Download Proposal to South American Classification Committee

Recognize Icterus pyrrhopterus as a separate species from
Icterus cayanensis
Proposal (418) to South American Classification Committee
The southern populations of the Icterus cayanensis complex occur
mostly south of the Amazon and comprise four named subspecies
(pyrrhopterus, tibialis, periporphyrus, and valencio-buenoi). The four
southern subspecies are here proposed to constitute a separate species,
with the scientific name Icterus pyrrhopterus Vieillot 1819 (based on Azara
No. 74), type locality Paraguay. The name pyrrhopterus has nomenclatural
priority over the other three. The combination Icterus pyrrhopterus (or
Xanthornus pyrrhopterus) has been widely used in the past, and well into
the 20th century.
(A problem outside this proposal refers to the specific status of the
two Amazonian populations Icterus cayanensis and I. chrysocephalus,
regarded as conspecific in Blake [1966] and in SACC.)
Arguments for the species recognition of the southern pyrrhopterus
populations include:
a) DNA data show the southern groups to be reciprocally
monophyletic with the Amazonian groups, with no evidence of hybridization
(D´Horta et al. 2008, Omland et al. 1999, Sturge et al. 2009).
b) Although in the map of D´Horta et al. (2008) nominate Amazonian
form cayanensis and pyrrhopterus are shown as allopatric, field data from
Beni, Bolivia, indicate local coexistence of both forms, at least during
October-November (austral spring). Populations separated by only 4 km
show characters of nominate cayanenis, or pyrrhopterus. No intermediate
individuals are reported (data of B. Hennessey and S. Herzog, published in
Jaramillo and Burke 1999). This coexistence could be explained by
northward seasonal movements of pyrrhopterus populations. However,
pyrrhopterus appears resident in Argentina at least as far south as Buenos
Aires province (Narosky and Di Giacomo 1993). Also, during the late
austral winter (August-September), pairs or small groups of pyrrhopterus
commonly visit blooming Tabebuia trees throughout northern Argentina and
Paraguay (Fraga in press). If some northward movement occurs, it should
have ended by this time.
c) The southern group differs from both Amazonian forms cayanensis
and chrysocephalus in being smaller in size, and having a more slender
body shape and more acrobatic feeding habits (D´Horta et al. 2008, Fraga
in press).
d) Habitat preferences for the southern pyrrhopterus group are broad
and include forest and woodland edges (even in dry woodland), clearings,
savannas, plantations, parks, gardens, and towns (D´Horta et al. 2008,
Fraga in press.). Breeding occurs up to 1700 m in northwestern Argentina,
probably higher up in Bolivia. Populations of pyrrhopterus are usually
abundant, and the species is currently expanding its range and numbers
west and south in Argentina (Fraga in press). The Amazonian groups
chrysocephalus and cayanensis prefer palm groves of Mauritia flexuosa
growing in swampy ground, or edges and canopy of humid forest (D´Horta
et al. 2008). Both Amazonian forms are often described as local or
uncommon (Hilty 2003).
Intraspecific variability within pyrrhopterus
D´ Horta et al. (2008) apply pure cladistic criteria and split pyrrhopterus and
tibialis as two phylogenetic species (besides questioning the validity of the
two other southern subspecies, a subject outside this proposal). As to their
main point, their analysis shows a huge area of intermediate specimens
(estimated in 2,915, 400 km2) connecting tibialis and pyrrhopterus in
eastern Brazil, making these two forms invalid species under the biological
species concept. Besides the huge intergrading zone, the habitat
preferences of tibialis and pyrrhopterus are quite similar (D´Horta et al.
2008), and the same applies to nesting behavior (Fraga in press).
Proposed English name for Icterus pyrrhopterus
The proposed English name for Icterus pyrrhopterus is Variable Oriole.
The name makes reference to the considerable geographic variation in
plumage. Individuals showing plumage variation may even occur far from
the ranges of others subspecies, as observed by D´Horta et al. (2008).
References
Blake E. R. 1968. Family Icteridae. Pp. 138–202 in: Paynter R. A. Jr. (ed.)
Check-list of birds of the World, vol. 14. Museum of Comparative Zoology,
Cambridge, MA.
D´Horta, F. M., J. M. Cardoso da Silva, and C. C. Ribas. 2008. Species
limits and hybridization zones in Icterus cayanensis–chrysocephalus group
(Aves: Icteridae). Biological Journal of the Linnean Society 95: 583–597.
Fraga, R. M. in press (or 2011). Family Icteridae. In Handbook of the Birds
of the World, Vol. 16. Lynx Edicions, Barcelona.
Hilty, S. 2003. Birds of Venezuela. Princeton Univ. Press. Princeton NJ.
Jaramillo, A., and P. Burke. 1999. New World blackbirds. The Icterids. A. &
C. Black Publishers, London.
Narosky, T. and A. Di Giacomo. 1993. Las aves de la provincia de Buenos
Aires, distribución y estatus. Vázquez Mazzini Editores, Buenos Aires.
Omland, K. E., S. M. Lanyon and S. J. Fritz. 1999. A molecular phylogeny
of the New World orioles (Icterus): the importance of dense taxon sampling.
Molecular Phylogenetics and Evolution 12:224-239.
Sturge, R., F. Jacobsen, B. B. Rosensteel, R. J. Neale and K. E. Omland.
2009. Colonization of South America from Caribbean Islands confirmed by
molecular phylogeny with increased taxon sampling. Condor 11: 575-579.
Rosendo M. Fraga, October 2009
Comments from Zimmer: “YES. Molecular evidence shows the two to be
reciprocally monophyletic, they assortatively mate without evidence of
hybridization in the narrow zone of overlap, and there are diagnosable
morphological differences (both in plumage and biometrics). The two
populations are also known to differ ecologically. The authors do not really
address vocal differences, but in my experience, these are also pretty
pronounced.”
Comments from Jaramillo: “YES. I recall we implied that cayanensis was
likely more closely related to chrysocephalus in our Icterid book. Apart from
plumage and habitat differences, most compelling at the time at least in
terms of separating cayanensis from pyrrhopterus was this area of possible
sympatry in Bolivia. Now new information is available that clarifies that
separating cayanensis and pyrrhopterus is a good course of action. An
open question is what the relationship between cayanensis and
chrysocephalus is.”
Comments from Robbins: “YES. All the available data support the
recognition of the southern pyrrhopterus as a species distinct from the
Amazonian and northern forms.”
Comments from Stiles: “YES, for reasons well summarized by Fraga and
other committee members. As an aside, the pronounced geographic
variation within pyrrhopterus should invite caution in splitting cayanensis
and chrysocephalus without strong evidence suggesting reproductive
isolation.”
Comments from Nores: “YES. Los análisis molecular de Omland et al. con
dos diferentes vías (citocromo b y ND2) muestran claramente que son dos
especies diferentes. Importante también es que hay una zona de
superposición sin hibridisación.”
Comments from Remsen: “YES. Although better resolution on potential
contact areas is desirable, I’d say that available data places burden-ofproof on conspecificity. I would note, however, that Chendo’s reason “d” is
virtually irrelevant. Widespread species tpyically have narrower habitat
distributions where they occur in Amazonia (e.g., Vireo olivaceus).
Geographic variation in habitat preference and relative abundance is a
widespread aspect of the biology of many species for which there is no
indication that more than one species is involved. I also worry about true
sympatry (breeding) vs. seasonal sympatry due to movements by
pyrrhopterus types.”