There’s No Such Thing as a Tree
Obviously, there are trees. But speaking phylogenetically, trees aren’t a thing. Some things that are trees evolved from things that are not trees and other things that are trees evolved into things that aren’t trees. Confused? This might clear things up.
“Trees” are not a coherent phylogenetic category. On the evolutionary tree of plants, trees are regularly interspersed with things that are absolutely, 100% not trees. This means that, for instance, either:
The common ancestor of a maple and a mulberry tree was not a tree.
The common ancestor of a stinging nettle and a strawberry plant was a tree.
And this is true for most trees or non-trees that you can think of.
See also there’s no such thing as a vegetable and there’s no such thing as a fish.
What would the evolutionary tree of salmon, lungfish, and cows be? The answer, it appears at first glance, is simple. Salmon and lungfish, being fish, would cluster nicely together on one branch, and very non-fishy cows would be off on a separate branch. Right? Wrong. Contrary to what you might expect, what you see above is their evolutionary tree. Working up from the root, the lineage that leads to salmon branches off first. Keep tracing up the tree, and you’ll see that the lineage from which the salmon branched off eventually branches into two new lineages: the one leading to lungfish and the other leading to cows. In other words, a cow and a lungfish are more closely related to one another than either is to salmon.
(via @smorewithface)
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