The Sibley–Ahlquist taxonomy is a
bird
Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
taxonomy
image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy
Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...
proposed by
Charles Sibley and
Jon E. Ahlquist. It is based on
DNA–DNA hybridization studies conducted in the late 1970s and throughout the 1980s.
DNA–DNA hybridization is among a class of comparative techniques in
molecular biology
Molecular biology is a branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, biomolecular synthesis, modification, mechanisms, and interactio ...
that produce distance data (versus character data) and that can be analyzed to produce phylogenetic reconstructions only using
phenetic tree-building algorithms. In DNA–DNA hybridization, the percent similarity of DNA between two species is estimated by the reduction in
hydrogen bonding
In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ...
between
nucleotides
Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...
of imperfectly complemented heteroduplex DNA (i.e., double stranded DNAs that are experimentally produced from single strands of two different species), compared with perfectly matched homoduplex DNA (both strands of DNA from the same species).
Characteristics
The classification appears to be an early example of
cladistic classification because it codifies many intermediate levels of taxa: the "trunk" of the family tree is the class
Aves
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight ...
, which branches into subclasses, which branch into infraclasses, and then "parvclasses", superorders, orders, suborders, infraorders, "parvorders", superfamilies, families, subfamilies, tribes, subtribes and finally genera and species. However the classification study did not employ modern cladistic methods, as it relies strictly on DNA-DNA hybridization as the sole measure of similarity.
The Sibley–Ahlquist arrangement differs greatly from the more traditional approach used in the
Clements taxonomy.
Showing major changes from Clements, the Sibley–Ahlquist orders are as follows:
* Enlarged Struthioniformes replaces the
ratite
Ratites () are a polyphyletic group consisting of all birds within the infraclass Palaeognathae that lack keels and cannot fly. They are mostly large, long-necked, and long-legged, the exception being the kiwi, which is also the only nocturnal ...
orders Rheiformes (
rheas), Casuariiformes (
cassowaries and
emu
The emu (; ''Dromaius novaehollandiae'') is a species of flightless bird endemism, endemic to Australia, where it is the Tallest extant birds, tallest native bird. It is the only extant taxon, extant member of the genus ''Dromaius'' and the ...
s), and Apterygiformes (
kiwis) and Struthioniformes (
ostriches).
* Tinamiformes (
tinamous) is unchanged.
* A greatly enlarged Ciconiiformes includes the previous Sphenisciformes (
penguin
Penguins are a group of aquatic flightless birds from the family Spheniscidae () of the order Sphenisciformes (). They live almost exclusively in the Southern Hemisphere. Only one species, the Galápagos penguin, is equatorial, with a sm ...
s), Gaviiformes (
divers), Podicipediformes (
grebe
Grebes () are aquatic diving birds in the order (biology), order Podicipediformes (). Grebes are widely distributed freshwater birds, with some species also found in sea, marine habitats during Bird migration, migration and winter. Most grebes f ...
s), Procellariiformes (
tubenoses), Pelecaniformes (
pelican
Pelicans (genus ''Pelecanus'') are a genus of large water birds that make up the family Pelecanidae. They are characterized by a long beak and a large throat pouch used for catching prey and draining water from the scooped-up contents before ...
s and allies), Ciconiiformes (
stork
Storks are large, long-legged, long-necked wading birds with long, stout bills. They belong to the family Ciconiidae, and make up the order Ciconiiformes . Ciconiiformes previously included a number of other families, such as herons and ibise ...
s and allies), Falconiformes (
birds of prey
Birds of prey or predatory birds, also known as (although not the same as) raptors, are hypercarnivorous bird species that actively predation, hunt and feed on other vertebrates (mainly mammals, reptiles and smaller birds). In addition to speed ...
), Charadriiformes (
wader
245px, A flock of Red_knot.html" ;"title="Dunlins and Red knot">Dunlins and Red knots
Waders or shorebirds are birds of the order Charadriiformes commonly found wikt:wade#Etymology 1, wading along shorelines and mudflats in order to foraging, ...
s,
gull
Gulls, or colloquially seagulls, are seabirds of the subfamily Larinae. They are most closely related to terns and skimmers, distantly related to auks, and even more distantly related to waders. Until the 21st century, most gulls were placed ...
s,
terns, and
auk
Auks or alcids are birds of the family Alcidae in the order Charadriiformes. The alcid family includes the Uria, murres, guillemots, Aethia, auklets, puffins, and Brachyramphus, murrelets. The family contains 25 extant or recently extinct speci ...
s), and the family Pteroclidae (
sandgrouse
Sandgrouse is the common name for Pteroclidae (), a family (biology), family of sixteen species of bird, members of the order Pterocliformes (). They are traditionally placed in two Genus, genera. The two central Asian species are classified as ...
).
* Anseriformes (
duck
Duck is the common name for numerous species of waterfowl in the family (biology), family Anatidae. Ducks are generally smaller and shorter-necked than swans and goose, geese, which are members of the same family. Divided among several subfam ...
s and allies) is unchanged.
* Modified Galliformes landfowl. Chachalacas moved to Craciformes.
* New Craciformes
chachalacas etc. Previously part of Galliformes.
* Modified Gruiformes
Cranes. Button-quails moved to Turniciformes.
* New Turniciformes
button-quails etc. Previously part of Gruiformes.
* Modified Columbiformes
doves. Sandgrouse moved to Ciconiiformes.
* Psittaciformes
cockatoo
A cockatoo is any of the 21 species of parrots belonging to the family Cacatuidae, the only family in the superfamily Cacatuoidea. Along with the Psittacoidea ( true parrots) and the Strigopoidea (large New Zealand parrots), they make up t ...
s and
parrot
Parrots (Psittaciformes), also known as psittacines (), are birds with a strong curved beak, upright stance, and clawed feet. They are classified in four families that contain roughly 410 species in 101 genus (biology), genera, found mostly in ...
s unchanged.
* New Musophagiformes
turacos. Previously part of Cuculiformes.
* Modified Cuculiformes
cuckoo
Cuckoos are birds in the Cuculidae ( ) family, the sole taxon in the order Cuculiformes ( ). The cuckoo family includes the common or European cuckoo, roadrunners, koels, malkohas, couas, coucals, and anis. The coucals and anis are somet ...
s. Turacos moved to Musophagiformes.
* Modified Strigiformes
owls. Enlarged to include Caprimulgiformes (
nightjar
Nightjars are medium-sized nocturnal or crepuscular birds in the family Caprimulgidae and order Caprimulgiformes, characterised by long wings, short legs, and very short bills. They are sometimes called bugeaters, their primary source of food ...
s, owlet-nightjars, frogmouths, oilbirds, potoos).
* Modified Apodiformes
swift
Swift or SWIFT most commonly refers to:
* SWIFT, an international organization facilitating transactions between banks
** SWIFT code
* Swift (programming language)
* Swift (bird), a family of birds
It may also refer to:
Organizations
* SWIF ...
s. Hummingbirds moved to Trochiliformes.
* New Trochiliformes
hummingbird
Hummingbirds are birds native to the Americas and comprise the Family (biology), biological family Trochilidae. With approximately 366 species and 113 genus, genera, they occur from Alaska to Tierra del Fuego, but most species are found in Cen ...
s. Previously part of Apodiformes.
* Coliiformes
mousebirds unchanged.
* Trogoniformes
trogons unchanged.
* Modified Coraciiformes
rollers.
* New Upupiformes
Hoopoe. Previously part of Coraciiformes.
* New Bucerotiformes
hornbills. Previously part of Coraciiformes.
* New Galbuliformes
jacamars and
puffbirds. Previously part of Piciformes.
* Modified Piciformes
woodpeckers
* Passeriformes
perching bird
A passerine () is any bird of the Order (biology), order Passeriformes (; from Latin 'sparrow' and '-shaped') which includes more than half of all bird species. Sometimes known as perching birds, passerines generally have an Dactyly#In birds, ...
s unchanged.
Some of these changes are minor adjustments. For instance, instead of putting the swifts, treeswifts, and hummingbirds in the same order that includes nothing else, Sibley and Ahlquist put them in the same superorder that includes nothing else, consisting of one order for the hummingbirds and another for the swifts and treeswifts. In other words, they still regard the swifts as the hummingbirds' closest relatives.
Other changes are much more drastic. The penguins were traditionally regarded as distant from all other living birds. For instance, Wetmore put them in a superorder by themselves, with all other non-ratite birds in a different superorder. Sibley and Ahlquist, though, put penguins in the same superfamily as divers (loons), tubenoses, and
frigatebird
Frigatebirds are a Family (biology), family of seabirds called Fregatidae which are found across all tropical and subtropical oceans. The five extant species are classified in a single genus, ''Fregata''. All have predominantly black plumage, l ...
s. According to their phylogenetic analysis, penguins are closer to those birds than
heron
Herons are long-legged, long-necked, freshwater and coastal birds in the family Ardeidae, with 75 recognised species, some of which are referred to as egrets or bitterns rather than herons. Members of the genus ''Botaurus'' are referred to as bi ...
s are to
stork
Storks are large, long-legged, long-necked wading birds with long, stout bills. They belong to the family Ciconiidae, and make up the order Ciconiiformes . Ciconiiformes previously included a number of other families, such as herons and ibise ...
s.
The
Galloanserae (waterfowl and landfowl) has found widespread acceptance. The DNA evidence of Sibley–Ahlquist for the monophyly of the group is supported by the discovery of the fossil bird ''
Vegavis iaai'', an essentially modern but most peculiar waterfowl that lived near
Cape Horn
Cape Horn (, ) is the southernmost headland of the Tierra del Fuego archipelago of southern Chile, and is located on the small Hornos Island. Although not the most southerly point of South America (which is Águila Islet), Cape Horn marks the nor ...
some 66–68
million years ago
Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds.
Usage
Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...
, still in the age of the
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
s.
[Clarke ''et al.'' (2005)]
Classification
See also
*
Molecular phylogenetics
Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
*
Phylogenetic nomenclature
Phylogenetic nomenclature is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names as explained below. This contrasts with the traditional method, by which taxon names are defined by a '' type'', which c ...
*
Charles Sibley
*
Sibley–Monroe checklist
*
List of birds (based on the Clements taxonomy)
References
* (2005): Definitive fossil evidence for the extant avian radiation in the Cretaceous. ''
Nature
Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...
'' 433: 305–308.
PDF fulltext
* Sibley, Charles Gald & Ahlquist, Jon Edward (1990): ''Phylogeny and classification of birds''. Yale University Press, New Haven, Conn.
On the Phylogeny and Classification of Living Birds
by Charles G. Sibley
The Early History of Modern Birds Inferred from DNA Sequences of Nuclear and Mitochondrial Ribosomal Genes
by Marcel van Tuinen, Charles G. Sibley, and S. Blair Hedges
*, by Eric Salzman, ''Birding'', December 1993. The Web version lacks the illustrations, which show parts of the family tree, and includes only a partial bibliography, but adds a sequence down to the tribe level with detail on intermediate taxa (especially for the passerines).
{{DEFAULTSORT:Sibley-Ahlquist Taxonomy
Systems of animal taxonomy
Ornithology