Proposal (616) to South American Classification Committee

 

Split Cacicus leucoramphus from Cacicus chrysonotus

 

The paper by Alexis F.L.A. Powell, F. Keith Barker, Scott M. Lanyon, Kevin J. Burns, John Klicka, Irby J. Lovette (2013 “2014”) A comprehensive species-level molecular phylogeny of the New World blackbirds (Icteridae) Molecular Phylogenetics and Evolution, 71 (Dec.13): 94-112 offers radically new insights into the phylogeny of all four subfamilies included in the Icteridae: Sturnellinae: Meadowlarks; Cacicinae: Caciques and Oropendolas; Icterinae: Orioles; Agelaiinae: Blackbirds, Cowbirds and Grackles.

 

To quote from their abstract:Using mitochondrial gene sequences from all ~108 currently recognized species 7 and six additional distinct lineages, together with strategic sampling of four nuclear loci and 8 whole mitochondrial genomes, we were able to resolve most relationships with high confidence.  Our phylogeny is consistent with the strongly-supported results of past studies, but it also contains many novel inferences of relationship, including unexpected placement of some newly sampled taxa, resolution of relationships among major clades within Icteridae, and resolution of genus-level relationships within the largest of those clades, the grackles and allies. “

 

Below I have inserted part of Figure 4 from their paper focusing of the Cacicinae.  The node uniting Cacicus chrysonotus and Cacicus leucoramphus is the second deepest of the all of the species nodes in the Cacicinae. It is much deeper than the node joining Cacicus sclateri and Cacicus koepckeae and marginally deeper than the node joining the two species just mentioned and Cacicus chrysopterus.  It is also much deeper than the node joining Cacicus haemorrhous and Cacicus (was Ocyalus) latirostris and Cacicus (was Clypicterus) oseryi.

 

 

The range of Cacicus leucoramphus (northwest Venezuela to Ecuador) is distinct from that Cacicus chrysonotus pacificus (north Peru) and Cacicus chrysonotus chrysonotus of south Peru and north Bolivia.

 

Accordingly, I propose that Cacicus leucoramphus.be recognised as a species distinct form Cacicus chrysonotus.

 

References:

 

Alexis F.L.A. Powell, F. Keith Barker, Scott M. Lanyon, Kevin J. Burns, John Klicka, Irby J. Lovette (2013 “2014”) A comprehensive species-level molecular phylogeny of the New World blackbirds (Icteridae) Molecular Phylogenetics and Evolution, 71 (Dec.13): 94-112

 

John Penhallurick

 

 

Comments from Remsen:  “NO. I appreciate the point that these two differ in the same ways that C. sclateri and C. koepckeae do in terms of plumage but are roughly 3X more differentiated at the neutral loci sampled.  However, the design of this study is inadequate for addressing differences at this level of taxonomy because the two samples of leucoramphus were taken from N. Ecuador (Imbabura), roughly 1800 km from the nearest population of chrysonotus in southern Peru.  Not only would isolation-by-distance come into play dramatically here, but those 1800 km cross multiple major biogeographic boundaries, especially the MaraĖon, that would likely create strong genetic subdivisions in any montane cloud-forest bird.  To use genetic data to address species limits in these allopatric taxa, sampling would have to be directed at the potential contact zone in southern Peru.  Hellmayr (1938, Catalogue of Birds of the Americas) noted that there are plumage hints of possible gene flow between these two.  [The Bond (1953) reference in our footnote also evidently mentions this also but I can’t find my copy to check.]  Note also that Powell et al., almost certainly aware of the limitations of their data with respect to species limits in these taxa, did not mention it in their discussion of classification and treat the two as subspecies in their tree.  There is no relevant evidence in Powell et al. that chrysonotus and leucoramphus should be treated as separate species.”

 

Comments from Cadena: “NO. Sure, genetic divergence is strong, but this may well reflect variation within a single biological species. Using genetic distance as a yardstick to assess species status is extremely problematic for various reasons (in brief, the correlation between time and reproductive isolation is rather messy), and I see no strong published evidence based on other traits (voices, behavior, plumage variation) to support this proposed split.”

 

Comments from Dan Lane: I agree with Van that the Powell et al. (2013) paper can hardly be used to make taxonomic changes of this nature given the limited sampling of individuals, the geographic distance between the individuals sampled, and the genes used. But in addition to that, I have further concerns about the above proposal. First, the suggestion that C. leucoramphus be separate from C. c. “pacificus” (sic, should be peruvianus. Pacificus is part of the C. uropygialis/microramphus group) and C. c. chrysonotus is a novel taxonomy that has not been suggested anywhere before that I can find, and as such would require considerably more background to support. Cacicus leucoramphus, when split from C. chrysonotus, has always included peruvianus as both have the yellow wing patches. Assuming that this change to the organization of taxa within the complex was unintentional, an additional issue arises as there are, as Van also stated, specimens suggesting introgression between peruvianus and leucoramphus. I myself have collected such an individual in the Mantaro valley, Junin, which is near the supposed distributional break between peruvianus and leucoramphus. A more densely sampled study including all three named taxa, including populations such as that from the Mantaro valley, would be necessary to show conclusively whether or not chrysonotus, peruvianus, and leucoramphus are acting as good biological species or not. Until then, I would err on the side of caution and maintain them as one species.”

 

Comments from Stiles: “NO, for the reasons advanced by Van and Daniel. An 1800 km gap between two small samples makes the interpretation of the genetic differences equivocal. Without statistically and geographically meaningful samples of genetics, plumages and voice, the evidence for this split is insufficient to justify it.”

 

Comments from Nores: “YES. Although the data presented here are not sufficient to justify the split, the two taxa are too different (especially the lack of yellow on wings in chrysonotus). Note that Schulenberg et al. (Birds of Peru) and Hilty (Birds of Venezuela) treat chrysonotus and leucoramphus as separate species.”

 

Comments from Zimmer: “NO, for reasons already elucidated by Van, Daniel, Gary & Dan.”

 

Comments from Jaramillo: “YES – this is a poorly constructed proposal, but let’s not throw out the baby with the bathwater here. In our Icteridae book we had some information on this problem. First of all, Blake (1968), the Peter’s Checklist, actually considered chrysonotus separate from leucoramphus. To clarify as Dan has done, there is no pacificus involved in this issue (that is another issue), the three taxa fall into two groups with peruvianus being the southern form of leucoramphus. The two (chrysonotus with leucoramphus) were merged later based on intermediate looking specimens, as Dan confirms. However, it was not clear to me who first came up with the idea of the merger, it is too long since I looked into the issue, but I do not think it is based on anything other than the few specimens of southern birds with yellow feathers on the wing! The issue here is that chrysonotus with some yellow on the wing occur way south in the range, in Bolivia. It appears to me that these birds with some yellow on the shoulder are a variation that can pop out anywhere, not intermediates. This is similar to C. sclateri specimens that show some yellow on the rump both from Peru and Ecuador! It is just something that shows up, perhaps a “throwback” to an ancestral plumage state that is still in the bird’s genes?

 

“I would argue that these two taxa were lumped based on poor analysis of the data, birds that were thought to be intermediate are not, and I say we go back to Blake’s idea and treat the two as separate species given that coloration, voice, and genetics point to two sisters taxa that in all of those characteristics are as, or more, different than other Cacique species we currently recognize.

At the time of the book I had only heard the northern birds, and eventually in Bolivia I was able to hear and see the southern birds. Calls are consistently different, and call notes are important in flock cohesion in these social birds. Now we have some recordings of their songs and they are extremely different to my ears:

 

Song of leucoramphus: http://www.xeno-canto.org/63204

Song of chrysonotus: http://www.xeno-canto.org/1996

 

“Furthermore my limited personal experience with both of these birds is that the southern birds (in Bolivia) are much shyer and skulking, difficult to see. While northern birds (Ecuador) are much bolder and obvious. Of course that is a distance apart, and there could be clines in behavior.

 

“Below are specific parts from our book that deal with the problem:

 

Ridgely and Tudor (1989) state that the vocalisations of the northern leucoramphus group and the southern chrysonotus group to be similar. However, recordings of the primary call (the ‘wheehk’ or ‘whak’) call appear to show a difference. The southern birds sound higher pitched, metallic and quick; while the northern birds are lower pitched, harsher and more powerful sounding. More research needs to be done to elucidate how similar the vocalisations of northern and southern forms are. ….. [we now have a lot more information on xeno-canto to compare and confirm that these differences are real and throughout the distribution]

 

GEOGRAPHIC VARIATION Three subspecies that fall into two groups: leucoramphus [Northern Mountain Cacique] and chrysonotus [Southern Mountain Cacique]. These two forms were listed as separate species in Blake 1968, but more recently the two have been considered conspecific (Ridgely and Tudor 1989) mainly due to the presence of intermediate looking specimens. Specimens of peruvianus from Auquimarca, Peru show black fringes to the yellow wing coverts (Bond 1953). However, the vocalisations do not appear to be similar, as has been stated (Ridgely and Tudor 1989). The two are certainly good phylogenetic species, and perhaps even good biological species, more work needs to be done before a decision as to the systematic placement can be made.

      The Northern Mountain Cacique is composed of two races. C .c. leucoramphus lives from NW Venezuela, south along the E Colombian Andes to E Ecuador. It is described above. C. c. peruvianus inhabits the east slope of the Andes from Amazonas south to Junín. It is similar to leucoramphus, but has a heavier bill, with the culmen more noticeably arched. The bluish base to the bill is less extensive. As well, the concealed white collar is thinner in this form than in leucoramphus.

      The Southern Mountain Cacique, C. c. chrysonotus, is found south of Junín, Peru to Cochabamba, Bolivia. It lacks yellow on the wing coverts, however some individuals may show one or two yellow covert feathers or small yellow tips to several coverts. This is particularly true in the northern part of their range. However, some Bolivian chrysonotus specimens, far from where intergradation could be occurring, show yellow fringes to some of the wing coverts (Bond 1953).”

 

Comments from Dan Lane: “Reading the further responses in this proposal, I feel there are some clarifications of the situation that I am in a position to make.

 

“First of all, in response to the comment above by Nores, Birds of Peru (Schulenberg et al. 2007, 2010) did *not* separate C. chrysonotus from leucoramphus at the species level, we maintained them as conspecifics.

 

“Although I appreciate Alvaro’s comments on the subject, I think they oversimplify the situation regarding this complex. Hand-picking two recordings of what may or may not be homologous vocalizations from the broad repertoire of an oscine with a linear distribution isn’t a very satisfying comparison to me. Yes, the two recordings are both of songs, but are they the same song types given under the same circumstances? Do we really even know what kind of song types C. chrysonotus/leucoramphus has? Al’s comments from Proposal 624 suggest that he believes there are several song types within any given population of C. cela—an idea with which I agree—so why would this congener be any different? And as we know is true in icterids, dialect formation will be a serious issue to consider when dealing with geographic variation among populations within this complex. Take a look at all the recordings now available online:

 

http://www.xeno-canto.org/species/Cacicus-chrysonotus

http://www.xeno-canto.org/species/Cacicus-leucoramphus

 

see also: http://macaulaylibrary.org/search?location_id=&location_type_id=&location=&recordist=&recordist_id=&catalogs=&behavior=&behavior_id=&tab=audio-list&taxon_id=11995081&taxon_rank_id=67&taxon=mountain+cacique

 

“The Macaulay recordings include a selection which fills the noticeable gap from central Peru (La Libertad, Huánuco, Pasco depts..) among the Xeno-canto cuts. Listening to these cuts from San Martin to Bolivia, I hear no obvious, discrete break in vocalization types between peruvianus and chrysonotus to correspond to the turnover of plumage types. I have uploaded my own recordings of the complex, including several from the Mantaro valley (both sides), where birds with intermediate plumage are found (see a photo here of an intermediate bird that was collected from a flock that I had recorded):

 

https://www.flickr.com/photos/8013969@N03/13547056163/

 

“I should point out that I used recordings of C. c. peruvianus successfully to draw in the birds of intermediate plumage in Junin.

 

“Checking LSU specimens, we have 13 C. chrysonotus from Puno, Peru, and Bolivia. Of these, none show the yellow on the shoulder visible in the Junin photo linked above. Colombian birds in our collection appear smaller, with Bolivian birds appearing largest, but this could be Bergman’s Rule at work, as the increase in size appears clinal. Again, I’m really not impressed by the variation in voice among the recordings, especially when one compares recordings along the length of the distribution of the complex, rather than listening to extremes at distant points within it. The lack of a clear change in voice when one compares recordings from the Junin/Huancavelica/Cusco region of Peru, where the two 'species' turn over is particularly unconvincing as evidence that there are indeed two species, and added to this the presence of intermediate birds at this same area, it almost appears as if this is one of the few cases among Andean birds where allopatry does not stymie our application of the Biological Species Concept!

 

 “Regardless, I think that I would ‘throw the baby out’ with the present proposal. As it is worded, it does a very poor job of clarifying the situation. A new proposal, with real comparative data, would be needed (in my opinion) to make a strong case for the separation of the complex into two species. Those data should involve a much more directed study, including tissues from specimens from the turnover zone in Pasco/Junin/Huancavelica/Cusco, as well as from all along the distribution of the complex, as this is really necessary to make further sense of the situation here.”

 

Comments from Robbins: “NO.  After reading Dan Lane’s comments (especially those in response to Alvaro’s remarks), I feel that much more information is need in the region between the two extreme genetic samples.”

 

Comments from Pacheco: “NO. A partir das lúcidas colocaćões de Dan Lane, penso que é muito prematuro decidir algo sem a existźncia de uma revisčo consistente da relaćčo entre estes dois táxons.”