Proposal
(733) to South American Classification Committee
Elevate Zentrygon
linearis trinitatis to species rank
Effect on SACC list: if passed, this
proposal would add a species, Zentrygon
linearis, to the SACC list.
Background: Hellmayr & Seilern (1912) described Geotrygon linearis trinitatis
from the island of Trinidad, but this form was generally considered to be
indistinguishable from nominate linearis
(Mlíkovský 2016 and references therein). Chapman
(1914) described Geotrygon pariae
from the Península de Paria in Venezuela, but later
demoted it to a subspecies in subsequent publications (see Hellmayr &
Conover 1942 for a thorough synonimic list). Birds
from Trinidad, Tobago, Paria Peninsula, and the Turimiquire massif were
considered to belong to trinitatis by
Hellmayr & Conover (1942). Note that Mlíkovský
(2016) preferred to keep linearis in Geotrygon. I am here following the SACC
placement of linearis in Zentrygon.
New information: Mlíkovský
(2016) reviewed the taxonomy of Geotrygon
linearis trinitatis Hellmayr & Seilern 1912
by examining plumage features and measurements of museum specimens. His data
indicate that trinitatis is
diagnosable from nominotypical linearis
(see Figure 1 and Table 1 below), which led the author to propose full species
status for the former.
Recommendation: I agree in that trinitatis is diagnosable from linearis by its smaller size and
different nape color. I am less convinced that this automatically should be
considered as indicative of species status. Given the large number of
subspecies currently recognized within linearis,
I would like to see a comparative study that would help us have a better grasp
of how species-level taxa would look and sound. For example, my recordings of infusca from the
Santa Marta Mountains, nominate linearis
from the Andes of Lara in Venezuela, and trinitatis
from Paria suggest vocal differences, but a formal study is needed to address
consistency and diagnosability in vocal features relevant to mate choice. I
recommend a NO vote.
Table 1. Comparison of plumage
and morphometric data between Zentrygon
linearis linearis and Z. linearis trinitatis. Data extracted from Mlíkovský
(2016).
Taxa |
Wing-length (mm) |
Bill-length (mm) |
Bill-depth (mm) |
Nape color |
linearis |
all:
149-160 (8) males:
150-156 (4) females:
149 (1) |
15.8-17.7
(3) |
4.6-5.1
(3) |
Bronze |
trinitatis |
all:
140-150 (8) males:
140-150 (5) females:
139-146 (3) |
14.0-14.4
(2) |
4.2-4.6
(2) |
Dark
gray |
Figure 1. Comparison of
specimens of Zentrygon linearis linearis (two on the left) and Z. linearis trinitatis (two on the right). Pictures taken from
Figures 1 and 2 in Mlíkovský (2016).
References
CHAPMAN, F. M. 1914. Descriptions of a new genus and species
of birds from Venezuela. Bulletin of the American Museum of Natural History 33:
193-197.
HELLMAYR, C. E., AND B. CONOVER. 1942. Catalogue of birds
of the Americas. Field Museum Nat. History Publ., Zool. Ser., vol. 13., pt. 1,
no. 1.
HELLMAYR, C.E. AND SEILERN, J. VON 1912. [Description of
two new subspecies: Grallaria
guatimalensis aripoensis and Geotrygon linearis [sic] from the Island of Trinidad]. Bulletin of
the British Ornithologists’ Club 31: 13- 14
MLÍKOVSKÝ, J. 2016. Taxonomic status of Geotrygon linearis trinitatis Hellmayr
& Seilern, 1912 (Aves, Columbidae). Spixiana 39: 141-144.
Nacho Areta,
November 2017
___________________________________________________________
Comments
from Remsen:
“NO. Although this was a nice
contribution by Mlíkovský to validate that trinitatis is a diagnosable taxon and thus a valid subspecies, no
information is presented concerning species limits under BSC, e.g. for
allopatric taxa, a comparative analysis of differences in taxa ranked as
species vs. subspecies in Zentrygon
and relatives. Given the body mass
difference, I would not be surprised that the physics of sound production alone
produces a voice of a different pitch.
Anyway, clearly more data are needed.”
Comments
from Stiles:
“NO. Although the morphological and plumage differences do support ranking trinitatis as a diagnosable phylogenetic
species, I think that data on vocalizations (and hopefully, genetics) would be
necessary to establish it as a biological species. Again, a detailed analysis
of the various taxa currently in linearis
is definitely needed.”
Comments
from Pacheco:
“NO. The available information does not allow the treatment of full species
under the BSC.”
Comments
from Robbins:
"NO, for reasons pointed out in Nacho’s proposal."
Comments
from Stotz:
“NO, based on arguments presented in the proposal.”
Comments
from Jaramillo:
“NO. An analysis of voice would be
useful in this case. While he is at it, he should look into tobagensis White-tipped Dove,
which looks and sounds different to my eyes and ears.”
Comments
from Claramunt:
“NO.
Size differences and multiple plumage trait differences suggest species-level
differentiation but potential clinal variation cannot be ruled out without
seeing a detailed analysis of phenotypic variation.”