DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 11-12/2013 str. 35     <-- 35 -->        PDF

set covers 81 DNA-samples (42 ♂♂, 38 ♀♀ and 1 unsexed individual) widely distributed over 40 localities (Fig. 1) of the Danube watershed including northern and southern tributaries in Lower Austria.
DNA analysis – DNA analiza
Total genomic DNA was extracted using the DNeasy blood and tissue kit (Qiagen, Hilden, Germany) following the manufacturer’s protocol. The mtDNA control region (D-loop) was amplified using the universal primers DL-H16340 (5’-CCTGAAGTAGGAACCAGATG-3’) and Thr-L15926 (5’-CAATTCCCCGGTCTTGTAAACC-3’) and the protocol published by Vilà et al. (1999). This mtDNA region was chosen as it is known for its comparatively high, even intraspecific variability (cf. Sbisà et al. 1997) and the availability of reference sequences (see below). The cycle sequencing was processed by LGC Genomics GmbH (Berlin, Germany). Reference beaver D-loop sequences were obtained from the European Nucleotide Archive at the European Molecular Biology Laboratory (EMBL), originally generated by Ducroz et al. (2005: accession numbers AY623632–43), Durka et al. (2005: DQ088700–03), Fasanella et al. (unpubl. data: EU476079, GQ228450, JN655158–59), Lizarralde et al. (2008: AY787822–27, AY968083), and Horn et al. (2010: JF264886–88). We also deposited our new D-loop sequence variants at EMBL, under the accession numbers HF674455–58.
The 81 newly generated mtDNA sequences as well as the above 30 reference sequences were aligned using BioEdit 7.0.5.3 (Hall 1999) and restricted to a 455 bp alignment available for all 111 individuals. The hierarchical likelihood ratio test as implemented in Modeltest 3.06 (Posada & Crandall 1998) was used to detect the best evolutionary model based on our set of sequence data. The HKY85+Γ model found (see also Ducroz et al. 2005) was then run in PAUP* 4.0 (Swofford 2000) using the respective parameters in effect to generate a maximum likelihood (ML; Felsenstein 1981) tree reconstruction: πA= 0.3425, πC = 0.2547, πG = 0.1528, πT = 0.25; I = 0; Γ = 0.1381. We also generated neighbor-joining trees (NJ; Saitou & Nei 1987) based on HKY85 genetic distances and respective NJ bootstrap support values (Felsenstein 1985) running 10,000 replicates.
Results
Rezultati
Within our Lower Austrian beaver sampling of 81 individuals investigated so far, we found no evidence for the occurrence of C. canadensis as all D-loop sequences fell into the well-defined C. fiber cluster (Fig. 2; 100% bootstrap support). However, with respect to C. fiber our individual samples split into three unequal groups: one beaver from the Danube floodplains west of Vienna was identified representing the Eastern European beaver group, being most likely the West-Siberian subspecies C. f. pohlei (cf. Ducroz et al. 2005). The remaining 80 individuals split into two major lineages for which single reference mtDNA sequences could be identified (Fig. 2): the lineage "A" corresponds to a C. f. albicus x C. f. belorussicus/orientoeuropaeus sequence from Eastern Germany (locality "Halbe", published by Horn et al. 2010) without any DNA sequence variation within this group (41 sequences), and the lineage "B" (Fig. 2; 93% bootstrap support) to a beaver from Norway ("Bo i Telemark", published by Durka et al. 2005 as C. f. fiber). Within lineage "B" altogether 35 D-loop sequences were identical to the reference sequence, but additionally four sequences were identified all showing a joint single nucleotide mutation (i.e. EDFiba 03–04, Po000015, StP00001; Fig. 2). It has to be pointed out that often multiple samples from the same beaver territory were grouped inside both lineages "A" and "B" (e.g. BadDA, BaPira, Col, Woelbl etc.; Fig. 2). At least in four cases sexually mature individuals have been identified to form genetically mixed pairs representing both major mtDNA lineages. All the females from these mixed pairs already showed status of gestation. In other cases adult males identified showed a different genetic lineage compared to their assumed offspring (i.e. yearlings) belonging to the same family trapped within the same territory during the same season.
Discussion
Rasprava
Origin of the current Lower Austrian beaver population – Podrijetlo današnje populacije dabra u Donjoj Austriji
The three mtDNA groups found in our Lower Austrian beaver samples basically confirmed a variety of origins of the introduced beavers as documented by Sieber & Bauer (2001), i.e. C. f. fiber from Scandinavia (Norway and/or Sweden) and C. f. albicus x C. f. belorussicus/orientoeuropaeus, probably from Poland and Belarus. However, the cur­rent occurrence of C. canadensis was not confirmed (see also Halley & Rosell 2002; Kautenburger & Sander 2008), but instead, one beaver individual likely representing sub­species C. f. pohlei was detected. The latter result was surprising as from the literature there was no indication of a West-Siberian origin of reintroduced beavers in Austria. Although actually relict and reintroduced populations of beavers are growing together all over Central Europe, given their successful expansion (Halley & Rosell 2002, 2003; Dewas et al. 2012), it anyhow seems unlikely that beavers from the far West-Siberia entered Austria independently during this process. Presumably, documentation of the actual origin of reintroduced beaver individuals might have been imprecise, in a way that, for instance, reintroduced beavers from Belarus (cf. Sieber & Bauer 2001) need not to reflect solely autochthonous Belorussian material. In this