Proposal (803) to South American Classification Committee
Recognize the newly described Scytalopus alvarezlopezi
Scytalopus alvarezlopezi is described from the northern Western Andes of Colombia. The new species forms part of a distinctive clade of Scytalopus tapaculos (Rhinocryptidae) that also includes S. robbinsi from Ecuador and S. stilesi and S. rodriguezi, which occur on the Central and Eastern Andes of Colombia. Scytalopus alvarezlopezi is easily diagnosable from its near relatives by its song and mitochondrial DNA; differences in plumage also exist but are subtler. The species inhabits dense understory vegetation on the floors and lower slopes of ravines in cloud forest at elevations of 1300 to 2100 m. On the Pacific slope, its altitudinal distribution is sandwiched between those of S. chocoensis (below) and S. vicinior (above); the latter in turn is replaced higher up by S. spillmanni and S. latrans, but S. alvarezlopezi also occurs at ~2000–2100 m on eastern slopes just below the low ridgeline. All of the latter species are distinguished by vocal and plumage characters. Marked sexual differences in plumage exist in stilesi, but females have yet to be collected for alvarezlopezi and rodriguezi. We consider that S. alvarezlopezi is not threatened at present, but could be potentially vulnerable due to its restricted distribution; it is endemic to Colombia. For further details, consult the original paper in the Auk (reference below).
I strongly recommend a YES on this proposal.
F. G. Stiles, O. Laverde-R. and C. D. Cadena (2017) A new species of tapaculo (Rhinocryptidae: Scytalopus) from the Western Andes of Colombia. The Auk 134:377-392.
Gary Stiles, July 2018
Comments from Remsen: “YES. As long as vocal differences viewed as a proxy for assessment of potential gene flow and as a sufficient criterion for species delimitation, then this taxon must be recognized at the species level. And just to emphasize a point I make frequently, that it is diagnosable using DNA only shows that the population has been isolated for a sufficient time (or sufficient bottlenecks) to accumulate unique mutations at neutral loci and is not particularly relevant to taxon rank.”
Comments from Robbins: “YES. As Gary points out, it has a distinctive voice from its closest relatives.”
Comments from Areta: “YES. Unique song in comparison to closely related taxa provide a solid species-level diagnosis of S. alvarezlopezi.”
Comments from Pacheco: “YES. For its diagnostic vocal repertoire.”
Comments from Zimmer: “ “YES. Vocal differences between alvarezlopezi and its closest relatives, meet the “yardstick test” for recognition as a distinct species within this group of morphologically conservative group of suboscines.”
Comments from Claramunt: “NO. The proposed new species is not distinguishable from closest relatives in plumage or morphology, so the evidence relies on differences in songs and mitochondrial DNA. But sample sizes are extremely low. Only 6 recordings from only two localities were analyzed. Moreover those two localities are in relatively close proximity between each other but far away from the potential contact zone with S. stilesi. Therefore, it is impossible to assess the degree of geographic variation and potential clinal variation in songs. Similarly few songs were used from congeners for comparison, and again, from few localities minimizing any possibility of detecting geographic variation. No playback experiments are reported. Likewise, the genetic analysis is suggestive but used only 2 specimens of the new species and only 1 of its closest relative. Given the low levels of divergence and the low sample size, it is difficult to assess whether mitochondrial variation represents species phylogeny or intraspecific genealogy. In sum, the data is suggestive, but the evidence is dangerously scant.”
Comments from Cadena: “Additional Here’s a quick reaction to
Santiago’s comments on proposal 803.
“Being a coauthor of the description of S. alvarezlopezi, I will abstain from formally voting on this one,
but thought I would clarify a few things. First, Santiago rightly notes that
sampling for quantitative vocal analysis in the paper was based on a rather
limited number of recordings. There are, however, many other examples available
and they are all consistent with the vocal patterns described by Stiles et al.
For example, there are numerous recordings from various localities in XenoCanto
and the Macaulay Library:
“It is true of course, that all recordings are from a restricted geographical area, but this reflects that this hard-to-collect species has a rather restricted range. Nonetheless, recordings show no discernible geographic variation say, from Antioquia or Chocó south to Valle del Cauca.
“Santiago suggested the possibility of a contact zone between alvarezlopezi and stilesi, yet these birds occur on different cordilleras. S. alvarezlopezi is endemic to the western slope of the Western Andes (though it spills over a bit on to the eastern slope at low passes) whereas S. stilesi is endemic to the Central Andes. These two cordilleras are separated by the low-lying Cauca Valley where there is naturally no habitat for tapaculos, so I do not know where would a putative contact zone be.
“In contrast to the situation with stilesi, alvarezlopezi does coexist with several other species of Scytalopus in the Western Andes (with elevational segregation) and there is no vocal nor genetic evidence of intergradation with any of them. Species occurring on the same mountain slope include chocoensis, vicinior, spillmanni, and latrans.
“Unfortunately, alvarezlopezi is one of the very few species missing from our UCE dataset, but based on our now finished phylogenetic analysis of mtDNA data, it appears that alvarezlopezi is sister to robbinsi and not to stilesi.
Additional comments from Claramunt: “Ok, that’s reassuring. I can’t detect any geographic variation in the XenoCanto dataset. I based my judgment on the evidence presented in the paper and the proposal alone, and I was just (over)reacting to the low sample sizes analyzed in the paper. The paper actually says that only 3 recording of alvarezlopezi were analyzed (p. 383), which seems a typo since in the Appendix and figure 9 there are 5 data-points (but not 6, as I say in my comment, another typo). Even if you don’t vote, maybe you could comment on this lack of geographic variation, for there record.
“Also, we can discard the existence of a contact zone in present times, I’ll give you that. But historical contact (las glacial maximum?) may also be relevant as they may produce character clines across now disconnected populations. So, populations in geographical proximity, even if not in actual contact, are of interest, in my mind.”
Comments from Stotz: “YES. I am helped by the discussion between Santiago and Daniel making me more comfortable with the recognition of alvarezlopezi.”
Comments from Jaramillo: “YES. I have seen and heard this species, perhaps even recorded it. Indeed, it is vocally quite distinctive, and that is key in Scytalopus.”