Proposal (784) to South American Classification Committee

 

 

Split Grallaricula leymebambae from G. ferrugineipectus

 

This proposal is based on excerpts from the following paper. Where mentioned, figure and table numbers are kept the same as in the paper for ease of reference to the publication.

 

Van Doren BM, Freeman BG, Aristizábal N, Alvarez-R M, Perez-Emán J, Cuervo AM, Bravo GA. 2018. Species limits in the Rusty-breasted Antpitta (Grallaricula ferrugineipectus) complex. Wilson Journal of Ornithology. doi: 10.1676/16-126.1.

 

Background

 

The Rusty-breasted Antpitta (Grallaricula ferrugineipectus) is a small antpitta in the family Grallariidae distributed from Venezuela to Bolivia. Three subspecies are currently recognized, each of which inhabits a distinct montane region: G. f. ferrugineipectus is found in northern and western Venezuela and the Sierra Nevada de Santa Marta in adjacent northern Colombia; G. f. rara in the Eastern Andes of Colombia and the Sierra de Perijá, which straddles the Colombia-Venezuela border; and G. f. leymebambae in the Andean foothills from extreme southern Ecuador to western Bolivia.

Current knowledge of the distribution of the species has been improved by recent discoveries of populations outside its traditionally known range. Although its presence in Peru north of the Marañón River had been documented since the mid-1950s based on 2 specimens taken independently by M. Koepcke and T. A. Parker in Cancheque, Piura (Schulenberg and Parker 1981, Parker et al. 1985), there are now recent records in the departments of Piura (Vellinga et al. 2004) and Lambayeque (Angulo Pratolongo et al. 2012), as well as in the Ecuadorian provinces of Loja and Pichincha (Athanas and Greenfield 2016; P. Coopmans, ornithologist, unpubl. data, collected 1994-2003). Likewise, only in the early 1980s was the species first recorded in Bolivia (Schulenberg and Remsen 1982). More recently, MAR and collaborators discovered a population in the Cauca Valley of the Central Andes in the department of Caldas, Colombia that seems to be geographically isolated from other conspecific populations. Taxonomic affinities of these populations have never been formally assessed, and their taxonomic treatment has been assumed to correspond to that of the geographically closest populations.

Populations differ somewhat in elevational distribution and habitat; subspecies rara and ferrugineipectus inhabit forested foothills from ~250 to 2200 m asl. (Krabbe and Schulenberg 2003), and the Cauca Valley antpittas are currently known only from one locality at 1000–1100 m asl. Hereafter, these 3 populations will be referred to as the northern group. By contrast, birds belonging to the southern group (populations from Ecuador, Peru, and Bolivia) range substantially higher and inhabit montane forest from 1750 to 3350 m asl. (Ridgely and Tudor 2009). Southern group birds seem closely tied to bamboo in the genus Chusquea (Fjeldså and Krabbe 1990, Athanas and Greenfield 2016). This habitat association has not been documented for the northern group, which can tolerate some degree of habitat degradation (Hilty and Brown 1986, Niklison et al. 2008, N. Athanas, Tropical Birding Tours, 2017, pers. comm.).

The 3 subspecies of G. ferrugineipectus were described based on differences in plumage and morphology. The subspecies rara is the most divergent with respect to plumage, with a rich rufous-brown underside and clear rufous tones on the crown and face, in contrast to the dark brown to slate-brown upperside and rufous underside of subspecies ferrugineipectus and leymebambae. These latter 2 subspecies both lack rufous on the head, have duller underparts, and show an obvious white throat crescent; G. f. leymebambae differs from G. f. ferrugineipectus in larger size and darker overall coloration (Greeney 2013). Songs of the species also vary across its geographic range. Most noticeably, G. f. leymebambae gives slower and higher-pitched songs than G. f. ferrugineipectus (Krabbe and Schulenberg 2003). The song of G. f. rara is poorly known and not described in recent reference volumes (Krabbe and Schulenberg 2003, Greeney 2013). Finally, recordings from northwest Ecuador demonstrate that this population’s songs seem slower than those of other populations (e.g., see XC35333 on xeno-canto.org).

Because populations of G. ferrugineipectus are distributed allopatrically throughout the tropical mountains of northern South America, reproductive isolation between subspecies cannot be directly assessed. Early on, systematists proposed arrangements of species-level taxonomy based on plumage differentiation within this complex. For example, G. f. rara was originally described as a species because of its distinctive plumage (Hellmayr and Madarász 1914), while G. f. leymebambae was first described as a subspecies (Carriker 1933). More recently, differences in distribution, morphology, and vocalizations between G. f. leymebambae and the northern group have led some authors (e.g., Ridgely and Tudor 2009, BirdLife International 2017) to classify it as a distinct species; however, no formal comparative analysis had systematically examined genetic, vocal, and morphological variation within this complex.

 

 

New Information

 

Maximum-likelihood and Bayesian analyses produced identical topologies supporting the non-monophyly of Grallaricula ferrugineipectus. Northern populations (i.e., G. f. ferrugineipectus, G. f. rara, Cauca Valley, and Sierra Nevada de Santa Marta) form a strongly supported clade that is sister to Andean populations of G. nana (albeit with low support in the Bayesian species tree), whereas populations from Peru and Bolivia (i.e., G. f. leymebambae) are recovered as sister to G. lineifrons (Fig. 2 and 3). The time-calibrated species tree estimated that the most recent common ancestor between northern and southern groups split between 10.8 and 16.8 million years ago (mya; Fig. 3). Additionally, northern populations of G. ferrugineipectus exhibit some degree of geographic structure and differentiation not entirely consistent with current subspecific boundaries.

Northern and southern groups significantly differed in the mean values of 13 of 15 vocal traits; however, mean note maximum frequency was the only vocal character for which 95% prediction intervals did not overlap (Figure 5; Table 1). To place this result into context, we considered the number of vocal characters for which 95% prediction intervals did not overlap between currently recognized Grallaricula species. The southern group differed from G. nana in only one vocal character (song pace), whereas populations in the northern group differed from G. nana in 3 characters: mean note maximum frequency, the frequency slope of the song, and the position of the maximum frequency in the song. Both northern and southern groups differed from G. lineifrons by several vocal traits (7 and 4, respectively), and G. nana differed from G. lineifrons by 8 vocal traits (Table 1). Although northern and southern groups differed significantly from one another in the mean value of all 6 morphological characters, none was diagnosable at the 95% prediction level.

         Discriminant function analysis performed well at separating northern and southern groups based on both vocal and morphological traits (Figure 7). For vocal traits, the cross-validated correct classification rate was 100% for the northern group and 97.6% for the southern group. The single discriminant factor loaded most heavily for mean note maximum frequency. For morphological traits, the cross-validated correct classification rate was 95.5% for the northern group and 100% for the southern group; the discriminant factor was primarily composed of tarsus and tail length.

 

Proposed Change

 

We found that Grallaricula ferrugineipectus, as currently recognized, is polyphyletic. The southern subspecies G. f. leymebambae is more closely related to G. lineifrons and G. flavirostris than it is to the northern subspecies G. f. ferrugineipectus and G. f. rara; in turn, these northern populations are more closely related to G. nana than to G. f. leymebambae. In fact, the split between the northern and southern clades likely represents the earliest divergence within the genus Grallaricula (Fig. 2, GAB unpubl. data), and the age of this split is close to the start of diversification of the Hylopezus-Myrmothera-Grallaricula clade, estimated at ~13–21 mya (Ohlson et al. 2013). Hence, G. ferrugineipectus as currently defined is polyphyletic and comprises populations that belong to divergent and distinctive clades. We therefore propose to elevate G. f. leymebambae to species rank. We recommend the complex be considered to consist of 2 species and, provisionally, 2 subspecies:

 

Species Grallaricula ferrugineipectus (Sclater 1857)

     Subspecies Grallaricula f. ferrugineipectus (Sclater 1857)

     Subspecies Grallaricula f. rara Hellmayr and Madarász 1914

Species Grallaricula leymebambae Carriker 1933

 

 

References

 

Angulo Pratolongo, F., J. N. Flanagan, W.-P. Vellinga, and N. Durand. 2012. Notes on the birds of Laquipampa Wildlife Refuge, Lambayeque, Peru. Bulletin of the British Ornithologists' Club 132:162-174.

Athanas, N., and P. J. Greenfield. 2016. Birds of Western Ecuador: A Photographic Guide. Princeton University Press, Princeton.

BirdLife International. 2017. Species factsheet: Grallaricula leymebambae. Downloaded from http://www.birdlife.org/.

Carriker, M. A. 1933. Descriptions of New Birds from Peru, with Notes on Other Little-Known Species. Proceedings of the Academy of Natural Sciences of Philadelphia 85:1-38.

Fjeldså, J., and N. Krabbe. 1990. Birds of the high Andes: a manual to the birds of the temperate zone of the Andes and Patagonia, South America. Zoological Museum, University of Copenhagen, Copenhagen, Denmark.

Greeney, H. F. 2013. Rusty-breasted Antpitta (Grallaricula ferrugineipectus) in T. S. Schulenberg, editor. Neotropical Birds Online. Cornell Lab of Ornithology, Ithaca.

Hellmayr, E., and J. Madarász. 1914. Description of a new Formicarian-bird from Columbia. Annales Musei Nationalis Hungarici 12:88.

Hilty, S. L., and W. L. Brown. 1986. A guide to the birds of Colombia. Princeton University Press, Princeton, New Jersey.

Krabbe, N. K., and T. S. Schulenberg. 2003. Rusty-breasted Antpitta (Grallaricula ferrugineipectus) in J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, editors. Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona.

Niklison, A. M., J. I. Areta, R. A. Ruggera, K. L. Decker, C. Bosque, and T. E. Martin. 2008. Natural history and breeding biology of the Rusty-breasted Antpitta (Grallaricula ferrugineipectus). The Wilson Journal of Ornithology 120:345-352.

Ohlson, J. I., M. Irestedt, P. G. Ericson, and J. Fjeldså. 2013. Phylogeny and classification of the New World suboscines (Aves, Passeriformes). Zootaxa 3613:1-35.

Parker, T., T. S. Schulenberg, G. R. Graves, and M. J. Braun. 1985. The avifauna of the Huancabamba region, northern Peru. Pages 169–197 in P. Buckley, M. Foster, E. Morton, R. Ridgely, and F. Buckley, editors. Ornithological Monographs no. 36: Neotropical Ornithology. American Ornithologists' Union, Washington, DC.

Ridgely, R. S., and G. Tudor. 2009. Field guide to the songbirds of South America: the passerines. University of Texas Press, Austin, Texas.

Schulenberg, T., and J. Remsen. 1982. Eleven bird species new to Bolivia. Bulletin of the British Ornithologists' Club 102:52-57.

Schulenberg, T. S., and T. A. Parker. 1981. Status and distribution of some northwest Peruvian birds. Condor 83:209-216.

Sclater, P. L. 1857. Descriptions of Twelve New or Little‐known Species of the South American Family Formicariidæ. Pages 129-133 in Proceedings of the zoological Society of London. Wiley Online Library.

Vellinga, W.-P., J. N. Flanagan, and T. R. Mark. 2004. New and interesting records of birds from Ayabaca province, Piura, north-west Peru. Bulletin of the British Ornithologists' Club 124:124-142.

 

 

Table 1. Vocal traits that differ between northern and southern Rusty-breasted Antpittas and 2 congeners following the 95% prediction interval test. Numbers refer to the following traits: (1) mean note peak frequency bandwidth (Hz); (2) mean note bandwidth (Hz); (3) mean note maximum frequency (Hz); (4) duration of song (s); (5) mean duration of each note (s); (6) rate of note delivery (notes per s); (7) frequency slope of the song (Hz per note); (8) song peak frequency bandwidth (Hz); (9) song bandwidth (Hz); and (10) position of the highest frequency note.

 

 

G. ferrugineipectus (North)

G. nana

G. lineifrons

G. ferrugineipectus (South)

3

6

3, 7, 8, 9

G. ferrugineipectus (North)

 

3, 7, 10

3, 4, 5, 6, 7, 8, 9

G. nana

 

 

1, 2, 4, 5, 6, 7, 8, 10

 

 

 

Figure 2. Maximum-likelihood phylogeny of a subset of the Grallariidae. Note that Grallaricula ferrugineipectus sensu lato (in bold) is polyphyletic. Black circles at nodes indicate bootstrap support values >70 based on 999 maximum-likelihood replicates.

 

 

 

Figure 3. Bayesian estimate of phylogenetic relationships and divergence times among a subset of the Grallariidae. Grallaricula ferrugineipectus sensu lato is polyphyletic; the northern and southern groups (G. f. ferrugineipectus and G. f. leymebambae) last shared a common ancestor around 13 million years ago (mya). Bars at nodes indicate the 95% highest posterior density for the inferred divergence time estimates. Numbers at nodes indicate posterior probability support values.

 

 

Figure 5. First 2 factors from discriminant function analysis separating Rusty-breasted Antpitta subpopulations by variation in 15 vocal traits. Black ellipses are 95% prediction ellipses for northern and southern groups; colored ellipses are 75% prediction ellipses for subspecies.

 

 

Figure 7. First 2 factors from discriminant function analysis separating Rusty-breasted Antpitta subpopulations by variation in 6 morphological traits. Black ellipses are 95% prediction ellipses for northern and southern groups; colored ellipses are 75% prediction ellipses for subpopulations.

 

Benjamin M. Van Doren, April 2018

 

 

 

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Comments from Remsen: “YES.  Strongly supported phylogenetic data make elevation of leymebambae to species rank essentially mandatory.

“We need to think about English names (not mentioned in the paper).  Because leymebambae was incorrectly included in Grallaricula ferrugineipectus, this isn’t really a split but an “extraction.” Therefore, I see no need to change the English name of properly defined Grallaricula ferrugineipectus (Rusty-breasted Antpitta) – it’s not really a parent-daughter thing in the phylogenetic sense.”

 

Comments from Robbins: “YES, phylogenetic data clearly demonstrate that northern and southern ferrugineipectus are not sisters.  Although it is not too surprising that northern birds are more closely related to nana than leymebambae, I am shocked that southern leymebambae is sister to lineifrons!”

 

Comments from Stiles: “YES. Clearly two species are involved.  Running through the various “brown” names in Smithe, here are two suggestions: Sepia-breasted (if the breast is really that much darker), or Russet-breasted, which is a shade browner than “Rusty”. Confusingly similar? Perhaps, but also recognizes the fact that the two are sufficiently similar to have been considered conspecific  ever since leymebambae was described.”

 

Comments from Pacheco: “YES. The evidence gathered clearly supports this proposition.”

 

Comments from Areta: “YES, a long overdue species treatment now solidly substantiated with genetic, morphological and vocal data. It is finally great to see these "enanos cachigordetes" treated as separate species (as Paul Schwartz aptly called them a long time ago).”

 

Comments from Stotz: “YES. Lots of data from a variety of sources.  On English names, I don't think I have any clever ideas what to do.  Best I can come up with is Ferruginous-breasted for the northern group and Leymebamba for the southern group based on scientific names. Leymebamba is a bad name, obviously. Maybe Rufous-breasted?”