Again, if we go several nodes deeper into that tree, we find that all of the other members of that clade have purple lines. So again, this tells us a great deal about the most likely explanation for the evolution of their color patterns. That's the ancestral condition within that monophyletic group that we're studying. They had purple lines and that one lineage, when it split off, its common ancestor had opaque white lines and that you can see the increasing degree of similarity between sister taxa as you go higher up in that branching diagram. So again, by having this hypothesis of phylogeny, we can say a great deal about the evolution of these color patterns in these different lineages of nudibranchs.

One of the things that we find, here again, are the species that were found in the Hawaiian Islands. We find that all of those were the ones with white lines. Well, if we go way over here, we find another species that's found in the Hawaiian Island and lo and behold, when we look at it, it has a color pattern with opaque white lines. They don't stand out as greatly, but we know that it is in a different portion of that phylogenetic tree. The most likely explanation is that it evolved once in this lineage and that it evolved independently as a case of convergence in this lineage. To say that it evolved independently within these different lineages requires four evolutionary steps as opposed to one. And the principal of phylogenetic systematics, of parsimony, says that you prefer the simpler explanation, because it requires fewer evolutionary steps.

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