Fig. 1

Establishing a shared phylogenetic clade cut-off value for BHV-1, EHV-1, and SuHV-1. To establish and initial cut-off value, pairwise p-distance values were calculated for BHV-1, EHV-1, and SuHV-1 using multiple sequence alignments. Frequency vs. p-distance histograms were generated for each of the three viruses (a, b and c). An initial cut-off of 0.01 was chosen, based on a shared p-distance value that divides the observed p-distances into two groups simultaneously for all three viruses (vertical dotted line; panels a, b, and c). Groups with p-distances <0.01 are colored salmon, while groups with p-distances >0.01 are colored teal. To evaluate the validity of the initial cut-off, variance analysis was performed, where variation between groups and within groups was examined. Panels e, f, and g show the individual rescaled F curves (gray dotted line) for each of the three viruses, as well as the sum of the curves in black. It is important to note the individual rescaled F and F sum curves cannot be directly compared as they are scaled differently, and do not correspond to the y-axis values. The F values were rescaled so as not to weight one virus more than the rest. The sum of the rescaled F curves shows a peak at 0.01, which validates the initial cut-off. The values of the unscaled, and rescaled F values are located in Additional file 1: Tables S2, and S3 respectively