Proposal (643) to South American Classification Committee
Recognize Scytalopus gonzagai as a valid species
Effect on South American CL: This proposal would add a recently described species to our main list.
Maurício, Belmonte-Lopes, Pacheco, Silveira, Whitney & Bornschein (2014) recently described a new species of tapaculo, Scytalopus gonzagai from Bahia, Brazil. The new species is known from only 5 localities distributed in 2 distinct mountain ranges, 1 on the eastern slopes of the Planalto da Conquista, between the municipalities of Boa Nova and Iguaí, and another in the Serra das Lontras, ~100 km to the southeast and only 37 km from the coast.
Scytalopus gonzagai is unambiguously distinguished from its closest relatives by 4 suites of characters: (1) morphometrics–body proportions, (2) plumage color, (3) vocalizations, and (4) genetics. Using each of these character sets, separately or in combination, one can distinguish with 100% confidence the new species from its sister lineages.
Because the new species is a fully diagnosable entity with diagnostic character states that are constant over a considerable geographic area, it fulfills the requirements of the Phylogenetic Species Concept (PSC) to be recognized as valid. However, evaluating it under the framework of the Biological Species Concept (BSC) is more difficult because the new species is allopatric relative to S. speluncae, thus avoiding any direct assessment of reproductive isolation or cohesion. Using the “degree of differentiation criterion”, in which one must to consider the amount of phenotypic differentiation among sympatric species of the same genus or species-group (Silva and Straube 1996), we selected an example of sympatry among Brazilian Scytalopus to calibrate our comparisons. It is now well-known that the songs of all species in the S. speluncae group are very similar, differing only in pace or in a few parameters such as note frequency and length (Bornschein et al. 1998, 2007; Maurício 2005).
Songs of S. iraiensis and southern S. speluncae differ diagnostically only in frequency – the former having lower pitched notes – and in the modulation of a few “warming” notes of the beginning of the song of the former; they also differ in habitat preferences (the former lives in dense tall-grass in marshes, rarely entering forest cover; the latter inhabits forest, and locally tall-grass in high altitude fields), in contact calls and some plumage characters (gray shading of the underparts); in terms of size, they overlap broadly in all measurements (Bornschein et al. 1998, 2007; Maurício 2005). Despite being not radically distinct from each other, S. iraiensis and southern S. speluncae maintain their phenotypic and genetic integrity along their largely sympatric ranges, with no signs of hybridization (Bornschein et al. 1998, 2007; Mata et al. 2009; Whitney et al. 2010; GNM and MRB, pers. obs.).
Recommendation: I recommend a "YES" vote on accepting this tapaculo as a new biological species to our list. As the differences between S. gonzagai sp. nov. and both southern and northern S. speluncae in terms of song (pace and note shape) and plumage/ proportions (barring pattern and bill/wing and tail/wing relationships) are similar or greater in magnitude to those observed between S. iraiensis and [sympatric] southern S. speluncae, we argue that, if eventually coming into secondary contact with S. speluncae, the new species would maintain its identity as a reproductively isolated unit; in other words, S. gonzagai sp. nov. would be more appropriately ranked as a species – instead of a subspecies – under the BSC.
BORNSCHEIN, M. R., G. N. MAURÍCIO, R. BELMONTE-LOPES, H. MATA AND S. L. BONATTO. 2007. Diamantina Tapaculo, a new Scytalopus endemic to the Chapada Diamantina, northeastern Brazil (Passeriformes: Rhinocryptidae). Rev. Bras. Orn. 15(2): 151-174.
BORNSCHEIN, M. R., B. L. REINERT & M. PICHORIM 1998. Descrićčo, ecologia e conservaćčo de um novo Scytalopus (Rhinocryptidae) do sul do Brasil, com comentários sobre a morfologia da família. Ararajuba 6: 3–36.
MATA, H., C. S. FONTANA, G.N. MAURÍCIO, M.R. BORNSCHEIN, M.F. VASCONCELOS & S. L. BONATTO 2009. Molecular phylogeny and biogeography of the eastern tapaculos (Aves: Rhinocryptidae: Scytalopus, Eleoscytalopus): Cryptic diversification in Brazilian Atlantic Forest. Molecular Phylogenetics and Evolution 53: 450–462.
MAURÍCIO, G.N. 2005. Taxonomy of southern populations in the Scytalopus speluncae group, with description of a new species and remarks on the systematics and biogeography of the complex (Passeriformes: Rhinocryptidae). Ararajuba 13: 7–28.
MAURÍCIO, G.N., R. BELMONTE-LOPES, J. F. PACHECO, L.F. SILVEIRA, B. M. WHITNEY & M.R. BONSCHEIN. 2014. Taxonomy of ‘‘Mouse-colored Tapaculos’’ (II): An endangered new species from the montane Atlantic Forest of southern Bahia, Brazil (Passeriformes: Rhinocryptidae: Scytalopus). Auk 131. DOI: 10.1642/AUK-14-16.1
SILVA, J.M.C. & F.C. STRAUBE 1996. Systematics and biogeography of Scaled Woodcreepers (Aves: Dendrocolaptidae). Stud. Neotrop. Fauna Environ. 31: 3–10.
WHITNEY, B. M., M.F. VASCONCELOS, L.F. SILVEIRA, & J.F. PACHECO 2010. Scytalopus petrophilus (Rock Tapaculo): A new species from Minas Gerais, Brazil. Revista Brasileira de Ornitologia 18: 73–88.
José Fernando Pacheco, Giovanni Maurício & Marcos Ricardo Bornschein, September 2014
Note from Remsen on English name: The original paper used the English name “Bahian Mouse-colored Tapaculo” as the recommended English name. However, this would conflict with general principles of English names in that there is already a species “Mouse-colored Tapaculo” (S. speluncae) without a modifier, and thus the traditional name Mouse-colored Tapaculo would require a modifier if “Bahian Mouse-colored Tapaculo” were adopted. (This is not the Brazilian authors’ fault! – the Auk was asleep at the wheel on this.). So, we will need a separate proposal on English names. The name “Bahia Tapaculo is preoccupied by Eleoscytalopus psychopompus, so use of “Bahian” even in a compound name would create confusion.
Comments from Stiles: “YES, there seems no question that gonzagai is a fully diagnosable species – and given the very similar plumages of several species of Colombian Scytalopus that are vocally and genetically quite distinct, I see no problem with regard to the BSC in recognizing it as a species.”
Comments from Jaramillo: “YES – given the controversy regarding Scytalopus from this part of the world, I was prepared for something a bit more complex. However, it seems to be a relatively straightforward decision. This is a new taxon, although there is a level of subjectivity to the consideration as a species or subspecies. However, currently I see that the decision to consider this as a species is based on the comparison taxa, which are considered species, and so this is the correct course of action.”
Comments from Remsen: “YES, based on vocal differences and comparisons to S. iraiensis and S. speluncae, between which there is no sign of gene flow.”
Comments from Zimmer: “YES. I’m happy to see this one finally published. I have audio and video recordings (made in 2006) of multiple individuals of S. gonzagai from the Serra das Lontras-Javi, and the then-observed vocal and morphological distinctions from “northern” and “southern” S. speluncae were consistent with those nicely detailed by Mauricio et al (2014), and, in my opinion, solidly support separate species status, especially when applying the yardstick of differences between other recognized species in the group (particularly speluncae versus iraiensis). As for English names, I kind of like the name “Lontras-Javi Tapaculo” which pinpoints the massif that encompasses perhaps the bulk of the species’ range, as well as the place where Bret and Luís Fabio collected the first voice-recorded specimen.”