Proposal (284) to South American Classification Committee

 

Recognize Hemispingus piurae as a species

 

Effect on SACC: This would split Hemispingus piurae from H. melanotis.

 

Background & New information: Our current classification considers the taxon piurae to be a subspecies of H. melanotis, following most recent classifications.

 

Garc’a-Moreno et al. (2001) published a phylogenetic hypothesis based on mtDNA sequences of 9 of the 12 traditionally recognized species, and also analyzed 20 morphological characters (plumage patterns and leg and bill size and shape). The gene sampling was poor (only 310 bp of ND2), and some of the morphological "characters" represent arbitrary breaks on continuous variation (e.g., in bill curvature, wing-tail ratio, wing-tarsus ratio).

 

One of their conclusions was that piurae deserved species rank. Here is what they wrote:

 

"Within our limited sampling, we could not detect any differences to warrant separation of the east- and west-slope subspecies melanotis and ochraceus, neither at the molecular level nor based on the plumage characters. H. melanotis piurae, on the other hand, was genetically so distinct that it was never shown to be the sister to the other subspecies of H. melanotis. This taxon is morphologically the most distinctive taxon in the melanotis group (originally described as a separate species), being most similar to H. m. castaneicollis from southeastern Peru and Bolivia. H. m. piurae has unique vocalizations (P. Greenfield and N. Krabbe, pers. com.) and inhabits a distinct habitat of fairly dry cloud forest, as opposed to humid forests and bamboo thickets. Taking those facts together in the context of our results, we think this taxon may deserve its original species status: Piura Hemispingus (H. piurae)."

 

Ridgely and Greenfield (2001) also treated piurae as a species, with the following statement:

 

"H. piurae here considered a species distinct from H. melanotis ... Piurae differs strikingly in plumage, and though similar, their vocalizations also differ."

 

Ridgely and Greenfield (2001) also treated ochraceus of the Western Andes as yet another species.

 

Garc’a-Moreno & FjeldsŒ. (2003) re-analyzed the same data set but added H. parodii and Cnemoscopus to the analysis. Using Maximum Likelihood and Maximum Parsimony, they found strong bootstrap support for piurae as basal to melanotis + frontalis. A third analysis, using Minimum Evolution did not recover this relationship, but nodes did not receive high bootstrap support.

 

Analysis and Recommendation: Again, we have the same situation faced in so many of these "species limits" problems, namely sharp field people strongly suspect that the taxon deserves species rank because of vocal differences that parallel plumage differences, but the documentation of the vocal differences has not been published, much less formally analyzed. The difference with this one is that genetic data also support a split in that the Garc’a-Moreno et al. phylogeny shows strong support for piurae as basal to melanotis + frontalis (the latter considered a separate species in all classifications). The problem is that although definitely suggestive, the genetic data, with only 300 bps of mtDNA, cannot really be taken seriously, and they could also be due to incomplete lineage-sorting or hybridization.

 

As for the plumage differences, as noted by Garc’a-Moreno et al., these aren't so dramatic when one compares piurae to distant castaneicollis; the head patterns of these two (white superciliary and black throat) are nearly identical, and overall they are much more similar to each other than either is to nominate melanotis (no superciliary, pale throat) of e. Ecuador. [By the way, southern populations of berlepschi (c. Peru, no superciliary, pale throat), which the above authors would presumably treat in melanotis, have darkish throats like piurae and castaneicollis.

 

When we have more data on voice and genes, I think that we can make an informed decision. Until genetic sampling is more thorough in terms of genes, base-pairs, and populations, and until the presumed vocal differences are documented and analyzed, I recommend we stick with current species limits. Kevin Burns will undoubtedly generate new genetic data on these taxa, and so I do not think we have to wait long for better data.

 

References:

Ridgely and Greenfield. 2001. Birds of Ecuador

GARCêA-MORENO, J., AND J. FJELDS. 2003. Phylogenetic relationships among Hemispingus tanagers. Ornitologia Neotropical 14: 363-370.

GARCêA-MORENO, J., J. OHLSON, AND J. FJELDS. 2001. MtDNA sequences support monophyly of Hemispingus tanagers. Molecular Phylogenetics & Evolution 21: 424-435.

 

Van Remsen, June 2007

 

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Comments from Stiles: "NO, at least for now. Such a small genetic sample is not very convincing, and use of songs as taxonomic characters for species limits in oscines is dicey given the really striking differences in song dialects in many cases - Zonotrichia capensis is a nice case in point. If better genetic data and a convincing morphological/vocal analysis are forthcoming, I'll go along with it, but not until then."

 

Comments from Cadena: "NO. The genetic data are weak, and the other sources of variation have not been rigorously analyzed."

 

Comments from Robbins: "NO. Lets wait for a more extensive and clear cut data set before recognizing piurae as a species."

 

Comments from Zimmer: "NO. The genetic data are weak, vocal differences have not been analyzed (and we are dealing with oscine passerines, as noted by Gary), and a more rigorous analysis is expected to be published soon - let's wait."

 

Comments from Nores: "YES. Para mi las diferencias morfol—gicas que presenta (especialmente en la cabeza) con respecto a melanotis son lo suficientemente importantes como para ser considerada especie. Adem‡s, si hay un estudio molecular (aunque sea un poco liviano) que apoya su separaci—n, parece apropiado hacerlo."

 

Comments from Jaramillo: "YES - The weak molecular dataset, in conjunction with plumage details and at least qualitative differences in voice (macro-geographic patterns in voice of oscines can be phylogenetically informative I would add) put me on the Yes side of the fence. Admittedly, I can see the NO point of view as being logical and reasonable, but feel that this split is OK as it stands."

 

Comments from Pacheco: "NO. Neste caso, prefiro aguardar pela disponibilidade de mais dados e melhor an‡lise da informa‹o para dar o meu endosso a este split."