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"The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth.
The green and budding twigs may represent existing species; and those produced during former years may represent the long succession of extinct species...As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever-branching and beautiful ramifications."
Charles Darwin wrote that in The Origin of Species.
Others agreed. (About the branching tree part; there's been some disagreement about whether the "tree" a simile or a metaphor).
The simile led to the field of phylogeny, which uses the metaphor (I'm not taking sides) to explain how every living organism on earth is linked to every other living organism. Yeah, we're related to a lot more than just apes.
Want to see how? You can. It's a work in progress, (well obviously, I guess, but I mean phylogenists are still working out some already existing relationships); you can find it at the Tree of Life web project.
The basic idea behind phylogeny is that members of a taxonomic group should be more closely related to each other than to anything outside the group. Members of a species have an ancestor in common that's more recent than any of them have with any organism not in the species.
At first, phylogeny was mostly morphological and behavioral. (If it walks like a duck, talks like a duck and looks like a duck, it's Anatidae). But that didn't hold us back. We love putting things into categories and we did it with enthusiasm, even before we knew what the categories were.
Then we found out about DNA which led to the discovery that phylogeny was kind of a mess. For instance, genetically a swan really is just an ugly duck, as are geese. Except for Anseranas semipalmata, the magpie goose, which walks like a duck, talks like a duck and looks like a duck but isn't Anatidae. It's in it's own family called Anseranatidae.
For the last couple of decades, botanists have been sorting through DNA data to determine just how different flora are related. The result has been a significant amount of reclassification.
It has hit some families harder than others. Scrophulariaceae, for instance, the figwort family.
Not long ago it was a robust family with 275 genera and more than 5,000 species. Then DNS evidence showed that a lot of those species were polyphyletic. That's the technical term for the opposite of inbred -- they look related, but they're not.
By the time the geneticists were through with Scrophulariaceae it was down to about 1200 species in 95 genera.
Of course, we being Homo sapiens, the debate hasn't been always scientific or technical. At the dawn of the scientific revolution, when the shift to reason and empirical research was just beginning, David Hume was doing the color commentary. Although he was rooting for reason, he saw good reason getting shot down by eloquence, authority and nostalgia. "The victory is not gained by the men at arms, who manage the pike and the sword," he said, "but by the trumpeters, drummers, and musicians of the army.” Things have changed, but not entirely.
In the 1990s botanists in Europe took a closer look at the 200 species in the genus Chrysanthemum. In the light of new genetic information they decided to rearrange things.
With good science behind them, they pulled a few species of Chrysanthemum out of the genus and put them into the genus Dendranthema. Among those species was Chrysanthemum X morifolium, the common Chrysanthemum. The chrysanthemum verbally and taxonomically extinct?
In Steinbeck's "The Dendranthema," the old man would break Elisa's heart and crush her ego by tossing a bunch of Dendranthema? The emperor of Japan would honor distinguished people with the Supreme Order of the Dendranthema? In Belgium people would remember the dead by placing Dendranthema on their graves? That last one almost sounds appropriate. "The Dendranthema of death."
Well it turns out gardeners and florists can be every bit as fierce as trumpeters, drummers and musicians. They mobbed the International Botanical Congress of 1999 and the botanists retreated.
They retreated, they didn't surrender. They re-rechristianed the species Chrysanthemum indicum, as a synonym for Dendranthema indicum. ITIS, however, lists Chrysanthemum indicum as a "not accepted" synonym for Dendranthema indicum).
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