Wednesday, June 29, 2011

What's in a name?

It's this bird's fault.

American Redstart, Setophaga ruticilla, Oxbow NWR (May 2011)

Every summer the American Ornithologists' Union announces changes in classification and naming in the July issue of its journal, The Auk. The most anticipated change this July is an overhaul of the Parulidae, the wood warblers. Based on DNA analysis by Irby Lovette (interviewed in Birding), his proposal calls for radical changes to both classification and nomenclature which have been summarized by Kenn Kaufman and David Sibley (see especially his useful visual summary). Let's consider the most interesting change. Here is where our friend Setophaga ruticilla comes in.

A name is an arbitrary signifier; it does not "point" to anything in nature which "requires" that name.  But what happens when names change? What happens, as Lovette is proposing, when the Parulas, Hooded Warbler, and American Redstart join the venerable genus Dendroica, which contains everything from Yellow to Kirtland's to Cerulean? This new, expanded grouping would seem to recognize the genetic filiation of these warblers, but are they really closely related? Do they naturally form a genus? As David Sibley comments, "DNA evidence and the resulting 'tree' gives us a fairly objective picture of the relationships within the family, but it’s a complex picture of repeated branching. Converting that information into a few simple categories like families and genera is subjective. Even with all of this data, the decision about where to draw the line when lumping and splitting genera is still arbitrary." American Redstart and Hooded Warbler are not suddenly revealed to be lost cousins, only that they represent, along with the existing members of Dendroica, a grouping of parallel branches of similar "genetic distance" in the family tree of the Parulidae (see Sibley's version of the tree in the AOU proposal).

But the genetic insight of this regrouping is not what's getting all the press. It's the wholesale renaming caused by the inclusion of Northern Redstart. By the rules of priority in nomenclature the inclusion of Setophaga ruticilla, which was named before the genus Dendroica, requires the renaming of the new grouping, the Setophaga. Thus, in one stroke Dendroica is no more. It's a similar story in Wilsonia; having lost Hooded, Wilson's and Canada now join Red-faced, Cardelina rubrifrons, which (you guessed it) also has naming priority. Wilsonia is also no more. All but Bachman's, Blue-Winged, and Golden-Winged leave Vermivora to form a new genus, Oreothlypis. And so on. It's breathtaking.

What's in a name? Everything and maybe nothing. But of course, a warbler by any other name still sounds as sweet.

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