m mark/unmark (sub-)tree
i invert marks of (sub-)tree
x expand (Marked->Unmarked->All)
c collapse (Terminal->All)
If you point to a subtree with the mouse while pressing one of these keys, the action is performed on the subtree. Otherwise (if you point somewhere outside of the tree) the whole tree is targeted.
If you press < SHIFT + Key > the function works on the opposite set:
Instead of the subtree, the rest of the tree is targeted.
Instead of the whole tree, all species NOT in tree are targeted.
If you press < CTRL + Key > the function works on ALL species (if it makes sense).
RETURN toggles the folding of the selected group.