Allelic diversity among 5387 isolates of 12 commonest spoligotype of bovine tuberculosis (bTB) in GB. The allelic diversity is a measure of genotype diversity within each spoligotype. In short, the allelic diversity measures the probability of seeing the same VNTR variant of a spoligotype (that is, genotype) if one randomly picks two isolates from a large, randomly collected, population of isolates with the same spoligitype. Only one isolate from each breakdown was used in this analysis [hence 'freq (unique)] Attribution statement: ©Crown Copyright, APHA 2016