Morpho

The pluggable controlled vocabulary UI is useful for keywordSets, but also the same widget could be used for picking coverage values for taxonomic coverage from the taxonomic hierarchy. (see old bug 345)

Taxonomic Coverage:
I'm assuming you would first select a "Classification System" (constrained
vocabulary) and then based on that selection you would be able to select
value[s] from the list that were present in your dataset.
Perhaps the lookup will go beyond a static XML list and can use webservices
much like the NBII lookup used in the FIRST project.