Proposal (659) to South American Classification Committee
Elevate Xiphorhynchus fuscus atlanticus to species rank
Effect
on SACC: This proposal, if
passed, would split the Lesser woodcreeper Xiphorhynchus fuscus into two
species (X. fuscus and X. atlanticus).
Background: The Lesser Woodcreeper Xiphorhynchus
fuscus Vieillot (1818) inhabits the Atlantic forest of Brazil, eastern Paraguay
and Argentina (Misiones), from sea level up to about 1200 m.a.s.l. There are
four subspecies: atlanticus, brevirostris (also known as pintoi),
tenuirostris and the nominal subspecies. Subspecies atlanticus is
restricted to northeastern Brazil, to regions north to the Rio São Francisco
(states Piauí, Ceará, Rio Grande do Norte, Pernambuco, Alagoas and Sergipe).
Specifically, it inhabits the rainforests of the coastal range, and of the
isolated tops of humid highlands surrounded by dry forests (Caatinga).
According
to a mitochondrial and nuclear genetic study, only the subspecies atlanticus
is monophyletic (Cabanne et al., 2008). Also, atlanticus is the only subspecies
isolated genetically and geographically. Besides, subspecies atlanticus is
considered to differ by song, but there is not published a formal study on it
(Cabanne in prep). According to this
background, atlanticus is considered a full species by some taxonomic
authorities, such as the Brazilian list of birds (Comitê Brasileiro de
Registros Ornitológicos, 2014).
New
information:
Cabanne
et al 2014 studied body size and plumage color of populations of X. fuscus and
found that atlanticus can be differentiated by plumage (Fig. 3 and 5 of
cited paper) and body size (Fig. 6 and 8 of cited paper), which is complemented
with the previous genetic results showing that the population is genetically
isolated (Cabanne et al., 2008). Subspecies atlanticus is the
darkest and most brownish population and the only one presenting plain
undertail coverts. The other subspecies have striated undertail covers. In
relation to body size, X. fuscus atlanticus represents the population
with the largest birds. The other populations have a bill 7.5% to 14% smaller
than in atlanticus, as well as wing and tail length 5% to 10% smaller
and tarsi 2.5% to 9% smaller than the ones found in atlanticus.
Recommendation:
I
recommend elevating subspecies atlanticus to species rank. Cabanne et al.
(2014) concluded that the subspecies could be considered an independent
evolutionary lineage and a full species according to the General Lineage
Concept, the Biological concept and the phylogenetic species concept. The
population is genetically isolated, and diagnosable by plumage and body size
characters.
If
passed, the English name of the Xiphorhynchus atlanticus could be
Northern Lesser Woodcreeper.
Literature
Cited:
Cabanne GS, Trujillo-Arias N, Calderón L, D’Horta
F M, Miyaki CY. 2014. Phenotypic evolution of an Atlantic Forest passerine (Xiphorhynchus
fuscus): biogeographic and systematic implications. Biological Journal
of the Linnean Society, Early view, DOI:10.1111/bij.12362.
Cabanne GS, d'Horta FM, R. Sari EH,
Santos FR, and Miyaki CY. 2008. Nuclear and mitochondrial phylogeography of the
Atlantic forest endemic Xiphorhynchus fuscus (Aves: Dendrocolaptidae):
biogeography and systematics implications. Molecular Phylogenetics and
Evolution 49: 760-773.
Comitê Brasileiro de Registros
Ornitológicos (2014) Listas das aves do Brasil. 11ª Edição. Available
at <http://www.cbro.org.br>.
Accessed: November 15, 2014.
Gustavo Sebastián
Cabanne (November 2014)
_________________________________________________________________
Comments
solicited from Curtis Marantz: “My personal experience with Xiphorhynchus fuscus is relatively
limited, but I have seen and heard both X.
f. atlanticus and at least one and possibly more of the more southerly
occurring populations. I have also seen the earlier paper by Cabanne and
I have spoken with him about this subspecies, but I have not read the more
recent publication. Based on my experience, I would say that the northern birds
do look and sound rather different from the southern birds, and my
recollection of the paper on genetic differentiation is that Cabanne did a good
job of showing the genetic differentiation of this taxon, which may indeed
represent a full species based on the Biological Species Concept.
However, I cannot now recall just how different the vocalizations of
these birds are from the southern populations, and I would suggest that without
a quantitative analysis of the vocalizations, it would be premature to
elevate X. f. atlanticus to a full
species based on the BSC. If such a vocal analysis is in preparation, I
recommend holding off on making any decisions about this split until said
analysis has been completed. Moreover, vocal variation is marked in other
species of Xiphorhynchus, some of which
also have larger repertoires than do many suboscines, so any vocal analysis
should include at least moderately large numbers of songs from multiple
individuals in each population. At present, the genetic and morphological
analyses really only indicate, in my opinion, a well-defined
and geographically isolated subspecies, so in the absence of work on
interbreeding in a zone of contact a vocal analysis would be an important
requirement for making a taxonomic change at the species level.”
Comments
from Nores: “NO, for now. I agree with Marantz that is
rather a well-defined and geographically isolated subspecies. If such a vocal
analysis is in preparation, I hope to see the results before making any
decisions about this split.”
Comments
from Zimmer: “NO. Let me start by saying that I believe Cabanne
is correct in his assertion that atlanticus
is deserving of recognition as a species distinct from the rest of the fuscus-group under even the BSC. It differs both vocally and morphologically
from all other populations of “Lesser Woodcreepers”. I also believe that a comprehensive vocal
analysis will reveal a significant split between nominate fuscus and tenuirostris. However, Curtis Marantz is also correct in
pointing out that we still haven’t seen any kind of published, comprehensive
vocal analysis of this group, and without that, we are left only with genetic
distance and consistent, but minor morphological variation involving allopatric
populations. Because the prevailing SACC
philosophy has been to require peer-reviewed, published analyses before making
proposed changes, then, in the absence of such a published analysis, I feel
that I have to vote NO, even though I really feel that Cabanne has it right.”
Comments
from Remsen: “NO –
Kevin’s comments mirror mine exactly.
This seems to be a split that needs one more paper to support it.”
Comments from Robbins: “NO for now. However, that tentative decision is not
because of the genetic and morphological data, which do support recognition;
however, no vocal data are presented. As
I’ve made abundantly clear to this committee, I don’t need to see a summary of
the vocal data in print, but I do want those data referenced via online sources
so that everyone is looking at the same data set. So, I’m fine with the author and the sponsor
of this proposal presenting those via online resources.”
Comments
from Areta: “NO
until the vocal analysis is published. I have been struck by the vocal
differences between birds in Misiones (Argentina, southern fuscus) and those at Ilha Grande (Rio de Janeiro, Brazil,
apparently northern fuscus) and I
have recorded both taxa extensively. Based
on genetic data, it seems like the clade brevirostris-tenuirostris,
northern fuscus and southern fuscus might all merit full species
status together with atlanticus. Until the taxonomy of the complex is solved, I
feel uncomfortable splitting just one taxon based only on plumage and genetic
data.”
Comments from Cadena: “NO for now. Let's
revisit this once vocal analyses have been completed and published on. We have
tons of cases of lowland birds showing marked genetic divergence coupled with
phenotypic diagnosability across barriers and we do not treat these as separate
species unless it can been shown they also differ in traits relevant to species
recognition/mating.”
Comments from Stiles: “NO for now, until the vocal data are
published.”
Comments
from Stotz: “NO. Will need to
see the vocal data, but I think likely there are multiple species here.”