Frequency of the number of Links per Node per group.

The Frequency (%) was grouped in five classes according to the number of links in the nodes: 1) 2 to 6 links, 2) 7 to 12 links, 3) 13 to 18 links, 4) 19 to 24 links and 5) 25 and more links. The nodes with more than 19 links were considered as hubs. By this definition, less than the 10% of the nodes in BC should be considered as hubs. Also BC group is the one that present the lower frequency of hubs, followed by H and BBP group.