Another user asked today if it was possible to extract the tags that were used by a group from an API call in Connotea. The answer is that yes it is.
A normal API call on a group will look like:
http://www.connotea.org/data/group/Human%20Mitochondrial%20Phylogeny
But if you want to get the tags used by the group directly then you can use the following call:
http://www.connotea.org/data/tags/group/Human%20Mitochondrial%20Phylogeny
Which will also tell you how many times each tag has been used, and by how many people!