Comparative genetic diversity in a sample of pony breeds from the U.K. and North America: a case study in the conservation of global genetic resources.

Most species exist as subdivided ex situ daughter population(s) derived from a single original group of individuals. Such subdivision occurs for many reasons both natural and manmade. Traditional British and Irish pony breeds were introduced to North America (U.S.A. and Canada) within the last 150 years, and subsequently equivalent breed societies were established. We have analyzed selected U.K. and North American equivalent pony populations as a case study for understanding the relationship between putative source and derived subpopulations. Diversity was measured using mitochondrial DNA and a panel of microsatellite markers. Genetic signatures differed between the North American subpopulations according to historical management processes. Founder effect and stochastic drift was apparent, particularly pronounced in some breeds, with evidence of admixture of imported mares of different North American breeds. This demonstrates the importance of analysis of subpopulations to facilitate understanding the genetic effects of past management practices and to lead to informed future conservation strategies.

Maternal lineages in native Canadian equine populations and their relationship to the Nordic and Mountain and Moorland pony breeds.

A 378-bp section of the mitochondrial displacement loop was used to estimate genetic diversity in the native Canadian equine populations. The inclusion of 10 Mountain and Moorland, 3 Nordic pony breeds, 2 feral populations, and 5 horse breeds were also investigated as they may have influenced the development (or rejuvenation) of the native Canadian populations. A total of 281 samples were sequenced, which produced 75 haplotypes derived from 54 informative sites. On further investigation, 36 of these 75 haplotypes were found to be previously unreported. Overall, total diversity was lowest in the feral Sable Island population with a haplotype diversity (0.27 ± 0.12), nucleotide diversity (0.0007 ± 0.0004), and pairwise difference of 0.286 ± 0.317. This is not surprising due to the geographic isolation of this population. Haplotype diversity was highest (1.00 ± 0.13) in the New Forest population, pairwise difference was highest (8.061 ± 4.028) in the Icelandic breed, whereas nucleotide diversity was highest in the Exmoor breed (0.0209 ± 0.0025). Within the Canadian populations, haplotype diversity was highest in the Newfoundland pony (0.96 ± 0.08), whereas pairwise difference and nucleotide diversity was highest in the Canadian horse (7.090 ± 3.581 and 0.0188 ± 0.0042, respectively). Three different estimates of genetic distances were used to examine the phylogenetic relationships amongst these populations. All 3 estimates produced similar topologies. In general, the native Canadian populations were highly represented in the D clade, with particular emphasis in the D1 and D2 clades. This is an important factor when considering the phylogenetic conservation of these Canadian equine populations.