Proposal (357) to South American Classification Committee
Treat Anas puna as a subspecies of Anas versicolor
Effect on South American Checklist: This proposal remove a species to the Main List by reducing A. puna to a subspecies of A. versicolor.
Background: Our current Note is as follows:
22. Anas puna and A. versicolor are sometimes (e.g., <?> Peters 1931, Johnsgard 1978, 1979, Carboneras 1992f, Dickinson 2003) considered conspecific, but most classifications (e.g., Hellmayr & Conover 1948a, Meyer de Schauensee 1970, Blake 1977, Fjeldså & Krabbe 1990) consider them to be separate species. They form a superspecies (Sibley & Monroe 1990), and genetic data (Johnson & Sorenson 1999) confirm that they are sister species. Proposal needed.
This situation is similar in many ways to that in Proposal on Anas flavirostris/andium, and I repeat some of that text here. At the outset, it seems to me that they should be treated in the same way, one way or another, in contrast to our current classification. I do not have any first-hand knowledge of the taxa involved, nor am I aware of recent data that address the problem directly. This is one of those cases in which the classification in Dickinson (2003), which formed our baseline list, was changed just before publication, thus generating a discrepancy between SACC and its stated starting point. We have to address this with a proposal.
Anas puna is found exclusively in the Andes from Peru to n. Argentina. It differs from A. versicolor of the lowlands of southern South America primarily in having an all blue bill (yellow basal half in versicolor) and an all-white face (buff in versicolor); there are other differences in pattern in the sides and flanks, and puna is also larger. They are nicely illustrated in Jaramillo (2003). They are allopatric as far as is known.
Johnsgard (1978, 1979) treated them as conspecific, so that implies (to me) that at least at that time there were no known behavioral/display/vocal differences between the two groups, nor are any differences referenced in HBW (Carboneras 1992f).
Johnson & Sorenson (1999) included both in their mtDNA analysis and found them to be more different from one another in terms of genetic distance (mtDNA) than other pairs of Anas treated as species, e.g., A. discors/cyanoptera, A. platyrhynchos/rubripes/fulvigula, and A. clypeata/rhynchotis. I would not use of genetic distance measures alone to determine taxonomic rank, but the data are of interest, nonetheless.
Analysis: In the absence of any data on gene flow, we are left to assign species rank based on comparative analysis. Because both treatments have wide acceptance in the literature, I do not think that we have to demand strong data to change from our current classification.
With minimum conviction, I recommend a NO vote on the lump on the following basis. First, as noted in Proposal 356, I cannot think of a case of two taxa of ducks known to interbreed freely that have such different bill colors. [Please correct me if wrong.] Second, as far as I know, an explicit rationale for their treatment as a single species has not been published (although I have not checked the Delacour literature).
Van Remsen, May 2008
Comments from Stiles: "NO. I think that the evidence from ecology, distribution, morphometrics, coloration and genetics all favor maintaining puna as a separate species from versicolor - the evidence seems stronger here than for the preceding case and this treatment seems to have been used more often in the recent past (including by Blake, who did not split andium from flavirostris)."
Comments from Robbins: "NO, for lumping, for the following reasons: to be consistent with how I voted in proposal 356, and the genetic data, in comparison to other anatids that we treat as species, support species recognition."
Comments from Nores: "NO. Yo considero que este es un caso similar al de A. flavirostris/andium, con el agregado de que un análisis genético los muestra bien diferentes, y por lo tanto hay que tratarlos de la misma manera. Lo que sí, vuelve a llamarme la atención el uso variable que se hace en SACC de los análisis genéticos para resolver problemas taxonómicos. Nunca se bien en qué medida un análisis genético es suficiente para resolver un problema. Yo hice dos propuestas basadas en análisis genéticos (No. 264 y 349) y ninguna pasó, y ahora veo en esta propuesta que el análisis de mtDNA de Johnson & Sorenson (1999) no debería ser usado solo para determinar status taxonómico. En otras propuestas, por el contrario, el hecho de que haya un análisis molecular, es "palabra santa".
Comments from Zimmer: "NO, for reasons stated by others."
Comments from Stotz: "NO. Certainly this pair seems a stronger case for splitting that andium and flavirostris. The genetic evidence supports maintaining the status quo of two species."
Comments from Jaramillo: "NO - I know these two taxa quite well, and they are very different from each other visually, in bill color, habitat, elevation range, and size. Anas puna is actually quite a bit larger than versicolor. The differences between these two ducks seems to me much greater than that of andium/flavirostris and is comparable to differences seen in species of wigeon, and shoveler species to give examples. These are clearly two good species."
Comments from Pacheco: "NO. Voto não, sem porém acrescentar novidades."