Isolation of populations of the Mongolian gazelle Procapra gutturosa (Artiodacrtyla, Bovidae) in the past: Analysis of mtDNA fragments with different mutation rates

Abstract

The Mongolian gazelle is one of the few CentralAsian ungulates that have retained high numbers andvast geographic ranges. To date, there is no commonopinion on the population structure of this species. Toclarify this issue, we analyzed tissue samples ofgazelles from eastern Mongolia and neighboringregions with respect to two fragments of mtDNA differ-ing from each other in mutation rate: a fragment of thecytochrome b gene and the hypervariable fragment ofthe D-loop. We obtained the first data on the nucleotidesubstitution accumulation rates in these fragments ofthe genome of this species. It was found that the cur-rent, single population of gazelles is genetically hetero-geneous and includes two differentiated phylogeneticgroups. The two genetically different groups wereprobably formed within this steppe species more than100 000 years ago, when the gazelle geographic rangewas split by a forest zone during the interglacial epoch.The molecular genetic analysis of the fragments ofthe cytochrome b gene and D-loop was performed insamples of different tissues (muscles, dry skins, andhorns) of 13 Mongolian gazelles collected in Russia,Mongolia, and China between 1999 and 2005. We alsoused tissues of the Mongolian gazelle horn from thecollection of Zoological Institute of the Russian Acad-emy of Sciences (no. 8343) collected in 1914. ATibetan gazelle (goa or Tibetan gazelle, Procapra pic-ticaudata) from the collection of Zoological Institute(no. 602) obtained in 1874 and a Persian gazelle(Gazella subgutturosa) obtained from Mongolia in2005 were used as outgroups. The DNA isolation andthe amplification of the D-loop fragment were per-formed as described earlier [2–3]. The PCR of the cyto-chrome b gene fragment was carried out with the use ofthe primers Glu-(L14724) (TGATATGAAAAAC-CATCGTTG) and Cb2-(H15174) (CCCTCAGAAT-GATATTTGTCCTCA) as follows: (I) 3 min at 94°C;(II) 15 s at 94°C, 15 s at 50°C, and 45 s at 72°C(35 cycles); (III) 6 min at 72°C. The nucleotidesequence in the mtDNA fragment studied was deter-mined by means of an ABI 310 automatic analyzerusing a Big Dye kit (Applied Biosystems). The Mega3.0 and Arlequin 2.000 software was used for statisticaltreatment [4–5].We found seven haplotypes of a 375-bp fragment ofthe cytochrome b gene, five of which were unique, in asample of 13 specimens. The nucleotide diversity (π)was 0.5 ± 0.3%. In the same specimens, we found12 unique haplotypes of a 644-bp fragment of theD-loop; the nucleotide diversity was there 5.2 ± 0.7%.All nucleotide sequences have been inputted to theinternational genetic database GenBank (DQ266310,DQ266321– DQ266324, DQ266326, DQ266332–DQ266334, DQ266336, DQ266337, DQ266352, andDQ269150–DQ269162). Phylogenetic analysisshowed that all haplotypes from the studied sample fellinto two groups (Figs. 1, 2). It is noteworthy that thedistribution of the specimens between these two groupswas the same for the cytochrome b gene and the D-loophypervariable fragment. In neither case did we foundany association between the current territorial distribu-tion and genetic relationship between the animals.Therefore, we hypothesized that, in the past, there weretwo isolated populations of gazelles, which intermixedafterwards. The intergroup genetic distance (Net dis-tance, D) between these two clusters calculated for thecytochrome b gene fragment was 0.4%. Comparisonwith outgroups showed that the genetic distancebetween the Tibetan and Mongolian gazelles was 3.2%and that between all gazelles and the Persian gazellewas 11.4%.According to paleontological data, there were twoevolutionary lineages of gazelles in the late MioceneEpoch. One of them has led to the currently existingMongolian and Tibetan gazelles and the other, to thePersian gazelle [6]. Gazella gaudryi from the lateMiocene and early Pliocene Yushi sediments in China