Genetic diversity and patterns of population structure in Creole goats from the Americas.

Biodiversity studies are more efficient when large numbers of breeds belonging to several countries are involved, as they allow for an in-depth analysis of the within- and between-breed components of genetic diversity. A set of 21 microsatellites was used to investigate the genetic composition of 24 Creole goat breeds (910 animals) from 10 countries to estimate levels of genetic variability, infer population structure and understand genetic relationships among populations across the American continent. Three commercial transboundary breeds were included in the analyses to investigate admixture with Creole goats. Overall, the genetic diversity of Creole populations (mean number of alleles = 5.82 ± 1.14, observed heterozygosity = 0.585 ± 0.074) was moderate and slightly lower than what was detected in other studies with breeds from other regions. The Bayesian clustering analysis without prior information on source populations identified 22 breed clusters. Three groups comprised more than one population, namely from Brazil (Azul and Graúna; Moxotó and Repartida) and Argentina (Long and shorthair Chilluda, Pampeana Colorada and Angora-type goat). Substructure was found in Criolla Paraguaya. When prior information on sample origin was considered, 92% of the individuals were assigned to the source population (threshold q ≥ 0.700). Creole breeds are well-differentiated entities (mean coefficient of genetic differentiation = 0.111 ± 0.048, with the exception of isolated island populations). Dilution from admixture with commercial transboundary breeds appears to be negligible. Significant levels of inbreeding were detected (inbreeding coefficient > 0 in most Creole goat populations, P < 0.05). Our results provide a broad perspective on the extant genetic diversity of Creole goats, however further studies are needed to understand whether the observed geographical patterns of population structure may reflect the mode of goat colonization in the Americas.

Genetic relationships among American donkey populations: insights into the process of colonization.

This study presents the first insights into the genetic diversity and structure of the American donkey metapopulation. The primary objectives were to detect the main structural features underlying variability among American donkey populations, identify boundaries between differentiated gene pools, and draw the main colonization pathways since the introduction of donkeys into America in the 15th century. A panel of 14 microsatellite markers was applied for genotyping 350 American donkeys from 13 countries. The genetic structure of this metapopulation was analysed using descriptive statistics and Bayesian model-based methods. These populations were then compared to a database containing information on 476 individuals from 11 European breeds to identify the most likely ancestral donor populations. Results showed the presence of two distinct genetic pools, with confluence of the two in Colombia. The southern pool showed a unique genetic signature subsequent to an older founder event, but lacked any significant influence of modern gene flow from Europe. The northern pool, conversely, may have retained more ancestral polymorphisms and/or have experienced modern gene flow from Spanish breeds. The Andalusian and, to a lesser extent, the Catalan breeds have left a more pronounced footprint in some of the American donkey populations analysed.

Porcine colonization of the Americas: a 60k SNP story.

The pig, Sus scrofa, is a foreign species to the American continent. Although pigs originally introduced in the Americas should be related to those from the Iberian Peninsula and Canary islands, the phylogeny of current creole pigs that now populate the continent is likely to be very complex. Because of the extreme climates that America harbors, these populations also provide a unique example of a fast evolutionary phenomenon of adaptation. Here, we provide a genome wide study of these issues by genotyping, with a 60k SNP chip, 206 village pigs sampled across 14 countries and 183 pigs from outgroup breeds that are potential founders of the American populations, including wild boar, Iberian, international and Chinese breeds. Results show that American village pigs are primarily of European ancestry, although the observed genetic landscape is that of a complex conglomerate. There was no correlation between genetic and geographical distances, neither continent wide nor when analyzing specific areas. Most populations showed a clear admixed structure where the Iberian pig was not necessarily the main component, illustrating how international breeds, but also Chinese pigs, have contributed to extant genetic composition of American village pigs. We also observe that many genes related to the cardiovascular system show an increased differentiation between altiplano and genetically related pigs living near sea level.

Origins and genetic diversity of New World Creole cattle: inferences from mitochondrial and Y chromosome polymorphisms.

The ancestry of New World cattle was investigated through the analysis of mitochondrial and Y chromosome variation in Creoles from Argentina, Brazil, Mexico, Paraguay and the United States of America. Breeds that influenced the Creoles, such as Iberian native, British and Zebu, were also studied. Creoles showed high mtDNA diversity (H = 0.984 +/- 0.003) with a total of 78 haplotypes, and the European T3 matriline was the most common (72.1%). The African T1a haplogroup was detected (14.6%), as well as the ancestral African-derived AA matriline (11.9%), which was absent in the Iberian breeds. Genetic proximity among Creoles, Iberian and Atlantic Islands breeds was inferred through their sharing of mtDNA haplotypes. Y-haplotype diversity in Creoles was high (H = 0.779 +/- 0.019), with several Y1, Y2 and Y3 haplotypes represented. Iberian patrilines in Creoles were more difficult to infer and were reflected by the presence of H3Y1 and H6Y2. Y-haplotypes confirmed crossbreeding with British cattle, mainly of Hereford with Pampa Chaqueño and Texas Longhorn. Male-mediated Bos indicus introgression into Creoles was found in all populations, except Argentino1 (herd book registered) and Pampa Chaqueño. The detection of the distinct H22Y3 patriline with the INRA189-90 allele in Caracú suggests introduction of bulls directly from West Africa. Further studies of Spanish and African breeds are necessary to elucidate the origins of Creole cattle, and determine the exact source of their African lineages.