Conference Agenda

Anthropogenic hybridization is a risk to many wild species in diverse ecosystems. Where related domestic species are abundant, this can result in hybridization and, over time, a hybrid swarm. In Dalmatia in southern Croatia, and parts of Bosnia and Herzegovina, armed conflict during the 1990s caused large-scale human movements and abandonment of domestic animals, including dogs (Canis lupus familiaris), which are known to hybridize with wolves (C. lupus). Wolves at population expansion edges are particularly vulnerable, and wolves recolonized Dalmatia around the same time. Earlier studies in this area have identified hybrids and individuals with atypical phenotypes classified as wolves based on limited sets of microsatellite markers. With a recent panel of 96 single nucleotide polymorphism (SNP) markers to detect wolf-dog hybridization and introgression in Europe, we found several second-generation backcrosses to wolves (BC2w). Our results indicate that hybridization occurred over a decade ago, followed by introgression. Moreover, introgression appears spatially restricted, despite a wider area with similar environmental conditions. Importantly, the SNP panel can detect introgression up to and including BC2w, and later-generation backcrosses likely exist undetected. Whole-genome sequencing combined with ecological and behavioural research are needed to assess introgression and its long-term impacts on wolf genomes and phenotypes.

The range of the European wildcat (Felis silvestris) extends into anthropogenic landscapes where it overlaps with domestic cats (Felis catus). Genetic monitoring has identified patch-like geographic variation in hybridization events across Europe, with several regions showing high rates of hybridization and even hybrid swarm formation. In contrast, hybridization rates appear low in other regions, and genome-wide studies have revealed overall limited long-term domestic cat introgression in the genomes of wildcats. Currently, new genomic marker systems optimized for high-resolution hybrid detection enable systematic assessments of regional hybridization rates. Here, we discuss how recent methodological improvements and genomic data coverage can be used to investigate the observed spatial variation in hybridization rates as well as the long-term consequences of domestic cat introgression for the persistence of the endangered wildcat. For instance, surveys of the hybrid swarm in Scotland suggest that its rapid formation was fostered through selective advantages for wildcats with domestic cat ancestry. Such findings raise the question under which conditions mixing between wild and domestic congeners may constitute a potential evolutionary advantage regarding rapidly changing anthropogenic environments.

The European mink (Mustela lutreola) is one of the most critically endangered mammal species in the world. It only survives in few geographical spots situated in North Western Russia, in the Danube Delta in Romania, in Ukraine (Oriental population), and in South Western France and Northern Spain (Occidental population).

Our genetic analyses evidenced a signal of hybridization and introgression with the European polecat, in the Occidental population. Backcrosses were also evidenced, confirming that hybrids were fertiles.

This hybridization appeared asymmetric, as only pure polecat males mate with pure European mink females. Levels of hybridizations were low in the studied areas, with around 3% of the analysed individuals. This would suggest that hybridization is still a uncommon event. However, this trend could change rapidly and could have a deeper impact on the long term survival of the species.

With genomic methods, we might be able to identify current or historical introgressions at a finer scale. Whole-genome and RAD sequencing are presently performed in our laboratory to better understand the impact of hybridization on the European mink genome. This analysis is improved using a chromosome-scale reference genome created through the ERGA (European Reference Genome Atlas) pilot project.

Traditionally, hybridisation has been viewed as detrimental to population fitness and is often viewed as a result of anthropogenic actions. Concerns regarding hybridisation have often centred around the loss of genetic “purity” and local adaptation. However, in some cases, hybridisation between species or populations may be facilitated by entirely natural processes and/or may benefit species fitness by creating new genetic diversity, and thus adaptive potential, for selection to act upon. In Western Canada, glacial cycles have dictated the colonization-expiration-recolonization histories of terrestrial species. Here we document the hybridisation of two ancient lineages of caribou. Using SNP genotypes at ~43,000 loci for ~700 caribou, we examined: (i) how historical hybridisation post-glaciation contributes to genetic diversity of populations within the hybrid zone, (ii) whether selection favours ancestry from either linage at genomic regions, and (iii) whether greater genetic diversity is positively correlated with variance in phenotypic traits. Several caribou populations in the area are endangered and declining due to habitat loss and human activities mediated by wolf predation. However, we also examined whether: (iv) genetically diverse populations had increased survival, reproduction and trends. Thus, our aim is to examine how hybridisation may provide the adaptive variance required for species persistence in a changing world.

Water frogs of the genus Pelophylax have been widely traded by humans across all European countries for decades, and they have suddenly become invasive in most of them. Their spread threatens the persistence of native populations, mainly via competition and hybridization. As aliens show high morphological similarity compared to native taxa, they are often unnoticed in the wild, with dramatic drawbacks for conservation. Diagnostic molecular markers allow us to track both invasion patterns and their outcomes in invaded populations. During the last decade, we carried out an extensive survey of alien invaders throughout Italy, where hybridogenetic systems perpetuate ancient lineages via hemiclonal reproduction, providing the fact-finding background to evaluate possible managing strategies. Protected areas play a key role in reaching this goal. Recently, we surveyed water frog populations in the Aspromonte Mountain massif (Calabria, southern Italy) and surrounding areas, pointing out the presence of invaded populations. For the first time, we identified polyploid hybrids carrying alien genome, whose evolutionary fate is hard to foresee. We claim the urgent implementation of effective managing practices to prevent the further spread of aliens in this highly biodiverse region as a case in point for the conservation of Italian hybridogenetic systems.