Proposal (314) to South American Classification Committee
Revise the generic limits 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 Phaeprogne 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 reviser 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 Phaeprogne), 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 Phaeprogne)
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 melanoleuca (new combination; syn: Diplochelidon)
Orochelidon flavipes (new combination)
Orochelidon andecola (new combination; syn: Haplochelidon)
Atticora tibialis (new combination, syn: Neochelidon)
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.
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
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 Š NO
D - YES. Est‡ muy claro que al pasar tibialis a Atticora el gˇnero Notiochelidon pasa a sinonimia y por lo tanto se crea la necesidad resurgir los m‡s antiguos de cada grupo: Pygochelidon y Orochelidon.
E - YES, pero no entiendo por quˇ reconocer Alopochelidon y no Phaeprogne, que est‡ en una situaci—n similar? Pienso que habr’a que separar Alopochelidon y Phaeprogne como gˇneros diferentes o incluir Alopochelidon en Orochelidon y Phaeprogne 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."
Additional comments from Stiles: "I agree with Miguel that the evidence from the paper cited would accord Phaeprogne generic status, but I eschewed taking this step because of a communication from Sheldon that further evidence regarding the situation of Phaeprogne 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 s‹o: a) NO, b) YES, c) NO, d) NO, e) YES."