Proposal (864) to South American Classification Committee
Elevate Podiceps occipitalis juninensis to species rank
Background. The form of Silvery Grebe from the Central Andes was originally named as a subspecies, and indeed bears close resemblance to the nominate race of Patagonia, except when the latter is in its striking breeding plumage. Lacking a distinct non-breeding plumage, juninensis is actually more similar to Junín Grebe Podiceps taczanowskii in all adult plumages except for its smaller overall size but relatively longer wings, to the extent that specimens can be difficult to distinguish even in the hand (Peters and Griswold 1943). Until recently, juninensis has generally been treated as a subspecies, although Chubb (1919) treated it as Podiceps juninensis, without further comment but citing Ogilvie-Grant (1898) who, however, had clearly captioned his account, which followed that of P. occipitalis, “Subsp. a. Podicepes juninensis”.
New Information. More recently, some authors have suggested that juninensis may be better treated as a full species, and del Hoyo and Collar (2014) split juninensis on the grounds of morphology, non-migratory behavior, lack of distinct breeding plumage, and higher-pitched voice. In a phylogeny of cytb and COI (see screenshot below), Ogawa et al. (2015) found that juninensis, taczanowskii, and occipitalis formed a clade, but that the two samples of juninensis (which were not reciprocally monophyletic) were basal to the clade containing taczanowskii, with the single sample of nominate occipitalis embedded within taczanowskii. Ogawa et al. (2015) suggested that the lack of reciprocal monophyly between the two juninensis samples may be due to the isolated Colombian Andes population possibly being a genetically distinct undescribed taxon. In any case, according to this phylogeny, juninensis is less closely related to taczanowskii and occipitalis than the latter two are to each other, and the estimated age of divergence between juninensis and taczanowskii + occipitalis is a little more than 1.5 myr.
Fig. 2A of Ogawa et al. (2015).
Conclusions. The case of P. occipitalis juninensis seems a somewhat analogous situation to Andean Teal Anas andium and Puna Teal Spatula puna, which are now considered full species by SACC (Remsen et al. 2020), and a stronger case for species status than the Colombian Grebe P. andinus, which is embedded within Eared Grebe P. nigricollis as currently recognized.
Proposed Changes. A YES vote for Part A of this proposal (strongly recommended) would be for the treatment of juninensis as a full species, Podiceps juninensis.
As for English names (if A passes), ‘Northern Silvery Grebe’ was used for P. juninensis and ‘Southern Silvery Grebe’ for P. occipitalis by del Hoyo and Collar (2014); they are apt and have gained currently through HBW/BLI and e.g. Guevara et al. (2016), but they are a bit long and bland. The group names used by Clements et al. (2019) are ‘Andean’ and ‘Patagonian’, respectively; if used in combination with ‘Silvery’, ‘Patagonian Silvery Grebe’ is overlong with 9 syllables. Only two grebes are widespread in the Andes, and only one is widespread yet a breeding near-endemic to Patagonia (though Great Grebe Podiceps major comes close). A hybrid option would be ‘Andean Grebe’ and ‘Silvery Grebe’, which has the advantage of retaining the name of the most widespread form.
Thus, if voting yes for A please vote on Part B for either ‘Northern Silvery Grebe’ and ‘Southern Silvery Grebe’; ‘Andean Grebe’ and ‘Patagonian Grebe’, ‘Andean Grebe’ and ‘Silvery Grebe’, or a suggested permutation of these.
Chubb, C. (1919). Notes on collections of birds in the British Museum, from Ecuador, Peru, Bolivia, and Argentina. Part II. Podicipediformes―Accipitriformes. Ibis 1919: 256–290.
Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan, and C. L. Wood (2019). The eBird/Clements Checklist of Birds of the World: v2019. Downloaded from https://www.birds.cornell.edu/clementschecklist/download
del Hoyo., J., and N. J. Collar (2016). HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions, Barcelona.
Guevara, E. A., T. Santander G., A. Soria, and P.-Y. Henry (2016). Status of the Northern Silvery Grebe Podiceps juninensis in the northern Andes: recent changes in distribution, population trends and conservation needs. Bird Conservation International 26: 466–475.
Ogawa, L. M., P. C. Pulgarin, D. A. Vance, J. Fjeldså, and M. van Tuinen (2015). Opposing demographic histories reveal rapid evolution in grebes (Aves: Podicipedidae). The Auk: Ornithological Advances 132: 771–786.
Ogilvie-Grant, W. R. (1898). Catalogue of the Birds in the British Museum. Vol. 26. Steganopodes (Cormorants, Gannets, Frigate-Birds, Tropic-Birds, and Pelicans), Pygopodes (Divers and Grebes), Alcae (Auks), and Impennes (Penguins). Trustees, London.
Peters, J. L., and J. A. Griswold, Jr. 1943. Birds of the Harvard Peruvian Expedition. Bulletin of the Museum of Comparative Zoology 92: 280–327.
Remsen, J. V., Jr., J. I. Areta, C. D. Cadena, S. Claramunt, A. Jaramillo, J. F. Pacheco, J. Perez Emán, M. B. Robbins, F. G. Stiles, D. F. Stotz, and K. J. Zimmer (Version 11 February 2020). A Classification of the Bird Species of South America. American Ornithological Society. http://www.museum.lsu.edu/~Remsen/SACCBaseline.htm
Pamela C. Rasmussen, July 2020
Note on Remsen for voting: Unless one of the proposed English names gets a 2/3 majority from English name subcommittee, I’ll convert the results into a separate proposal that uses the winner of this vote as the starting point.
from Robbins: “YES. To help evaluate differences in breeding plumage that Pam
mentions, I'm pasting in a few eBird checklists that have unequivocal birds in
breeding plumage of each occipitalis taxon:
Comments from Areta: “NO. The issue with these grebes is not so easy from my perspective, and while there are extremes of (mostly) geographically structured morphological variation that have been usually recognized as juninensis, taczanowskii, and occipitalis, I feel that more information is needed to recognize juninensis as a full species. The situation might be more fluid than what current studies show, and we may be jumping the gun by simplifying the case.
“It is worth noting that in several paragraphs Ogawa et al. 2015 refer to "incipient species" and not to "full species" when mentioning taczanowskii and andinus. The first two paragraphs of the discussion show the careful approach of the authors when dealing with taxonomic treatment of these forms. And the last paragraph of Ogawa et al. 2015 (p.781) indicates that "we conclude that the now extinct P. andinus represented a newly established lineage and incipient species among Podicipedidae. Furthermore, and consistent with a tendency for rapid speciation in grebes, P. andinus may represent one of several incipient species, as is indicated by DNA barcode data on P. taczanowskii (Junin Grebe; this study) and the Aechmophorus occidentalis–A. clarkii (Western Grebe– Clark’s Grebe) complex"
“First of all, Thomas Valqui first and myself later found many individuals at Lake Junin (where taczanowskii and juninensis coexist) that were difficult to identify to species. This may suggest that there is ongoing hybridization between them (perhaps triggered by the recent population declines in taczanowskii? for which see Valqui 1994. Or perhaps this was always the case?). I am unaware of published information in this regard.
“Second, the phylogenetic relationships shown in the Cyt-b+COI tree differ from the control region (Figure 3 in Ogawa et al. 2015). If we focus on the Cyt-b+COI tree, then both taczanowskii and juninensis would be non-monophyletic: with one juninensis (from Lake Junin) being more closely related to occipitalis+taczanowskii than to the other juninensis (from Lagunillas); similarly, the clade of occipitalis+taczanwoskii shows that the single sample of occipitalis is more closely related to a taczanowskii than to the other sample of taczanowskii. In looking at the control region inset (Clade I), the Colombian birds seem more distinct than juninensis, occipitalis and taczanowskii from Peru and Argentina, while the relationships among the latter three differ from those in the Cyt-b+COI tree: there is a polytomy involving occipitalis (Argentina), taczanowskii (Junin) and a clade including one taczanowskii (Junin) and one juninensis (Peru). Thus, for different reasons, taczanowskii and juninensis are not monophyletic in both datasets. The only solid conclusion that I can draw from Ogawa et al. (2015) is that genetic differentiation between juninensis, taczanowskii and occipitalis is reduced, and that more samples and further genetic analyses are needed to understand how genetic variation parses out among. I do not think that paper provides compelling evidence for a split (and the paper itself does not claim this).
“To conclude, I find the genetic data presented in Ogawa et al. (2015) as insufficient evidence to elevate juninensis to species. A stronger case for the split could possibly be made by integrating vocalizations (there are no published analyses, not even spectrograms), differences in plumage patterns (indeed, taczanowskii is more similar to juninensis than to occipitalis) and geographic distributions while assessing for the existence of intermediates in a comparative phylogenetic framework (this is missing, as no one has really looked into this). The plumage differences between juninensis/taczanowskii and occipitalis seem clear, but are not as marked as those between undisputed species. As Alvaro mentioned for Chile, occipitalis and juninensis also overlap to some extent in the Puna of NW Argentina, but no one (to my knowledge) has studied the situation in detail. Until solid genetic and natural history data is properly analyzed, I prefer to err on the side of caution by leaving juninensis as an arguably quite diagnostic subspecies of occipitalis. In the long run, the evidence may show that occipitalis and juninensis are different species, but this evidence should be gathered systematically, carefully analyzed and published. At present, I see many gaps, conflicting data and key unanswered questions to make this decision.
“See: Valqui, T. (1994) The extinction of the Junin Flightless Grebe? Cotinga 1: 42–44.”
information on these from Chile: On several occasions we have seen occipitalis
in flocks of juninensis in Lake Chungara up by the Peru/Bolivian
borders. Steve Howell has also found them up there in flocks of juninensis.
This is in the October-November time frame, so breeding season. Note that there
is a well-documented record of occipitalis in southern Peru. Apart from
the golden plumes, look at the dark throat and chin which juninensis
will not show. This is a September record, so pre-breeding season for occipitalis. https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Febird.org%2Fchecklist%2FS48454501&data=02%7C01%7Cnajames%40lsu.edu%7C47c87a67084743b1da2008d82cdfaea8%7C2d4dad3f50ae47d983a09ae2b1f466f8%7C0%7C1%7C637308686527250172&sdata=MV6m%2FzrQxA50OX1ezO6LZWWnfRMMxopJ2yCC4fzyxVI%3D&reserved=0
“There is no way to assess what is going on, other that there is sometimes sympatry during the early part of the breeding season (on Chungara we see nests of juninensis in Oct-Nov). The occipitalis may be migrants that will leave, I don't know? I assume that is the case. There is no evidence of hybridization that we know of. But do keep in mind that occipitalis, unlike juninensis, is highly migratory. Migration and distinct change from a breeding to a non-breeding plumage is of interest, versus juninensis that looks about the same year round and is resident.”
Comments from Claramunt: “NO. Differences in facial patterns are very suggestive, I admit I was tempted to vote YES, but we need some minimal analysis of the geographic distribution of the character to evaluate the potential existence of intermediate populations. And then, the Ogawa et al. paper shows a very complicated picture of mitochondrial relationships with no clear genetic clades coinciding with taxonomy nor with phenotypic similarity, suggesting no clear separation of species-level lineages, including taczanowskii. I could not find the DNA sequences in GenBank, so no chance of doing some further analyses (strange, I think The Auk requires publication of sequences). Rather than splitting juninensis, these results rise the question of whether taczanowskii should be considered a separate species (cf. also Nacho’s comment).”
Additional comments from Jaramillo: “I was looking through where the closest points of contact may be between these two forms, and seeing if I could come up with some imagery. An interesting record I found is this one from Jujuy in January with both forms together. Apart from the throat coloration differences, and the golden plumes versus silvery the crown/nape contrast is another difference. The form juninensis has a darker crown, not as contrasting as on occipitalis. They also look different from behind. In any case, I thought this record of sympatry would be interesting:
Additional comments from Claramunt: “Alvaro, I hear you. Phenotypically, they seem two different species, in my mind. But the genetic data suggest a different scenario. The facial pattern may be the result of a single (or just minimal) genetic difference in a background of genomic uniformity (or at least not diverging). The genetic basis of the trait may not allow for intermediate forms and interbreeding may be invisible. Then the presence of both phenotypes in a single population can be interpreted as a local polymorphism and a confirmation that the two phenotypes behave, socially, as a single species. The point is that, without additional data, we cannot interpret co-occurrence as evidence of reproductive isolation.
“If they are breeding sympatrically, observing whether pairs sort out by phenotype or whether there are phenotypic intermediates would be very informative.”
Comments solicited from Jon Fjeldså: “I am glad to see that you take up the ranking of these grebes, as I was quite irritated to see P. occipitalis and juninensis being split in The HBW/BirdLife illustrated checklist. However, I can probably blame myself, since nearly 40 years ago I myself published some evidence for splitting them (see Fjeldså J 1982. Some behaviour patterns of four closely related grebes, Podiceps nigricollis, P. gallardoi, P. occipitalis and P. taczanowskii, with reflections on phylogeny and adaptive aspects of the evolution of displays. Dansk Orn. Foren. Tidsskr. 76: 37-68. Here, I described some differences in displays and calls between silvery grebes in Peru and southern Patagonia. However, these populations are far apart, and I really don't know how much variation there could be in behavior within the large intervening area. In fact, there seems to be a good deal of flexibility in grebe behavior, in whether they use face-to-face dancing or parallel rushes or 'barging'.
“Since then, I discovered perfectly intermediate specimens (between occipitalis and juninensis) in museum material from around Coquimbo in Chile. This suggested a rather narrow zone of genetic mixing in the zone of contact between southern and northern morphotypes, but in fact there are also indications of geneflow over deeper time since juninensis birds from northern Chile, Bolivia and southern Peru (Puno, Arequipa) generally have somewhat golden/brass-like luster to the ear plumes (but white throats), in contrast to dull greyish-brown ear-plumes in all populations from Junín and Ancash through Ecuador and Colombia. So clearly there is a rather gradual transition in morphology between occipitalis and juninensis (but no detectable difference between Junín-Ancash and the northern Andes).
“The result by Ogawa et al. was surprising (note that I was co-author here), because of the genetic break between specimens from the south+Junín+Ancash and the northern Andes. So there is a discordance between morphological and molecular signals here. I think many more genetic samples are needed (with multiple markers for telling apart effects of gene flow and ancestral polymorphism) before we can tell whether there is a basis for splitting up the Silvery Grebe. With present techniques, it should be quite straight-forward to obtain adequate genetic data (broad geographical sampling) from toepads of museum specimens, with no need for collecting fresh samples.
“P. taczanowskii is another issue. Although placed next to an occipitalis sample in the Fig. by Ogawa et al., there is no doubt from my old work in Junín that this population, which probably originated during a period of glacial isolation in the Junín Basin, is reproductively isolated from juninensis. P. juninensis and taczanowskii may sometimes display together, but using rituals that have nothing to do with pair formation (but rather a sign of mild/ritualized aggression), and in many contexts, for instance during foraging, they decidedly avoid one another. They are clearly aware that they are different. I am rather skeptical about claims of intergradation by the two species in lake Junín. On the contrary, my morpho-data (in several publications) indicate divergence (ecological character displacement), but I have seen one bird that could be an hybrid (but casual hybrids are also known between occipitalis and gallardoi, and between other well-marked grebe species). To check if there could have been a recent breakdown in the genetic integrity of taczanowskii I checked photos available on Google (assuming that most of these have been uploaded in recent years). One bird labelled as taczanowskii was a clear occipitalis, 3 were difficult to identify (because of angle of view, or resolution), but 71 were clearly taczanowskii. Therefore, I don't see any evidence of hybridization but rather think that some people have difficulties with identifying the species. Again: more genetic data are needed. Ogawa et al. provided some indication that isolated local populations of grebes can rapidly diverge and evolve their own integrity, although they are nested within widespread species in phylogenies using few genetic markers.
“There is no reference to any of my old papers (1980s) on Peruvian grebes in the reference list to Proposal 864 (reprints of these should be deposited in several American museums, and at least they are summarized in my 2004 book 'The Grebes' from Oxford Univ. Press).
“My conclusion: Keep occipitalis and juninensis as one species and maintain taczanowskii (as well as andinus, based on the arguments provided by Ogawa et al.) (a separate question is then whether Podiceps nigricollis should be split up with separate species in the Nearctic and in the Old World (and maybe a third species in South Africa).
“I hope this is useful for your decision.”
Comments from Bonaccorso: “NO. The case is complicated in so many dimensions (plumage, vocalizations, natural history, distributions) and so unclear regarding phylogenetic evidence (e.g. cytb and COI vs. control region) that I think that elevating this taxon to species requires a paper on its own. As said before, a systematic revision of all qualitative and quantitative evidence and, probably, more genetic information will be needed to make an informed decision.”
Comments from Pacheco: “NO. Further studies may show that occipitalis and juninensis are different species, but this evidence still needs to be collected in the key areas and analyzed in an integrated manner. As highlighted by Nacho, the article by Ogawa et al. does not provide convincing evidence for a division.”
Comments from Zimmer: “NO. I was on the fence with this one, mainly due to occipitalis being migratory and having distinct breeding and non-breeding plumages, in contrast to juninensis. However, after considering comments from several other committee members, and, in particular, Jon Fjeldså, I am persuaded that we simply don’t know enough about what is going on to justify splitting at this time.”
Additional comments from Jaramillo: “I realize that I am against the tide here, but that is fine. I think longer term with more data we will sort this one out as two species. There seem to be some unusual aspects in grebes that I certainly do not understand. Aechmophorus grebes breed sympatrically, sometimes hybridize but actually tend to mate assortatively from what I understand. Vocal differences are there, but minor really, plumage and bill color differences consistent but minor. Podiceps nigricollis has these relatively large genetic differences between populations (New World and Old World separated 1 million years ago), yet little morphological, or at least plumage differences. In the New World we have three examples at least of flightlessness developing, and for the most part the plumage of these birds has remained (at least 2 of 3) quite similar if not nearly identical to the flying sister species. In all cases the sister is sympatric with the flightless population. It is a mystery to me how this happens, was it sympatric speciation? If so, how come the plumages are so conserved? Then we have the rather spectacular array of face/neck ornamentation in this group, and often a molt into a dull non-breeding plumage. Surely these ornaments are of some use, some purpose and some use in pair formation.
“In any case, I considered Santiago’s points and I do not think that this is what is going on. I do not think that this is a morph, or at least a situation where hybrids may go undetected due to a genetic situation where intermediates would not be expressed. As I looked at more photos, there does seem to be a zone where you can find intermediates, and Fjeldså noted this as well. I am not sure about his interpretation of a wide zone of gene flow. But there is a contact zone, and certainly some hybridization. As such perhaps some would suggest that this be studied in more context, and that is reasonable. But at this point the differences in ecology, display features (breeding plumes), resident vs migrant situation, and seemingly little or a narrow zone of interbreeding. I am sticking with my YES vote to split these two.”
Comments from Remsen: “NO. Alvaro may be correct, but this is a complicated case that needs more research before we make a change, as noted by several comments above, including Jon’s, whose input is much appreciated.”