Proposal (#314) to South American Classification Committee
Rearrange the genera of Neotropical swallows
This proposal would rearrange the genera of South American swallows according to the molecular data of Sheldon and collaborators resulting in the sinking of some genera, resurrection of others and reassignment of species among them.
The generic arrangement of Neotropical swallows
has long been problematic, being based essentially on the criteria
of Ridgway (1903,1904), which produced a number of monotypic genera
based upon characters of the foot (especially degree of syndactyly),
wing and tail shape, bill and coloration. Most of these show some
degree of homoplasy on the phylogeny, thus a generic revision
is needed (see also Parkes 1993). For over 15 years Sheldon and
colleagues have been working on a phylogeny of the swallows using
a variety of molecular techniques: DNA-DNA hybridization (Sheldon
& Winkler 1993), and sequencing of mitochondrial (Sheldon
et al. 1999, Whittingham et al. 2002) and now mitochondrial and
nuclear DNA (Sheldon et al. 2005); a further MS on the martins
(Progne et al.) is under review, so I will not propose
changes in this genus here. Taxon sampling has been progressively
denser, and each successive study tends to support conclusions
of the previous ones, and the results also agree nicely with nest
architecture (Winkler & Sheldon 1993). The latest study includes
a fully resolved phylogeny of the New World swallows, thus it
is time to apply these results to our SACC list.
The swallows of the New World fall into two large clades; one,
most diverse in the Old World, includes the genera Hirundo
and Petrochelidon (the latter being clearly recognizable
as distinct). The rest of our species fall into a clade of the
New World Swallows "proper". This clade first breaks
into two diverse clades: Tachycineta and Riparia,
and what might be called the "Atticora group"
(Atticora Boie 1826 is the oldest generic name in the group),
which includes the rest. (Sheldon et al. (2005) and Whittingham
et al. (2002) recommending not subdividing Tachycineta,
which I accept). This group in turn divides (at about the same
level of genetic distance as that between Tachycineta and Riparia)
into two: Stelgidopteryx and Progne, and the remaining
species. Taking the first group, Stelgidopteryx and Progne
clearly merit generic status; the possible splitting off of
Phaeoprogne and species limits in Progne are treated
in the aforementioned MS and any proposal on these should await
acceptance of same.
The second group is more complex. One solution would be to assign
all of these to a large and quite heterogeneous Atticora;
the alternative would be to split this group into several smaller
but much better-defined genera. The clade breaks into three smaller
clades: a) cyanoleuca and melanoleuca, for which
the name Pygochelidon Baird 1865 would be appropriate,
as the type species of Atticora is fasciata. (A
generic synonym for melanoleuca is Diplochelidon Ridgway
1903). The second clade includes the species Alopochelidon
fucata, Notiochelidon flavipes, N. murina and Haplochelidon
andecola. This group breaks first into fucata and
the remaining three. The oldest generic name for this group would
be Notiochelidon Baird 1865, but its type species pileata
falls with Atticora in the phylogeny. Likewise, flavipes
has also been placed in Pygochelidon in the past, but
as the type species of this genus (cyanoleuca) is
in the previous clade, it too is unavailable. The oldest available
generic names for this group are Alopochelidon (for fucata)
and Orochelidon (type species murina), which were
described by Ridgway on the same page of the same publication
in 1903. Two alternatives are available: place all in one genus,
or split into two. If the first were to be adopted, I suggest
Orochelidon as the better genus name under the first revisor
principle, as three of the four species are Andean. The second
choice seems the better to me, as in its foot morphology, coloration
and distribution Alopochelidon fucata stands apart (and
"Alopochelidon" translates to "fox-colored
swallow", referring to the extensive rufous of this species;
its dorsum is brown rather than steely blue-black, its wings are
less pointed and it shows less syndactyly than the Orochelidon
group). The third group includes the species Atticora
fasciata, Neochelidon tibialis and Notiochelidon pileata
(the type species of Notiochelidon). Genetic distances
support including all three in a single genus, which would be
Atticora Boie 1826.
For the purposes of this proposal, I propose a series of alternatives:
A) Lump Progne (including Phaeoprogne),
Stelgidopteryx, Atticora, Pygochelidon, Alopochelidon, Orochelidon,
Notiochelidon and Neochelidon into Atticora.
I recommend a NO on this proposal as the resulting genus would
be highly heterogeneous and virtually undiagnosable.
B) Recognize Tachycineta and Riparia, and Stelgidopteryx
and Progne (including Phaeoprogne)
C) Lump Pygochelidon, Alopochelidon, Orochelidon, Neochelidon
and Notiochelidon into Atticora. I recommend
a NO on this proposal as again, the resulting genus would be decidedly
heterogeneous.
D) Recognize Pygochelidon, Orochelidon and Atticora.
E) As D), but split Alopochelidon from Orochelidon.
Of these two, I recommend NO on D) and YES on E) in the interests
of diagnosability, but I could understand a yes on D (and the
corresponding NO on E).
In short, I recommend a NO vote on A), C) and D) and a YES vote on B) and E): If these are accepted, our SACC list for the swallows would look as follows:
Pygochelidon cyanoleuca
Pygochelidon melanoleuca (new combination;
syn: Diplochelidon)
Alopochelidon fucata
Orochelidon murina
Orochelidon flavipes (new combination)
Orochelidon andecola (new combination; syn: Haplochelidon)
Atticora fasciata
Atticora tibialis (new combination, syn: Neochelidon)
Stelgidopteryx ruficollis
Progne tapera
Progne subis
Progne dominicensis
Progne cryptoleuca
Progne chalybea
Progne elegans
Progne murphyi
Progne modesta
Tachycineta bicolor
Tachycineta stolzmanni
Tachycineta albiventer
Tachycineta leucorrhoa
Tachycineta meyeni
Riparia riparia
Hirundo rustica
Petrochelidon pyrrhonota
Petrochelidon fulva
Petrochelidon rufocollaris
If proposal A were to be accepted, all species from cyanoleuca through modesta would be assigned to Atticora; if D were to be accepted our list would place all species from cyanoleuca through tibialis in Atticora. I fail to see anything useful in accepting A and rejecting the rest, as this would imply wholesale lumping throughout the family, which would simply obscure the branching pattern of the phylogeny and render generic diagnoses all but impossible.
I thank Storrs Olson for helpful comments
and for unearthing the Ridgway 1903 reference.
References:
Parkes, K. C. 1993. Systematics and nomenclature of the Andean
swallow "Petrochelidon" andecola. Auk
110:947-950.
Ridgway, R. 1903. Descriptions of new genera, species and subspecies
of American birds. Proc. Biol. Soc. Wash. 16:105-112.
Ridgway, R. 1904. The birds of North and Middle America, vol.
3. Bull. Natnl. Mus. Nat. Hist 50, part 3.
Sheldon, F. H. & D. W. Winkler. 1993. Intergeneric phylogenetic
relationships of swallows estimated by DNA-DNA hybridization.
Auk 110:798-824.
Sheldon, F. H., L. A. Whittingham, R. G. Moyle, B. Slikas &
D. W. Winkler. 2005. Phylogeny of swallows (Aves: Hirundinidae)
estimated from nuclear and mitochondrial DNA sequencing. Mol.
Phylog. Evol. 35:254-270.
Sheldon, F. H., L. A. Whittingham & D. W. Winkler. 1999. A
comparison of cytochrome b and DNA hybridization data bearing
on the phylogeny of swallows (Hirundinidae). Mol. Phylog. Evol.
11:320-331.
Whittingham, L. A., B. Slikas, D. W. Winkler & F. H. Sheldon.
2002. Phylogeny of the tree swallows (Aves: Tachycineta)
estimated by Bayesian analysis of mitochondrial DNA sequences.
Mol. Phylog. Evol. 22:430-451.
Zimmer, J. T. 1955. Studies of Peruvian birds, no. 66: the Swallows.
Amer. Mus. Nat. Hist. Novitates, no. 1723.
F. Gary Stiles, Sept. 2007
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Comments from Robbins: "Gary's recommendations seem reasonable ("no" for A, C, D; "yes" for B & E), although I have no issues with placing Alopochelidon fucata in Orochelidon."
Comments from Nores:
"A - NO.
B - YES, aunque ver E
C - NO
D - YES. Está muy claro que al pasar tibialis a
Atticora el género Notiochelidon pasa a sinonimia
y por lo tanto se crea la necesidad resurgir los más antiguos
de cada grupo: Pygochelidon y Orochelidon.
E - YES, pero no entiendo porqué reconocer Alopochelidon
y no Phaeoprogne, que está en una situación
similar? Pienso que habría que separar Alopochelidon
y Phaeoprogne como géneros diferentes o incluir
Alopochelidon en Orochelidon y Phaeoprogne en
Progne."
Comments from Cadena: " I agree with Gary, so a. NO, b. YES, c. NO d. NO, and e. YES. I would add on C that if I am understanding which support values go with which nodes in Sheldon et al. 2005, support for the clade formed by these taxa in the analyses is weak. Regarding D and E, it is important to bear in mind that our current classification recognizes Alopochelidon, so the analyses basically support its uniqueness as a monotypic genus. If we were starting from scratch I would probably favor E because a single genus for all the members of that clade is more informative about relationships than having two separate genera, one of which is monotypic. However, because D implies fewer changes in taxonomy, I prefer that alternative given the status quo."
Comments from Zimmer: "YES, for reasons elucidated by Gary. So, a) NO, b) YES, c) NO, d) NO, and e) YES."
Additonal comments from Stiles: "I agree with Miguel that the evidence from the paper cited would accord Phaeoprogne generic status, but I eschewed taking this step because of a communication from Sheldon that further evidence regarding the situation of Phaeoprogne was in the works (manuscript submitted?) which might change this, hence it would be prudent to await the pertinent publication."
Comments from Remsen: "For reasons elucidated by Gary, a) NO, b) YES, c) NO, d) NO, and e) YES."
Comments from Stotz: "(A) NO, (B) YES, (C) NO, (D) YES, (E) NO. Basically I agree with Gary on this. I went for the alternate treatment of fucata in Orochelidon rather than as a monotypic genus because this is a completely new understanding of what its nearest relatives are and I think leaving it as a monotypic genus obscures that fact."
Comments from Pacheco: "Ponderando acerca do arrazoado apresentado pelo Gary os meus votos são: a) NO, b) YES, c) NO, d) NO, e) YES."