Proposal (771) to South American Classification Committee
Break up Megascops guatemalae
into several species (II)
A. Recognize M. centralis as a separate species
B. Recognize M.
roraimae group as a separate species
Effect
on AOU SACC classification: The widespread species Megascops guatemalae would be broken up into several species-level
taxa such that M. guatemalae (and
potentially a separate M. vermiculatus)
would be restricted to Middle America, thus extralimital to SACC’s region, and M. centralis, and M. roraimae (the latter containing napensis and pallida)
present within SACC territory.
Background: Way back in 2001, SACC
Proposal #12
suggested the splitting up of Megascops
guatemalensis, a species that spanned Middle and South America from Mexico
to Bolivia and the Guianan Shield. In the proposal, Mark Robbins laid out the
situation as it was in the early 2000s regarding the complex, with little more
than a few published sound recordings, the bizarre Marshall et al. (1991)
cassette tape review/publication, and some field guides that had jumped on
board with splitting the complex without any formal study as reference. The
proposal was soundly rejected by the committee, and rightly so. However, in the
past few years, a smattering of new publications, and a fair number of sound
recordings (easily accessible online) have come out that provide some of the
missing pieces to this situation, and I think it can be viewed again in
slightly better light.
New
information:
Two new publications, particularly, have shed light on the taxonomy of several
members of Megascops, and taken
together, they may finally be sufficient to allow SACC to act on the M. guatemalae complex. The first was
Dantas et al. (2016), who provided a phylogenetic analysis of the genus (albeit
incomplete), and Krabbe (2017), who reviewed the genus, assembling and
analyzing vocalizations. In the case of the M.
guatemalae complex, Dantas et al. (2016) provided a phylogenetic structure
that was not well resolved, but showed that the southern taxa form one clade
apart from the Mexican taxa. Dantas et al. said of this:
“The position of
another well-supported group within this sub-clade, M. guatemalae/vermiculatus, is unresolved (Fig. 1); in contrast,
internal relationships in this clade are all well supported and within-species
divergences are relatively high. For example, two samples of M. guatemalae (M. g. guatemalae and M. g.
thompsoni) from Mexico are 1.8% divergent from one another (uncorrected
mitochondrial p-distance) and are monophyletic with respect to the M. vermiculatus group. Within M. vermiculatus, the Tepuian (roraimae) and Andean (napensis) populations are sisters, with
the Panamanian sample (vermiculatus)
sister to these two. Pairwise uncorrected genetic distances between M. guatemalae and M. vermiculatus samples ranged from 8.4% to 9.4%, with distances
within M. vermiculatus ranging from
3.5% (roraimae–napensis) to 6.3% (vermiculatus–napensis).”
The
portion of the tree in question is here:
I
must point out, based on the locality of the “M. vermiculatus vermiculatus” specimen used here, it is very likely
that specimen actually represents Hekstra’s (1982) taxon centralis--true vermiculatus
is from Costa Rica and into the western 1/3 of Panama’s Caribbean slope (using
Xeno-canto sound recordings as a basis for identification). Thus, true vermiculatus is not included in this
tree, which muddies the conclusions a bit. However, Krabbe (2017) provided a
sound analysis that should help bridge some of the deficiencies of the tree. In
his paper, Krabbe stated:
“Although
slight vocal differences of M.
[guatemalae] vermiculatus in pitch and pace from M. g. guatemalae and M.
guatemalae hastatus are suggested, sample sizes are small and no recording
of the N Nicaraguan form M. guatemalae
dacrysistactus was included in the comparison. Additional material is
needed to assess the rank of vermiculatus.
The data indicate distinct vocal differences in all measurements between M. [guatemalae] centralis (Hekstra) and
geographically adjacent forms in the clade (vermiculatus,
pallidus, napensis), strongly supporting the suggested species rank of M. centralis (Ridgely & Greenfield
2001, Gill and Donsker 2016). M.
[guatemalae] pallidus (Hekstra) has been overlooked by most authors and
deserves mention. The similarity in plumage pattern, tarsal feathering, size
and proportions to Mexican guatemalae
of a specimen (AMNH120332) from the Paria Peninsula, coastal mountains of
Venezuela, led Chapman (1931) to conclude that it was specifically distinct
from roraimae. Hekstra (1982b) named
birds from the coastal mountains of Venezuela pallidus (including in that form AMNH476699 [type], FMNH91892, FMNH91893,
and four additional specimens in AMNH [2], British Museum and Frankfurt Museum)
and also described them as being very similar in plumage and tarsal feathering
to guatemalae. It would appear that pallidus is a valid taxon. Birds from
the coastal mountains vocalize similarly to birds from the eastern slope of the
Serranía de Perijá, and usually differ in both pitch and change of pitch from M. [guatemalae] roraimae. However, some
recordings of the two are indistinguishable suggesting that despite the
morphological differences, pallidus
may have been correctly referred to roraimae
by König et al. (1999).
“Analyses
of the material indicate no consistent vocal difference between M. [guatemalae] napensis and M. [guatemalae] roraimae. Differences
between them in plumage and slightly in proportions and tarsal feathering
(Chapman 1931) support the validity of the taxon napensis, but their similar vocalizations suggest that napensis was correctly ranked as a
subspecies of roraimae by Ridgely and
Greenfield (2001).”
Thus,
Krabbe (2017) provided persuasive evidence that both of Hekstra’s (1982) taxa, centralis and pallidus, were valid (they have ignored by many authorities,
including SACC, as per Proposal #12). Furthermore, by voice, Krabbe (2017)
provided strong evidence that M.
centralis (type locality in Darién, Panama) is deserving of species status
as it is the most different singer of all the M. guatemalensis complex. Using vocalizations to establish its
distribution, the points on the Xeno-canto map here
(https://www.xeno-canto.org/species/Megascops-centralis) do an adequate job
showing that it extends from the Canal Zone of Panama east into the lower
Magdalena valley of northern Colombia and south along the Pacific slope of the
Andes to southern Ecuador. Given that M.
vermiculatus is separated from South American taxa by the very distinctive M. centralis, and then the Andes, we
could provisionally consider it specifically distinct from them, and let the
NACC sort out the status of vermiculatus
with respect to M. guatemalae. Based on Krabbe’s (2017)
comments above, and my own impression of voice from listening to recordings
available on Xeno-canto, it seems that the best move for the remainder of the
South American M. guatemalae complex
(including roraimae, napensis, and pallida) is to retain them all in a
polytypic M. roraimae. Recordings
available here:
https://www.xeno-canto.org/species/Megascops-napensis
https://www.xeno-canto.org/species/Megascops-roraimae
https://www.xeno-canto.org/species/Megascops-vermiculatus
Analysis
and recommendation: There are two basic changes to be made here, so I will
split them into two votes:
A)
Based
on the above voice evidence, I think that the
separation of Megascops centralis
from the remainder of the M. guatemalae
complex is a given. It is a very distinctive bird compared to the remainder
of the group. If this is done, the English name Choco Screech-Owl has been applied to this taxon, and is appropriate.
I recommend a YES vote on this.
B)
Although the evidence is
less compelling, separate the remaining cis-Andean taxa of the complex
(roraimae, napensis, and pallida) from the Middle American
forms (guatemalae, hastatus, thompsoni, tomlini, cassini,
fuscus, dacrysistactus, and vermiculatus), as this makes sense from
a biogeographical standpoint. Whether to separate vermiculatus from the remainder of Middle American guatemalae is beyond the jurisdiction of
SACC. M. vermiculatus does sound
rather more like the roraimae group
than guatemalae does to my ear, but
with M. centralis intervening, I feel
comfortable not considering these disjunct taxa conspecific. Thus, I weakly
suggest a YES for this vote as well. If this passes, then the name with
priority is M. roraimae, and the English name Foothill Screech-Owl seems appropriate for the cis-Andean taxa, as
all are found in foothill elevations.
Literature
cited:
Dantas, S. M., J. D. Weckstein, J. M. Bates, N. K. Krabbe, C. D. Cadena,
M. B. Robbins, E. Valderrama, and A. Aleixo. 2016. Molecular systematics of the new world screech-owls (Megascops: Aves, Strigidae):
biogeographic and taxonomic implications. Molecular Phylogenetics and Evolution
94:626-634.
Hekstra, G.
P. 1982. Description of twenty-four new subspecies of American Otus (Aves, Strigidae). Univ. Amsterdam
Bull. Zool. Museum 9:49-63.
Krabbe, N. K. 2017.
A new
species of Megascops
(Strigidae) from the Sierra Nevada de
Santa Marta, Colombia, with notes on voices of New World screech-owls. Ornitología Colombiana 16: 1-27.
Marshall, J. T., R. A. Behrstock, and C. König. 1991.
Special review: Voices of the New World Owls (Strigiformes: Tytonidae,
Strigidae). The Wilson Bulletin 103:311-338.
Daniel Lane, January
2018
Note from Niels Krabbe: "I had left the specific information for a future
paper on the rank of vermiculatus,
but as Dan has let out the cat, I should inform that the sample labeled as vermiculatus in the Dantas et al. 2016
paper is indeed centralis. I had a
sample from a bird Tom Schulenberg and I collected after tape-recording it in
El Oro, Ecuador sequenced (GenBank KU521767), and (after removal of primer
remains) it matches the bird from the canal zone in Panama (KT799255)
perfectly, leaving no doubt they are the same taxon."
__________________________________________________________
Comments
from Stiles:
"A. YES, no problem here, given the definite vocal distinction and genetic
evidence. B. YES; Foothill Screech-Owl is a good name, and the biogeographical
situation also supports considering these as subspecies of roraimae rather than vermiculatus,
which would appear to be a separate, monotypic species (though that is
NACC’s decision)."
Comments
from Robbins:
"A. YES. As I pointed out in Proposal 12, the voice (now
readily available to all via online sources) of centralis is quite unique and it certainly deserves species status."
Comments from Areta: "A. YES. I had a hard time with
this one, until I asked Niels for more information to help dispel my doubts. My
central objections were as follows: "It is frequently the case that Megascops species have short and long
songs, and a plethora of little-studied and seldom-recorded calls. Although
vocal differences are certainly suggestive, I am not convinced that available
recordings of vermiculatus are of
vocalizations homologous to those of centralis.
What if those recordings by centralis
are of the short song and most recordings of vermiculatus of the long song? Why would these two taxa lack any
short and long song differentiation? Are they closely related to each other?
Note also that species in the same clade as "centralis", M.
guatemalae and roraimae/napensis, have the two song-types. If
Dantas et al. (2016) erred in identifying the sample of centralis as vermiculatus
as suggested by Dan, then we would be relying upon an apparently incomplete set
of vocalizations, and without DNA backup, to make this split." Niels
indicated that centralis is a
well-known species that never gives a longer song, which convinced me that the
comparisons between vermiculatus and centralis are good to support the split.
"B. A hesitant YES. It seems that
vocalizations of roraimae differ to
some extent from those of vermiculatus
and napensis. However, more thorough
vocal analyses of napensis, vermiculatus and roraimae and genetic data from vermiculatus
would be welcome to better understand species limits here."
Comments from Zimmer:
“YES. This one is a slam-dunk in my
opinion. The vocal distinctions between centralis and all taxa in the complex to
the north/west and south/east are diagnosable, substantial, and constant, and
do not reflect any inadequacies of sampling bias as questioned by Nacho. This one is overdue. B)
Recognize M. roraimae group as
a separate species. YES, on the
biogeographic grounds articulated by Dan in the Proposal – the range of vermiculatus/guatemalae is separated
from that of the roraimae-group by
the Andes and by the range of the vocally very different centralis.”
Comments
from Jaramillo:
“A YES - I would say a YES on Choco
Screech-Owl as the English name as well.
B
YES – And for English Name, Foothill Screech-Owl seems good.”:
Comments from Pacheco: “A) YES. The vocal distinctions between the
centralis and all taxa in the complex are relevant. B) YES. The proposed
arrangement is biogeographically coherent.”