Creek Running North

I have a coffee date tomorrow with Olle Pellmyr, a research ecologist out of the University of Idaho at Moscow, who has spent the last I don’t know how long studying the suite of ecological interactions among yucca moths and yuccas. He gave a short presentation today at UC Berkeley, which I went to. I learned a couple of fascinating things, which I will withhold (probably unnecessarily, but just to be on the safe side) because he hasn’t published them yet.

There’s one thing I’d like to write about here, but just to be cautious I’ll check with him tomorrow. It’s the kind of thing that 99 percent of people would hear, nod, and shrug, and the remaining one percent — probably all of them California naturalist types — would have their world view shattered.  [Update: it’ll have to wait until he publishes. Or just buy my book when I write it!]

Not that that hasn’t happened with some frequency of late. The dreadnought reference work published in 1993 by UC Berkeley, the Jepson Manual: Higher Plants of California put Joshua trees (and all other yuccas and nolinas and agaves and their kin) in the lily family, Liliaceae. Taxonomists have spent a lot of time focusing on that particular family: it’s rather dysfunctional. Taxonomists these days generally try to make each taxon represent a single clade — that is to say, a single (pair of) organisms and all its/their descendants. (There’s some talk of radically restructuring the whole “phylum-class-order-family” hierarchy and just naming successive nested clades. Look for that to happen sometime after all now-living biologists are safely dead.) The lily family was historically a sort of a garbage dump, taxonomically speaking, a junk drawer for certain monocots fitting a rather vague description. As we learned more about the phylogeny — the family trees — of individual species, Liliaceae became less and less defensible as a taxon if you included all those onions and asparagus and Joshua trees. It turned out that the family wasn’t monophyletic: it didn’t represent just one single clade. And so after a bunch of individual taxonomists had made a whole lot of different withdrawals of whole ranges of plants from the lily family, the Angiosperm Phylogeny Group (APG) formalized the breakdown of the lily family (still in progress), with the new, pared down Liliaceae properly including just a few close relatives of Lilium.

Joshua trees’ place in the whole thing is still muddled. Most recent treatments I’ve read put Yuccas in the Agave family, which was split so far out of the lily family that it’s not even in the order Liliales anymore, but in the the order Asparagales. The APG went on, provisionally, to abolish the Agave family and a few related families, and put all of their members into the Asparagus family. The Agavaceae has an asterisk, though, in APGII: if you prefer, you can use the Agave family without being wrong. These family trees, after all, are hypotheses, not facts.

In fact, the current hypothesis is that there are no facts.

Anyway, this is all background for the somewhat recent news that the Agave family got whittled down from its earlier descriptions, with the Nolinas given their own families and the Dracaenas likewise, and then the APG dropped the new families and put all their members into the Ruscaceae, thus ensuring marketing opportunities for updated desert field guides for the next several generations. Yes, my head hurts too. We’re almost done. Even more recently, the Agave family — if that is its real name — had a few things added to it. Camassia, for one, and Chlorogalum, both of which I planted out front among the Yuccas and Agaves, and Hesperocallis, for which I’d give my left arm if I could grow it in my front yard here.

And botanists have also put Hosta in the Agave family. For now, at least.

Shorter me: according to current botanical taxonomy, this:

is not nearly as closely related to this:

as it is to this:

I live for little things like this these days.

Posted by: Chris Clarke
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