The guans are a number of bird

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

which make up the largest group in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Cracidae The chachalacas, guans and curassows are birds in the family Cracidae. These are species of tropical and subtropical Central and South America. The range of one species, the plain chachalaca, just reaches southernmost parts of Texas in the Unite ...

. They are found mainly in northern

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

, southern

Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...

, and a few adjacent

Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...

islands. There is also the peculiar

horned guan The horned guan (''Oreophasis derbianus'') is a large, turkey-like bird native to Central America. It is the only species in the genus ''Oreophasis''. Taxonomy The holotype specimen of "''Oreophasis Derbianus'' " G.R. GrayGen. Bds., 3, 1844, p. ...

(''Oreophasis derbianus'') which is not a true guan, but a very distinct and ancient cracid with no close living relatives (Pereira ''et al.'' 2002).

Systematics and evolution

The

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

of the group is fairly well resolved due to comprehensive analyses of

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

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, ...

, and mt and

nDNA Nuclear DNA (nDNA), or nuclear deoxyribonucleic acid, is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA and plastid DNA coding for the rest. I ...

sequence In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is calle ...

s (Pereira ''et al.'' 2002, Grau ''et al.'' 2005). The position of ''Penelopina'' and ''Chamaepetes'' - peculiar genera of which the former, uniquely among guans and more in line with

curassow Curassows are one of the three major groups of cracid birds. They comprise the largest-bodied species of the cracid family. Three of the four genera are restricted to tropical South America; a single species of ''Crax'' ranges north to Mexico. ...

s, shows pronounced

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

- relative to each other is not determinable with certainty at present, but all evidence suggests that they are 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 ...

guans. Their distribution is fairly far northwards, with 2 of their 3 species living in

. This indicates that the guans' origin is in the northern

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

region, in the general area of

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

or perhaps

Ecuador Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ''Eku ...

; the date of their initial radiation is not well resolved due to the lack of

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

evidence but can be very roughly placed around 40–25 mya (

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

, perhaps some time earlier). The two basal lineages diverged during the

Burdigalian The Burdigalian is, in the geologic timescale, an age (geology), age or stage (stratigraphy), stage in the early Miocene. It spans the time between 20.43 ± 0.05 annum, Ma and 15.97 ± 0.05 Ma (million years ago). Preceded by the Aquitanian (sta ...

, around 20–15 mya.(Pereira ''et al.'' 2002) The two larger genera diverged around the same time, spreading mainly southwards all over tropical South America in the process (Pereira ''et al.'' 2002). It appears as if the present-day distribution of the piping-guans is much

relict A relict is a surviving remnant of a natural phenomenon. Biology A relict (or relic) is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas. Geology and geomorphology In geology, a r ...

ual, due to

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

s fragmenting lowland habitat. ''Aburria'' were apparently being driven into refugia of suitable

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

time and again during the

Late Pliocene Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...

by a combination of this and, possibly, competition with the more diverse and generally more adaptable ''Penelope'' (Grau ''et al.'' 2005). If taken as a subfamily, the group also includes the

chachalaca Chachalacas are galliform birds from the genus ''Ortalis''. These birds are found in wooded habitats in the far southern United States (Texas), Mexico, and Central and South America. They are social, can be very noisy and often remain fairly c ...

s, but the horned guan is excluded and found in its monotypic subfamily.

Genera and species

References

* , Richard; O'Neill, John Patton & Eckelberry, Don R. (1991): ''A guide to the birds of Trinidad and Tobago'' (2nd edition). Comstock Publishing, Ithaca, N.Y.. * Grau, Erwin T.; Pereira, Sérgio Luiz; Silveira, Luís Fábio; Höfling, Elizabeth & Wanjtal, Anita (2005): Molecular phylogenetics and biogeography of Neotropical piping guans (Aves: Galliformes): ''Pipile'' Bonaparte, 1856 is synonym of ''Aburria'' Reichenbach, 1853. ''Molecular Phylogenetics and Evolution'' 35: 637–645. PDF fulltext
* Pereira, Sérgio Luiz; Baker, Allan J.& Wajntal, Anita (2002): Combined nuclear and

mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

sequences resolve generic relationships within the Cracidae (Galliformes, Aves). ''Systematic Biology'' 51(6): 946–958. PDF fulltext
{{DEFAULTSORT:Guan (Bird) Cracidae pl:Penelopy