Does the application of geometric morphometric methods on skull allow a differentiation of domestic sheep breeds?

Abstract

Geometric morphometric methods (GMM) make it possible to study shape and size independently. The skulls of 58 adult specimens of different domestic breeds of Ovis were analysed by means of GMM in order to know if shape and size would allow their racial grouping. For this purpose, breeds were grouped a priori in four groups according to the general area of the origin of each breed:"West Mediterranean" (Fardasca breed, n=21),"Central Europe" (German breeds, n=12, Friesland, n=3 and Ile de France, n=2),"East Mediterranean" (Karaguniko, n=5, Kephalonia, n=1, Khios, n=2, and one unknown breed but of Greek origin) and"Hebrides Islands" (Hebridean breed, n=7). A picture on the lateral aspect of each skull was taken and fourteen landmarks were placed on each. Skull variation was decomposed in both size (centroid size: CS) and shape components. No allometry appeared, and size differences between groups were significant only for Eastern group (Greek breeds), probably due to the influence of Asiatic breeds. Central Europe group presented the highest variation, probably because it encloses different morphological breeds, such Friesland and Ile de France. According to shape, significant differences appeared between groups except between West and East Mediterranean breeds for the discriminant function. Shape differences were mainly focused on basilar aspect of the skull. 63.8% of the specimens were properly classified a posteriori, increasing only to 70.6% of proper classification when size was used. The results suggest that a rather low discrimination among breeds appears and that size does not add much more information.