Proposal (#385) to South American Classification Committee
Effect on SACC: This would split a current species into two.
Background: Maculirostris was described in 1883 as a subspecies of Turdus ignobilis, but two years later, its describer, Berlepsch, treated it as a species, as did Chapman (1926) in his Ecuador monograph. However, Hellmayr (1934) lumped it with Turdus nudigenis, with the following statement: “an exact duplicate of T. n. nudigenis and differing mainly by the lesser extent of the bare skin around the eye.” Ripley (1964 – Peters Check-list) continued to treat it as a subspecies of nudigenis.
Ridgely & Tudor (1989) elevated maculirostris to species rank with the following note: “it lacks the wide bare ocular area so distinctive in T. nudigenis (the eye-ring of maculirostris is comparable in width to that of T. grayi), differs in its forest-based habitat, and has a widely disjunct range.” This treatment was followed by Sibley & Monroe (1990), Clement (2000), Restall et al. (2006), and Collar (2005) despite the absence of any formal analysis and no data on voice. In their defense, the rationale for the original lump was of the same caliber. Dickinson (2003) and Schulenberg et al. (2007) treated maculirostris as a subspecies of nudigenis.
Voelker et al. (2007) sequenced mtDNA (ND3, ND2, cyt-b) from 60 (!) of the world’s 65 Turdus (see proposal 338). A node that unites maculirostris, nudigenis, haplochrous, and grayi received strong support (>95% Bayesian, maximum parsimony > 50%, ML bootstrap 83%. Within the branching pattern has maculirostris as sister to the other three, thus making our existing nudigenis paraphyletic with respect to grayi and haplochrous. However, the branching pattern has no statistical support other than a 57% bootstrap value for a sister relationship between nudigenis and haplochrous.
Nylander et al. (2008) sequenced mitochondrial (12S, cyt-b) and nuclear (3 introns) DNA for 60 Turdus species. They found the same grouping and the same topology (although they did not report support values … or at least I can’t find them). I am also unable to tell whether the critical section of their tree is determined solely by the one gene in common to both studies, cyt-b.
I listened to the songs and calls available at Xeno-Canto and was unable to hear any consistent differences in songs or calls between the two. However, I couldn’t hear any clear differences between grayi and nudigenis, at least in terms of that mewing call; unfortunately there does not seem to be a full song of nominate continental nudigenis at xeno-canto. Obviously, this doesn’t mean much except that someone ought to do a formal analysis of vocalizations in this group. I am impressed with how similar these three are in terms of plumage, and in the study skins, the eye-ring of nudigenis isn’t nearly as impressive as it would be in the field. I can certainly see why Hellmayr used the term “exact duplicate” (although I’m not sure what at “inexact duplicate” would be).
Analysis and Recommendation: I don’t think there is a strong case either way, and I have no recommendation to make. I will wait to see what others say before I vote. One could vote NO based on (1) the absence of compelling evidence to change from our current treatment, and (2) no vocal differences between the two have been documented. Keep in mind that the genetic data basically represent an mtDNA gene tree, not necessarily a species tree. One could vote YES on the basis that our current treatment rests on one sentence in Hellmayr (1934) and that if grayi and nudigenis are ranked as separate species, then so should maculirostris, because in some ways it is closer in plumage and biogeography to grayi than it is to nudigenis (and is there any case of a species in Turdus within which there is geographic variation in eyering development?).
CLEMENT, P. 2000. Thrushes. Princeton University Press, Princeton.
COLLAR, N. 2005. Family Turdidae (thrushes). Pp. 514-807 in "Handbook of the Birds of the World, Vol. 10. Cuckoo-shrikes to thrushes" (J. del Hoyo et al., eds.). Lynx Edicions, Barcelona.
HELLMAYR, C. E. 1934. Catalogue of birds of the Americas. Field Mus. Nat. Hist. Publ., Zool. Ser., vol. 13., pt. 7.
NYLANDER, J. A. A., U. OLSSON, P. ALSTRÖM, AND I. SANMARTíN. 2008. Accounting for phylogenetic uncertainty in biogeography: a Bayesian approach to dispersal-vicariance analysis of the thrushes (Aves: Turdus). Systematic Biology 57: 257-268.
RESTALL, R., C. RODNER, AND M. LENTINO. 2006. Birds of northern South America. An identification guide. Christopher Helm, London.
RIDGELY, R. S., AND G. TUDOR. 1989. The birds of South America, vol. 1. Univ. Texas Press, Austin.
RIPLEY, S. D. 1964. Subfamily Turdinae. Pp. 13-227 in "Check-list of birds of the World, Vol. 10" (Mayr, E., and R. A. Paynter, Jr., eds.). Museum of Comparative Zoology, Cambridge, Massachusetts.
SCHULENBERG, T. S., D. F. STOTZ, D. F. LANE, J. P. O'NEILL, AND T. A. PARKER III. 2007. Birds of Peru. Princeton University Press, Princeton, New Jersey.
VOELKER, G., S. ROHWER, R. C. K. BOWIE & D. C. OUTLAW. 2007. Molecular systematics of a speciose, cosmopolitan songbird genus: defining the limits of, and relationships among, the Turdus thrushes. Molecular Phylogenetics and Evolution 42: 422-434.
Van Remsen, November 2008
Comments from Stiles: “YES. Although the formal evidence for recognizing maculirostris is admittedly thin, it includes some genetic, morphological, habitat and distributional information. Given that the original lumping was a Petersian fiat with no explicit analysis whatever presented, I feel that what we have available now shifts the burden of proof onto the lumpers. For what it’s worth, the single Colombian specimen of maculirostris was taken in humid Pacific foothill forest, a most unlikely habitat for either grayi or nudigenis – and a long way from the known ranges of either.”
Comments from Nores: “NO. Pienso que no hay ningún aspecto que realmente lo separe. El apoyo genético es débil. Las diferencias morfológicas son mínimas, y el principal caracter se da en otras especies: Turdus merula, por ejemplo, tiene subespecies sin círculo ocular. La distribución cae tanto en especie como en subespecie, ya que hay muchos ejemplos de especies que tienen una subespecie al este de los Andes y otra al oeste. Por ej. Trogon melanurus, Myrmotherula brachyura, etc. Tampoco veo importante lo del habitat. Hay también muchos ejemplos de especies en que las subespecies viven en diferentes hábitats, a veces muy distintos, como Thmnophilus caerulescens, Melanopareia maximiliani, Sittasomus griseicapillus, etc.”
Comments from Robbins: “YES, given the two new genetic data sets coupled with the fact that maculirostris does have very different habitat requirements and is widely disjunct from mainland nudigenis (I have field experience with both) I support this split.”
Comments from Zimmer: “YES. Treating it as conspecific with T. ignobilis makes no sense. Treating it as conspecific with nudigenis is more defensible, but as noted by Ridgely and others, there is a big difference in the extent of the bare ocular skin of the two species, not to mention habitat differences and range disjunction. Based on my own field experience with all of the species involved, I’d say that the vocalizations of maculirostris are every bit as similar to those of grayi as they are to those of nudigenis, and I don’t think we want to lump those two taxa.”
Comments from Jaramillo: “YES – This is a really interesting case, in particular when thinking about the vocal similarity of various taxa in this group. But then again, Turdus in general do not strike me as all that different overall in terms of song, calls are another story, but still taxa that appear to be good species in Turdus but which are closely related do tend to have rather similar calls. For example, Turdus rufitorques (Rufous-collared Robin), which is strikingly different visually from Turdus migratorius (American Robin), is surprisingly similar in calls and voice. So the similarity in vocalizations does not bother me too much in this case, although it would be nice if there were greater differences, and as Van says a study does need to be performed to better understand voice in this group. The genetic, plumage, orbital ring, and habitat differences add up to convince me that maculirostris should be treated as a separate species.”
Comments from Pacheco: "YES. Diante do exposto, eu creio que a melhor solução seja tratá-lo em separado – o lumping foi arbitriamente implementado – até que novas informações estejam disponíveis.”