Proposal
(738) to South American Classification Committee
Elevate Crypturellus
noctivagus zabele to species rank
Background: From SACC notes: “Tomotani and Silveira (2016) provided
evidence that the subspecies zabele
might merit treatment as a separate species from Crypturellus noctivagus.”
Pezus zabele Spix,
1825 (= Crypturellus noctivagus zabele)
was described as a separate species, but was later considered a synonym of noctivagus (Hellmayr 1906, Peters
1931). With more available material,
Hellmayr & Conover (1942) recognized two subspecies, reviving the name zabele for the inland northeastern
Brazilian birds and distinguishing them from nominate C. noctivagus (from the east and south Brazil) by an overall paler
color, a well-defined superciliary stripe, and broader bars in the wing-coverts
and remiges. They also noticed possible
sexual dimorphism in C. n. zabele.
Subsequently, all works (e.g. Blake 1977, Davies 2002) followed the taxonomy
proposed by Hellmayr & Conover (1942).
Regarding distributions, the two taxa
do not overlap. Crypturellus n. zabele
is endemic to the Caatinga, also marginally inhabiting the Cerrado, and occurs
in northeastern Brazil from Piauí to northwest Minas Gerais states, whereas C. n. noctivagus is endemic to the
Atlantic Forest, occurring from Bahia to Rio Grande do Sul states.
Consistent differences in plumage color
and pattern, morphometric characters, color of tarsus, egg color and egg shape
were found by Tomotani and Silveira (2016) after analyzing 67 skins of adult Crypturellus noctivagus, including the
holotypes of both taxa (i.e., the nominal noctivagus
and zabele), and 12 eggs.
The voice of C. n. zabele also seemed to have a slightly lower frequency than
that found in C. n. noctivagus, but
there was a great overlap between the two taxa (sample size: n = 10 for C. n. noctivagus, n = 5 for C. n. zabele; Tomotani and Silveira,
2016).
The overall plumage of C. n. zabele is paler than that of C. n. noctivagus and they also differ in
morphometric characters and egg shape and color. However, the most striking
differences appear when we compare the tarsus coloration and the females’ breast
plumage. These diagnostic characters are critical to the recognition of these
taxa as two distinct, independent lineages, which must be considered as
separated species under the Phylogenetic Species Concept (Tomotani and
Silveira, 2016).
It seems
to me that under the BSC the treatment must remain unchanged.
Literature
Cited:
Blake, E. R. 1977. Manual of Neotropical birds, v. 1.
Chicago: University of Chicago Press.
Davies, S. 2002. Ratites and tinamous (Bird families of the
world). Oxford: Oxford University Press.
Hellmayr, C. E. 1906. Revision der Spix´schen Typen brasilianischer Vögel.
Abhandlungen der Mathematisch-Physikalischen Klasse der Königlich Bayerischen
Akademie der Wissenschaften, 22: 561-726.
Hellmayr, C. E. and B. Conover. 1942. Catalogue of the birds
of the Americas and adjacent islands. Field Museum of Natural History,
Zoological Series, 13, pt. 1, 1-636.
Peters, J. L.
1931. Check-list of birds of the
world, vol. 1. Harvard University Press, Cambridge, Massachusetts.
Tomotani, B. M. and L. F. Silveira. 2016. A reassessment of
the taxonomy of Crypturellus noctivagus
(Wied, 1820). Revista Brasileira de Ornitologia, 24: 34-45.
Fernando Pacheco, January 2017
___________________________________________________________
Comments
from Remsen:
“NO. Absence of discrete vocal
differences suggests subspecies rank under BSC framework in Tinamidae. The number and quality of other differences,
however, suggests that this is one of those inevitable borderline cases.”
Comments
from Stiles:
“NO. The existence of the morphological variation cited in itself is sufficient
for recognition of zabele as a good
subspecies and perhaps as a phylogenetic species, but especially in tinamous,
divergence in vocalizations should also be evident, but Fernando notes much
overlap here, such that I agree with his assessment that under the BSC, its
status should not change.”
Comments
from Areta:
“NO. The
minor color differences in tarsi (olivaceus yellow in noctivagus, pure yellow in zabele),
plumage (paler in the dimorphic zabele)
and eggs (greenish in noctivagus,
bluish in zabele) and lack of
diagnostic vocal differences in these tinamous support their treatment at the
subspecific level.”
Comments from Zimmer: “NO. As
stated by Fernando, the vocalizations are not diagnosably different, which, I
would think, for evaluating species-limits in tinamous, would be a
deal-breaker. The stated plumage,
bare-parts and eggshell color differences are certainly worthy of being
recognized at the subspecific level, but no more, in my opinion. As regards Alvaro’s concerns about the
differences in habitat preferences between the two taxa: they may not be as different as it
sounds. I have always found zabele to be in the taller, more humid
micro-climates within the caatinga,
particularly in what might most properly be called mata-de-cípo, or vine forest, with lusher vegetation and, often,
with significant patches of terrestrial bromeliads. I don’t seem to find them in the really arid,
scrubby caatinga. At least in the southern part of its range, noctivagus seems to be most common in
some of the taller coastal restinga
woodland formations, growing on sandy soils, with dense understory growth, and
abundant terrestrial bromeliads. Even up
in Espírito Santo, near the northern limit of its range, the forest habitats
where I tend to find them most often, have a different, more stunted feel to
them, with a densely vegetated understory and seemingly growing on poorer
soils. So, there are some distinctions,
yes, but they are perhaps subtler than implied by caatinga/cerrado versus mata
Atlantica.”
Comments
from Jaramillo:
“NO ... although, I am most troubled though by the difference in habitat of the
two forms. A major habitat shift like this seems unusual in a subspecies, but
then again, there just may not have been enough time since the shift, for
biological species level differences to evolve.”
Comments
from Claramunt:
"NO. The photographs show striking differences
between specimens of noctivagus and zabele but
the analysis of character variations suggest more overlap and intermediate
phenotypes (Table 2). The most distinctive characters are tarsus color but were
assessed in an unknown subsample of the skins examined, and lack of solid gray
breast in females, but sample size is low (three female zabele skins).
In addition to a larger sample of the most diagnostic traits, what is missing
is an analysis of the geographic variation of characters and an analysis of
potential intermediate individuals. That analysis could demonstrate whether noctivagus
and zabele maintain phenotypic integrity in multiple traits despite
parapatry (suggesting reproductive isolation) or, alternatively, represent an
intraspecific cline associated with a strong environmental gradient."
Comments
from Robbins:
"NO. The lack of vocal differentiation is my main concern. Also,
points made by Claramunt need to be addressed before elevating this to species
rank."
Comments
from Cadena:
“NO. I agree that differences might be
sufficient to recognize diagnosable taxa (i.e. phylogenetic species), but I see
no compelling evidence to recognize these taxa as distinct reproductively
isolated populations.