osteology
Osteology () is the scientific study of bones, practised by osteologists. A subdiscipline of anatomy, anthropology, and paleontology, osteology is the detailed study of the structure of bones, skeletal elements, teeth, microbone morphology, funct ...
and
biogeography
Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, ...
data concluding that the
wattled guan
The wattled guan (''Aburria aburri'') is a species of bird in the family Cracidae. It is a fairly large black cracid with blue-based, black-tipped beak and a long, red-and-yellow Wattle (anatomy), wattle.
It is found in Colombia, Ecuador, Peru, ...
belongs in the same genus as these and is a hypermelanistic piping guan. Thus, ''Pipile'' became a
junior synonym
The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently.
* In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...
of ''Aburria'', though this conclusion was not accepted by the South American Checklist Committee, or evaluated by the IOC, so the classification remains in Pipile.
The same results also showed that the light-faced taxa ''pipile, cumanensis'' and ''cujubi'' are not, as was sometimes suggested, conspecific. However, free interbreeding between '' A. cujubi'' and '' A. cumanensis grayi'' in eastern Bolivia, creating a "hybrid swarm", casts doubt on this conclusion for the two species named.
It was possible to confidently resolve that the white-faced species form a
clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
, whereas the more basal black-faced forms are of less certain relationship. Possibly, the black-fronted piping guan is the
basalmost
In phylogenetics, basal is the direction of the ''base'' (or root) of a rooted phylogenetic tree or cladogram. The term may be more strictly applied only to nodes adjacent to the root, or more loosely applied to nodes regarded as being close to th ...
wattled guan
The wattled guan (''Aburria aburri'') is a species of bird in the family Cracidae. It is a fairly large black cracid with blue-based, black-tipped beak and a long, red-and-yellow Wattle (anatomy), wattle.
It is found in Colombia, Ecuador, Peru, ...
in regard to its congeners is not all too well resolved. Blue wattles evolved only once, in a lineage which seems to have originated north of the
Amazon River
The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in South America is the largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the Nile.
The headwaters of t ...
. The piping guans'
radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:
* ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
began in the latter half of the Early Pliocene, roughly 4–3.5
mya
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Brands and product names
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Codes
* Burmese ...
. The white-faced lineage emerged around 3 mya and its present diversity began to evolve around the Pliocene- Pleistocene boundary, when the ancestors of the red-throated piping guan and the blue-wattled taxa split. Due to not being calibrated by material evidence such as fossils, the divergence times cannot be estimated with a high confidence.
The origin of the genus was possibly in the general area of eastern
Bolivia
, image_flag = Bandera de Bolivia (Estado).svg
, flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center
, flag_alt2 = 7 × 7 square p ...
, at the very margin of its current range. From the phylogeny outlined above, the piping guans would be expected to have originated in the southern Brazilian lowlands. However, although the relationships of the genera of guans are not entirely clear, it seems most likely that the group originated in the northern Andes region: The northernmost guan genera '' Chamaepetes'' and '' Penelopina'' appear to be basal divergences, and ''Pipile'' is most likely closer to '' Penelope'' (which represents a generally southward radiation out of the northern Andes) than to these.
Thus it appears most likely that the present genus diverged in the eastern foothills of the Andes somewhere in the vicinity of Bolivia, far to the northwest from where its origin would be presumed from the phylogeny and present-day distribution of ''Pipile'' alone. Two considerations are worthy of note: First, the time at which the ancestor of the piping guans diverged from ''Penelope'' has been roughly dated to the Burdigalian, some 20-15 mya, which leaves a considerable gap during which no surviving piping guan lineage evolved. Secondly, it is notable that in the Late Pliocene, rising sea levels transformed much of the South American lowlands into brackish lagoon habitat unsuitable for piping guans. Thus, the present distribution is apparently a relict, and extinction of populations/displacement by the more resilient ''Penelope'' guans seems to have played as much or possibly more of a role in shaping the diversity of piping guans of our time than emergence of new lineages.