Brown bear (Ursus arctos) phylogeography in northern Eurasia
Date
2013-01-28
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Abstract
Fülogeograafia on valdkond, mis on keskendunud liigisiseste ja lähiliikidevaheliste geneetiliste liinide ruumilist paiknemist mõjutavate seaduspärasuste ja protsesside uurimisele. Looduslike imetajaliikide hulgas on seni olnud üheks mudelliigiks pruunkaru, seda eelkõige tänu laiale levikule, arvukatele luuleidudele ja emakarude filopatrilisusele. Käesolev doktoritöö vaatleb pruunkaru emaliini fülogeograafiat (analüüsides mitokondriaalse DNA (mtDNA) järjestusi) Põhja-Euraasias, pöörates erilist tähelepanu Loode-Euraasia populatsioonile. Hoolimata asjaolust, et see piirkond moodustab enamiku antud liigi tänapäevasest levikualast ning hõlmab suure osa maailma karupopulatsioonist, oli Põhja-Euraasia kohta käiv fülogegraafiline informatsioon seni puudulik. Antud töö tulemused viitavad, et tänapäeval on kõik pruunkaruliinid Põhja-Euraasias suhteliselt lähedalt seotud ja peale viimase jääaja maksimumi toimus tugev demograafiline ekspansioon ning ükski geograafiline tõke ei olnud piisavaks takistuseks pruunkarude migratsioonile üle Mandri-Euraasia põhjaosa. Loode-Euraasia pruunkaru populatsiooni detailne analüüs mitokondri genoomi täisjärjestuste alusel selgitas välja viis selgesti eristatavat, geograafiliselt piiritletud ja ainult osaliselt kattuvat haplogruppi. Analüüsid näitasid, et need viis haplogruppi moodustusid jääajajärgsel perioodil ning peegeldavad seega kombinatsiooni jääajajärgsest migratsioonimustrist ja hilisemast demograafilisest ajaloost. Et selles töös sekveneeriti 95 mitogenoomi, siis võimaldas see esimest korda analüüsida ka pruunkaru mitokondri genoomide liigisisest variatsiooni. Positiivne evolutsiooniline valik tuvastati valgugeenile ND6. Antud töö tulemused pakuvad olulist baasinformatsiooni pruunkaru efektiivsete majandamis- ja kaitsestrateegiate väljatöötamiseks Euraasias.
Phylogeography is a discipline that focuses on the principles and processes affecting the spatial distribution of genetic lineages, within and among closely related species. Among wild mammals, the brown bear (Ursus arctos) has become a model species for phylogeographic analysis, due to wide distribution, the availability of numerous subfossils and its female philopatry. Current thesis examined brown bear matrilineal phylogeography (by analysing mitochondrial DNA (mtDNA) sequences) in northern Eurasia with particular focus on the population in north-west Eurasia. Prior to the studies performed in the frame of this thesis, information on brown bear phylogeography was largely lacking for northern Eurasia, which nonetheless constitutes a major part of the species’ current distribution and contains the majority of the world’s brown bear population. The results suggest that all contemporary brown bears in northern Eurasia are relatively closely related and after the Last Glacial Maximum, brown bears underwent a sudden demographic expansion and no significant geographic barrier was found to restrict migration across northern continental Eurasia. Detailed analysis of the north-west Eurasian brown bear population using complete mitochondrial sequences revealed five divergent, geographically confined and only partially overlapping haplogroups. Our analysis demonstrated that these five haplogroups formed during the post-glacial period and thus reflect a combination of postglacial migration patterns and more recent demographic history. Ninety-five complete mitogenomes, sequenced during this study, allowed us to make the first analysis of intra-specific variation among brown bear mitogenomes. Positive selection was found to act on the gene ND6. The results of this study provide scientific data that is potentially very useful for the development of effective management and conservation strategies for Eurasian brown bears in the near future.
Phylogeography is a discipline that focuses on the principles and processes affecting the spatial distribution of genetic lineages, within and among closely related species. Among wild mammals, the brown bear (Ursus arctos) has become a model species for phylogeographic analysis, due to wide distribution, the availability of numerous subfossils and its female philopatry. Current thesis examined brown bear matrilineal phylogeography (by analysing mitochondrial DNA (mtDNA) sequences) in northern Eurasia with particular focus on the population in north-west Eurasia. Prior to the studies performed in the frame of this thesis, information on brown bear phylogeography was largely lacking for northern Eurasia, which nonetheless constitutes a major part of the species’ current distribution and contains the majority of the world’s brown bear population. The results suggest that all contemporary brown bears in northern Eurasia are relatively closely related and after the Last Glacial Maximum, brown bears underwent a sudden demographic expansion and no significant geographic barrier was found to restrict migration across northern continental Eurasia. Detailed analysis of the north-west Eurasian brown bear population using complete mitochondrial sequences revealed five divergent, geographically confined and only partially overlapping haplogroups. Our analysis demonstrated that these five haplogroups formed during the post-glacial period and thus reflect a combination of postglacial migration patterns and more recent demographic history. Ninety-five complete mitogenomes, sequenced during this study, allowed us to make the first analysis of intra-specific variation among brown bear mitogenomes. Positive selection was found to act on the gene ND6. The results of this study provide scientific data that is potentially very useful for the development of effective management and conservation strategies for Eurasian brown bears in the near future.
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