscoring the potential utility of the existing reference librariy for the development of diagnostic ‘mini-barcodes’.
Glires represent a eutherian clade consisting of rodents and lagomorphs (hares, rabbits, and pikas). Chromosome evolution of Glires is known to have variable rates in different groups: from slowly evolving lagomorphs and squirrels to extremely rapidly evolving muroids. Previous interordinal homology maps between slowly evolving Glires were based on comparison with humans. Here, we used sets of chromosome-specific probes from Tamias sibiricus (Sciuridae), Castor fiber (Castoridae) and humans to study karyotypes of six ground squirrels (genera Marmota and Spermophilus) and one tree squirrel (genus Sciurus), mountain hare (genus Lepus), and rabbit (genus Oryctolagus). These data supplemented with GTG banding comparisons allowed us to build comparative chromosome maps. Our data showed the absence of previously found squirrel associations HSA 1/8 and 2/17 in the Eurasian ground squirrels--sousliks and woodchucks, and disruptions of squirrel HSA 10/13 and HSA 8/4/8/12/22 syntenies in the four Spermophilus species studied here. We found that the karyotypes of Sciuridae and Leporidae are highly conserved and close to the Rodentia ancestral karyotype, while Castoridae chromosomes underwent many more changes. We suggest that Lagomorpha and Sciuridae (in contrast to all other rodent families) should be considered as core Glires lineages, characterized by cytogenetically conserved karyotypes which contain chromosomal elements inherent to karyotype of common Glires ancestor. Our data allowed us to further refine the putative ancestral karyotypes of Rodentia. We also describe here the putative ancestral karyotypes of Glires and lagomorphs.
The mole vole subgenus Ellobius is currently considered to include three species: Ellobius talpinus (distributed from SE Europe and Turkmenistan through Kazakhstan to SW Siberia), Ellobius alaicus (S Tianshan, Pamir‐Alay) and Ellobius tancrei (East and West Central Asia, from the Amu‐Darya to Mongolia and N China). A study focusing on the genetic variation in Ellobius from Mongolia was conducted using one mitochondrial and three nuclear markers. Two divergent allopatric lineages endemic to East Central Asia were revealed. The first lineage occurs from Dzungaria eastwards to central Mongolia and represents E. tancrei sensu stricto. The second lineage is found in East Gobi only and corresponds to a taxon described as Ellobius orientalis, which has been traditionally treated as a subspecies of E. tancrei. However, molecular and chromosome data indicate that orientalis is related not to E. tancrei but to E. talpinus, which is separated from the former by a distribution gap of ~2,000 km. The taxonomic status of the East Gobi mole vole is ambiguous, and its genetic distance from E. talpinus s. str. falls into the range characteristic for closely related vole species or semi‐species. According to molecular estimates, the two taxa have been isolated since the late Middle Pleistocene. A similar divergence is observed between the East and West Central Asian lineages of E. tancrei. E. alaicus is placed as sister to the latter rendering E. tancrei sensu lato paraphyletic. The revealed phylogeographic pattern implies that East Central Asia was colonized by mole voles through multiple eastward dispersal events.
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