Proposal (885) to South
American Classification Committee
Revise the generic classification of the
Two recent studies proposed alternative generic
classifications for the Xolmiini: Ohlson et al 2020 and Chesser et al 2020.
Their proposals were largely coincident but differed in how broad the genus Nengetus should be. Our subproposals
here broadly coincide with these two papers but differ in the treatment of Nengetus.
We recommend a YES vote to all of the
pyrope in Pyrope (YES) or do something else (NO)
The highly distinctive Patagonian forest pyrope was found as stemming from a deep
node in both studies, supporting the recognition of the old genus Pyrope, of which it is the type species.
rufipennis in Cnemarchus (YES) or leave in Polioxolmis
Both species in this clade are rather elongated,
upright-perching, high-altitude specialists that deliver shrill whistles and
share the same tail pattern. We favor merging them in a single genus, which
would emphasize the common theme between them in plumage, habitat associations
and vocalizations. This treatment has been followed in the past (see table from
Chesser et al 2020).
Restrict Xolmis to irupero and velata (YES) or do something else (NO)
This is a rather straightforward decision, as
both species formed a coherent clade in both studies and the type species of Xolmis is irupero.
D) Use Myiotheretes for 4 species (YES) or
merge Myiotheretes under Nengetus (NO).
Myiotheretes is a very homogeneous genus comprising four
Andean species of reddish/brownish birds that deliver simple monotone flat
whistles and inhabit the tree-line zone. The continued recognition of Myiotheretes implies stability and is
consistent with the recovery of this clade in both studies.
et al. (2020) proposed to merge Myiotheretes
in an expanded (and heterogeneous) Nengetus,
stemming from the placement of cinereus
in their phylogeny. However, this merger is not consistent with the position of
cinereus in the work by Chesser et al.
(2020) and would create a large and very heterogeneous grouping of birds. The
best way out of this is to recognize Myiotheretes,
which would imply no change in our classification.
E) Use Nengetus only for cinereus and Neoxolmis
for coronatus, rubetra, salinarum, and rufiventris (YES) or use Nengetus for all the taxa (NO)
As in the case of Myiotheretes, the rather obscure genus Nengetus is again at the center of conflict. Both studies advocate
a rather broad use for Nengetus, but
we believe this is not good for two reasons 1) it creates too heterogeneous
groupings and 2) it disrupts stability.
for restricting usage of Nengetus for
The type of Nengetus
is cinereus, a widespread species
with distinctive plumage that lives in open savanna areas. This distinctiveness
is also evident in the deep genetic divergence with other species in the clade.
Besides these aspects, cinereus does
not walk on the ground regularly or at all (unlike the other species usually
placed in Neoxolmis) and inhabits
more humid and generally lowland areas (reaching higher altitude in southern
Brazil, a pattern exhibited by many "Pampas" birds), whereas the
other species are all exclusive to arid areas mostly in the extreme southern
portion of the continent. Finally, the position of cinereus might be open to discussion (see contrasting results in
Ohlson et al 2020 and Chesser et al 2020 discussed also in Subproposal D); thus,
we do not recommend expanding Nengetus
any further beyond its type species, cinereus.
for placing four species in Neoxolmis
The four species that would be included in Neoxolmis (rufiventris, rubetra, salinarum and coronatus) are all species of dry, extreme areas that regularly
walk on the ground (less often in coronatus).
Their nests are made of sticks on the ground or in shrubs are remarkably
similar, as are their eggs. They form a monophyletic group in both the Ohlson
et al. (2020) and Chesser et al. (2020) studies. Traylor (1979) and Lanyon
(1986) already recognized a close relationship of rufiventris+rubetra/salinarum
when placing them together in the genus Neoxolmis
(see table from Chesser et al 2020 above). In sum, they form a far more
coherent grouping when cinereus is
excluded. Moreover, using Neoxolmis
has the advantage of using a name that has already been in wide use and which
recognizes that they are in some way akin to "Xolmis". Having direct field experience with all the Xolmiini
species, and with 3/4 species being endemic breeders to Argentina, we are
convinced that using Neoxolmis is the
best possible solution, which is consistent with genetic evidence, supported by
field data and which best serves stability.
We think that, based on the deep genetic divergence
and plumage differences, the Argentine endemic breeder coronatus may merit a new genus. However, no such genus name is
available and at present it seems easier and less disrupting to place it in Neoxolmis together with the other
species in this clade of austral birds.
Recognize Syrtidicola for fluviatilis (YES) or keep in Muscisaxicola (NO)
A deep divergence time, possible sister
relationship to Satrapa and
morphological and ecological differences (e.g., very short tail, lowland
inhabitant of riverine sand bars) lead Chesser et al. (2020) to describe a new
genus for fluviatilis.
Sequence. The sequence we need to adopt would be this one
(YES) or another one (NO):
Recognize Heteroxolmis. The Black-and-white Monjita was found to not even belong in the
Xolmiini, so a return to the genus Heteroxolmis
is warranted. It was found to be more closely related to other "warm"
grassland specialists (Alectrurus
spp. and Gubernetes yetapa) in the
Fluvicolini. Ohlson et al 2020 stated:
"Recognize Heteroxolmis Lanyon, 1986 (type = Tyrannus dominicanus (Vieillot) for Xolmis dominicanus and remove it from Xolmini
to Fluvicolini. The distinctiveness of dominicanus
from other Xolmis species was
recognized by Lanyon (1986) based on morphological characters of the nasal
capsule and syrinx, but he regarded the two genera as close relatives. Among the character states that
motivated a separation from Xolmis is
a fully ossified nasal capsule, including alinasal
walls and turbinals, which is also found in Alectrurus
Vieillot, Gubernetes Such, Fluvicola Swainson and Arundinicola d’Orbigny (Lanyon 1986). As
the gender of Heteroxolmis is
feminine (see Lanyon 1986, fig. 24), the name of the species becomes Heteroxolmis dominicana.”
vote would resolve Xolmis dominicanus
as Heteroxolmis dominicana and place
it in the sequence between Alectrurus
Nacho Areta & Mark Pearman, September 2020
Chesser, R.T., M. G. Harvey,
R. T. Brumfield and E.P. Derryberry (2020) A revised classification of the
Xolmiini (Aves: Tyrannidae: Fluvicolinae), including a new genus for
Muscisaxicola fluviatilis. Proceedings of the Biological Society of Washington
Ohlson J.I., M. Irestedt,
H. Batalha Filho, P.G.P. Ericson and J.
Fjeldså (2020) A revised classification of the fluvicoline
tyrant flycatchers (Passeriformes, Tyrannidae, Fluvicolinae). Zootaxa 4747:
Ohlson et al 2020
Chesser et al 2020
Chesser et al 2020
“YES to all proposals except E. With
regard to E, looking at the genetic data it does not make sense to break up
this clade by separating cinereus from the others. If one was going to apply a consistent
treatment (note the branch length of coronatus is similar to cinereus),
one either treats these as three different genera or all the same. The latter seems more reasonable to me.”
“YES to all. When behavior, ecology and biogeography
are combined, I agree with Kevin that cinereus is best separated in a
Comments from Lane: “A) YES. B) NO. These two species
don't strike me as being all that similar in their behaviors, particularly the
Kestrel-like hovering that is so characteristic of Polioxolmis. I would
prefer to keep them as two monotypic genera. C) YES. D) YES. E) YES. F) YES
(emphatically!). G) YES. H) YES.”
Comments from Claramunt: “YES to all.
“After going back and forth on E, I ended up liking the proposed
solution: a monotypic Nengetus plus a diverse Neoxolmis.
Morphology, plumage and behavior are not of much use here as there is no
satisfactory way of subdividing the entire clade based on these. Excluding cinerea
doesn’t make the remaining Neoxolmis a nice homogeneous bunch. And even
separating coronata does not solve the issue, as rufiventris is fairly different
from rubetra and salinarum. What persuaded me at the end was the
argument of nomenclatural stability. This is because: 1) the resurrection of
the obscure Nengetus would affect only a single species (cinerea);
2) At least rufiventris, and rubetra and salinarum
according to some classifications, would retain their traditional generic
names; 3) The nomenclature would not change even if cinerea is found to
be closer to Myiotheretes (as in Ohlson et al.). So, at the end,
stability prevailed over my dislike for monotypic genera.”
Comments from Jaramillo:
“A. YES – The loss of Pyrope
never quite sat well with me; this new dataset correlates with the fact that
this is quite a different bird from typical Xolmis.
B. No – I agree with
Dan, that they should be left as monotypic genera.
C. YES – is it velata
or velatus though?
D. YES – retain Myiotheretes
for the 4 species, retaining a well-defined and morphologically cohesive genus.
E. YES – I hesitated,
thinking that coronatus perhaps deserved to be separate. However, it is
already in Xolmis with various of the other species that will now go to Neoxolmis
and I was OK with that. Definitely cinereus is the odd one out here, a
rather shrike like species, quite unlike the rest.
F. YES – and note that
I would be amenable to a separate genus for maculirostris as well. Not
only due to the different morphology of that bird, but a distinct voice, unlike
the very vocally simple Muscisaxicola (in the strict sense)
G. YES – adopt the new sequence.
H. YES – rather unexpected in some ways. It was
always different, but I would have expected it was a relative to true Xolmis
as we knew it. The membership in the grassland tyrants makes a certain amount
of logic as well.”
Comments from Pacheco: “YES to all proposals except E,
for consistency with the adoption of expanded Nengetus implemented by
Comments from Remsen: “YES to all, except that using
the Chesser et al. tree, Xolmis must precede Pyrope following