Proposal (600) to South American Classification Committee
Split Xiphorhynchus ocellatus into three species, and treat X. pardalotus as basal to them
Effect on SACC: Xiphorhynchus ocellatus would be split into X. chunchotambo, X. beauperthuysii, and X. ocellatus. Xiphorhynchus pardalotus would be placed immediately before X. chunchotambo.
Background: Genetic data (Aleixo 2002) indicate that Xiphorhynchus pardalotus, sometimes considered a member of the X. spixii superspecies, and X. ocellatus are sister species, as proposed by Zimmer (1934a); Aleixo (2002) found that pardalotus is embedded within taxa currently treated under X. ocellatus (see Note 21), and this should be reflected in linear sequence. Derryberry et al. (2011) found that X. pardalotus was the sister to their single population sample of X. ocellatus.
New Information: A recently published multilocus phylogenetic analysis on the Xiphorhynchus pardalotus/ocellatus complex (Sousa-Neves et al., 2013) recovered a basal position for X. pardalotus with respect to X. ocellatus, and the division of X. ocellatus into three well-supported major clades (PP ≥ 0.95), based on gene trees and coalescent-based species-tree analyses. The authors sampled 35 individuals of most subspecies recognized to the complex, except X. ocellatus lineatocapilla and X. pardalotus caurensis, whose morphological diagnoses and validity remain controversial (Marantz et al., 2003). The recovered major clades within X. ocellatus correspond to the proposed species below:
Xiphorhynchus chunchotambo: distributed in the lower eastern Andean slopes and adjacent lowland Amazonia from southern Colombia, eastern Ecuador, eastern Peru, northern Bolivia, and the southeastern part of the Brazilian state of Acre;
Xiphorhynchus beauperthuysii: distributed north of the Amazon from the western banks of the Negro River in the Brazilian state of Amazonas through southern Venezuela (Amazonas), southern Colombia (Amazonas), eastern Ecuador, and northern Peru east of the Napo river, with an apparently isolated population inhabiting sandy-soils forests near Jeberos;
Xiphorhynchus ocellatus: Distributed south of the Amazon in northeastern Peru (east of the lower Ucayali River) to the Madeira – Tapajós interfluve in the Brazilian states of Amazonas, Acre, Rondônia, and Pará and also Pando in northern Bolivia.
Analysis/Recommendation: Despite incongruence between the species and the gene trees – in the mitochondrial gene tree, X. ocellatus is paraphyletic with respect to X. pardalotus, for example (see also Aleixo 2002 and Derryberry et al. 2011) - the coalescent multi-locus and concatenated trees recovered with overall high statistical support the reciprocal monophyly among X. pardalotus, X. chunchotambo, X. beauperthuysii, and X. ocellatus, which is consistent with a high degree of evolutionary independence and reproductive isolation among these clades (see also Guilherme & Aleixo 2008 discussion on a contact zone between X. ocellatus and X. chunchotambo in eastern Acre). Even though a formal quantitative analysis is not presented, vocal types among these clades are also very distinct (see Xeno-Canto recordings and Sousa-Neves et al. 2013). In fact, significant vocal variation appears to exist also within at least one of these clades (X. chunchotambo), indicating that probably additional cryptic species will be uncovered by future studies (Sousa-Neves et al. 2013).
We therefore strongly recommend a YES vote on this proposal, which we divide into three parts:
A. Recognize Xiphorhynchus chunchotambo as a separate species from X. ocellatus.
B. Recognize Xiphorhynchus beauperthuysii as a separate species from X. ocellatus.
C. Move X. pardalotus in the linear sequence to precede these taxa.
ALEIXO, A. 2002. Molecular systematics and the role of the "várzea"-"terra firme" ecotone in the diversification of Xiphorhynchus woodcreepers (Aves: Dendrocolaptidae). Auk 119: 621-640.
DERRYBERRY, E., S. CLARAMUNT, G. DERRYBERRY, R. T. CHESSER, J. CRACRAFT, A. ALEIXO, J. PÉREZ-ÉMAN, J. V. REMSEN, JR., AND R. T. BRUMFIELD. 2011. Lineage diversification and morphological evolution in a large-scale continental radiation: the Neotropical ovenbirds and woodcreepers (Aves: Furnariidae). Evolution 65: 2973-2986.
GUILHERME, E., AND ALEIXO, A., 2008. Primeiros registros de Xiphorhynchus chunchotambo (Tschudi, 1844) (Dendrocolaptidae) no Brasil. Rev. Bras. Orn. 16: 44–46.
MARANTZ, C. A., A. ALEIXO, L. R. BEVIER, AND M. A. PATTEN. 2003. Family Dendrocolaptidae (woodcreepers). Pp. 358-447 in "Handbook of the Birds of the World, Vol. 8. Broadbills to tapaculos." (J. del Hoyo et al., eds.). Lynx Edicions, Barcelona.
SOUSA-NEVES, T, ALEIXO, A., SEQUEIRA, F. 2013. Cryptic patterns of diversification of a widespread Amazonian Woodcreeper species complex (Aves: Dendrocolaptidae) inferred from multilocus phylogenetic analysis: implications for historical biogeography and taxonomy. Molecular Phylogenetics and Evolution 68: 410-424.
ZIMMER, J. T. 1934a. Studies of Peruvian birds, No. 15. Notes on the genus Xiphorhynchus. American Museum Novitates 756: 1-20.
Sidnei Dantas and Alexandre Aleixo
Note from Remsen: A separate proposal on English names will be needed if A and B pass.
Comments from Stiles: “YES on A, B and C. My only gripe is having to live with an orthographic horror like beauperthuysii in Leticia – but I´d already noted the vocal and morphological differences between this taxon and the birds (chunchotambo) at the base of the Andes in Caquetá!”
Comments from Pacheco: “[YES on A, B and C.] O arranjo proposto é fortemente apoiado nos resultados de um conjunto de estudos.”
Comments from Remsen: “In general, everyone should take note that this study reveals the importance of multilocus studies in separating gene trees from species trees.”
A. “NO. Although I am fairly certain from qualitative descriptions of vocalizations that chunchotambo deserves species rank, until these differences are explicitly presented and quantified, I object to elevating it to species rank. It would take someone about a day of work to put together a little paper on this taxon’s voice and compare it to ocellatus (s.s.). I think we should adhere to minimum standards of rigor before making changes to the classification.”
B. “NO. Without vocal data, all we have no evidence that beauperthuysii is anything other than a valid subspecies.”
C. “YES. Sousa-Neves et al. confirm conclusively that pardalotus is misplaced in the linear sequence.”
Comments from Cadena: “NO. The multilocus genetic data are highly suggestive of the existence of more than one species, but they may represent variation existing among allopatric populations of a single species. I listened to recordings and, sure, they sound different, but no formal analysis has been published. I thus agree with Van in that we are not quite there in terms of evidence to propose the three-way split.”
Comments from Zimmer:
“A. NO. Based on vocal differences, I feel pretty certain that a split is called for, but as noted by Van and Daniel, there has been no published vocal analysis to demonstrate this. Setting aside the vocal differences, I’m not enthusiastic about splitting on the genetic data alone, which, although certainly suggestive, could still reflect variation between long isolated populations of the same species. I would welcome a published vocal analysis, which, I anticipate will provide us with all the justification needed for making the split.
“B. NO, for similar reasons as in Part A.
“C. YES. Evidence for this seems pretty solid.”