EXTENSIVE INTERBREEDING OCCURRED AMONG MULTIPLE MATRIARCHAL ANCESTORSDURING THE DOMESTICATION OF DOGS - EVIDENCE FROM INTERSPECIES AND INTRASPECIES POLYMORPHISMS IN THE D-LOOP REGION OF MITOCHONDRIAL-DNA BETWEEN DOGS AND WOLVES

To test the hypothesis that the domestic dogs are derived from several different ancestral gray wolf populations, we compared the sequence o f the displacement (D)-loop region of the mitochondrial DNA (mtDNA) fr om 24 breeds of domestic dog (34 individual dogs) and 3 subspecies of gray wolf(Canis lupus lupus, C. l. pallipes and C. l. chance; 19 indiv iduals). The intraspecific sequence variations within domestic dogs (0 .00 similar to 3.19%) and within wolves (0.00 similar to 2.88%) were c omparable to the interspecific variations between domestic dogs and wo lves (0.30 similar to 3.35%). A repetitive sequence with repeat units (TACACGTA/GCG) that causes the size variation in the D-loop region was also found in both dogs and wolves. However no nucleotide substitutio ns or repetitive arrays were specific for domestic dogs or for wolves. These results showed that there is a close genetic relationship betwe en dogs and wolves. Two major clades appeared in the phylogenetic tree s constructed by neighbor-joining and by the maximum parsimony method; one clade containing Chinese wolf(C. l. chance) showed extensive vari ations while the other showed only slight variation. This showed that there were two major genetic components both in domestic dogs and in w olves. However, neither clades nor haplotypes specific for any dog bre ed were observed, whereas subspecies-specific clades were found in Asi atic wolves. These results suggested that the extant breeds of domesti c dogs have maintained a large degree of mtDNA polymorphisms introduce d from their ancestral wolf populations, and that extensive interbreed ings had occurred among multiple matriarchal origins.