Such expressions as that famous one of Linnæus, and which we often meet with in a more or less concealed form, that the characters do not make the genus, but that the genus gives the characters, seem to imply that something more is included in our classification, than mere resemblance. I believe that something more is included; and that propinquity of descent,—the only known cause of the similarity of organic beings,—is the bond, hidden as it is by various degrees of modification, which is partially revealed to us by our classifications (Darwin, 1859, p. 413f).

Friday, 4 February 2011

So Long, and Thanks for All the Fish

It’s time to say goodbye to Paraphyly Watch, paraphyly, holophyly and all who sailed in them. It was fun while it lasted but all good things must come to an end and, alas, as you can see, we are moving on, redesigning, removing and rolling on. The year 2010 witnessed a spate of relevant papers to the Watch but time and inclination prevent us from devoting ourselves to their contents and absorbing their message. Save one last remark.

For us, organisms and taxa, taxa and areas call our attention, and our time might be more usefully spent elsewhere, doing these other things. It is these other things our blog will now be chiefly devoted, such that we might find subjects worthy of study, particularly classification and all its implications. Evolution is one such implication. Evolution, too, is a subject we find of interest. Hennig devoted many pages to the subject of classification – and evolution, as it happens. Our view contrasts with that of Cavalier-Smith:

“Real evolution often ignores Germanic cladistic logic; its messiness and lack of rules makes classification an art where compromise is necessary and rigid formalism harmful” (Cavalier-Smith 2010, p. 115).

German logic? ‘Real’ evolution? Classification as ‘art’? Cavalier-Smith continues:

“I agree with Mayr (1974), Halstead (1978) and others that the Hennigian perspective impedes realistic scientific discussion of phylogenetic history, because of its evolutionarily unrealistic formalism based on an intellectually impoverished view of the complexities of actual phylogenies, especially its failure to come to grips with evolutionary transformation, the reality of ancestors, and not least its dogmatism” (Cavalier-Smith 2010, p. 116).

“Realistic scientific discussion of phylogenetic history”? Cavalier-Smith embraces paraphyly; it looms large in his many works, they are sprinkled liberally among his various, ever-changing classifications, his artworks(Cavalier-Smith 2010, p. 115, fig. 1). An aversion to paraphyletic groups is, of course, anti-evolutionary:

“Cladistic aversion to paraphyletic groups, and lumping of paraphyly and polyphyly as ‘non-monophyly’, are logically flawed and anti-evolutionary” (Cavalier-Smith 2010, p. 117, legend to fig. 2).

János Podani (2010) echoes the sentiment:

“For pattern cladists, paraphyly is a less useful concept, because paraphyly together with polyphyly are “explanations for non-groupings, or more accurately, excuses for the absence of monophyly” (Williams, 2007). Paraphyletic and polyphyletic groups are therefore referred to “non-monophyletic groups” (Williams & Ebach, 2007; definition P4). For pattern cladists, non-monophyletic groups do not exist, being unnatural (“nongroups”). The approach is an evidently non-evolutionary one, paraphyly and polyphyly having very different evolutionary implications (Cavalier-Smith, 2010)” (Podani 2010, 1014).

Non-evolutionary? Anti-evolutionary?

Hörandl & Stuessy, when summarising the various concepts of paraphyly, understood it as a tool for classification – and evolution. For them “Cladistics put considerations of evolution, i.e., phylogeny, back into classification” – but left a bit out. They cite, with approval, Podani. With respect to monophyletic classification they suggest it “neglects important evolutionary processes” – which must be ‘Real’ evolution (Hörandl & Stuessy 2010, p. 1646)

The statements above, from Cavalier-Smith, Podani, Hörandl & Stuessy: Are any true, or even any part of them true?

It is time to say goodbye to Paraphyly Watch and paraphyly. It is time to devote our attention to classification, what we see is the saviour of comparative biology, maybe even all of biology.

Cavalier-Smith, T. 2010. Deep phylogeny, ancestral groups and the four ages of life. Phil. Trans. R. Soc. B 365: 111—132, doi: 10.1098/rstb.2009.0161

Hörandl, E. & Stuessy, T.F. 2010. Paraphyletic groups as natural units of biological classification. Taxon 59: 1641—1653
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Podani, J. 2010. Monophyly and paraphyly: A discourse without end? Taxon 59: 1011—1015.

2 comments:

Orwin O'Dowd said...

I was powerfully struck reading the Nature pages on epigenesis by the implication that an individual is not an instance of a species type. A phenotype is an organism, and develops subject to species constraints. This allows for more than one view of comparative data. Do you have a view on epigenesis?

ZL "Kai" Burington said...

Drs. Williams and Ebach,

Would it be possible for you to weigh in on the recent review of your book by Ferris in Cladistics? I would be most interested to see your reaction.

~Z. Burington