Molecular analysis of hybridisation between wild and domestic cats (Felis silvestris) in Portugal: implications for conservation

Abstract

The endangered European wildcat (Felis silvestris silvestris) is represented, today, by fragmented and declining populations whose genetic integrity is considered to be seriously threatened by crossbreeding with widespread free-ranging domestic cats. Extensive and recent hybridisation has been described in Hungary and Scotland, in contrast with rare introgression of domestic alleles in Italy and Germany. In Portugal, the wildcat is now listed as VULNERABLE in the Red Book of Portuguese Vertebrates. Nevertheless, genetic diversity of populations and the eventual interbreeding with domestic cats remain poorly studied. We surveyed genetic variation at 12 autosomal microsatellites for 34 wild and 64 domestic cats collected across Portugal. Wild and domestic cats were significantly differentiated both at allele frequencies and sizes (F ST =0.11, R ST = 0.18, P < 0.001). Population structure and admixture analyses performed using Bayesian approaches also showed evidence of two discrete groups clustering wild and domestic populations. Results did not show significant genetic divergence among Northern, Central and Southern wildcats. Six morphologically identified wildcats were significantly assigned to the domestic cluster, revealing some discrepancy between phenotypic and genetic identifications. We detected four hybrids (approximately 14%) using a consensus analysis of different Bayesian model-based software. These hybrids were identified throughout all sampled areas, suggesting that hybridisation is of major concern for the appropriate implementation of wildcat conservation strategies in Portugal.

Detection of hybrids in nature: application to oaks (Quercus suber and Q. ilex)

“…C Burgarella et al individuals with qXTq and leaving the others unassigned (Oliveira et al, 2007). Alternatively, q values for all hybrid categories (F1 hybrids, backcrosses) can be combined (Vähä and Primmer, 2006) to distinguish hybrids regardless of their category (criterion 2).…”

“…Cork oaks and holm oaks are easily discriminated by a few morphological traits, including bark (that is, cork layer is found exclusively in Q. suber), leaf and fruit features (Amaral Franco, 1990). Some concerns exist about the effect of hybridization on cork quality and on breeding programs of Q. suber (Oliveira et al, 2007). Within the section Cerris (subgenus Quercus), Q. suber and Q. ilex belong to different clades (groups Cerris and Ilex, respectively), which are thought to have diverged during the middle Tertiary (Manos et al, 2001).…”

Hybridization versus conservation: are domestic cats threatening the genetic integrity of wildcats (Felis silvestris silvestris) in Iberian Peninsula?

“…Sampling comprised 44 wildcats from North (4), Centre (9) and South (31) of Portugal; 31 wildcats from Granada (22), Asturias (3) and Basque Country (6); and 109 feral and purebred domestic cats distributed across the Iberian Peninsula (figure 1). This new sample set corresponds to an increase of approximately 50% relative to the one analysed in Oliveira et al (2007). Putative wildcat samples were opportunistically collected or were obtained from collaborative ecological studies.…”

“…Several genetic approaches have been extensively and successfully used to address this problem in different taxa (Rhymer & Simberloff 1996;Allendorf et al 2001), especially in cases where phenotypical classifications of hybrid classes or even parental groups are dubious, as occur between wild and domestic cats and their hybrids (Daniels et al 1998;Beaumont et al 2001). The ability to genetically distinguish admixed individuals within sympatric populations of closely related (sub)species can provide invaluable resources for wildlife management, and has proved to be essential in studies of population structure and admixture in wildcat populations (Daniels et al 1998;Oliveira et al 2007). Similarly to most organisms, intraspecific distinction among Felis silvestris is barely based on diagnostic genetic differences and, consequently, the identification of parental and hybrid individuals is based on probabilistic assessments (Nielsen et al 2006).…”

“…Starting from reference molecular data in Oliveira et al (2007), we extended the admixture analyses to other areas in the Iberian Peninsula by improving both sample size and the geographical range. In this study, we present a first descriptive step to aid the regional and global conservation of this small feline in the Iberian Peninsula by investigating, for the first time, the differentiation between wild and domestic cats and by further evaluating the degree and extent of introgressive hybridization across different areas in Iberia.…”