Molekularni diverzitet i genetički signali lokalnih adaptacija vrste Lepus europaeus Pallas, 1778 u heterogenim uslovima sredine

Abstract

U ovom radu sagledan je molekularni diverzitet, filogeografska struktura, prostorna distribucija molekularnog diverziteta, kao i prisustvo selekcionih signala i genetičkih signala lokalnih adaptacija kod 251 jedinke vrste Lepus europaeus (Pallas, 1778) sa teritorije Evrope i Bliskog Istoka, a na osnovu analize varijabilnosti sekvenci D petlje mtDNK, MT-ND2, MT-ND6, MHCDQA, MHC-DQB i TLR2 gena. Uočen je visok nivo parametara molekularnog diverziteta za sve ispitivane molekularne markere. Utvrđeno je postojanje filogeografske strukturiranosti vrste na osnovu mtDNK, kao i asimetričan protok gena jedinki sa teritorije Anadolije na teritoriju Balkana na osnovu D petlje mtDNK, MT-ND2 i MT-ND6 gena, dok je na osnovu sekvenci D petlje mtDNK uočena gotovo tri puta veća stopa protoka gena sa Balkana u centralnu i zapadnu Evropu. Utvrđeno je prisustvo signala poizivne selekcije u okviru MT-ND6 gena, kao i efekat klimatskih parametara (precipitacije) na distribuciju proteinskih varijanti ND6C i ND6F, kao moguća posledica regionalnih adaptacija na razlike u sredinskim uslovima. Pokazano je odsustvo signala filogeografske strukturiranosti na osnovu MHC-DQA, MHC-DQB i TLR2 gena. Uočeno je postojanje prostorne strukturiranosti na osnovu gena imunskog sistema, i definisane su dve prostorne grupe, jedna koja je obuhvatala jedinke sa teritorije Bliskog Istoka, i druga koja je obuhvatala jedinke sa teritorije Evropi. Više vrednosti parametara molekularnog diverziteta uočene su u anadolijskoj grupi, u poređenju sa evropskom grupom. Uočen je signal delovanja pozitivne i negativne selekcije u MHC-DQA i MHCDQB genima, kao i signal negativne selekcije u TLR2 genu. Pokazan je efekat klimatskih parametara na distribuciju najzastupljenijih proteinskih varijanti MHC-DQA i MHC-DQB gena kao indirektni pokazatelj imunogenetičkih adaptacija na sredinski uslovljene pretpostavljene razlike u distribuciji patogena. Mehanizam oblikovanja varijabilnosti MHC gena rezultat je uzajamnog delovanja mutacija, rekombinacija i selekcije.

In this doctoral dissertation, molecular diversity, phylogeographic structure, spatial distribution of molecular diversity, detection of possible selection signals shaping the evolution of these genes, as well as the presence of local/regional adaptations in correlation was examined in 251 brown hares from Europe and the Middle East based on the analyses of mitochondrial D loop, mitochondrially Encoded NADH Dehydrogenase 2 (MT-ND2), mitochondrially Encoded NADH Dehydrogenase 6 (MT-ND6), exon 2 of MHC Class II genes MHC-DQA,MHC-DQB and Toll Like Receptor 2 (TLR2) gene sequences. A high level of molecular diversity was found based on the all applied markers. Strong signal of phylogeographical and spatial structuring was observed for mtDNA, most likely as a consequence of climatic perturbations during the Pleistocene. The evolutionary development of hares from Anatolia/Israel to the Balkans, and furthermore to central and western Europe was suggested by several lines of evidences, which include dating the population demography based on D-loop sequences, the observed migration patterns, results of demographic tests, and apparent reduction in molecular diversity indices along this trajectory. Positive selection acting on MT-ND6 gene was detected, together with significant climatic effect shaping the distribution of the most prevalent protein variants found in this gene, supposedly as a consequence to local/regional adaptations due to the environmentally induced different energetic requirements and optimization of OXPHOS genes. On the other side, less evident phylogeographic signal and absence of strong structuring was revealed in MHC genes. High diversity at MHC genes seems to be shaped by the interplay of recombination, selection mechanisms and adaptations. Balancing selection seems to maintain a high molecular diversity within these genes, while directional selection promotes local/regional adaptations to pathogenic landscapes, as indirectly suggested by a significant effect of climatic parameters on the distribution of protein variants in both examined MHC genes.