Abstract
Through thousands of years of breeding and strong human selection, the dog (Canis lupus familiaris) exists today within hundreds of closed populations throughout the world, each with defined phenotypes. A singular geographic region with broad diversity in dog breeds presents an interesting opportunity to observe potential mechanisms of breed formation. Italy claims 14 internationally recognized dog breeds, with numerous additional local varieties. To determine the relationship among Italian dog populations, we integrated genetic data from 263 dogs representing 23 closed dog populations from Italy, seven Apennine gray wolves, and an established dataset of 161 globally recognized dog breeds, applying multiple genetic methods to characterize the modes by which breeds are formed within a single geographic region. Our consideration of each of five genetic analyses reveals a series of development events that mirror historical modes of breed formation, but with variations unique to the codevelopment of early dog and human populations. Using 142,840 genome‐wide SNPs and a dataset of 1,609 canines, representing 182 breeds and 16 wild canids, we identified breed development routes for the Italian breeds that included divergence from common populations for a specific purpose, admixture of regional stock with that from other regions, and isolated selection of local stock with specific attributes.
Highlights
Arising from wild gray wolves on the Eurasian continent over 15,000 years ago, the dog (Canis lupus familiaris) was the first species to be domesticated (Frantz et al, 2016; Freedman et al, 2014; Nobis, 1979; Savolainen, Zhang, Luo, Lundeberg, & Leitner, 2002)
We investigated 23 dog populations of Italian origin (Table 1, Figure 1) and a sampling of seven wild wolves belonging to the Italian gray wolf population which were collected from the Italian Apennine mountain ranges
We examined a set of three breeds for which we collected samples in both the United States and Italy: Italian Greyhounds (Figure 1a), Cane Corsos (Figure 1v), and Neapolitan Mastiffs (Figure 1w)
Summary
Arising from wild gray wolves on the Eurasian continent over 15,000 years ago, the dog (Canis lupus familiaris) was the first species to be domesticated (Frantz et al, 2016; Freedman et al, 2014; Nobis, 1979; Savolainen, Zhang, Luo, Lundeberg, & Leitner, 2002). Most prior attempts to address the genetic history and composition of so called “niche” dog populations have used low depth genome coverage incorporating only SNPs, microsatellites, or mitochondrial DNA, and utilizing a small number of breeds which are frequently chosen for their modern population numbers (Ceh & Dovc, 2014; Kang et al, 2009; Pires et al, 2006; Puja, Irion, Schaffer, & Pedersen, 2005; Suarez et al, 2013) These approaches address only superficial relatedness, diminishing the impact of artificial selection, natural divergence, and directed hybridization of breeds, which are evident only through analysis of deep genetic data. Identity-by-descent haplotype sharing, and admixture, we identify specific instances of three modes by which dog breeds have been formed: (1) specialization of breeds through segmentation within a phenotypically similar population; (2) directed attainment of common species-wide phenotypes within multiple diverse regionally isolated gene pools; (3) introduction of desired characteristics through introgression with distantly related populations
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