Morphometric analysis of the mandibles of the European water vole, Arvicola terrestris (Linnaeus, 1758)

Tema magistrske naloge je bila morfometrična analiza variabilnosti mandibule pri velikem voluharju, Arvicoli terrestris (Linnaeus, 1758). Raziskovani material je zajemal 597 osebkov z različnih geografskih območij: iz Avstrije, Bolgarije, Nemčije, Španije, Švice, s Češke, Madžarske in Slovaške. Material izvira iz različnih muzejskih zbirk. Zaradi izredne ekološke plastičnosti velikega voluharja, največje evropske voluharice, prihaja med populacijami do izrazite variabilnosti v telesni velikosti in obliki. Namen dela je bil s pomočjo geometrijske morfometrije odkriti, ali obstajajo razlike v velikosti in obliki spodnje čeljustnice (mandibule) med živalmi z različnih geografskih območij, in oceniti razlike med spoloma. Po določitvi 13 oslonilnih točk na mandibulah smo opravili uni- in multivariatne analize. Preverjanje morebitnih razlik v velikosti in obliki je potekalo ločeno. Pri preverjanju sekundarnega spolnega dimorfizma smo ugotovili, da ne prihaja do razlik med spoloma, zato smo v nadaljevanju raziskave oba spola obravnavali skupaj. V nadaljevanju smo pri preverjanju geografske variabilnosti v velikosti mandibul znotraj vrste Arvicola terrestris prepoznali tri velikostne razrede. V najmanjši razred so se uvrščale mandibule vseh osebkov iz Avstrije in večine osebkov iz Švice, največje mandibule pa so imeli osebki, ulovljeni na območju Bolgarije, Madžarske in Nemčije. Izstopal je material iz Španije, ki je zajemal devet osebkov vrste Arvicola sapidus. Tudi pri preverjanju geografske variabilnosti v obliki smo opazili razlike. Te smo zaznali tako na sprednjem predelu z meljaki kot tudi na veji mandibule s tremi odrastki. Celotna mandibula postaja krajša in kompaktnejša. Pri analizi kopičenja na osnovi oblike smo prepoznali sedem skupin, ki so bile geografsko ustrezne.The subject of the master’s thesis was a morphometric analysis of the variability of the mandible in the European water vole, Arvicola terrestris (Linnaeus, 1758). The research material included 597 specimens from different geographic areas: Austria, Bulgaria, Germany, Spain, Switzerland, the Czech Republic, Hungary and Slovakia. The material originates from various museum collections. Because of the extraordinary plasticity of the European water vole, the largest European vole species in Europe, there are significant interpopulation variations in its body size and shape. The aim of this master’s thesis was to determine, by means of geometric morphometrics, whether there are differences in the size and shape of the jawbone (mandible) between animals from different geographic areas, and to evaluate differences between the sexes. After determining thirteen landmarks on mandibles, the univariate and multivariate analyses were conducted. The verification of differences in size and shape took place separately. Because no secondary sexual dimorphism was detected, both genders were considered together in the continuation of the study. Three distinct size classes within the Arvicola terrestris species were identified when examining the geographic variability in the size of the mandible. The smallest class included the mandibles of all specimens from Austria and most specimens from Switzerland whereas specimens caught in the territory of Bulgaria, Hungary and Germany had the largest mandibles. The material from Spain was the most distinct and comprised nine specimens belonging to the species Arvicola sapidus. The analysis of the geographic variability in the shape of the mandible also showed differences. They were detected both in the front molar region as well as in the ramus with three processes. The whole mandible thus becomes shorter and more compact. Seven geographically corresponding groups were identified in the cluster analysis based on shape