Proposal (858) to South American Classification Committee

A: Rank Scytalopus latrans intermedius as a species. B: call it Utcubamba Tapaculo

Elevating Scytalopus latrans intermedius to species rank is long overdue. For nearly two decades it has been known to give song and calls differing drastically from the two other forms of S. latrans. Genetic comparisons now show that it is not closely related to them.

Background Zimmer (1939) described intermedius from the Río Utcubamba drainage in the northern Central Andes of Peru and ranked it as a subspecies of a broad Unicolored Tapaculo (S. unicolor) that also included latrans, subcinereus and parvirostris. Both parvirostris and nominate unicolor were later elevated to species rank on vocal grounds (Krabbe & Schulenberg 1997, Coopmans et al. 2001). This left intermedius with latrans and subcinereus in Blackish Tapaculo (S. latrans), although this made little biogeographical sense. The song of intermedius was finally described by Schulenberg et al. (2007) as being faster paced, but otherwise fairly similar to that of Large-footed Tapaculo (S. macropus) and very different from that of latrans and subcinereus. Freeman and Montgomery (2017) reported lack of response from latrans to playback of intermedius and suggested that on basis of that alone, intermedius should be ranked as a biological species. Finally, Cadena et al. (2020) published genetic comparisons showing that intermedius is sister to S. macropus and only distantly related to latrans and subcinereus, which are closer related to other forms; they too pointed out that intermedius should be ranked as a species.

Known localities in northern Peru and southern Ecuador of Zimmer’s broad Scytalopus unicolor. Blue pins intermedius; green unicolor; white subcinereus; yellow latrans; red squares S. parvirostris. Purple pins in Cajamarca (Tambillo, Chira, Cutervo) represent vocally and genetically unknown specimens that have been referred to S. l. latrans. Also shown is S. macropus (white triangles) now known to be sister to intermedius. The rivers Marañón-Amazonas, Utcubamba and Huallaga are drawn in black.

1 s long sections of song of Scytalopus macropus (Huánuco; 2019-06-16-ARETA827), S. intermedius (ML129556), S. l. latrans (eastern form) (ML92829), and S. latrans subcinereus (ML21910).

Extract of ND2 gene tree of the macropus and femoralis clades. (From Cadena et al. 2020).

Remarks:

Zimmer (1939) was not aware of the true identity of S. acutirostris (sensu Krabbe & Schulenberg 1997), which is also uniform dark gray and which locally (Atalaya, Cordillera Colán, Puerta del Monte) coexists with the slightly larger intermedius. The question therefore arises, if the type of intermedius might not represent that species. This could only be definitively dismissed through the sequencing of DNA from a toepad of the type specimen, but seems unlikely, as the bill is thin and pointed in acutirostris, heavier and slightly peculiarly shaped (see below) in intermedius. Even if against all odds it did turn out to be the case, the present proposal is about recognizing a distinct species, not nomenclature.

Both voice and genetics show a close relationship between the medium-sized intermedius (16.7-22 g) and the partly sympatric and huge Scytalopus macropus (32.5-42.5 g). Interestingly, Zimmer (1939) suspected a relationship between them. Under the remarks in his discussion of S. macropus he wrote: “Furthermore, the texture of plumage and the various tones of gray and brown are most like those of the unicolor group. The shape of the bill is peculiar, being marked by a decided concavity above the nostrils but convexity distally and also is most nearly approached by some examples of the unicolor group, particularly u. intermedius.”

Conclusion: There is thus overwhelming evidence that intermedius should be ranked as a biological species. It is known from altogether 20 localities, principally in the Río Utcubamba drainage, but in the west ranging to above the right bank of the Río Marañón (near Tullanya), in the east to above the left bank of the Río Huallaga, where ranging south at least to central San Martín (Puerta del Monte). Its elevational range is 2560-3600 m (average 3050 m). On the east slope and above the right bank of the northern end of the Utcubamba it appears to be replaced below by S. parvirostris and above by S. acutirostris. On the ridge between the Marañón and Utcubamba it is replaced above by S. altirostris.

SECTION B

English name: Two vernacular names for intermedius have been discussed: Leymebamba Tapaculo and Utcubamba Tapaculo. There is already a Grallaricula leymebambae (Rufous-breasted Antpitta), but it is a widespread species, so the name has lost its ring of endemism. Admittedly, it was the material from the immediate vicinity of Leimebamba, where only one species of Scytalopus occurs, that unequivocally united vocal, genetic and morphological material, but it would remain a historical reason for the name. Utcubamba Tapaculo is a little more difficult to pronounce, but more informative, calling attention to endemism in the valley. If you favor Utcubamba Tapaculo, vote YES for section B.

References:

Cadena D. C., Cuervo, A. M., Céspedes, L. N., Bravo, G. A., Krabbe, N., Schulenberg, T. S., Derryberry, G. E., Luis Silveira, L. F., Derryberry, E. P., Robb T. Brumfield, R. T. & Fjeldså, J. (2020). Systematics, biogeography and diversification of Scytalopus tapaculos (Rhinocryptidae), an enigmatic radiation of Neotropical montane birds. The Auk 137: 1-30. https://doi.org/10.1093/auk/ukz077

Coopmans, P., Krabbe, N. & Schulenberg, T. S. 2001. Vocal evidence of species rank for nominate Unicolored Tapaculo Scytalopus unicolor. Bulletin of the British Ornithologists' Club 121: 208-213.

Freeman, B. G., and G. A. Montgomery (2017). Using song playback experiments to measure species recognition between geographically isolated populations: A comparison with acoustic trait analyses. The Auk: Ornithological Advances 134:857–870. https://doi.org/10.1642/AUK-17-63.1

Krabbe, N. & Schulenberg, T. S. 1997. Species limits and natural history of Scytalopus tapaculos (Rhinocryptidae), with descriptions of the Ecuadorian taxa, including three new species. Pp. 46-88 in Remsen, J. V. [Ed.] Studies in Neotropical ornithology honoring Ted Parker. Ornithological Monographs 48.

Schulenberg, T. S., D. F. Stotz, D. F. Lane, J. P. O’Neill, and T. A. I. Parker (2007). Birds of Peru. Princeton University Press, Princeton, NJ, USA.

Zimmer, J.T. 1939. Studies of Peruvian birds. No. XXXII. The genus Scytalopus. American Museum Novitates 1044.

Niels Kaare Krabbe, June 2020

Comments from Remsen: “A. YES. Congruent genetic and vocal data align this with S. macropus, not S. latrans.” B. YES, for reasons stated in proposal – a memorable and unique English name.”

Comments from Stiles: “YES on both A and B, for the reasons stated.”

Comments from Bonaccorso: “YES. I really don´t see so much difference between the songs of Scytalopus macropus and S. intermedius (compared to the other sonograms presented). Still, the genetic differentiation between these two taxa is deep, and the separation of S. intermedius from other S. latrans is clear.”

Comments from Jaramillo: “A. YES. B. YES – Either name could work, no preference.”

Comments from Zimmer: “YES, due to congruence between vocal, genetic and morphological data sets. B. YES, given the endemism of the species to the Utcubamba drainage, this seems like the perfect choice in a group where good descriptive names are nearly impossible to come by for most taxa.”

Comments from Areta: “A. YES. It is great to finally see all the pieces fitting together, which convincingly indicate species status for intermedius.”

Comments from Robbins: “A. YES. The genetic data by Cadena et al. (2020) clearly underscores why this taxon should be treated as a species.”

Comments from Pacheco: “A. YES. Well founded.”