Range-wide patterns of human-mediated hybridisation in European wildcats

Abstract

Hybridisation between wild taxa and their domestic congeners is a significant conservation issue. Domestic species frequently outnumber their wild relatives in population size and distribution and may therefore genetically swamp the native species. The European wildcat (Felis silvestris) has been shown to hybridise with domestic cats (Felis catus). Previously suggested spatially divergent introgression levels have not been confirmed on a European scale due to significant differences in the applied methods to assess hybridisation of the European wildcat. We analysed 926 Felis spp. samples from 13 European countries, using a set of 86 selected ancestry-informative SNPs, 14 microsatellites, and ten mitochondrial and Y-chromosome markers to study regional hybridisation and introgression patterns and population differentiation. We detected 51 hybrids (four F1 and 47 F2 or backcrosses) and 521 pure wildcats throughout Europe. The abundance of hybrids varied considerably among studied populations. All samples from Scotland were identified as F2 hybrids or backcrosses, supporting previous findings that the genetic integrity of that wildcat population has been seriously compromised. In other European populations, low to moderate levels of hybridisation were found, with the lowest levels being in Central and Southeast Europe. The occurrence of distinct maternal and paternal markers between wildcat and domestic cat suggests that there were no severe hybridisation episodes in the past. The overall low (< 1%) prevalence of F1 hybrids suggests a low risk of hybridisation for the long-term genetic integrity of the wildcat in most of Europe. However, regionally elevated introgression rates confirm that hybridisation poses a potential threat. We propose regional in-depth monitoring of hybridisation rates to identify factors driving hybridisation so as to develop effective strategies for conservation.

Endoparasites of European Wildcats (Felis silvestris) in Greece

“…These are important threats causing a decreasing population trend, which has already resulted in veiled extinction in some areas. In fact, an extended recent survey in different areas of Europe has revealed varying hybridisation levels in the examined animals and has shown possible extinction of the Scottish population [ 2 , 4 ]. The European wildcat is the only wild felid with confirmed reproducing populations in Greece and low levels of hybridisation, and it lives in several habitats including agricultural areas and wetlands [ 4 , 5 ].…”

Integrating multiple datasets into spatially-explicit capture-recapture models to estimate the abundance of a locally scarce felid

“…Using SCR models on camera-trapping records, Kilshaw et al (2015) estimated 0.68 wild-living Scott et al (1993) cats/km 2 in Scotland, but their estimate included both wildcats and hybrids. Despite the phenotypical compatibility of all our captured individuals with pure wildcats', one out of four individuals was genetically identified as a hybrid (F1) with domestic cats (Tiesmeyer et al 2020). Therefore, the true density of pure wildcats in our study area might be even lower than the nominal values estimated.…”

“…The most likely cause for the current low wildcat density within CNP should be low prey abundance (wild rabbit and small mammals), which hampers reproduction and forces felids to roam over large home ranges (Ferreras et al 2011;Monterroso et al 2016). Other causes that could have further contributed to the dampening of the European wildcat population at our study area could be hybridization with domestic cats and disease transmission between the two counterparts (López-Martín et al 2007;Oliveira et al 2008;Tiesmeyer et al 2020). If this is the case, then the low-density wildcat population at CNP could have entered into an extinction vortex (Palomares et al 2012), likely initiated by prey scarcity, and potentially leading to an accelerated hybridization with domestic cats and disease transmission (López et al 2009;Meli et al 2010).…”

“…No domestic cats were captured during the survey. Genetic analyses of four of the captured wildcats revealed that all were pure wildcats except one individual (FSC04), which was a first-or second-generation hybrid with domestic cat (Tiesmeyer et al 2020).…”

“…The main threats for the Iberian wildcat populations include hybridization with domestic cats (e.g. Oliveira et al 2008;Tiesmeyer et al 2020), mortality due to non-selective methods of predator control, habitat loss and fragmentation (López-Martín et al 2007). Diseases may also pose a threat, although their relative importance is currently unknown.…”