Genetic diversity and population structure of the grey wolf (Canis lupus Linnaeus, 1758) and evidence of wolf × dog hybridisation in the centre of European Russia

A universal panel of STR loci for the study of polymorphism of the species Canis lupus and forensic identification of dog and wolf

Commercial panels of microsatellite (STR) loci are intended for DNA analysis of the domestic dog (Canis lupus familiaris) and, therefore, when genotyping the Grey wolf (Canis lupus lupus), most markers reveal significant deviations from the Hardy-Weinberg equilibrium and have a low informative value, which complicates their use in a forensic examination. The aim of this study was to select STR markers that equally effectively reflect population polymorphism in the wolf and the dog, and to create a universal panel for the identification of individuals in forensic science. Based on the study of polymorphisms of 34 STR loci, a CPlex panel of 15 autosomal loci and two sex loci was developed, which is equally suitable for identifying wolfs and dogs. Analysis of molecular variance (AMOVA) between samples revealed significant differentiation values (FST = 0.0828, p < 0.05), which allows the panel to be used for differentiating between wolf and dog samples. For the first time in the forensic examination of objects of animal origin in the Republic of Belarus, population subdivision coefficients (θ-values) were calculated for each of the 15 STR loci of the test system being reported. It was shown that the values of the genotype frequency, when averaged over all studied animals without and with considering the θ-value, differ by three orders of magnitude (3.39 · 10-17 and 4.71 · 10-14, respectively). The use of population subdivision coefficients will provide the researcher with the most relevant results of an expert identification study. The test system was validated in accordance with the protocol of the Scientific Working Group on DNA Analysis Methods. A computational tool was developed to automate the analysis of genetic data on the wolf and dog in the forensic examination; two guides were approved for practicing forensic experts. This methodology is being successfully used in expert practice in investigating cases of illegal hunting, animal abuse and other offenses in the Republic of Belarus.

Assessment of genetic diversity, population structure and wolf-dog hybridisation in the Eastern Romanian Carpathian wolf population

The Carpathian Mountains have been constantly inhabited by grey wolves and present one of the largest distribution areas in Europe, comprising between 2300 and 2700 individuals in Romania. To date, however, relatively little is known about the Romanian wolf population. We aimed to provide a first assessment of genetic diversity, population structure and wolf-dog hybridisation based on 444 mostly non-invasively collected samples in the Eastern Romanian Carpathians. Pack reconstruction and analysis of population genetic parameters were performed with mitochondrial DNA control-region sequencing and microsatellite genotyping. We found relatively high levels of genetic diversity, which is similar to values found in previous studies on Carpathian wolves from Poland and Slovakia, as well as to the long-lasting Dinaric-Balkan wolf population. We found no significant population structure in our study region, suggesting effective dispersal and admixture. Analysis of wolf-dog hybridisation using a Single Nucleotide Polymorphism panel optimised for hybrid detection revealed low rates of admixture between wolves and domestic dogs. Our results provide evidence for the existence of a genetically viable wolf population in the Romanian Carpathians. The genetic data obtained in this study may serve as valuable baseline information for the elaboration of monitoring standards and management plans for wolves in Romania.

Overview of Current Research on Wolves in Russia

This paper provides an overview of wolf research in Russia at the beginning of the 21st century. Wolf research covered various directions, including population density estimation, management methods and minimization of human-wildlife conflicts, general and behavioral ecology, behavior, wolf population genetics and morphology, paleontology, dog domestication, helminthology and the wolves’ role in the rabies transmission. Some studies are performed with state-of-art methodology using molecular genetics, mathematical modeling, camera traps, and GPS telemetry.

Genetic diversity and mate selection in a reintroduced population of gray wolves

The genetic composition of an individual can markedly affect its survival, reproduction, and ultimately fitness. As some wildlife populations become smaller, conserving genetic diversity will be a conservation challenge. Many imperiled species are already supported through population augmentation efforts and we often do not know if or how genetic diversity is maintained in translocated species. As a case study for understanding the maintenance of genetic diversity in augmented populations, I wanted to know if genetic diversity (i.e., observed heterozygosity) remained high in a population of gray wolves in the Rocky Mountains of the U.S. > 20 years after reintroduction. Additionally, I wanted to know if a potential mechanism for such diversity was individuals with below average genetic diversity choosing mates with above average diversity. I also asked whether there was a preference for mating with unrelated individuals. Finally, I hypothesized that mated pairs with above average heterozygosity would have increased survival of young. Ultimately, I found that females with below average heterozygosity did not choose mates with above average heterozygosity and wolves chose mates randomly with respect to genetic relatedness. Pup survival was not higher for mated pairs with above average heterozygosity in my models. The dominant variables predicting pup survival were harvest rate during their first year of life and years pairs were mated. Ultimately, genetic diversity was relatively unchanged > 20 years after reintroduction. The mechanism for maintaining such diversity does not appear related to individuals preferentially choosing more genetically diverse mates. Inbreeding avoidance, however, appears to be at least one mechanism maintaining genetic diversity in this population.

Consequences of Hybridization in Mammals: A Systematic Review

Hybridization, defined as breeding between two distinct taxonomic units, can have an important effect on the evolutionary patterns in cross-breeding taxa. Although interspecific hybridization has frequently been considered as a maladaptive process, which threatens species genetic integrity and survival via genetic swamping and outbreeding depression, in some cases hybridization can introduce novel adaptive variation and increase fitness. Most studies to date focused on documenting hybridization events and analyzing their causes, while relatively little is known about the consequences of hybridization and its impact on the parental species. To address this knowledge gap, we conducted a systematic review of studies on hybridization in mammals published in 2010-2021, and identified 115 relevant studies. Of 13 categories of hybridization consequences described in these studies, the most common negative consequence (21% of studies) was genetic swamping and the most common positive consequence (8%) was the gain of novel adaptive variation. The total frequency of negative consequences (49%) was higher than positive (13%) and neutral (38%) consequences. These frequencies are biased by the detection possibilities of microsatellite loci, the most common genetic markers used in the papers assessed. As negative outcomes are typically easier to demonstrate than positive ones (e.g., extinction vs hybrid speciation), they may be over-represented in publications. Transition towards genomic studies involving both neutral and adaptive variation will provide a better insight into the real impacts of hybridization.

Identification of Wolf-Dog Hybrids in Europe – An Overview of Genetic Studies

Significant development of genetic tools during the last decades provided opportunities for more detailed analyses and deeper understanding of species hybridization. New genetic markers allowed for reliable identification of admixed individuals deriving from recent hybridization events (a few generations) and those originating from crossings up to 19 generations back. Implementation of microsatellites (STRs) together with Bayesian clustering provided abundant knowledge regarding presence of admixed individuals in numerous populations and helped understand the problematic nature of studying hybridization (i.a., defining a reliable thresholds for recognizing individuals as admixed or obtaining well-grounded results representing actual proportion of hybrids in a population). Nevertheless, their utilization is limited to recent crossbreeding events. Single Nucleotide Polymorphisms (SNPs) proved to be more sensible tools for admixture analyses furnishing more reliable knowledge, especially for older generation backcrosses. Small sets of Ancestry Informative Markers (AIMs) of both types of markers were effective enough to implement in monitoring programs, however, SNPs seem to be more appropriate because of their ability to identify admixed individuals up to 3rd generations. The main aim of this review is to summarize abundant knowledge regarding identification of wolf-dog hybrids in Europe and discuss the most relevant problems relating to the issue, together with advantages and disadvantages of implemented markers and approaches.