How the west was won: genetic reconstruction of rapid wolf recolonization into Germany's anthropogenic landscapes

Abstract

Following massive persecution and eradication, strict legal protection facilitated a successful reestablishment of wolf packs in Germany, which has been ongoing since 2000. Here, we describe this recolonization process by mitochondrial DNA control-region sequencing, microsatellite genotyping and sex identification based on 1341 mostly non-invasively collected samples. We reconstructed the genealogy of German wolf packs between 2005 and 2015 to provide information on trends in genetic diversity, dispersal patterns and pack dynamics during the early expansion process. Our results indicate signs of a founder effect at the start of the recolonization. Genetic diversity in German wolves is moderate compared to other European wolf populations. Although dispersal among packs is male-biased in the sense that females are more philopatric, dispersal distances are similar between males and females once only dispersers are accounted for. Breeding with close relatives is regular and none of the six male wolves originating from the Italian/Alpine population reproduced. However, moderate genetic diversity and inbreeding levels of the recolonizing population are preserved by high sociality, dispersal among packs and several immigration events. Our results demonstrate an ongoing, rapid and natural wolf population expansion in an intensively used cultural landscape in Central Europe.

Fig. 1. Wolf study area and sampling localities cover the whole of Germany and are divided into the 16 federal states (black lines).

Shown are the number of successfully genotyped samples collected between 2003 and April 2016 (blue circles) in 12 federal states (labelled with grey initials, see Tables S1–S3). The smaller map shows the wolf distribution across Europe in 2011 with permanent occurrence (dark pink) and sporadic occurrence (pale pink) according to Chapron et al. (2014) and the confirmed wolf occurrence in Germany for 2015 (red) according to the Dokumentations- und Beratungsstelle des Bundes zum Thema Wolf (2017).

Fig. 2. Pedigree of reproducing German wolves in the monitoring period 2005–2015 reconstructed from a combination of microsatellite, mtDNA and field data.

Bold black lines symbolize successful reproductions between female (circles) and male (squares) wolves, double bold black lines highlight breeding of full-siblings, while thin black lines indicate parent–offspring relationships. Four individuals are illustrated twice (arrow with dashed grey line). Individuals with known source pack carrying haplotype HW01 (unfilled), individuals with unknown source pack carrying HW01 (filled with black) and individuals with unknown source pack carrying haplotype HW02 (filled with dark grey). Individuals found dead are crossed out. Individuals with missing genotype are indicated in light grey with Roman numerals. Breeding pairs in which both breeders were not genotyped are not depicted. Framed with a grey dotted line are the first (GW023f and I from 2000 to 2001) and the second breeding pair (GW023f and GW064m from 2002 to 2004) in the Muskauer Heide (MH), which are not included in the further analyses on trends of genetic diversity and inbreeding of breeding pairs until 2015 (see ‘Materials and Methods’).

Fig. 3. Trends in genetic diversity and exponential increase of breeding pairs in Germany between 2005 and 2015.

a Yearly numbers of genotyped breeding pairs (black squares) compared to the numbers of all confirmed breeding pairs (grey unfilled squares). b Yearly haplotype frequency (HW01 [black triangles] and HW02 [grey unfilled triangles]) of breeders. c Mean yearly observed (Ho; black diamonds), unbiased expected (He; grey unfilled diamonds) heterozygosity levels and d mean number of alleles (Na; black dots) of the breeding individuals. e Yearly average pedigree-based inbreeding coefficients (mean Fp) of the offspring from the breeding pairs (black asterisks). f Yearly frequency of breeders with unknown source packs (black crosses). g Genotyped breeding pairs in the different territories. For breeding pairs that persisted over several years, lines connect the respective years.

Fig. 4. Schematic representation of breeder dispersal and pack dynamics during wolf recolonization in Germany from 2005 to 2015.

Shown are wolf territories where a newly established pair reproduced for the first time (grey circles) in the study area (divided into the federal states [grey lines]). Only breeders with known source pack are shown (females [orange arrows] and males [blue arrows]). Breeding partners with unknown source pack are indicated by a blue (male), an orange (female) or a pink (male and female) border around the respective territories, while breeders with missing genotype are indicated by a green border (one parent). The cyan border around DZ indicates the male with unknown source pack and the female with missing genotype. Wolf territories in which genotypes were missing for both breeders are not depicted.

Fig. 5. Linear dispersal distances [km] of breeding wolves in Germany for the years 2005 to 2015.

a Dispersal distances for females (n = 48) and males (n = 31) that reproduced in the respective years for the first time. b Dispersal distances for all females (n = 48) and males (n = 31) with known natal packs. c Dispersal distances for females (n = 43) and males (n = 31), excluding the five females that stayed and reproduced in their natal territory. No significant differences between dispersal distances of females and males were detected.