Relationship in the IoM space between the significant clusters found, shown as a dendrogram using the Mahalanobis distance between the clusters in this space (see main text for details). Using this Mahalanobis distance, the clusters are further joined up to a cut-off threshold (red dashed line) taken to be 3.3. The labels for the clusters are given on the x-axis, and the clusters that are joined to form larger groups have links of the same colour. Using this distance cut, we find 7 preliminary main groups, 1 cluster pair and 19 individual clusters.