Proposal (95) to South American Classification Committee

 

Split Avocettula from Anthracothorax

 

The monotypic genus Avocettula was merged into Anthracothorax by Schuchmann (1999), and this was followed by Dickinson (2003); thus, our baseline classification started with this merger.

 

The monotypic genus Avocettula had been universally recognized for the species recurvirostris Swainson 1822 from the time Reichenbach named it in 1849 until Schuchmann (1999) lumped it into Anthracothorax. The unique bill was the main justification for separate generic status of recurvirostris. However, in most major treatments of the Trochilidae (Cory 1918, Peters 1945) the two genera were placed together in the sequence, presumably reflecting the similarities in plumage pattern between recurvirostris and some species of Anthracothorax. Schuchmann, in lumping them, stated that "other (than the bill) details of morphology and nest structure" supported the lumping. Whether the "other details of morphology" went beyond plumage pattern, and just which details of nest structure, were not specified (and do not appear to have been published). Thus, the published evidence boils down to a conflict between plumage pattern (supporting) and bill structure (not supporting) the merger. The similarity in plumage pattern is undeniable, but other striking plumage similarities (e.g., Androdon and Eutoxeres condamini, Damophila, and Thalurania) have been shown by genetic evidence not to indicate closest relatives. Nest structure can be quite plastic depending upon the site chosen, and similarities in nest site might select for similar structures. Recurvirostris appears to agree with Anthracothorax in choosing exposed sites and building a relatively small nest, but so does the unrelated Heliomaster ... at the very least, a more detailed analysis including other taxa of similar habits seems called for. If generic status is to have ecological implications (i.e., members of a genus should be broadly similar in ecology), then one might wish to keep Avocettula separate - its feeding niche should surely be strikingly different from that of typical Anthracothorax. Many details of morphology have not been examined between the two - wing shape, foot morphology, etc. - hence more data here would also be welcome. It is worth noting that recurvirostris is much smaller than any true Anthracothorax, perhaps another indication of ecological distinctness. Most of all, genetic data could help settle the question, but to my knowledge no such data are available for recurvirostris.

 

Sequencing of DNA of this species and several Anthracothorax seems called for: if recurvirostris were to occupy a branch peripheral to Anthracothorax sensu stricto, it could be retained as a monotypic genus; if it be found to arise from amidst the Anthracothorax group, lumping would be justified to avoid a paraphyletic Anthracothorax

 

In the absence of such data, I believe that the case for lumping such a long-recognized genus is insufficient and recommend a YES for this proposal.

 

Gary Stiles, January 2004

 

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Comments from Remsen: "YES. As noted by Gary, the rationale provided for the merger is tantalizing but insufficient, and in retrospect, it should have joined the many HBW changes to hummingbird classification that I edited out of Dickinson (2003)."

 

Comments from Robbins: "YES. Gary makes a number of good points and I agree that until molecular data are provided that Avocettula should continue to be recognized."

 

Comments from Zimmer: "YES. Morphological differences in bill shape (and the implied ecological differences) along with extreme biometric differences trumps similarities in plumage patterns in my mind (at least until a molecular analysis is published). A comparable situation that comes to mind is the similarity in plumage patterns between males and females of Formicivora iheringi to the corresponding sexes of Myrmotherula axillaris, even though other morphological, biometric and vocal characters suggest no close relationship between the two species."

 

Comments from Nores: "YES. Pienso que morfológicamente es lo suficientemente diferente como para ser considerado un género aparte. Además, no habiendo estudios genéticos que demuestren que Avocettula y Anthracothorax pertenecen al mismo género, pienso que lo apropiado es mantener los dos géneros separados."

 

Comments from Jaramillo: "YES. That odd bill shape is a fine generic character from my perspective. That doesn't mean that Avocettula and Anthracothorax may not be closely related, but that isn't the issue here. Putting a taxon that is so different in so many ways into Anthracothorax decreases the information value of that genus, there is no compelling reason to do this."

 

Comments from Schulenberg: "YES. I am not thrilled with monotypic genera. I also no idea what Avocettula is most closely related to, or is not related to. And I recognize that the former status quo, in this case a monotypic genus, has no basis behind it. But that's often the way the things are. I think that the proper approach is, not to change the status quo with equally unsupported changes (as was done by the authors of the Handbook of the Birds of the World taxonomy), but to stick with the status quo unless and until we have good evidence to make a change.

 

“So, my vote is to go back to the status quo, right or wrong, until we have substantive evidence for making a change."