Thursday, January 20, 2011

The Botanical Taxonomist's Junk Drawer

The spreadsheet I use as the master census for all my indoor plants has a column for the family of each plant. Most of the time, filling it in is straightforward. Stenocereus is in the Cactaceae. Vriesea is in the Bromeliaceae. Phalaenopsis is in the Orchidaceae. However: a fairly large subset of plants were problematic, when it came to determining family affiliation, because the usual sources of information didn't agree.

Aloe vera.

For example: is Aloe vera in the Asphodelaceae, as Wikipedia claims, or should I go with and put it in the Aloaceae? Or maybe GRIN and Tropicos are more authoritative, in which case I should put it in the Xanthorrhoeaceae. Or maybe the old cactus and succulents book I bought at a secondhand store a few weeks ago should be considered, in which case there is a case to make for the Liliaceae. Without a compelling reason to take one source over the others,1 I was left to guess, or go with the first one I encountered, or whatever.

And this scenario happened over and over and over, see below.2
  • Dracaena: Ruscaceae, Ruscaceae, Asparagaceae, Asparagaceae
  • Agave: Agavaceae, Agavaceae, Asparagaceae, Asparagaceae, Amaryllidaceae
  • Chlorophytum: Agavaceae, Liliaceae, Asparagaceae, Asparagaceae
  • Sansevieria: Ruscaceae and Agavaceae, somehow; Ruscaceae; Asparagaceae; Asparagaceae
  • Haworthia: Asphodelaceae, Aloaceae, Xanthorrhoeaceae, Xanthorrhoeaceae, Liliaceae
  • Cordyline: Agavaceae, Asparagaceae, Asparagaceae, Asparagaceae
  • Aspidistra: Ruscaceae, Ruscaceae, Asparagaceae, Asparagaceae
  • Beaucarnea: Ruscaceae, Ruscaceae, Asparagaceae, Liliaceae

Sansevieria trifasciata 'Moonglow.'

Which is discouraging, if you like to know how your houseplants are related to one another.

But then, a couple weeks ago, The Phytophactor (whom you should really be reading, by the way) posted a link to The Plant List, an on-line database of plant names. TPL isn't the only database on-line that includes the obsolete names, but it does appear to be up-to-date,3 and it's the only one I know of that's been endorsed by the Phactor, as he calls himself sometimes, so, you know, whatever the hell. So I looked up every genus of plant I've got, checking to see that I had the right family written down, and -- hold on to your mind securely, now, because I am going to BLOW IT4 -- every single one of the cases I was unsure about, according to TPL, belongs in the Asparagaceae.

Aloe? Asparagaceae.

Dracaena? Asparagaceae.

Aspidistra, Haworthia, Aloe, Beaucarnea, Agave, Sansevieria, Chlorophytum? All Asparagaceae.

Cordyline fruticosa 'Kiwi.'

Now. There's no particular reason to believe that TPL is more right about this than Tropicos, or GRIN. There may in fact not even be a way to be right about this at the moment, given that taxonomy is normally a somewhat fluid science, and this has only gotten worse lately, with the arrival of cheaper gene sequencing and all the close genetic analysis it permits. But one will notice that TPL's Asparagaceae-as-junk-drawer policy has one big advantage over Tropicos and GRIN, which is that it's really, really simple. Faced with a dauntingly huge number of unclassified or ambiguously-classified plants, one can take fifteen minutes or so to put them all in the Asparagaceae and then take the whole department out for drinks for the rest of the day. Which is why I'm happy to ignore the possible existence of (for example) the Xanthorrhoeaceae, which is sickeningly difficult to type anyway,5 and follow their lead. If taxonomic consensus changes later, as it surely will, well, at least I know I didn't waste a lot of time learning useless information.6

So if you're ever in a situation where you have to name a houseplant's family, and you have no idea -- which, okay, I can't think of any plausible scenarios when that might happen, but you never know -- guess the Asparagaceae. Everybody else is.


1 Okay, it's not that tough of a decision: GRIN and Tropicos are the best bets, because Wikipedia and collect their information from their users, and one hopes that GRIN and Tropicos have higher standards than that. And the book, being from 1958, doesn't really have a chance of being correct. But still -- unless I'd heard otherwise at some point, I used to assume that family assignments were fairly solid, and that information from one source ought to agree with information from the others, so frequently I only looked at one source and went with whatever it said. So in a lot of cases I didn't know what GRIN and Tropicos said.
2 (In order, references are: Wiki, dave, GRIN, Tropicos. When there's a fifth, it's the 1958 book.)
3 Mostly I'm assuming it's up to date because it includes such personal bugbears as the reclassification of Dracaena marginata as Dracaena reflexa var. angustifolia, which is so obviously wrong that I refuse to accept it, and I am confident that future taxonomists are going to back me up on this one. Sadly, the more plausible substitution of Dracaena fragrans for D. deremensis is there too: I'm reluctant to give up the name D. deremensis.
4 Original source of this line: Sady Doyle. Ordinarily I wouldn't give credit, but ordinarily I'd try harder to change the line to make it my own, too. Also I think Sady is awesome.
5 Seriously, like two thirds of the name is "aceacaceaeceae." How are my fingers supposed to keep that straight? I suppose at least I can be grateful that I'll probably never have to prounounce it.
6 For the record, I'm not actually accusing TPL of being lazy. I'm sure they have their reasons for classing all these together, which are all scientifically-based and everything. I'm agreeing out of laziness, though.


Hermes said...

Amusing post. I rather like taxonomy being in flux, annoying as it may be at times. Thus Science moves forward. Its too much cerrtainty that I distrust.

Pat said...

As Missouri Botanical Garden run Tropicos we can assume this collaboration with Kew trumps any previous lists. I'll certainly be using it in future. I didn't know I was growing so many sparrow grasses.

Paul said...

Plant taxonomy like astrology for plants- amusing and confounding and a joke on anyone who takes it too seriously.

Anonymous said...

Ah! Gene sequencing etc. are part of what's happening, but you are also encountering the great battle between the "Lumpers" and the "Splitters." I think you are a lumper. Welcome to the fold! Though the splitters will tell you we take pretty much anyone.

CelticRose said...

@Anonymous: Lol!

I pretty much gave up on taxonomy a long time ago. It changes too often and no one can agree on what to call anything. I just use whatever name will be recognizable to most people and don't lose any sleep over whether it's "correct" or not.

mr_subjunctive said...

Anonymous at 6:23 PM:

Temperamentally, I think I'm actually a splitter. (One could argue that a true lumper wouldn't bother to figure out the families of his plants in the first place: he'd just call them all plants and move on.) It's only when I have no way of determining what's going on and expect it all to be thrown out within ten years anyway that I become a lumper.

Peter said...

We don't agree with the lumping. I don't have a definitive other answer, but I can assure you that lumping is bad.

B. said...

A good aggregator of authorities on taxonomy is, the Encylopedia of Life. It seems to eschew the Junk Drawer effect of polyphyleticism.