Steep clines within a highly permeable genome across a hybrid zone between two subspecies of the European rabbit

• Published in: Molecular ecology Vol. 22; no. 9; pp. 2511 - 2525
• Main Authors: Carneiro, Miguel, Baird, Stuart J. E, Afonso, Sandra, Ramirez, Esther, Tarroso, Pedro, Teotónio, Henrique, Villafuerte, Rafael, Nachman, Michael W, Ferrand, Nuno
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.05.2013; Blackwell
• Subjects: Animals; Biological and medical sciences; Biological evolution; Classical genetics, quantitative genetics, hybrids; cline theory; DNA, Mitochondrial - genetics; Europe; Female; Fundamental and applied biological sciences. Psychology; Gene Flow; Gene Frequency; Genetic Loci; Genetics of eukaryotes. Biological and molecular evolution; Genome; Genomics; Genotype; hybrid zone; Hybridization, Genetic; hybrids; introgression; Linkage Disequilibrium; loci; Male; mitochondrial DNA; Models, Genetic; Molecular Sequence Data; nucleotide sequences; Polymorphism, Single Nucleotide; Population genetics; Population genetics, reproduction patterns; Rabbits; Rabbits - genetics; reproductive isolation; sex chromosomes; Species Specificity; X Chromosome - genetics; Y Chromosome - genetics; Europe; Hybrid zone; cline theory; Reproductive isolation; Theory; Sex chromosome; Lagomorpha; sex chromosomes; Population genetics; Vertebrata; Gene flow; Oryctolagus cuniculus; Mammalia; Genome
• ISSN: 0962-1083; 1365-294X
• DOI: 10.1111/mec.12272

Maintenance of genetic distinction in the face of gene flow is an important aspect of the speciation process. Here, we provide a detailed spatial and genetic characterization of a hybrid zone between two subspecies of the European rabbit. We examined patterns of allele frequency change for 22 markers located on the autosomes, X‐chromosome, Y‐chromosome and mtDNA in 1078 individuals sampled across the hybrid zone. While some loci revealed extremely wide clines (w ≥ 300 km) relative to an estimated dispersal of 1.95–4.22 km/generation, others showed abrupt transitions (w ≈ 10 km), indicating localized genomic regions of strong selection against introgression. The subset of loci showing steep clines had largely coincident centers and stepped changes in allele frequency that did not co‐localize with any physical barrier or ecotone, suggesting that the rabbit hybrid zone is a tension zone. The steepest clines were for X‐ and Y‐chromosome markers. Our results are consistent with previous inference based on DNA sequence variation of individuals sampled in allopatry in suggesting that a large proportion of each genome has escaped the overall barrier to gene flow in the middle of the hybrid zone. These results imply an old history of hybridization and high effective gene flow and anticipate that isolation factors should often localize to small genomic regions.