Proposal (827) to South American Classification Committee
Revise the classification and linear sequence of the Tyrannoidea: (A) Recognize a new family Onychorhynchidae; (B) Modify linear sequence of families; (C) Add three subfamilies to the Tyrannidae
Background: The proposal below by Dale Dyer (included here with his permission) was submitted to the North American Classification Committee and was passed: http://checklist.aou.org/assets/proposals/PDF/2018-C-amended.pdf. See also Chesser et al. (2018) [59th Supplement]. NACC member comments can be accessed here: 2018-C-3.
This is a follow-up proposal for items relevant to SACC. This will be a little confusing because some of the changes endorsed by NACC were already in place in our classification. A synopsis of the changes endorsed by SACC are as follows; treat each as a subproposal, organized by sequence in which they appear in Chesser et al. (2018):
A. Recognize a new family Onychorhynchidae (to include Onychorhynchus, Terenotriccus, Myiobius). In addition to the studies cited below, Oliveros et al. (2019) showed that Onychorhynchus + Myiobius were sister to Oxyruncidae, not Tyrannidae sensu lato, with an estimated divergence time in early Miocene ca. 23 mya (note here in all such divergence time estimates that there are “credibility intervals” of ca. 5 my around the estimates)
B. Rearrange sequence of families from our current sequence (Tyrannidae, Oxyruncidae, Cotingidae, Pipridae, Tityridae) to reflect new phylogenetic data, including most recently Oliveros et al. (2019), to:
Onychorhynchidae (if A above approved)
C. Add three subfamilies to the Tyrannidae in the following sequence to reflect deep divergence of these lineages. More recently, Oliveros et al. (2019) estimated the oldest divergence (Pipritinae vs. rest) at early Miocene ca.20 mya, and the youngest (Rhynchocyclinae vs. Tyranninae) at ca. 18 mya. Oliveros et al. (2019) treated these lineages at the family level to be consistent with the ages of other lineages ranked as families elsewhere in the Passeriformes, and in fact older than the oldest node that unites all our oscine families from Passeridae through Thraupidae and their spinoffs … but that’s a separate issue for another time. Chesser at al. (2018) added three additional subfamilies (Rhynchocyclinae, Elaeniinae, Fluvicolinae) that I recommend that we temporarily include in a broader Tyranninae because (1) some South American tyrannid genera have not been included in genetic analyses, and (2) a more comprehensive phylogeny of the suboscines using extremely dense taxon-sampling and genomics is in progress (R. Brumfield and colleagues).
Recommendation: Although there will likely be more changes to come in terms of subfamilies and much to come on their composition, I think the changes above are a conservative, safe start, so I recommend a YES on all three.
Van Remsen, May 2019
Original NACC proposal by Dale Dyer:
Revise the classification and linear sequence of the Tyrannoidea
In recent years several studies have been published on the systematics of the Tyrannoidea complex and the Tyrannidae more narrowly (including Ohlson et al. 2008, Rheindt et al. 2008, Tello et al. 2009, and Ohlson et al. 2013). These studies reached conclusions that are mostly consistent amongst themselves but that show a number of discrepancies with the taxonomy and sequence of the AOS North American checklist.
The current AOS classification of Tyrannidae is based mostly on various morphology-based publications of Traylor and Lanyon from the late 20th century. Each of the recent studies consists of analyses of molecular data. Tello et al. (2009, see tree below) has nearly complete genus sampling, and Ohlson et al. (2013, see tree below) employed the most molecular data. Both papers present taxonomic recommendations along with phylogenetic hypotheses.
Although the checklist has been responsive to some of these studies in the creation of the Tityridae and by resolving most of the incertae sedis genera (2010, 2011 supplements), its treatment of Tyrannidae is unchanged from the 7th edition (AOU 1998). These recent studies, employing new data and analytic tools, support many elements of the preceding taxonomic work. A small number of revisions to the checklist could accommodate their new insights.
Below I offer a series of recommendations to bring the checklist into closer accord with what I believe are currently the most strongly supported phylogenetic hypotheses. For sequence of genera within subfamilies, I have followed Ohlson et al. (2013). AOS sequence of higher ranked taxa is maintained in most cases. Appropriate taxonomic rank for various clades is controversial, and to address this I offer some alternatives (I believe that they can be voted on simultaneously). For reasons for adopting family rank in this complex for small and aberrant taxa see Ohlson et al. 20131 (p. 21) and Tello et al. 20082 (p. 448). Approval of 1b and 2-10 would result in a taxonomy which matches the recommendations of Ohlson et al. (2013).
1. Onychorhynchus, Terenotriccus and Myiobius are currently placed in Tyrannidae (Fluvicolinae). All studies found these three genera to form a clade and that their closest relatives are outside of the Tyrannidae.
1a) Place these genera, along with Oxyruncus, into Tityridae. These genera were found to be sister to Oxyruncus, and that resulting group sister to the genera that compose the current Tityridae (Tello et al. 2009, Ohlson et al. 2013). Merging them into Tityridae is the recommendation of Tello et al. (p. 441).
1b) If 1a fails, place these three genera in a new family, Onychorhynchidae Tello, Moyle, Marchese & Cracraft 2009, following Tityridae in sequence, with Oxyruncus remaining in Oxyruncidae. This is the recommendation of Ohlson et al. (p. 20).
1c) If 1a fails and 1b passes, move Oxyruncidae to follow Onychorhynchidae, to reflect its sister relationship to Onychorhynchinae.
2. Change the composition and sequence of the group which includes Myiornis through Tolmomyias (the AOS's current Platyrinchinae) by adding Mionectes, Leptopogon, Phylloscartes and Pseudotriccus (all moved from Elaeniinae). All studies found a strongly supported clade (the Pipromorphinae of Ohlson et al. 2008 and Rheindt et al. 2008, and the Rhynchocyclidae of Tello et al. 2009 and Ohlson et al. 2013) which includes the following genera from our region:
(Note that Platyrinchus is not a member of this clade.)
3. Place Platyrinchinae at the beginning of Tyrannidae. Platyrinchus and the genera above (plus some South American genera, and also Piprites) were found to be sister to the remaining tyrannid subfamilies (Elaeniinae, Hirundineinae, Fluvicolinae and Tyranninae), and thus should be placed first (Ohlson et al. 2008, Tello et al. 2009, Ohlson et al. 2013).
4. Restrict Platyrinchinae to Platyrinchus (see Ohlson et al. 2013, pages 20, 30 - note that the South American genera Neopipo and Calyptura would also be included in this taxon). Adopt the name Rhynchocyclinae Bonaparte 1854 for the remainder of the subfamily (listed as Mionectes through Todirostrum in 2 above), which would follow Platyrinchinae (see Tello et al. 2009, pp. 447-8). All authors found this to be an early divergence (see Ohlson et al. 2013, fig. 4). Note that the authors advocating separation of Platyrinchus from the Rhynchocyclus group also advocate 5, below.
5. If 4 passes, raise the rank of both Platyrinchinae and Rhynchocyclinae to family level (becoming Platyrinchidae and Rhynchocyclidae), and place them prior to Tyrannidae. The divergences between these two groups, and to the remaining Tyrannidae, were found to be very deep (see Ohlson et al. 2013, fig. 4). For family rank see Ohlson et al. 2013 and Tello et al. 2009, pp. 446-8 (although the latter paper does not offer a taxonomic treatment for Platyrinchus).
(Note - the findings of Ohlson et al. 2013 and Tello et al. 2009 also appear to justify an alternative treatment in which the family Platyrinchidae would include subfamilies Rhynchocyclinae and Pipritinae, in addition to Platyrhinchinae. Because neither author recommended this treatment, I decline to propose it here.)
6. Merge the monotypic genus Nesotriccus into Phaeomyias, as species Phaeomyias ridgwayi. Zucker et al. (2016) found this species nested within Phaeomyias murina. The authors propose splitting P. murina into three species. Setting aside the problem of species limits, maintenance of a monotypic genus for this taxon is incompatible with their results.
7. Change the composition of Elaeniinae by subtracting Mionectes, Leptopogon, Phylloscartes and Pseudotriccus (see 2), and by:
7a) moving Sublegatus to Fluvicolinae. See Tello et al. 2009, Ohlson et al. 2008, Rheindt et al. 2008, and Ohlson et al. 2013, all of which place Sublegatus within Fluvicolinae.
7b) Adopt the following sequence for Elaeniinae:
Phaeomyias (including Nesotriccus)
8. Change the composition of Fluvicolinae by subtracting Onychorhynchus, Terenotriccus and Myiobius from Tyrannidae (see 1), adding Sublegatus from Elaeniinae (see 7a), and by:
8a) moving Machetornis to Tyranninae. See Ohlson et al. 2008, Tello et al. 2009, and Ohlson et al. 2013, which placed Machetornis within Tyranninae.
8b) Adopt the following sequence for Fluvicolinae:
Aphanotriccus (not sampled in these studies, but sister to Lathrotriccus - see Cicero & Johnson 2002)
Xenotriccus (not sampled in these studies)
9. For Tyranninae, with Machetornis added (see 8a), adopt following sequence:
Deltarhynchus (position uncertain - see Ohlson et al. 2008, page 327)
Conopias (not sampled in these studies)
10. Change the treatment of Piprites by creating a new family Pipritidae Ohlson, Irestedt, Ericson & Fjeldså 2013, including only Piprites, and placing it at the beginning of the Tyrannoidea (before Platyrinchidae if 5 passes). Family rank is the recommendation of Ohlson et al. 2013 (p. 29).
Piprites is currently incertae sedis within the Tyrannioid superfamily [note that the list of species on the AOS website http://checklist.aou.org/taxa/ appears to be in error in listing Piprites as subfamily incertae sedis within the Tyrannidae. The 7th edition (page 416) lists it as one of "seven genera as a group, incertae sedis, to acknowledge that they are unequivocally tyrannoid but of uncertain affinity within the superfamily." The 52nd supplement (page 605) removed the other six genera from this category, but did not transfer the position of Piprites - "After the account for Tyrannus savana, change the heading Genera INCERTAE SEDIS to Genus INCERTAE SEDIS . . . The genus Piprites has presented a taxonomic challenge for more than a century. Recent genetic studies indicate that it is either the sister group to the Tyrannidae (Ericson et al. 2006, Ohlson et al. 2008) or an isolated lineage near the base of the Tyrannidae (Tello et al. 2009)." Piprites is not addressed in any subsequent supplement.]
This taxon was found to be sister to the Platyrinchus and Rhynchocyclus clades, and its divergence with those groups and with the remainder of Tyrannidae appears quite old (Ohlson et al. 2013).
1 Ohlson et al. 2013 (page 21) - "The last decades has seen a drastic overturning of the conventional view of avian systematic relationships, making it ever harder to adhere to a “traditional view” in classification. There has been a general tendency in the past to merge small and aberrant taxa into larger families, both as a means of maintaining a simple classification, and because of a lack of a strict phylogenetic approach and data that could guide the taxonomic decisions in a transparent way. Even with a more well founded phylogenetic basis there has often been a reluctance to erect new family-level taxa, especially for small clades of “problematic” affinities. This has left a number of distinctive and comparatively old clades hanging in a taxonomic limbo, awaiting additional data that would allow inclusion in a well-established family. It has also led to a neglect of patterns that might determine the fate of clades, whether they fail to diversify, become relictual or undergo great phylogenetic expansion. Treating these small clades as family level taxa highlights their distinctiveness, deep evolutionary history and their hitherto unresolved relationships.
The phylogenetic tree of the NWS, like that of almost every other large radiation, contains lineages of widely different species richness and several taxa whose systematic positions have been contentious. Large amounts of data have been employed to clarify the phylogenetic positions of various debated taxa of NWS. We argue that the failure so far in associating these taxa, such as Platyrinchidae, Oxyruncus and Xenops unambiguously with any larger clades cannot be explained solely by insufficient data. Instead, these taxa stand out as isolated clades that were part of rapid successions of divergence events along with clades that today are rich in species (Fig. 4). These small clades are distinctive and internally coherent in terms of ecology and morphology and they have independent evolutionary histories that are likely to span at least 20 million years. Keeping these taxa in taxonomic limbo (i.e. as incertae sedis) becomes harder to justify and here we opt to highlight their isolation, distinctiveness and old age by treating them as family level taxa. Looking at avian systematics as a whole, there are many small families that most ornithologists would never consider subsuming into more inclusive taxonomic entities, even if their sister relationships are unambiguous (consider merging the Shoebill into Pelecanidae, for example). Concerning the New World suboscines, we would in several cases argue in favour of recognizing these clades as family level taxa, despite the “relatively little content” of monotypic families (Tello et al. 2009). These taxa are all “isolated” early offshoots from the larger radiations, and they are in most cases ecologically and morphologically distinctive from their closest living relatives. In our view, a treatment as family level taxa is more informative about the nature and phylogenetic position of taxa like Oxyruncus, Xenops, Tachuris and Platyrinchus compared to subsuming them into the larger groups from which they diverged early in their histories."
2 Tello et al. 2008 (page 448) "In our effort to construct a phylogenetic classificatory framework with some long-term stability, we are eliminating the traditional, expanded concept of the Tyrannidae because nodes along the spine of that clade are nearly all ambiguously supported, including the basal node. In contrast, our concepts of Tyrannidae and Rhynchocyclidae are strongly monophyletic and thus likely to provide long-term stability for their names. We note, however, that if Platyrhynchus (sic) is confirmed to be the sister to the rhynchocyclines, then the family-group name would revert to Platyrhynchidae."
Cicero, C. and N. K. Johnson. 2002. Phylogeny and character evolution in the Empidonax group of Tyrant Flycatchers (Aves: Tyrannidae): a test of W. E. Lanyon's hypothesis using mtDNA sequences. Molecular Phylogenetics and Evolution 22: 289-302.
Ohlson, J., J. Fjeldså, and P. G. P. Ericson. 2008. Tyrant flycatchers coming out in the open: Phylogeny and ecological radiation of Tyrannidae (Aves, Passeriformes). Zoologica Scripta 37: 315-335.
Ohlson, J. I., M. Irestedt, P. G. P. Ericson, and J. Fjeldså. 2013. Phylogeny and classification of the New World suboscines (Aves, Passeriformes). Zootaxa 3613: 1-35.
Rheindt, F. E., J. A. Norman, and L. Christidis. 2008. Phylogenetic relationships of tyrant-flycatchers (Aves: Tyrannidae), with an emphasis on the elaeniine assemblage. Molecular Phylogenetics and Evolution 46: 88-101.
Tello, J. G., R. G. Moyle, D. J. Marchese, and J. Cracraft. 2009. Phylogeny and phylogenetic classification of the tyrant flycatchers, cotingas, manakins, and their allies (Aves: Tyrannides). Cladistics 25: 1-39.
Zucker, M. R., et al. 2016. The Mouse-colored Tyrannulet (Phaeomyias murina) is a species complex that includes the Cocos Flycatcher (Nesotriccus ridgwayi), an island form that underwent a population bottleneck. Molecular Phylogenetics and Evolution 101: 294-302.
Submitted by: Dale Dyer, Field Associate, Department of Ornithology
American Museum of Natural History, New York
Date of Proposal: 6 February 2017
Comments from Robbins: “827A. YES. 827B. YES, this a logical consequence of supporting 827A. 827C. YES, makes sense that we not recognize the three other subfamilies yet, given the number of South American genera not represented in the Oliveros et al. (2019) paper.”
Comments from Pacheco: “827A. YES; 827B. YES; 827C. YES. The broad and very recent multi-author (32!) paper justifies adjustments in sequencing and recognition of these higher taxa.”
“A. YES. The main reason to recognize a new family Onychorhynchidae would be that these genera were found to be outside of the Tyrannidae and closer to Oxyruncusand the Tityridae in Tello et al. and Ohlson et al., although the relevant nodes were supported only in the Bayesian analysis. The main analysis of UCE data in Oliveros et al. (2019) confirmed a sister relationship between onychorhynchids and Oxyruncus, but together they were the sister clade to the remaining Tyrannidae (concatenated ML bootstrap: 97%). However, species-tree methods could not resolve relationships among these groups except for one algorithm that actually placed onychorhynchids and Oxyruncus sister to the Tityridae (bootstrap: 84%), like in Tello et al. and Ohlson et al. Because the later relationship appears in three independent datasets (RAG genes of Tello et al., nuclear introns of Ohlson et al, and UCE-species tree of Oliveros et al), I suspect that it is actually the true history. Even if onychorhynchids and Oxyruncus were sister to the Tyrannidae, it may make sense to separate them anyways in order to “decompress” the excessive diversity of the traditional Tyrannidae. Despite their morphological heterogeneity, onychorhynchid genera share some traits such as the well-developed rectal bristles, the light rump, and seem similar in ecologically and behavior.
“B. YES for now. The sequence is based on the concatenated ML in Oliveros et al. Although I suspect that Onychorhynchidae + Oxyruncus may be sister to the Tityridae, this is a temporary solution and at least closely related families are adjacent in any case.
“C. YES. But we also need to recognize Rhynchocyclinae and Tachurisinae as they may not be sister to the Tyranninae (see Tello et al. and Ohlson et al., and the species-tree analyses in Oliveros et al. supplement). Elaeniinae and Fluvicolinae are a different story; they are definitely closely related to the Tyranninae and we could end up recognizing them but at the level of tribes.
Comments from Jaramillo: “A – YES. B – YES. C – YES. No comments that add anything to what has already been noted by other members.”
Comments from Areta:
“A.YES, among the several oddballs in the “Tyrannidae”, these ones stand out, and the deep divergence and phylogenetic position suggested by different genes suggests that recognition of Onychorhynchidae is desirable.
“C. YES, although I believe that Pipritinae and Platyrinchinae also fit the bill for family status.
Comments from Stotz: “YES to all. Probably not the last word, but seems like the best current approach.”