[Taxacom] Robust argument

Bob Mesibov mesibov at southcom.com.au
Sun Jun 28 19:15:45 CDT 2009


One of the advantages of subscribing to the TAXACOM digest, as opposed to getting every message posted separately, is that you get your perspective back between reads.

I do apologise, Rich, for misinterpreting your position. It comes from my confusing 'evolutionary history' sensu me with 'evolutionary history' sensu phylogeneticists. Sorry, I seem to do this a lot.

The latter is a barebones tree showing hypothesised relationships between living terminals. As Richard Zander points out, it's an inference of sister group relationships. In an indeterminate number of details, it's also a representation of ancestor-descendant relationships. You can build such a tree with any sort of character data from the terminals, and in 2009 the quickest and easiest way is to use sequences rather than hard-won, sometimes iffy data from morphology.

Trees like this are both useful and defensible for classifications. I think I agree with you that for this limited end, there's a lot of overlap between sequence information and morphological information, and if you've got the whole genome to play with, then build trees with it and don't worry about morphology. If you include morphological data as well, you risk blurring the inference with redundancy. You also throw in noise from differential 'epigenetic' effects of environment on phenotype expression.

The tree I'm talking about is a drastic simplification of 'evolutionary history' sensu me, which includes lots of events and patterns which - as we both agree - are not inferrable from sequence data. To try to infer this vastly more complicated  history, you need lots of morphology, because morphology is so much more sensitive to selection than sequences, and lots of biogeography, because history contains addresses, and whatever fossils you can find.

This is what Michael Ivie so nicely wrote about here, when puzzling over Montserrat. It's what awes me about the chemical ecology of terrestrial arthropods and their plant associations. The phylogeneticists have their sequence inference hammer and they're banging away at every nail in sight. Evolutionary historians sensu me are still thinking about what tools we need and how we might use them. The tree-builders are pasting their simple black-and-white abstractions on every wall in the gallery, and it annoys me sometimes - OK, it annoys me a lot of the time - that they've hidden the richly detailed and beautiful oil paintings underneath, and are getting astronomical prices for their 'art'.

Privilege of getting old: you're expected to curmudge now and then.
-- 
Dr Robert Mesibov
Honorary Research Associate
Queen Victoria Museum and Art Gallery, and
School of Zoology, University of Tasmania
Home contact: PO Box 101, Penguin, Tasmania, Australia 7316
(03) 64371195; 61 3 64371195
Website: http://www.qvmag.tas.gov.au/mesibov.html




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