Domestic cat gene introgression into wild cat in Europe

Randi, E., Pierpaoli, M., Beaumont, M., Ragni, B., & Sforzi, A. (2001). Genetic identification of wild and domestic cats (Felis silvestris) and their hybrids using Bayesian clustering methods. Molecular Biology and Evolution, 18(9), 1679-1693.

Crossbreeding with free-ranging domestic cats is supposed to threaten the genetic integrity of wildcat populations in Europe, although the diagnostic markers to identify "pure" or "admixed" wildcats have never been clearly defined. Here we use mitochondrial (mt) DNA sequences and allelic variation at 12 microsatellite loci to genotype 128 wild and domestic cats sampled in Italy which were preclassified into three separate groups: European wildcats (Felis silvestris silvestris), Sardinian wildcats (Felis silvestris libyca), and domestic cats (Felis silvestris catus), according to their coat color patterns, collection localities, and other phenotypical traits, independently of any genetic information. For comparison, we included some captive-reared hybrids of European wild and domestic cats. Genetic variability was significantly partitioned among the three groups (mtDNA estimate of F(ST) = 0.36; microsatellite estimate of R(ST) = 0.30; P < 0.001), suggesting that morphological diversity reflects the existence of distinct gene pools. Multivariate ordination of individual genotypes and clustering of interindividual genetic distances also showed evidence of distinct cat groups, partially congruent with the morphological classification. Cluster analysis, however, did not enable hybrid cats to be identified from genetic information alone, nor were all individuals assigned to their populations. In contrast, a Bayesian admixture analysis simultaneously assigned the European wildcats, the Sardinian wildcats, and the domestic cats to different clusters, independent of any prior information, and pointed out the admixed gene composition of the hybrids, which were assigned to more than one cluster. Only one putative Sardinian wildcat was assigned to the domestic cat cluster, and one presumed European wildcat showed mixed (hybrid) ancestry in the domestic cat gene pool. Mitochondrial DNA sequences indicated that three additional presumed European wildcats might have hybrid ancestry. These four cats were sampled from the same area in the northernmost edge of the European wildcat distribution in the Italian Apennines. Admixture analyses suggest that wild and domestic cats in Italy are distinct, reproductively isolated gene pools and that introgression of domestic alleles into the wild-living population is very limited and geographically localized.

Pierpaoli, M., Birò, Z.S., Herrmann, M., Hupe, K., Fernandes, M., Ragni, B., Szemethy, L. & Randi, E. (2003). Genetic distinction of wildcat (Felis silvestris) populations in Europe, and hybridization with domestic cats in Hungary. Molecular Ecology 12: 2585-2598.

The genetic integrity and evolutionary persistence of declining wildcat populations are threatened by crossbreeding with widespread free-living domestic cats. Here we use allelic variation at 12 microsatellite loci to describe genetic variation in 336 cats sampled from nine European countries. Cats were identified as European wildcats (Felis silvestris silvestris), Sardinian wildcats (F. s. libyca) and domestic cats (F. s. catus), according to phenotypic traits, geographical locations and independently of any genetic information. Genetic variability was significantly partitioned among taxonomic groups (FST = 0.11; RST = 0.41; P < 0.001) and sampling locations (FST = 0.07; RST = 0.06; P < 0.001), suggesting that wild and domestic cats are subdivided into distinct gene pools in Europe. Multivariate and Bayesian clustering of individual genotypes also showed evidence of distinct cat groups, congruent with current taxonomy, and suggesting geographical population structuring. Admixture analyses identified cryptic hybrids among wildcats in Portugal, Italy and Bulgaria, and evidenced instances of extensive hybridization between wild and domestic cats sampled in Hungary. Cats in Hungary include a composite assemblage of variable phenotypes and genotypes, which, as previously documented in Scotland, might originate from long lasting hybridization and introgression. A number of historical, demographic and ecological conditions can lead to extensive crossbreeding between wild and domestic cats, thus threatening the genetic integrity of wildcat populations in Europe.

Lecis, R., Pierpaoli, M., Biro, Z. S., Szemethy, L., Ragni, B., Vercillo, F., & Randi, E. (2006). Bayesian analyses of admixture in wild and domestic cats (Felis silvestris) using linked microsatellite loci. Molecular Ecology, 15(1), 119-131.

Methods recently developed to infer population structure and admixture mostly use individual genotypes described by unlinked neutral markers. However, Hardy–Weinberg and linkage disequilibria among independent markers decline rapidly with admixture time, and the admixture signals could be lost in a few generations. In this study, we aimed to describe genetic admixture in 182 European wild and domestic cats (Felis silvestris), which hybridize sporadically in Italy and extensively in Hungary. Cats were genotyped at 27 microsatellites, including 21 linked loci mapping on five distinct feline linkage groups. Genotypes were analysed with structure 2.1, a Bayesian procedure designed to model admixture linkage disequilibrium, which promises to assess efficiently older admixture events using tightly linked markers. Results showed that domestic and wild cats sampled in Italy were split into two distinct clusters with average proportions of membership Q > 0.90, congruent with prior morphological identifications. In contrast, free-living cats sampled in Hungary were assigned partly to the domestic and the wild cat clusters, with Q < 0.50. Admixture analyses of individual genotypes identified, respectively, 5/61 (8%), and 16–20/65 (25–31%) hybrids among the Italian wildcats and Hungarian free-living cats. Similar results were obtained in the past using unlinked loci, although the new linked markers identified additional admixed wildcats in Italy. Linkage analyses confirm that hybridization is limited in Italian, but widespread in Hungarian wildcats, a population that is threatened by cross-breeding with free-ranging domestic cats. The total panel of 27 loci performed better than the linked loci alone in the identification of domestic and known hybrid cats, suggesting that a large number of linked plus unlinked markers can improve the results of admixture analyses. Inferred recombination events led to identify the population of origin of chromosomal segments, suggesting that admixture mapping experiments can be designed also in wild populations.


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Home range of wild and domestic cats in Hungary

Biró, Z., Szemethy, L., & Heltai, M. (2004). Home range sizes of wildcats (Felis silvestris) and feral domestic cats (Felis silvestris f. catus) in a hilly region of Hungary. Mammalian Biology-Zeitschrift für Säugetierkunde,69(5), 302-310.

The most important factor concerning wild cat populations is the loss of habitat. Therefore, it is necessary to assess the size of the home ranges of wild and domestic cats along with the features of these areas (vegetation, elevation, proximity to human settlement, etc.). A total of 16 wildcats and 19 domestic cats were caught and fitted with radio collars within the period between 1989–1993. It was possible to analyze the radiotelemetry data of 4 wildcats and 3 domestic cats. It resulted that the wildcats occupied larger home ranges than the domestic cats, however, there were exceptions. Home range size variability was extensive in both species. The males occupied larger areas than the females. This was most likely due to the reproductional wandering of males into female home ranges. Also the overlap between the home ranges of males was larger than that of females. However, there were very small overlaps between the core areas. No cats used the same sites at the same time. This indicates that the home ranges of cats exist only in space and time as well. Although these animals are solitary, there was some indication that hierarchy exists between males.

Diet overlap between wild and domestic cat: advantages from being generalist

Biró, Z.,J. Lanszki, L. Szemethy, M. Heltai & E. Randi. 2005. Feeding habits of feral domestic cats (Felis catus), wild cats (Felis silvestris) and their hybrids: trophic niche overlap among cat groups in Hungary. Journal of Zoology, 266 (2): 187–196.

The feeding habits of feral domestic cats Felis catus (n=264), wild cats Felis silvestris (n=22) and their hybrids (n=30) were investigated in Hungary. Cat groups were identified taxonomically by morphological and molecular methods. Diet components were identified in stomach contents and faeces collected from the recta. In each cat group, abundant small mammals were dominant in the diet (relative frequency of occurrence: feral domestic cat, 61–82%, depending on regions; wild cat, 70%; hybrid, 59%). Birds were the second most important quarry (2–7%, 16% and 20%, respectively in the three cat groups), while the contribution of hares (1–2%, 5% and 3%, respectively) and other taxa was not significant. Every cat group preyed on small-sized animals (<50 g; 89–96%, 80% and 80%, respectively), terrestrial (91–98%, 84% and 86%, respectively) and wild (71–73%, 87% and 77%, respectively) prey. Standardized trophic niche breadth was typically very narrow (BA=0.07–0.16, 0.13 and 0.17, respectively). Feral domestic cats occasionally consumed household food (2–7%) and domestic animals (4–8%). This could mean that feral domestic cats have an advantage over wild cats that are food specialists. The trophic niche overlap between cat groups was high (77–88%). Food composition and feeding habits, (weight, zonation and environmental association of consumed prey) of feral domestic cats, however, was different compared to wild cats, which indicated the possibility of partial resource partitioning. The values for hybrids were between the two groups. As well as the stable presence of feral domestic cats (mean population density, D=1.34 individuals/1000 ha) based on field live-trapping, hybrids are also present (D=0.10), leading to continuous hybridization. This can threaten the population of wild cats, which are present at a low density (D=0.17).