Proposal (202) to South American Classification Committee

 

Reinstate Pipromorpha for the rufous Mionectes

 

Proposal: This proposal is for the reinstatement of the genus Pipromorpha for the rufous Mionectes species, M. oleagineus, M. macconnelli and M. rufiventris. This is a taxonomic chestnut with over 100 years' vintage of controversy. If this change were sanctioned, I understand that M. oleagineus may need revert to P. oleaginea to reflect the change in gender of the genus, though a nomenclatural expert could perhaps be consulted on this matter were the proposal to pass.

Taxonomic History

Mionectes species fall into two rather distinct groups: two green-and-yellow Andean species (M. olivaceus and M. striaticollis) and three rufous lowland species (M. oleagineus, M. macconnelli and M. rufiventris). Various of these taxa include a number of morphologically and possibly vocally distinctive races that may in time prove to deserve species rank (pers. obs.).

The rufous species, Mionectes oleagineus, M. macconnelli, and M. rufiventris have for much of their taxonomic history been placed in the genus Pipromorpha.

Mionectes and Pipromorpha were merged at some point in the 1800s (per Traylor, 1977, though I have not been able to locate the original reference). Ridgway (1907) proposed reinstating Pipromorpha, a key feature in his view being the presence of modified primaries in true Mionectes, versus their absence in Pipromorpha. Todd (1921) followed this treatment in a review of the Pipromorpha. Van Rossem (1938), however, later proposed merging Pipromorpha with Mionectes, based on the dubious proposition that some Pipromorpha also have modified ninth primaries. Zimmer (1941) considered that there was "little evidence of the suggested reduction in width of the ninth primary in Pipromorpha in comparison with the tenth although single specimens [of Pipromorpha] have a slight sinuation of the inner margin that reduces the width of the feather a little at that point". Zimmer (1941) thus suggested continuing to recognize Pipromorpha: "Two distinct patterns of coloration are presented, each involving more than one species. In Mionectes, the greatest modification occurs in the subexternal primary; in Pipromorpha the outer primary is most strongly modified In Mionectes, there often is a pronounced sexual difference in size markedly less obvious than in Pipromorpha."

This approach was followed by most authors (e.g., Phelps & Phelps 1950a, Meyer de Schauensee 1970 & 1978, Wetmore, 1972) until Traylor (1977)'s major phylogeny of the Tyrannidae. Traylor suggested that the two genera be merged, arguing that: "different shapes of the 9th primaries in adult males is a trivial character in a family where in a single genus such as Pseudocolopteryx, three species have different sets of primaries and the fourth has them all normal". Lanyon (1988), studying syringeal morphology and the nasal septum, found Mionectes and Pipromorpha to be identical structurally and together to show morphological features unique among the Tyrannidae. He concurred with Traylor's proposal.

Traylor (1977) proposed dispensing with 36 Tyrannidae genera. Almost all of the changes he proposed have been followed without much comment in the modern literature. However, the merger of Pipromorpha with Mionectes has remained controversial. Snow & Snow (1979) maintained Pipromorpha (not citing Traylor) in a discussion of the evolution of lek behaviour in the Pipromorpha. Hilty & Brown (1986) and Hilty (2003) each note "formerly in the genus Pipromorpha" alongside the relevant species accounts. Ridgely & Tudor (1994) refer to the rufous Mionectes as "former Pipromorpha" or "true Pipromorpha" (even in the plates) with the green Mionectes "true Mionectes". Collias (1997) refers to "Mionectes (including Pipromorpha)". Fitzpatrick (1980) refers to "Mionectes (includes Pipromorpha)". Chesser (2004) refers to "Mionectes / Pipromorpha". These publications taken as a whole and the long history of use of the genus prior to Traylor suggest an awareness of the existence of an alternative generic treatment among those interested in Neotropical birds and, arguably, some suspicion over Traylor's lump.

Similarities and differences between Mionectes and Pipromorpha:

Morphology and biology

In addition to cranial and syringeal morphology, other similarities between Mionectes and Pipromorpha include general proportions, a largely frugivorous diet (rare among the Tyrannidae), foraging strategy (see Fitzpatrick, 1980) lack of rictal bristles (also rare among the Tyrannidae), general size and general proportions, understorey foraging and primary or mature secondary forest habitat. Mionectes and Pipromorpha both make doomed (roofed) nests, as do other Pipromorphinae* such as Leptopogon, Corythopis and Hemitriccus (Collias, 1997).

 [* The Pipromorphinae is often used as a subfamily name to describe Mionectes and Pipromorpha (e.g. Wolters, 1977; Sibley & Ahlquist 1985a; Collias, 1977; Chesser, 2004) together with other closely related genera. A recent molecular study suggests that the Pipromorphinae includes Leptopogon, Hemitriccus, Todirostrum and Corythopis as well as Mionectes / Pipromorpha (Chesser, 2004).]

As noted by Zimmer (1941), suggestions that the genus Pipromorpha is supported only by differences in the modification of the ninth primaries (e.g. Traylor, 1977) are an exaggeration. Other differences between the two groups are summarised in the table below (compiled from leading literature sources, e.g. Zimmer, 1941, Hilty & Brown, 1986, Ridgely & Tudor, 1994 and fairly extensive personal field experience with all but one of the species involved): 

 

 Mionectes

 Pipromorpha

 Modified ninth primary

 No modified ninth primary

 Streaked underparts

 No streaked underparts

 Yellowish underparts

 Rufous or orange underparts

 White postocular patch

 No white postocular patch

 Greenish or bluish head

 Grey/rufous head

 Greenish back

 Brownish back

 Andean range (also ranging into Central America)

 Non-Andean (lowland) range

 Notable sexual dimorphism (size)

 Much less sexual dimorphism (size) though see Snow & Snow (1979) on small wing size differences

 Typically larger in all dimensions than Pipromorpha (bill, wings, tail, tarsus)

 Typically smaller in all dimensions than Mionectes(bill, wings, tail, tarsus)

Generally silent and inconspicuous (per Hilty & Brown, 1986; Ridgely & Tudor, 1994 etc.). I have only heard a true Mionectes call on a handful of occasions, despite it being one of the most abundant genera at almost every forest site I have studied in Colombia over the last 10 years or so.

Call not infrequently. Pipromorpha can regularly be located through field observations following a call.

 When calling, have quiet, thin "wiry" or "hummingbird-like" calls (summarised in Hilty & Brown, 1986; Ridgely & Tudor 1994).

 "Twittering" or "furnariid-like" calls (summarised in Ridgely & Tudor 1994).

 Rarely make "wing-flashing" movements (per Ridgely & Tudor, 1994)

 Frequently make "wing-flashing" movements (Snow & Snow, 1979; Ridgely & Tudor, 1994)

 May not be lek-forming (see further below); lek-forming is at least very rare

 All frequently lek forming (see further references and discussion below)

 

Molecular data

Chesser (2004) included M. (P.) oleagineus material in his molecular study but no true Mionectes. Bates & Zink (1994) included M. olivaceus in their analysis but no Pipromorpha. Neither of these studies suggests paraphyly of the genus, both studies showing a relatively close relation between Mionectes/Pipromorpha and Leptopogon, for example. I am not aware of any molecular study that has included representatives of both Pipromorpha and true Mionectes groups. Morphology, biogeography and behaviour each suggest strongly that the species in current Mionectes fall into two quite distinct groups and that greater Mionectes are rather different from other Tyrannidae. Whether the Pipromorpha/Mionectes separation should be recognized at the genus level is a question of degree. It is questionable whether the depth of the Mionectes/Pipromorpha node would be particularly illuminating. No one has ever doubted that (i) "true Mionectes"; (ii) "Pipromorpha" and (iii) greater Mionectes are each monophyletic. 

 

Vocalizations

Vocalizations are rather distinct between the two groups. The true Mionectes are generally silent. When they do call, they give "thin", "wiry" or "hummingbird-like" calls. Pipromorpha call regularly, linked with their lekking behaviour. Their calls are more twittering or furnariid-like, i.e. louder with a somewhat more liquid quality to them (above all described in Ridgely & Tudor, 1994 and other recent reference works). Although syringeal structures are similar (Lanyon, 1988), it seems likely that some vocal tract differences exist as between the two groups, giving rise to these different call qualities.

 

Behaviour - lekking

The Pipromorpha are all lek-forming, being the only Tyrannids confirmed to exhibit such behaviour (Snow & Snow, 1979; Wescott & Smith 1994; Fixo & Aleixo 1997). Pipromorpha at such leks frequently call and engage in wing-raising behaviour. Snow & Snow (1979) suggest that wing-raising may be to show off male wing emarginations, one of few sexual differences among Pipromorpha. Snow & Snow (1979) considered the evolution of lek-forming in the Tyrannidae to be restricted to the Pipromorpha. There is, however, a report of a congregation of male M. olivaceus observed in Panama (noted in Ridgely & Tudor, 1994). It may be that the very thin vocalizations made by the green Mionectes make any lek sites (if any do exist) difficult to detect. However, the lack of reports of lekking behaviour, a frequent interest of ornithological researchers where found, in two widespread species amounts to a somewhat "deafening silence". Further, lek-related behaviour common in Pipromorpha such as frequent wing-raising and vocalisations (Snow & Snow, 1979) are observed only very rarely in true Mionectes (e.g. Ridgely & Tudor, 1994). Whether true Mionectes do not lek at all or instead present some retarded/vestigial version of the Pipromorpha lek, this clear behavioural difference between the two groups amounts to additional grounds for the recognition of two genera. Much has been written of the unique evolution of lek behaviour within the Tyrannidae by Pipromorpha (e.g. Snow & Snow, 1979; Wescott & Smith 1994; Fixo & Aleixo 1997) and it would seem perhaps appropriate to recognise this feature at the genus level. The lek-forming behaviour of the Pipromorpha makes the name [= "Manakin-shape"] particularly apt for this group.

 

Conclusion: This proposal may lie close to the border of what people conceive a genus to be in ornithology. Whilst going against almost all recent taxonomic treatments, I would recommend reinstating Pipromorpha for the rufous Mionectes (= "YES" vote) on the basis of external morphology, range, behaviour and voice. I'll leave the last words to Zimmer (1941) as his views on this topic still make a great deal of sense today: "Possibly these features ought to be held as of no more than subgeneric value but the two groups are easily distinguished and I prefer to maintain their generic separation."

 

References (not on SACC list):

 

Bates J.B. & Zink R.M. 1994. Evolution into the Andes: molecular evidence for species relationships in the genus LeptopogonAuk 111(3): 507-515.

Capparella, A. & S. M. Lanyon. 1985. Biochemical and morphometric analyses of sympatric Neotropical sibling species, Mionectes macconnelli and M. oleagineusOrnithol. Monogr. 36: 347-355. 

Collias N.E. 1997. Of the origin and evolution of nest building by passerine birds. Condor 99(2): 253-270.

Fitzpatrick, J.W 1980. Foraging behaviour of Neotropical tyrant flycatchers. Condor 82: 43-57.

Pixo M.A. & Aleixo A. 1997. Lek behaviour of the gray-hooded flycatcher. Condor 100: 726-731.

Snow B.K. & Snow D.W. 1979. The Ochre-bellied Flycatcher and the evolution of lek behaviour. Condor 81: 286-292.

Todd W.E.C. 1921. Studies in the Tyrannidae I. A revision of the genus Pipromorpha. Proc. Biol. Soc. Wash. 34: 173-192.

Wescott D.A. & Smith J.N.M. 1994. Behaviour and social organisation during the breeding season in Mionectes oleagineus, a lekking flycatcher. Condor 96(3): 672-683.

Wolters H. 1977. Die Vogelwarten der Erde. Vol. 3. Paul Parcy, Hamburg & Berlin.

 

Thomas Donegan, February 2006

 

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Comments from Remsen: "YES. This is clearly a matter of taste, not science (because sister status seems unquestionable), but to my taste, the differences between these two groups warrant treatment as separate genera, as outlined above by Donegan. I have never liked the merger and have to force myself to call the Pipromorpha 'Mionectes.'" Sister genera yes, but congeners, no."

Comments from Stiles: "NO. Here, I disagree - the differences cited by Donegan are by no means as clear-cut as he suggests. To begin with, in my experience at least Mionectes olivaceus does have leks - exploded leks to be sure, but definitely leks! On its song perch, a male will wing-flick much as does oleagineus. There are numerous suboscine genera in which different species do or do not lek, or lek in different ways (v. gr., exploded vs. compact). Regarding primary emargination, there is enough variation among the races of oleagineus to convince me that this character is hardly of generic value.   The Costa Rican races of oleagineus show distinct dimorphism in this feature as well as being larger and more dimorphic in body mass, compared to the Colombian races. The songs do differ, but again, such characters are often subject to intense sexual selection, and phenotypic responses to this selection can be striking."

Comments from Nacho Areta: "I think that Thomas overstates the differences between Pipromorpha and Mionectes and overlooks similarities (e.g., by comparing each body part coloration he increases the number of characters suggesting differences). Both build spectacular mossy pensile nests different from other tyrants (including those in a light version of Pipromorphinae) and are frugivores which makes them quite distinctive. I disagree with the statement that true Mionectes are vocally inactive and that they rarely or never lek. Actually, it seems to be that both activities are related: lekking Mionectes olivaceus can be among the most continuous singers I have ever heard in the field. Also, lekking birds are at audible distance from each other which I would not considered an expanded lek (distance is sometimes less than 8m between displaying males). Finally, Mionectes are not absolutely "Andean" with at least a subspecies of olivaceus extending into the northern cordillera of Venezuela. And, for that matter, birds in the Pantepui cannot be considered strictly "lowland".

"I think that ecological and behavioral similarities are sound enough to keep both taxa as subgenera and to retain for both the genus Mionectes (which I think describes their riverine nesting habits)."

Additional comments from Thomas Donegan"A few small points on the two comments above. First, on Gary’s comments on emarginations, I quote Snow & Snow’s proposition that Pipromorpha wing-raising is to draw attention to this feature, but do not state this to be a difference between the two groups (note: this is not in table) nor is this suggested. Secondly, on exploded or non-exploded M. olivaceus leks, it is interesting to hear confirmation that these do exist (given the lack of published work on this and the fact I had not noted it myself). I stated in the proposal that true Mionectes calls are thin which may make any leks difficult to detect - which seems most likely to have been the case. Thirdly, nesting, foraging, frugivory and all the other similarities between these groups mentioned by Nacho and Gary are cited, referenced and noted in the proposal. On nests specifically, the Collias article cited notes the Pipromorpha/Mionectes nests to be of the same structure, as mentioned. However, it does not draw attention to similarities between Pipromorpha / Mionectes vs. other Pipromorphinae. Though I do not doubt what Nacho says and indeed, find it very interesting, I am not sure that lack of knowledge of (presumably) unpublished data amounts to overlooking similarities! I tried, whilst putting the case for this split, to cite and discuss or at least mention all the available evidence and alternative treatments. A white-wash is certainly not intended! Finally, on the range question, M. olivaceus of course extends into lowland regions, particularly away from the equator (as noted for M. olivaceus in C America in the proposal). And M. (P.) oleaginea and (I understand) M. (P.) macconnelli extend into the Andean foothills, where they are fully sympatric with "true Mionectes at multiple sites (in Colombia from 100 to about 500-1000m across most of the Andean foothills on both slopes). (There are of course lots of species in the same genus that are sympatric, Tangara being perhaps the best example). This proposal is, as Van Remsen states, a matter of taste. To my mind, the very different external morphology and voices of these forms place them into two separate groups that it is helpful to recognise at the genus level (even if we discount lekking). Throughout the tortuous history of the group, some have taken this view whilst others have taken the contrary view, which is why a proposal and a consensus is needed. Debate is good and it is pleasing to see this proposal provoking comment and a better understanding of the group."

Comments from Stotz: "NO. I agree with Van in every way, except the conclusion. I still think of the Pipromorpha as Pipromorpha rather than Mionectes. But they are clearly sisters, although not intermingled. Given that, the question is are we better served by lumping or splitting. Given my preference for the status quo in the absence of compelling arguments to the contrary, I think I view the nearly 30 years post-Traylor as a significant period that should only be overturned for strong reasons. Also given that there are only 5 species in the genus, we would be creating very small genera for no obvious reason. If genetic analysis showed that they were not sister (or if there were any suggestion from other studies of that), or showed a long branch between Mionectes (sensu stricto) and Pipromorpha, I would be willing to split. In the absence of that, I can't see what we gain."

Comments from Zimmer: "YES. This is a tough one. On the one hand, each of the two groups is quite uniform (in plumage and vocal characters) when considered separately, and quite different when viewed in the context of the other group. On the other hand, Doug's points are well taken. Assuming that the two groups (Mionectes and Pipromorpha) are one another's closest relatives, then I guess it comes down to what each of us perceives a genus to be. To my thinking, the species in each group are so much more similar to one another than any one of them is to any member of the other group, that the two groups really fit my concept of genera. I might also add that I think the vocal differences between these two groups are even greater than suggested in the proposal summary, and although I don't doubt for a minute the testimony that the two Mionectes species can be persistent vocalists, I find it hard to believe (based on my field experience with all of the species) that they come anywhere near being as persistently and conspicuously vocal as the Pipromorpha. I vote YES."

Comments from Robbins: "NO. As Gary correctly points out, this proposal does not accurately reflect morphological and behavioral data for the taxa involved. In addition to Mionectes lekking, the summary of plumage characters in Donegan's table overemphasizes differences between these two groups: there is considerable variation in size within and among Mionectes, and both groups have various degrees of ventral streaking. I vote "no" until there are appropriate genetic data to indicate that these two groups are as genetically differentiated as are other similar appearing tyrannid taxa that we consider generically distinct."

Comments from Silva: "YES. Hard decision, but I will vote for yes because the differences that were pointed out as well as because the distribution pattern that is well distinct (lowland vs. highlands). It will be nice to have a molecular phylogeny of this group as there are enough samples of them in most of the museums."

Comments from Pacheco: "YES. Difícil decisčo. Porém, diante das incertezas e da falta de um argumento robusto para asseverar o desmembramento do grupo em dois, voto pela manutenćčo do tratamento vigente."

Comments from Nores: "YES, aunque como puede deducirse de las diferentes opiniones emitidas al respecto, las diferencias no son tan marcadas como para pensar en algo definitivo. Yo veo ambos grupos bastante diferentes, particularmente en lo que se refiere al color. El color predominantemente rufo en el cuerpo es poco frecuente en Tyrannidae, y con pocas excepciones, es una característica genérica. Es el caso de Neopipo, Terenotriccus, Miyophobus, Pyrrhomyias, Myiotheretes, Cnemarchus, Hirundinea, Neoxolmis, Cassiornis y Attila. En los pocos casos que no es así, Myiarchus semirufus, Pachyramphus castaneus, Rhytipterna holerythra, no difieren marcadamente del resto, son sólo más rufos. En Mionectes y Pipromorpha los colores son muy diferentes: los primeros amarillos o verdosos muy rayados y los otros rufos muy poco rayados. Además, es notable el parche blanco detrás del ojo presente en Mionectes y ausente en Pipromorpha."

Comments from Jaramillo: "YES - I do think it is a matter of taste, but I am compelled by the vocal differences between the two groups. As separate groups the two genera are quite uniform and easily defined, I think it is less so when lumping the two under Mionectes. I find it more informative to keep Pipromorpha separate from Mionectes, than to lump them all under one genus."