Individual genotypes from environmental DNA: Fingerprinting snow tracks of three large carnivore species.

Continued advancements in environmental DNA (eDNA) research have made it possible to access intraspecific variation from eDNA samples, opening new opportunities to expand non-invasive genetic studies of wildlife populations. However, the use of eDNA samples for individual genotyping, as typically performed in non-invasive genetics, still remains elusive. We present successful individual genotyping of eDNA obtained from snow tracks of three large carnivores: brown bear (Ursus arctos), European lynx (Lynx lynx) and wolf (Canis lupus). DNA was extracted using a protocol for isolating water eDNA and genotyped using amplicon sequencing of short tandem repeats (STR), and for brown bear a sex marker, on a high-throughput sequencing platform. Individual genotypes were obtained for all species, but genotyping performance differed among samples and species. The proportion of samples genotyped to individuals was higher for brown bear (5/7) and wolf (7/10) than for lynx (4/9), and locus genotyping success was greater for brown bear (0.88). The sex marker was typed in six out of seven brown bear samples. Results for three species show that reliable individual genotyping, including sex identification, is now possible from eDNA in snow tracks, underlining its vast potential to complement the non-invasive genetic methods used for wildlife. To fully leverage the application of snow track eDNA, improved understanding of the ideal species- and site-specific sampling conditions, as well as laboratory methods promoting genotyping success, is needed. This will also inform efforts to retrieve and type nuclear DNA from other eDNA samples, thereby advancing eDNA-based individual and population-level studies.

Two decades of non-invasive genetic monitoring of the grey wolves recolonizing the Alps support very limited dog introgression.

Potential hybridization between wolves and dogs has fueled the sensitive conservation and political debate underlying the recovery of the grey wolf throughout Europe. Here we provide the first genetic analysis of wolf-dog admixture in an area entirely recolonized, the northwestern Alps. As part of a long-term monitoring program, we performed genetic screening of thousands of non-invasive samples collected in Switzerland and adjacent territories since the return of the wolf in the mid-1990s. We identified a total of 115 individuals, only 2 of them showing significant signs of admixture stemming from past interbreeding with dogs, followed by backcrossing. This low rate of introgression (<2% accounting for all wolves ever detected over 1998-2017) parallels those from other European populations, especially in Western Europe (<7%). Despite potential hybridization with stray dogs, few founders and strong anthropogenic pressures, the genetic integrity of the Alpine population has remained intact throughout the entire recolonization process. In a context of widespread misinformation, this finding should reduce conflicts among the different actors involved and facilitate wolf conservation. Real-time genetic monitoring will be necessary to identify potential hybrids and support an effective management of this emblematic population.

Howling from the past: historical phylogeography and diversity losses in European grey wolves.

Genetic bottlenecks resulting from human-induced population declines make alarming symbols for the irreversible loss of our natural legacy worldwide. The grey wolf (Canis lupus) is an iconic example of extreme declines driven by anthropogenic factors. Here, we assessed the genetic signatures of 150 years of wolf persecution throughout the Western Palaearctic by high-throughput mitochondrial DNA sequencing of historical specimens in an unprecedented spatio-temporal framework. Despite Late Pleistocene bottlenecks, we show that historical genetic variation had remained high throughout Europe until the last several hundred years. In Western Europe, where wolves nearly got fully exterminated, diversity dramatically collapsed at the turn of the twentieth century and recolonization from few homogeneous relict populations induced drastic shifts of genetic composition. By contrast, little genetic displacement and steady levels of diversity were maintained in Eastern European regions, where human persecution had lesser effects on wolf demography. By comparing prehistoric, historic and modern patterns of genetic diversity, our study hence traces the timeframe and the active human role in the decline of the grey wolf, an emblematic yet controversial animal which symbolizes the complex relationship between human societies and nature conservation.