RESUMEN
BACKGROUND: Based on the relatively homogeneous origin of the sheep breeds in Morocco that originate mainly from Iberia, it is highly relevant to address the question of how these very diverse sheep populations differentiated from each other. The Mountains of the High Atlas and Middle Atlas are expected to constitute North-South and West-East geographical barriers, respectively, which could have shaped the history of the differentiation of sheep breeds. The aim of this study was to test this hypothesis by considering the genetic structure and the spatial distribution of five major breeds (Sardi, Timahdite, Beni Guil, Boujaad and D'man) and one minor breed (Blanche de Montagne), by analysing the mtDNA control region, using 30 individuals per breed. RESULTS: Phylogenetic and network analyses did not indicate any clear separation among the studied breeds and discriminant component principal analysis showed some overlap between them, which indicates a common genetic background. The calculated pairwise FST values and Nei's genetic distances revealed that most breeds showed a moderate genetic differentiation. The lowest and highest degrees of differentiation were retrieved in the Beni Guil and Boujaad breeds, respectively. Analysis of molecular variance (AMOVA) indicated that more than 95% of the genetic diversity occurs within individuals, while between- and within-population variabilities represent only 1.332% and 2.881%, respectively. Isolation-by-distance, spatial Principal Component Analysis (sPCA), and spatial AMOVA analyses evidenced clear examples of geographical structuration among the breeds, both between and within breeds. However, several enigmatic relationships remain, which suggest the occurrence of complex events leading to breed differentiation. CONCLUSIONS: The approaches used here resulted in a convergent view on the hypothetic events that could have led to the progressive differentiation between the Moroccan breeds. The major split seems to be linked to the West-East barrier of the Middle Atlas, whereas the influence of the High Atlas is less obvious and incompletely resolved. The study of additional breeds that have settled near the High Atlas should clarify the relationships between the breeds of the West part of the country, in spite of their small population size.
Asunto(s)
Estructuras Genéticas , Variación Genética , Análisis de Varianza , Animales , Marruecos , Filogenia , Análisis de Componente Principal , Ovinos/genéticaRESUMEN
The present study aims to investigate the morphological characteristics of the Blanche de Montagne sheep breed, mainly known by its long white fleece. The morphological characterization was performed on a total of 70 unrelated individuals of both sexes, having between 2 and 8 teeth and belonging to 13 farms located in the Ouarzazate region. The body measurements studied were body weight, body length, chest circumference, height at withers, rump height, chest depth, chest width, hip width, head length, head width, ear length, ear width, horn length, cannon circumference, wool length, and tail length. These measurements averaged 28.2±8.10 kg, 65.8±6.25 cm, 73.5±6.71 cm, 59.5±4.39 cm, 59.5±4.72 cm, 27.4±2.90 cm, 19.8±2.70 cm, 21.0±2.14 cm, 19.2±1.57 cm, 11.0±1.01 cm, 9.71±1.02 cm, 5.47±0.53 cm, 43.2±13.8 cm, 7.44±0.77 cm, 10.9±3.56 cm, and 31.8±4.36 cm, respectively. Descriptive statistics presented an overall coefficient of variation less than 15%, showing a homogeneous morphostructure of the breed. Most characters were small in relation with the low productivity of pastures. Moreover, 77.5% of correlation coefficients among the different body measurements were positive and significant, reflecting the strong morphological harmony of the breed, suggesting a long period of adaptation to its environment. The variance analysis showed that sex influenced the measurements, with males having the highest values. Similarly, individuals with 6 or 8 teeth showed higher values than those with 2 or 4 teeth. Through the comparison with other Moroccan breeds, the variation of some morphological traits was found in relation to some climatic parameters (mainly winter temperatures) and feeding supplementation.
Asunto(s)
Ovinos , Lana , Análisis de Varianza , Animales , Peso Corporal , Granjas , Femenino , Masculino , FenotipoRESUMEN
The arrival of Neolithic culture in North Africa, especially domestic animals has been essentially documented from archaeological records. As the data relative to sheep are scarce, we studied the genetic relationship between Moroccan sheep breeds and Mediterranean ones using the sequencing of 628 bp of the mitochondrial DNA control region in 193 Moroccan individuals, belonging to six breeds, and 652 sequences from other breeds in Europe and Middle East. Through Network analysis and an original phylogenetically derived method, the connection proportions of each Moroccan breed to foreign ones were estimated, highlighting the strong links between Moroccan and Iberian breeds. The first founders of Moroccan sheep population were issued at 79% from Iberia and 21% from a territory between Middle East and Africa. Their calculated expansion times were respectively 7,100 and 8,600 years B.P. This suggests that Neolithization was introduced by a double influence, from Iberia and from another route, maybe Oriental or Sub-Saharan. The consequence of the environmental changes encountered by founders from Iberia was tested using different neutrality tests. There are significant selection signatures at the level of Moroccan and European breeds settled in elevated altitudes, and an erosion of nucleotide diversity in Moroccan breeds living in arid areas.