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 morfol—gicamente es lo suficientemente diferente como para ser
considerado un gŽnero aparte. Adem‡s, no habiendo estudios genŽticos que
demuestren que Avocettula y Anthracothorax pertenecen al mismo gŽnero,
pienso que lo apropiado es mantener los dos gŽneros 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.
ÒSo, my vote is to go back to the status quo,
right or wrong, until we have substantive evidence for making a change."