Proposal (728) to South American Classification Committee
Elevate Amaurospiza concolor aequatorialis to species rank
Background: Sharpe (1888) described Amaurospiza aequatorialis as a new species from the western foothills of the Andes of Ecuador. In the same work, Sharpe also recognized A. concolor and described A. axillaris from SE Brazil (now known as A. moesta). Hellmayr (1938) merged A. aequatorialis into A. concolor based on morphological similarity: “Though more adequate material is required to determine its characters, there can be no question as to A. aequatorialis being but a slightly differentiated race of Cabanis's Blue Seed-eater.” However, Hellmayr (1938) examined only four specimens, none of which in full adult male plumage. Lentino & Restall (2003) didn’t examined more specimens but found that aequatorialis has a unique wing formula within the genus; this, in addition to differences in plumage color and morphology between aequatorialis and concolor led them to suggest that aequatorialis may represent a separate species.
New information: Bryson et al. (2014) analyzed a multilocus dataset (ND2, ACO1, FGB5, and MYC) using traditional and species-tree phylogenetic analyses and found that their sample of aequatorialis was not closely related to nominate concolor from Central America. Instead, it grouped with A. moesta and A. carrizalensis. They concluded that aequatorialis should be elevated to species status. There is no published analysis of vocal data, but a cursory examination of songs available in Xeno-canto and the Macaulay Library suggests that the songs of aequatorialis have consistently lower frequency and a higher number of notes (8-9) than Central American concolor (5-6 notes).
Analysis and Recommendation: I think that the molecular evidence, in combination with the previous information on phenotypic differences, is sufficient to demonstrate that aequatorialis represents a separate lineage from A. concolor. Whereas potential reproductive isolation is difficult to assess, the phylogenetic information is clear regarding the existence of two lineages instead of one in the current A. concolor. Therefore, I recommend a Yes. This proposal would have the effect of eliminating A. concolor from the South American list and adding A. aequatorialis.
References:
BRYSON, R. W., J. CHAVES, B. T. SMITH, M. J. MILLER, K. WINKER, J. L. PÉREZ-EMÁN, J. & KLICKA. 2014. Diversification across the New World within the ‘blue ’cardinalids (Aves: Cardinalidae). Journal of Biogeography 41:587-599.
HELLMAYR, C. E. 1938. Catalogue of birds of the Americas and adjacent Islands. Field Museum of Natural History. Zoological Series 13:1-662.
LENTINO, M., & R. RESTALL. 2003. A new species of Amaurospiza blue seedeater from Venezuela. Auk 120: 600-606.
SHARPE, R. B. 1888. Catalogue of the Passeriformes, or perching birds, in the collection of the British museum. Fringilliformes, pt. III. in Catalogue of birds in the British Museum. Vol. 12. London.
Santiago Claramunt, October 2016
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Comments from Remsen: “NO, but only on the principle that all the critical data should be published, specifically in this case, sonograms of the relevant taxa. All that is need is a short note on Amaurospiza comparing songs with representative sonograms. I waivered on this one – clearly the “data” used to treat aequatorialis as a subspecies of concolor are not acceptable by current standards, and just as clearly, recent data indicate that if aequatorialis were to be treated as a subspecies of anything, it should be included in moesta. Nonetheless, to maintain our standards of rigor, in my opinion published sonograms are required (and availability of the songs and sonograms on xeno-canto, as useful as this is, does not count as published).”
Comments from Stiles: “A temporary NO as per Van - if vocal evidence is used to support this move, it should be published - a short note would do the trick.”
Comments from Pacheco: “A temporary NO for the reasons noted by Van.”
Comments from Robbins: “YES, regardless of one’s philosophy about whether we should be using vocal data from online sites for evaluating proposals (I think everyone on this committee knows that I support that), the genetic data are unequivocal. Aequatorialis is in the moesta/carrizalensis clade, so unless one treats all of the latter as a species (I don’t think anyone at this point would support that course of action), then one must treat aequatorialis as a species.”
Comments from Zimmer: “YES”, based upon the genetic findings of Bryson et al. (2014). At this point, a vocal analysis would be nice corroborating evidence, but not required in my opinion, to make the proposed move. As Mark points out, the genetic evidence reveals that aequatorialis is part of the moesta/carrizalensis clade, so we have to split it from concolor, and the only other option (than full-species status) would be to lump moesta, carrizalensis and aequatorialis, which I doubt would be palatable to anyone.”
Additional comments from Remsen: Concerning Mark and Kevin’s concern that the only option given the genetic data (aequatorialis[moesta+carrizalensis]) is to treat aequatorialis as a species is not necessarily the case. The node supporting that relationship has weak support (more than 50% but less than 70% BPP; Fig. B, where aequatorialis is represented as “concolor B”) and is based solely on mtDNA and from only a single specimen. Therefore, it is not unreasonable to treat that as a polytomy and pending additional data, tentatively as subspecies of A. moesta. That said, as indicated in my original comments, I predict that published vocal data will confirm that aequatorialis should be treated as a species.”
Additional comments from Claramunt: “I wanted to make two clarifications regarding the comments by Van above. First, Bryson et al. (2013) did use nuclear data. They used a large dataset of mtDNA but also sequenced three nuclear introns for the major linages, including one individual of the three currently recognized species of Amaurospiza plus a specimen of aequatorialis.
“Second, the node with low support mentioned by Van is not the relevant one. There is low support for the moesta-carrizalensis sister relationship, but that aequatorialis is closer to those two species as oppose to concolor is actually strongly supported in both the mitochondrial gene tree and the multilocus species tree (see image, "concolor B" is aequatorialis in the multilocus species tree).
“Therefore, the phylogenetic results are strong. This is not a case of nearly simultaneous diversification in a superspecies complex where relationships are difficult to recover. The South American clade is strongly supported and diverged from concolor about 6 million years ago. I agree that sample size is far from ideal for species delimitation, but I think it is sufficient in this case, given the magnitude of the divergences recovered and the concordant phenotypic variation.”
Additional comments from Remsen: “My comments are relevant only to whether aequatorialis can be considered, tentatively, a subspecies of A. moesta. The genetic data are obviously strong in refuting the current classification of aequatorialis as a subspecies of concolor – clearly, maintaining aequatorialis as a subspecies of concolor is untenable. My comments only address the whether the relationship in the tree, i.e. (aequatorialis((moesta+carrizalensis))) is sufficient for treating aequatorialis at equivalent rank to those two, i.e. all three as separate species. In Fig. 2, which is based mostly on mtDNA (with multilocus data for certain individuals), the node that indicates that moesta and carrizalensis are sisters to the exclusion of “concolor B” (i.e., aequatorialis) has a PP value between 0.70 and 0.95, thus weakly supported. In Fig. 3, the mtDNA tree, the node that places moesta and carrizalensis as sisters to the exclusion of “concolor B” (i.e., aequatorialis) has a PP value between 0.50 and 0.70, i.e. very weak. In the multilocus tree in Fig. 3, even the node that supports “concolor B” (i.e., aequatorialis) as more closely related to moesta+carrizalensis than to true concolor has only modest support (between 0.70 and 0.95). In summary, my point is only that the genetic data cannot be used to refute a temporary treatment of aequatorialis as a subspecies of moesta pending additional data. Although this at first seems biogeographically nonsensical, with moesta restricted to the Atlantic Forest region and aequatorialis to SW Colombia to NW Peru, such a distribution pattern recalls that of the sister taxa Claravis mondetoura and C. geoffroyi, also bamboo specialists.
“A corollary of the substandard support for the branching pattern among the three taxa is that the branch lengths separating aequatorialis, moesta, and carrizalensis are short, thus supporting a close relationship among the taxa that are difficult to recover.
“As I emphasized at the outset, my NO vote is based on the technicality that the vocal data comparing these three taxa have not been published, and I am confident that they will show that all three merit species rank.”
Comments from Areta: “NO, until vocal and more thorough genetic data are published. We have been working on the Amaurospiza for some time, and are still striving to get DNA from relicta toe-pads (the only taxon that we are missing to have complete taxon sampling). I want to publish on this with complete taxon sampling, which should give us a more accurate perspective of the taxonomy in the genus. Three years ago I gave a talk on this in Argentina and work is in progress: http://www.fcnym.unlp.edu.ar/uploads/docs/rao_2013.pdf (page number 13)”
Comments from Stotz: “YES I have gone back and forth on this. I think the fact that the current treatment as a subspecies of concolor is demonstrably wrong, we need to make a change. Even without the vocal data, I would be inclined to split aequatorialis from moesta and carrizalensis, based on the extreme range disjunction and distinct morphological features.”
Comments from Jaramillo: “YES – Guided by the molecular data, I am comfortable with making this choice now.”