“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.
And it’s not just ancestors! One thing that blew me away after moving from Finland to Germany was that while willows in Finland are predominantly shrubs or bushes, and maples are trees, in Germany willows grow to be trees, but maples mostly stay as vines.
There's a book: "Why Fish Don't Exist" which is pretty good. Evolutionary, my understanding is that things are usually named after their ancestry (phylogenetically?), while fish are basically... "have fish shape and is in water" which becomes awkward. Lungfish and coelacanths are a lot closely related to humans than to salmon.
