Fig. 2

Population structure and evolutionary relationship. PCA plotted by using R software with PC1 against PC2 (a) and PC1 against PC3 (b). Colours represent cattle populations from different geographical regions as described in Additional file 2: Table S1 and Additional file 1: Table S2. Here, PCA was constructed using samples from Europe (Holstein, blue), Asia for both pure Asian (orange) and crossbreed zebu (black) and Africa (Boran—green, Ankole—cyan, Kenana—yellow, Muturu—dark green, N'Dama—brown, Ogaden – pink and Nigeria). Nigerian cattle are in red. NJ phylogenetic tree of the relationships between Nigerian cattle and all other populations used in this study (c). Here the concatenated tree was constructed using B. bubalis as outgroup. The proportion of ancestry admixture for each individual’s genome assuming different number of ancestral populations (K = 2, 3 and 4) (d). The admixture plot indicates three possible clusters of cattle: the Nigerian cattle (red), the taurine (light blue) and the zebu and their crossbred (orange). The cross-population error plot shows optimum ancestral populations for inferring genetic admixture is at K = 3 (e)