Marine Murtskhvaladze

Geographic and genetic boundaries of brown bear (Ursus arctos) population in the Caucasus

The taxonomic status of brown bears in the Caucasus remains unclear. Several morphs or subspecies have been identified from the morphological (craniological) data, but the status of each of these subspecies has never been verified by molecular genetic methods. We analysed mitochondrial DNA sequences (control region) to reveal phylogenetic relationships and infer divergence time between brown bear subpopulations in the Caucasus. We estimated migration and gene flow from both mitochondrial DNA and microsatellite allele frequencies, and identified possible barriers to gene flow among the subpopulations. Our suggestion is that all Caucasian bears belong to the nominal subspecies of Ursus arctos. Our results revealed two genetically and geographically distinct maternal haplogroups: one from the Lesser Caucasus and the other one from the Greater Caucasus. The genetic divergence between these haplogroups dates as far back as the beginning of human colonization of the Caucasus. Our analysis of the least‐cost distances between the subpopulations suggests humans as a major barrier to gene flow. The low genetic differentiation inferred from microsatellite allele frequencies indicates that gene flow between the two populations in the Caucasus is maintained through the movements of male brown bears. The Likhi Ridge that connects the Greater and Lesser Caucasus mountains is the most likely corridor for this migration.

Systematics and evolutionary history of large endemic snails from the Caucasus (Helix buchii, and H. goderdziana) (Helicidae)

Abstract: Two species of genus Helix Linnaeus, 1758 (Mollusca: Gastropoda: Helicidae) endemic to the Caucasus region are known from Georgia and northeastern Turkey: Helix buchii Dubois de Montpereux, 1839 and the recently-described but disputed Helix goderdziana Mumladze, Tarkhnishvili and Pokryszko, 2008. The latter species is the largest land snail throughout non-tropical Eurasia. We compared shell shapes and genital morphology of the two species. We analyzed mitochondrial COI and nuclear 18S ribosomal RNA and ITS1gene fragments in 39 specimens of H. buchii and H. goderdziana from ten locations from the entire distribution range of these species, together with 13 specimens of the widespread H. lucorum Linnaeus, 1758 and H. pomatia Linnaeus, 1758. Based on shell morphology alone, most of the individuals of the two species can be discriminated using multivariate approaches. The species have different flagellum/diverticulum ratios, and the foot coloration is a fully diagnostic morphological character. Molecular genetic analysis revealed little variation in 18S+ITS1 fragment, and eleven COI haplotypes. Phylogenetic analyses support reciprocal monophyly of H. buchii and H. goderdziana. The genetic distances significantly correlate with the geographic and morphological distances; correlation of morphological distances with geography is insignificant. The basal lineages of both species are found within two distinct glacial refugia, a result which matches the separation of eastern and western evolutionary lineages of other relicts of the Western Caucasus. The present distribution of H. goderdziana coincides with the expected refugiai borders, whereas H. buchii is likely to have extended its geographical range since the last glaciation.

Human Paternal Lineages, Languages, and Environment in the Caucasus

ABSTRACT Publications that describe the composition of the human Y-DNA haplogroup in different ethnic or linguistic groups and geographic regions provide no explicit explanation of the distribution of human paternal lineages in relation to specific ecological conditions. Our research attempts to address this topic for the Caucasus, a geographic region that encompasses a relatively small area but harbors high linguistic, ethnic, and Y-DNA haplogroup diversity. We genotyped 224 men that identified themselves as ethnic Georgian for 23 Y-chromosome short tandem-repeat markers and assigned them to their geographic places of origin. The genotyped data were supplemented with published data on haplogroup composition and location of other ethnic groups of the Caucasus. We used multivariate statistical methods to see if linguistics, climate, and landscape accounted for geographical differences in frequencies of the Y-DNA haplogroups G2, R1a, R1b, J1, and J2. The analysis showed significant associations of (1) G2 with well-forested mountains, (2) J2 with warm areas or poorly forested mountains, and (3) J1 with poorly forested mountains. R1b showed no association with environment. Haplogroups J1 and R1a were significantly associated with Daghestanian and Kipchak speakers, respectively, but the other haplogroups showed no such simple associations with languages. Climate and landscape in the context of competition over productive areas among different paternal lineages, arriving in the Caucasus in different times, have played an important role in shaping the present-day spatial distribution of patrilineages in the Caucasus. This spatial pattern had formed before linguistic subdivisions were finally shaped, probably in the Neolithic to Bronze Age. Later historical turmoil had little influence on the patrilineage composition and spatial distribution. Based on our results, the scenario of postglacial expansions of humans and their languages to the Caucasus from the Middle East, western Eurasia, and the East European Plain is plausible.

Gene introgression between Gazella subgutturosa and G. marica: limitations of maternal inheritance analysis for species identification with conservation purposes

It has recently been suggested that goitered gazelles (Gazella subgutturosa and Gazella marica) have paraphyletic maternal origin, and that the mitochondrial cytochrome b gene fragment can be used for species identification prior to reintroduction of the gazelles. Although there is a large geographic area where the gazelles have intermediate morphology, previous researchers have not inferred any signs of mitochondrial haplotype introgression, and it is thought that the introgression, if it exists, is male-biased. We studied mitochondrial haplotypes of morphologically typical G. subgutturosa from two geographic locations. Goitered gazelles from eastern Turkey, morphologically identical to G. subgutturosa, had haplotypes identical to G. marica. This finding confirms ongoing maternal gene introgression from G. marica to G. subgutturosa. Our suggestion is that there is a natural gene flow between these two nominal species, and morphological characters together with recombinant genetic markers rather than mitochondrial DNA should be used to differentiate among individuals from areas close to the contact zone.

Phylogeography and morphological variation in a narrowly distributed Caucasian rock lizard, Darevskia mixta

The Caucasian rock lizard Darevskia mixta was sampled and studied from throughout its range, using mitochondrial cytochrome b sequences and scalation. The populations of the Greater and the Lesser Caucasus are reciprocally monophyletic matrilineally, and the respective lineages have been separated since the mid-Pleistocene. The lizards from the Greater Caucasus commonly have an unpaired preanal scale, whereas the lizards from the Lesser Caucasus have an additional scale behind the central temporal and subdivided interparietal scale more commonly than those from the Greater Caucasus. The Lesser Caucasus populations are further subdivided into two geographically distinct matrilineages, and are more diverse genetically and morphologically than the Greater Caucasus populations. The central part of the Lesser Caucasus is suggested to be the ancestral area for the entire D. mixta lineage. Successive Pleistocene periods of glaciation appear to be responsible both for the isolation of D. mixta from its common relatives, and for subdivision within D. mixta. Presence of D. mixta in NE Turkey is challenged.

Partial genomic survival of cave bears in living brown bears

Although many large mammal species went extinct at the end of the Pleistocene epoch, their DNA may persist due to past episodes of interspecies admixture. However, direct empirical evidence of the persistence of ancient alleles remains scarce. Here, we present multifold coverage genomic data from four Late Pleistocene cave bears (Ursus spelaeus complex) and show that cave bears hybridized with brown bears (Ursus arctos) during the Pleistocene. We develop an approach to assess both the directionality and relative timing of gene flow. We find that segments of cave bear DNA still persist in the genomes of living brown bears, with cave bears contributing 0.9 to 2.4% of the genomes of all brown bears investigated. Our results show that even though extinction is typically considered as absolute, following admixture, fragments of the gene pool of extinct species can survive for tens of thousands of years in the genomes of extant recipient species.Palaeogenomic data from four Late Pleistocene cave bears reveals that cave bears admixed with brown bears in the Pleistocene epoch, and despite cave bears going extinct during the Last Glacial Maximum, extant brown bears maintain a genomic contribution from cave bears.

Landscape Complexity in the Caucasus Impedes Genetic Assimilation of Human Populations More Effectively than Language or Ethnicity

ABSTRACT The analyses of 15 autosomal and 23 Y-chromosome DNA single-tandem-repeat loci in five rural populations from the Caucasus (four ethnically Georgian and one ethnically Armenian) indicated that two Georgian populations, one from the west and the other from the east of the Greater Caucasus Mountains, were both patrilineally and autosomally most differentiated from each other, and the other populations of Georgians and Armenians held an intermediate position between those two. This pattern may be due to human dispersal from two distinct glacial refugia in the last glacial period and the early Holocene, followed by less gene flow among the populations from the Greater Caucasus than among those from the rest of the Caucasus, where the populations have undergone substantial admixture in historical time. This hypothesis is supported by a strong correlation between genetic differentiation among the populations and landscape permeability to human migrations as determined by terrain ruggedness, forest cover, and snow cover. Although geographic patterns of autosomal and Y-chromosome DNA are not fully concordant, both are influenced by landscape permeability and show a similar east-west gradient. Our results suggest that this permeability was a stronger factor limiting gene flow among human populations in the Caucasus than were ethnic or linguistic boundaries.