Proposal (856) to South American Classification Committee

 

 

Resurrect Cyanophonia and revise the linear sequence of Euphoniinae (Fringillidae)

 

Effect on SACC: A “YES” vote on this proposal will resurrect Cyanophonia and place Euphonia cyanocephala, E. elegantissima, and E. musica within it. The linear sequence of species within Cyanophonia and Euphonia would also be revised to reflect new information on phylogenetic relationships.

 

Background and New Information:

Prior to the recent publishing of a phylogenomic study of the true-finch subfamily Euphoniinae, the most comprehensive molecular phylogeny of the group to date (Zuccon et al. 2012) found that Euphonia was paraphyletic with respect to Chlorophonia, the other genus in the subfamily. Specifically, Euphonia musica was found to be sister to Chlorophonia cyanea. The authors noted this taxonomic conflict but suggested that further sampling of species would be necessary to adequately resolve this issue. More recently, Imfeld et al. (2020) used target-capture and enrichment to sequence thousands of ultraconserved elements and mitogenomes for every Euphonia and Chlorophonia species presently recognized by the checklist committees of the American Ornithological Society. Every phylogenetic analysis performed in this study, whether with concatenation or species-tree methods, maximum likelihood or Bayesian approaches, or using nuclear or mitochondrial sequence data, found the three species of blue-hooded euphonias (Euphonia cyanocephala, elegantissima, and musica) to form a monophyletic clade sister to the 5 Chlorophonia species to the exclusion of all other euphonias (see figures and tables below).

 

 

Text Box: Figure 1. Time-scaled phylogeny of Euphoniinae. This tree is from Imfeld et al.’s Figure 4. The topology of this phylogeny was inferred by maximum likelihood estimation of a species tree from 4,944 UCE loci, and its branch lengths were optimized and time-scaled by a fossil-calibrated Bayesian analysis of 150 completely sampled UCE loci and cytochrome B sequences. The blue-hooded euphonia species, noted by an asterisk, form a monophyletic clade sister to the genus Chlorophonia to the exclusion of the remaining Euphonia species. The monophyly of this clade and its placement received uniformly high posterior support in both maximum likelihood and Bayesian analyses.

Table 1. Support metrics for the time-scaled phylogeny. This table is a pruned version of Table 2 from Imfeld et al. (2020) and corresponds to the node numbers in Figure 1 above. Abbreviations: localized posterior probability (LPP), gene concordance factor (gCF), site concordance factor (sCF), and internode certainty (IC).

 

 

Node

LPP

gCF

sCF

IC

Bootstrap

1

1

77.2

89.0

0.614

100

2

1

19.5

47.2

0.136

100

3

1

18.1

50.6

0.204

100

4

1

30.8

70.2

0.377

100

5

1

10.9

35.0

0.000

100

6

1

27.2

58.9

0.278

100

7

1

38.8

70.8

0.353

100

8

1

29.5

41.7

0.025

100

9

1

36.8

70.5

0.392

100

10

1

57.6

73.9

0.358

100

11

1

48.8

79.5

0.634

100

12

1

42.5

59.0

0.114

100

13

1

18.5

47.7

0.093

100

14

1

23.7

50.0

0.116

100

15

1

52.6

86.4

0.510

100

16

1

27.7

47.7

0.054

100

17

1

28.8

50.1

0.041

100

18

1

34.9

70.0

0.322

100

19

0.76

14.9

34.3

0.009

87

20

1

30.3

71.1

0.251

100

21

0.98

10.4

33.9

0.000

90

22

1

16.1

48.3

0.066

100

23

1

17.7

49.7

0.044

100

24

1

21.8

49.1

0.028

100

25

1

58.7

81.7

0.526

100

26

1

38.7

69.8

0.360

100

27

1

34.2

77.9

0.091

100

28

1

24.3

20.8

0.025

100

29

1

46.4

74.0

0.180

100

30

---

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31

1

79.1

96.3

0.643

100

32

1

72.9

93.1

0.584

100

33

1

54.4

69.8

0.157

100

 

 

 



Figure 2. Maximum-likelihood phylogenies Euphoniinae generated from concatenated UCE loci. These trees are from Imfeld et al.’s Figure 1. Black nodes indicate bootstrap support of 100%, and any node receiving <100% support has its value reported. The topologies of these trees, especially the one inferred from all UCE loci, are largely similar to the species tree topology presented above. Triangles adjacent to the right tree indicate conflicting nodes between the concatenated phylogenies.

 

Based on the new phylogenetic information presented in Imfeld et al. (2020), we also propose a new linear classification for the subfamily in the South American checklist:

 

Cyanophonia cyanocephala

 

Chlorophonia cyanea

Chlorophonia pyrrhophrys

Chlorophonia flavirostris

 

Euphonia saturata

Euphonia plumbea

Euphonia chlorotica

Euphonia finschi

Euphonia concinna

Euphonia trinitatis

Euphonia chrysopasta

Euphonia minuta

Euphonia chalybea

Euphonia violacea

Euphonia laniirostris

Euphonia fulvicrissa

Euphonia anneae

Euphonia xanthogaster

Euphonia mesochrysa

Euphonia cayennensis

Euphonia rufiventris

Euphonia pectoralis

 

Due to uncertainty in the phylogenetic placement of Euphonia jamaica and Euphonia saturata, we have decided to collapse the node containing jamaica, saturata, and the clade that contains the remaining species in ‘Euphonia clade I’ from Imfeld et al. (2020) into a polytomy. From this, jamaica should precede saturata based on the northwest-to-southeast rule and this also retains the current order of these two species in most classifications (Clements et al. 2019). Similarly, we collapsed the node containing Chlorophonia cyanea, C. pyrrhophrys, and, given this arrangement, cyanea should precede pyrrhophrys following current the linear sequence of the genus.

 

References:

Bonaparte, C.L.  1851.  Note sur les Tangaras, leurs affinités, et descriptions d’espèces nouvelles.  Revue et Magasin de Zoologie Pure et Appliquée 2(3): 129-138.

 

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. https://www.birds.cornell.edu/clementschecklist/download/ 

 

Imfeld, T.S., F.K. Barker, and R.T. Brumfield. 2020. Mitochondrial genomes and thousands of ultraconserved elements resolve the taxonomy and historical biogeography of the Euphonia and Chlorophonia finches (Passeriformes: Fringillidae). The Auk: Ornithological Advances 137: 1-25.

 

Zuccon D., Prŷs-Jones R., Rasmussen P.C., and Ericson P.G.P. 2012. The phylogenetic relationships and generic limits of finches (Fringillidae). Molecular Phylogenetics and Evolution 62(2): 581-596.

 

 

Tyler S. Imfeld and Nick A. Mason, May 2020

 

Note on voting from Remsen: let’s break into 2 parts: A. Cyanophonia. B. Linear sequence

 

 

 

Comments from Areta: “A. NO. Looking at the divergence times and phenotypic disparity within Euphonia, I feel comfortable with leaving the blue-headed birds in Chlorophonia. Females of Cyanophonia are very green, like Chlorophonias, and both male and females have plumage patterns shared with other Cyanophonia (most notably narrow foreheads, bluish crowns sometimes extending into semi-collars, and petit bills). Additionally, songs of at least some species seem similar to those of the blue-headed group in that they are jumbled series of quick notes, and their low-pitched whistles are remarkably similar and unlike calls of Euphonia.

 

“Alternatively, if we split Cyanophonia from Chlorophonia, then we would also be pressed hard to split Euphonia into more genera, given the depth of the nodes and the consistency in plumage and vocalizations of some of the groupings uncovered by Imfeld et al. (2020). This is the problem I see when we have no more options to discuss on how to sort generic limits in a comparative fashion. If there were sensible proposals on how to subdivide Euphonia to match the level of phenotypic disparity and node depth of Cyanophonia, I would be happy to reconsider my vote. For example, groups 1, 2 and 3+4+5 could be placed in different genera to match the split of Cyanophonia from Chlorophonia. Unless this is done, separating Cyanophonia seems to go against the generic concept being embraced for Euphonia.

 

‘The last, and worst, option would be to put all in Euphonia but it would add too much diversity to the already diverse Euphonia, and take the divergence times too deep into history for my taste.

 

“For these reasons, the simplest solution would be to put the blue-headed Euphonia in Chlorophonia and not in a separate genus, at least for the time being.

 

“B. YES.”

 

Comments from Remsen: “A. NO, for reasons outlined by Nacho.  These are great data, and a comprehensive phylogeny is a rare delicacy for us to deal with.  So, my “no” has nothing to do with the underlying data but only the more subjective area of how to implement it in classification.  Based on node depth and phenotypic heterogeneity, the implementation that I think is better is to just transfer the Cyanophonia group into Chlorophonia.  That way the information content of the classification would reflect the phylogeny in breaking the subfamily into two major lineages of roughly equivalent age, thus facilitating comparisons between the two groups; their estimated node ages (late Miocene, lining up nicely with similar estimates for the younger end of taxon traditionally ranked as genera in birds).  That Chlorophonia was already somewhat heterogeneous in pattern and size, and that true blue of the Cyanophonia group is also found in the plumages of 3 of 4 Chlorophonia species.

         “As noted by Nacho, a case could also be made for breaking Euphonia itself into two genera, both of which would be older than Cyanophonia; in fact, from my viewpoint, if we recognize Cyanophonia, then we should also recognize taxonomically at least two genera in the remaining euphonias, so I would vote no on the proposal on that basis alone.  As for combining all into a single genus, I would object to that for many reasons, including the new data in the paper that indicates a Miocene split.

         “Tangentially, this group would be a good one for using at least two subgenera to mark the major groups, assuming there is a name available for Group 1.

“B. YES (spot check of sequence indicates standard conventions followed, but I’ll check all.

 

Comments from Bonaccorso: “YES. Several arguments support this proposal, as follows:

 

“1) "Cyanophonia" is monophyletic and highly supported, and it is clearly diagnosable by plumage (all with ‘cyano’ hoods). 

 

“2) Although in terms of number of changes, it seems easier to change three Euphonia* to Chlorophonia, than three Euphonia* to "Cyanophonia", Chlorophonia is a name that we all associate with green species (all very similar). If we move Euphonia* to Chlorophonia, there will be three species of Chlorophonia that are not green (not ‘chloro’), and Chlorophonia will no longer be diagnosable based on plumage.

 

“3) I can't entirely agree with the argument that if we resurrect Cyanophonia we will have to split Euphonia. Splitting should not only be based on synapomorphies and time of divergence. Taxonomic stability should also be considered. Although some clades in Euphonia are diagnosable by plumage and voice, splitting Euphonia would create a lot of unnecessary change and confusion, especially for those who are not taxonomists.

 

“In conclusion, the resurrection of Cyanophonia allows for naming three phylogenetically diagnosable units (Cyanophonia, Chlorophonia, and Euphonia), having two morphologically diagnosable units (Cyanophonia and Chlorophonia), and maintaining two well-established genera (Chlorophonia and Euphonia), with minimum changes in the case of Euphonia.”

 

Comments from Jaramillo: “A. NO. I was thinking the same thing, having looked at the data, as what Nacho wrote. It seems that you either separate Euphonia into multiple genera or you include Cyanophonia in Chlorophonia. The least disruptive seems to enlarge Chlorophonia.

“B. YES.”

 

Comments from Zimmer: “A. NO, for reasons elucidated by Nacho and Van.  I’m normally a proponent of more narrowly defined genera, but, in this case, we have node depths that don’t support the move, at least, not without further splitting of Euphonia, which is actually more supported by the data than is the separation of Cyanophonia.  I would definitely be opposed to lumping everything into a very heterogeneous Euphonia, but I would be entirely comfortable with having cyanocephala and the other two “Cyanophonia” species placed within Chlorophonia.  I can’t say that I agree completely with Elisa’s Points #1 and #2 regarding Cyanophonia being “clearly diagnosable” based upon their blue hoods, and that Chlorophonia would no longer be diagnosable if the three Cyanophonia species were included therein.  If you look at Chlorophonia, 4 of the 5 species have a blue hood (pyrrhophrys and callophrys), a blue cap (occipitalis), or an extensively blue nape (cyanea) of a very similar shade of blue to that of Cyanophonia.  Only the rather divergent flavirostris lacks blue on the head/neck.  Additionally, if you look at Cyanophonia, the females of ALL three species are predominantly green, with yellowish median abdomens, and blue on the crown & nape – VERY similar in pattern and color tone & saturation to females of 2 of the aforementioned species (pyrrhophrys and callophrys) of Chlorophonia, and differing from females of the other 2 species (cyanea and occipitalis) primarily in the extent and distribution of blue on the head and nape.  When both sexes are considered, I would argue that neither powder blue on the head nor a predominantly green plumage is sufficient to diagnose either Chlorophonia or Cyanophonia from one another.

“B. YES, this linear sequence would appear to conform to our conventions.”

 

Comments from Claramunt: “YES. Resurrecting Cyanophonia makes perfect sense, resulting in a simple and descriptive classification.  Three genera for three nicely delineated groups: the typical euphonias (Euphonia), the blue-headed euphonias (Cyanophonia), and the green euphonias (Chlorophonia) (note the matching Greek names for color).  I really do not understand the arguments against this proposal. Merging Cyanophonia into Chlorophonia would disrupt the diagnosability and homogeneity of two clearly delineated groups. If the issue is the heterogeneity among typical euphonias, that should be dealt with in a different proposal, not by killing this one.”

 

Comments from Stiles: “YES.  Here, I agree with Santiago - the three groups so defined are phenotypically and genetically distinctive. If this requires subdividing Euphonia, then we can cross that bridge when we come to it; and I note that the species remaining in Tangara show some comparably deep divisions, if one were to further compromise stability for consistency.”

 

Comments from Pacheco: “A. NO. After reading the various arguments, I think that the results of phylogeny point to the inclusion of "Cyanophonia" in Chlorophonia as the most appropriate decision. B. YES.”