a. Neighbor-joining (NJ) tree showing evolutionary relationships of priority strains as inferred based on the Vkorc1 and its 5' region. Each strain is followed by the subspecies name and the haplotype group it belongs to [c.f. Additional file 1]. IN and WD indicate whether strains are inbred or wild derived, respectively. Too many inbred strains are represented by C57BL/6J since they share one haplotype. Numbers on the branch indicate the bootstrap values from NJ and MP analyses. b. The mean and standard variation of the phenotypes PT and BMD/C. The clades I-IV are shown on the X-axes and their corresponding PT, BMD and BMC measurements are shown on the Y-axes.