By default, the clade is identified by its number as found in the
`edge' matrix of the tree. If tips = TRUE
, the tips descending
from the identified node are returned, possibly together with the
node. If labels = TRUE
, the labels are returned (if the tree
has no node labels, then the node numbered is returned).
The node is identified by the shortest distance where the click
occurs. If the click occurs close to a tip, the function returns its
information.