Proposal (980) to South American Classification Committee

Treat Celeus grammicus as conspecific with Celeus undatus

Background: The treatment of Celeus grammicus as a separate species from Celeus undatus has long been considered questionable (Short 1972), because of their very similar plumage morphology. Field workers have known for decades that the vocalizations of these two taxa are extremely similar, if not inseparable (cf. Macaulay Library, xeno-canto). Benz and Robbins (2011) provided the first genetic perspective, establishing that they were indeed sister taxa and there was extremely low genetic differentiation between them. Because of limited sampling across the entire distribution of the two taxa, they refrained from suggesting that the two be treated as conspecific.

New Information: Sampaio et al. (2018) obtained much more complete sampling (n=56 individuals from 6 of the 7 subspecies) and a more in-depth genetic assay of the two, concluding that there was a lack of reciprocal monophyly in all phylogenetic analyses. They recommended that they be treated as a single species.

Recommendation: Plumage, vocalizations and genetic data unequivocally indicate that grammicus should be considered conspecific with undatus. Undatus (Linnaeus 1766) has priority over grammicus (Natterer and Malherbe 1845).

References:

Benz, B.W. and M.B. Robbins. 2011. Molecular phylogenetics, vocalizations and species limits in Celeus woodpeckers (Aves: Picidae). Molecular Phylogenetics and Evolution 56:29-44.

Sampaio, L., A. Aleixo, H. Schneider, I. Sampaio, J. Araripe, P.S.D. Rego. 2018. Molecular and plumage analyses indicate incomplete separation of two woodpeckers (Aves, Picidae). Zool. Scr. 47:418-427. https://doi.org/10.1111/zsc.12287

Short, L.L. 1972. Relationships among the four species of the subspecies Celeus elegans (Aves, Picidae). Am. Mus. Novitates 2487:1-26.

Mark Robbins, August 2023

Note from Remsen: If the proposal passes, we will need a separate proposal on the English name for the new, composite species.

Comments from Zimmer: “YES, for all of the reasons stated in the Proposal. This would constitute a welcome change for me – I’ve never been able to separate these two “species” vocally, and there are areas on the South Bank of the Amazon where North Bank undatus occurs to the exclusion of widespread South Bank grammicus, making you obligated, when working in a new location, to track down every vocalizing C. undatus/grammicus for visual confirmation of identity.”

Comments from Lane: “YES. I think the evidence makes this a pretty clear case, and agree with Mark's comments about vocal similarity.”

Comments from Areta: “YES. All lines of evidence support the conspecificity of grammicus and undatus, with the later having precedence.”

Comments from Remsen (revised, thanks to Alex Aleixo and Jacob Socolar pointing out to me that I had badly misread the results: “YES. Whether they are “reciprocally monophyletic” based on 3 mtDNA and 3 nDNA markers is, to me, irrelevant. However, In contrast to many studies that proclaim “reciprocal monophyly”, at least Sampaio et al. (2018) had a large N (= 57) with good geographic sampling, and so all genetic signs point towards no restrictions on gene flow

“Lester Short, who used almost any sign of gene flow to treat woodpecker (and other) taxa as conspecific, treated grammicus and undatus as separate species. He (Short 1982, Woodpeckers of the World, Delaware Museum of Natural History) based this on apparent parapatry in the Rio Negro region and close approach without signs of interbreeding in two other areas. Short (1982) claimed that these two species have diagnostic plumage characters that allow visual discrimination wherever they occur. However, Sampaio et al.’s (2018) analysis of 77 specimens clearly refuted that these two are diagnosable by plumage in the contact region, and found intermediate specimens that apparently Short did not examine.

“So, from three independent data sets (voice, plumage, mtDNA), all data indicate an absence of any barriers to gene flow, ergo the single species treatment is strongly supported.

Comments from Claramunt: “YES. Sampaio et al. (2017( clearly showed that this pair of woodpeckers lack gene tree reciprocal monophyly, and are not strictly diagnosable because some characters vary clinally, others are just polymorphic, and vocalizations are indistinguishable. The photos of the specimens clearly show intermediate specimens that show trait mosaicism (Figure 3). All this suggests that gene flow is ongoing, and this complex constitutes a single lineage and a single biological species.”

Comments from Bonaccorso: “YES. The molecular, vocal, and morphological evidence indicate these two taxa can be considered conspecifics.”

Comments from Stiles: “YES (I thought I had voted on this one but evidently a mistake – and seeing that it had passed without my vote, I had not added my vote until now.)

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