History and integrity of thoroughbred dam lines revealed in equine mtDNA variation

Abstract

Mitochondrial DNA (mtDNA) D-loop sequences (381 bp) from 100 thoroughbreds in 19 of the most common matrilineal female families were used to reconstruct a founder female population for the thoroughbred ( approximately 1650-1750 AD). Seventeen haplotypes were found to have contributed to the 19 female lineages. In order to place the reconstructed founder population in wider historical context, we examined, using both single strand conformation polymorphism and direct sequence analysis, variation in a 343 bp mtDNA fragment in that population and 13 other horse populations of disparate provenance. Interpopulation diversity analyses revealed no significant difference in variation between the thoroughbred founder population and the 13 other diverse horse populations and suggested a non-random partitioning of diversity among geographically diverse horse populations. Within thoroughbreds, almost half of the female families, which are each considered from pedigrees to have matrilines converging to one of>30 historically recognized female ancestors, contained sequences which were inconsistent with common descent. Examination of the anomalies in the context of pedigree records suggests the majority might be best explained as confusion of mares at the foundation stages, although some could have some bearing on more recent (19th century - 1980) lineages. We have used this combination of molecular and historical information to identify some of the founder dams and to make new interpretations about the early history of the thoroughbred.

Mitochondrial D-loop sequence variation among autochthonous horse breeds in Croatia

“…In terms of conservation, the observed phylogenetic relationships should help to preserve the more original genetic groups and protect their genetic variability. At a species level, horses possess relatively high haplotype diversity in the D-loop region of mtDNA (Kim et al, 1999;Vilà et al, 2001;Hill et al, 2002;Royo et al, 2005). The mean number of pairwise differences observed among all haplotypes was estimated at 8.81 or 2.72%.…”

“…Jansen et al (2002) reported extensive genetic diversity summarised in 93 different mtDNA types, grouped into 17 distinct phylogenetic clusters, and found that only a few of the phylogenetic clusters corresponded to groups of breeds or geographic areas. The examination of the horse population diversity at the mtDNA level has revealed a consistent absence of geographical structure (Hill et al, 2002).…”

“…Vilŕ et al (2001) reported that modern horse lineages coalesced at about 0.32 to 0.63 Ma, suggesting that domestic horses originated from multiple matrilines. Hill et al (2002) estimated that the average coalescence for modern horse mtDNA sequences was between 280 000 and 560 000 YBP. A wide variety of mitochondrial haplotypes of horse breeds clustered into seven different clades with low bootstrap support, indicating a high number of ancestral matrilines of ancient origin (Vilà et al, 2001).…”

“…The control region of the mitochondrial DNA (mtDNA) is, due to its high mutation rate, lack of recombinations and maternal inheritance, a very useful marker system for population and evolutionary biology. The mitochondrial DNA studies in horses have proved to be useful to characterize intra-and inter-breed relationships (Ishida et al, 1994;Ishida et al, 1995;Kavar et al, 1999;Kim et al, 1999;Vilà et al, 2001;Jansen et al, 2002;Hill et al, 2002;Mirol et al, 2002;Cozzi et al, 2004;Lopes et al, 2005;Royo et al, 2005;McGahern et al, 2006).…”

A pedigree-based analysis of mitochondrial DNA diversity in a dog population on the example of German Hovawarts

“…2). In this context, the results of mtDNA studies in horses, in which pedigree errors are usually identified (Hill et al, 2002;Kavar et al, 2002;Głażewska et al, 2007;Bower et al, 2013), are deserve attention. Of particular interest are the results presented by Hill et al (2000) and Bower et al (2013) on Thoroughbreds; these indicate that increased numbers of pedigree errors and haplotypes are identified when more detailed pedigree data are used.…”