Population genetic structure of brown bears in the Dinaric-Pindos region

Hočevar, Špela (author), Stronen, Astrid Vik (mentor), Skrbinšek, Tomaž (comentor)

Wide-ranging species such as the brown bear occur at low densities and require large areas to support long-term sustainable populations and are often sensitive to human-caused habitat fragmentation and disturbance. Although these species are capable of dispersing long distances, in some cases moving over several hundred kilometers, landscape modifications and other human development including major highways can limit dispersal and gene flow. It is generally considered that the Dinaric-Pindos population is a single population of brown bear, however, little is known about connectivity and gene flow within this population. We explored genetic structure of Dinaric-Pindos population using samples from across this populations’ area. The results from different methods consistently showed apparent structuring between the samples from the Dinaric part of the population and the Pindos part. Since our sampling still had a gap between Montenegro (most south Dinaric samples we had) and Prespa Lake Region (Pindos samples), we cannot know if there is some part of the population that would be intermediate between Dinaric and Pindos subpopulations, but the structuring would still be evident. The most probable explanation for the structuring are historic bottlenecks and fragmentation. In the past when the numbers of brown bears were smaller, the effects of the spatial barriers and fragmentation could have been stronger, since genetic drift increases in small and isolated population fragments and can cause rapid genetic differentiation between them. These genetic differences may indicate that there are (sub)populations that are demographically separated, which should be considered in management and conservation decisions. For this reason, we think that a coordinated transboundary monitoring of the entire Dinaric-Pindos region is essential for understanding connectivity and gene flow within this population and for its long-term conservation.

• Language: English
• Keywords: Ursus arctos, population genetic structure, Dinaric-Pindos population, connectivity, transboundary, gene flow
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: BF - Biotechnical Faculty
• Publisher: [Š. Hočevar]
• Year: 2025
• PID: 20.500.12556/RUL-169475
• UDC: 599.744.211:575.17(234.42)(043.2)
• COBISS.SI-ID: 238662659
• Publication date in RUL: 30.05.2025

Secondary language

• Language: Slovenian
• Title: Populacijska genetska struktura rjavega medveda v Dinarsko-Pindski regiji

Abstract

Visoko mobilne, široko razširjene vrste, kot je rjavi medved, se pojavljajo v nizkih gostotah in potrebujejo obsežna območja za dolgoročno vzdržne populacije, pogosto pa so občutljive na razdrobljenost okolja in druge motnje habitata, ki jih povzroča človek. Čeprav so te vrste sposobne prepotovati dolge razdalje, v nekaterih primerih več sto kilometrov, lahko spremembe v krajini in drugi posegi človeka, vključno z večjimi avtocestami in mesti, omejijo njihovo širjenje in pretok genov. Na splošno velja, da je na dinarsko-pindskem območju ena populacija rjavega medveda, vendar je o dejanski povezljivosti in genskem pretoku znotraj te populacije malo znanega. Populacijsko – genetsko strukturo populacije smo raziskali s pomočjo vzorcev iz celotnega območja. Rezultati, pridobljeni z različnimi metodami, so dosledno kazali jasno genetsko strukturiranost med Dinarskim in Pindskim delom populacije. V našem vzorčenju je sicer vrzel med vzorci iz Črne gore (južni del dinarskih vzorcev) ter vzorci iz območja Prespanskega jezera (pindski del vzorcev) zato ne moremo vedeti ali obstaja del populacije, ki bi povezala Dinarski in Pindski del, vendar bi kljub temu strukturiranost populacije ostala očitna. Najverjetneje je na tako strukturo vplivalo več dejavnikov, med njimi zgodovinska ozka grla in fragmentacija. V preteklosti, ko je bilo število rjavih medvedov manjše, so prostorske ovire in fragmentacija lahko imeli močnejši učinek, saj se genetski zdrs (drift) v majhnih in izoliranih fragmentih poveča in povzroči hitro genetsko diferenciacijo med njimi. Te genetske razlike lahko kažejo na (sub)populacije, ki so demografsko ločene, kar bi bilo treba upoštevati pri upravljavskih in naravovarstvenih odločitvah. Zaradi tega menimo, da je usklajeno čezmejno spremljanje celotne populacije medveda dinarsko-pindske regije bistvenega pomena za razumevanje povezanosti in genskega pretoka znotraj te populacije ter posledično velikega pomena za dolgoročno ohranitev medveda v tem prostoru.

• Keywords: Ursus arctos, populacijska genetska struktura, Dinarsko-Pindska populacija, povezljivost, genski pretok