Admixture and local breed marginalization threaten Algerian sheep diversity

Due to its geo-climatic conditions, Algeria represents a biodiversity hotspot, with sheep breeds well adapted to a patchwork of extremely heterogeneous harsh habitats. The importance of this peculiar genetic reservoir increases as climate change drives the demand for new adaptations. However, the expansion of a single breed (Ouled-Djellal) which occurred in the last decades has generated a critical situation for the other breeds; some of them are being subjected to uncontrolled cross-breeding with the favored breed and/or to marginalization (effective size contraction). This study investigated genetic diversity within and among six of the nine Algerian breeds, by use of 30 microsatellite markers. Our results showed that, in spite of the census contraction experienced by most of the considered breeds, genetic diversity is still substantial (average gene diversity ranging 0.68 to 0.76) and inbreeding was not identified as a problem. However, two breeds (Rembi and Taadmit) appeared to have lost most of their genetic originality because of intensive cross-breeding with Ouled-Djellal. Based on the above evidence, we suggest Hamra, Sidaoun, and D'man as breeds deserving the highest priority for conservation in Algeria

Scatterplot of the first two principal components of DAPC using breeds as prior clusters.

<p>Breeds are labeled inside their 95% inertia ellipses and dots represent individuals. The inset indicates the eigenvalues of the first five principal components.</p

Pair-wise F_ST among Algerian breeds (a) and Italian breeds (b), calculated with a common set of 15 microsatellites^* (with confidence intervals at 95%).

<p>Ba, Bagnolese; Co, Comisana; Ge, Gentile Di Puglia; La, Laticauda; Le, Leccese; Sa, Sarda.</p><p>*the common set of microsatellites was: MAF65, MAF214, OARFCB304, ILST11, OARAE129, OARFCB193, MAF209, OARJMP58, ILST5, OARFCB128, INRA63, BM1824, MAF33, MCM140, BM8125.</p><p>Pair-wise F_ST among Algerian breeds (a) and Italian breeds (b), calculated with a common set of 15 microsatellites^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122667#t003fn002" target="_blank">*</a>} (with confidence intervals at 95%).</p

Pair-wise F_ST among Algerian breeds (with confidence intervals at 95%).

<p>Pair-wise F_ST among Algerian breeds (with confidence intervals at 95%).</p

Genetic diversity measured by breed.

<p>n, sample size; n Loc. Samp., number of Locales Sampling; GF*¹, governmental farms; RM*², Regional market; MNA, Mean Number of Alleles; R, allelic Richness; PR, Private allelic Richness; H_e, expected heterozygosity; H_o, observed heterozygosity; HWE, Hardy Weinberg Equilibrium; FDR*³, loci in HWD after False Discovery Rate correction [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122667#pone.0122667.ref021" target="_blank">21</a>] and F_IS, inbreeding coefficient (estimator of Weir and Cockerham [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122667#pone.0122667.ref023" target="_blank">23</a>]).</p><p>Genetic diversity measured by breed.</p

Genetic structure of Algerian sheep breeds by Bayesian analysis with 30 microsatellite loci (K = number of clusters).

<p>(a) Analysis on the entire data set with increasing number of inferred clusters (K = 2 to K = 6); (b) Graph showing ΔK calculated according to Evanno et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122667#pone.0122667.ref030" target="_blank">30</a>]; (c) further analysis in the group of “white breeds” (Ouled-Djellal, Rembi and Taâdmit) and the group of the three other breeds (D’man, Hamra and Sidaoun).</p