The fungus-alga symbiosis that makes up a lichen is thought to have evolved multiple times independently in different fungal groups. however, lichens fall into three well-defined growth forms (see figure 31.22). how could you test the following hypotheses: hypothesis 1: crustose, foliose, and fruticose lichens each represent a monophyletic group; and hypothesis 2: each lichen growth form represents convergent evolution by taxonomically diverse fungi.