Cryptic species complex
In biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, a cryptic species complex is a group of species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 which satisfy the biological definition of species—that is, they are reproductively isolated from each other—but whose morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

 is very similar (in some cases virtually identical).

The species in a cryptic complex are typically very close relatives and in many cases cannot be easily distinguished by molecular phylogenetic studies. If lineage sorting has not yet been completed, members of a cryptic species complex widely share plesiomorphic haplotype
A haplotype in genetics is a combination of alleles at adjacent locations on the chromosome that are transmitted together...

s, while individual species might not have evolved distinctive autapomorphic mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...

s yet. But usually, individual species within the complex can be separated by analysing data from multiple sources, such as by comparing DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...

 analyses, bioacoustics
Bioacoustics is a cross-disciplinary science that combines biology and acoustics. Usually it refers to the investigation of sound production, dispersion through elastic media, and reception in animals, including humans. This involves neurophysiological and anatomical basis of sound production and...

 and thorough life history
Life history theory
Life history theory posits that the schedule and duration of key events in an organism's lifetime are shaped by natural selection to produce the largest possible number of surviving offspring...


They may be parapatric, are frequently sympatric, and are sometimes allopatric. Cryptic species complexes are not the same as populations undergoing speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...

: they typically represent a situation where speciation has already broken gene flow
Gene flow
In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...

 between populations, but where evolution has not progressed to a point where easily-recognizable adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s have taken place.

Cryptic species that do not form a complex may be somewhat more distantly related and simply represent lineages that have been so successful as to require little evolutionary change, possibly coupled with parallel evolution
Parallel evolution
Parallel evolution is the development of a similar trait in related, but distinct, species descending from the same ancestor, but from different clades.-Parallel vs...

. A famous example are the Eurasian and Short-toed Treecreeper
Short-toed Treecreeper
The Short-toed Treecreeper, Certhia brachydactyla, is a small passerine bird found in woodlands through much of the warmer regions of Europe and into north Africa. It has a generally more southerly distribution than the other European treecreeper species, the Common Treecreeper, with which it is...

s, perhaps the first cryptic species to be recognized as such (by Christian Ludwig Brehm
Christian Ludwig Brehm
Christian Ludwig Brehm was a German pastor and ornithologist. He was the father of Alfred Brehm.Brehm was born near Gotha, and studied at the University of Jena. In 1813 he became the minister at Renthendorf, a village sixty miles south of Leipzig, where he remained until his death...

 in 1820). Other ornithologists refused to accept that more than one species was involved until Brehm presented his bioacoustic studies, which left no room for doubt. The European Treecreeper has since been found to be a very close relative of the Himalayan Hodgson's Treecreeper
Hodgson's Treecreeper
Hodgson's Treecreeper, Certhia hodgsoni, is a small passerine bird from the southern rim of the Himalayas. Its specific distinctness from the Common Treecreeper was recently validated.-Description:...

, while the Short-toed Treecreeper is probably the sister species of the North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

n Brown Creeper
Brown Creeper
-Description:Adults are brown on the upperparts with light spotting, resembling a piece of tree bark, with white underparts. They have a long thin bill with a slight downward curve and a long tail. The male creeper has a slightly larger bill than the female...


A related concept is the superspecies
A superspecies is a group of at least two more or less distinctive species with approximately parapatric distributions. Not all species complexes, whether cryptices or ring species are superspecies, and vice versa, but many are...

. This is a clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 of at least two more or less distinctive species with approximately parapatric distributions. Not all cryptic species complexes are superspecies, and vice versa, but many are.


  • Algerian Barb (several species suspected)
  • Audubon's Shearwater
    Audubon's Shearwater
    Audubon's Shearwater, Puffinus lherminieri, is a common tropical seabird from the family Procellariidae. Sometimes called Dusky-backed Shearwater, the scientific name of this species commemorates the French naturalist Félix Louis L'Herminier....

     (several species suspected)
  • Asian glass catfishes (several cases known, most notoriously K. minor
    Ghost Catfish
    The Ghost Catfish , also known as the Phantom Catfish or Ghost Fish, is an Asian glass catfish. Until 1989, it was considered to be the same as the Glass Catfish , and even today the latter name is commonly seen in the aquarium fish trade. However, the larger K...

  • Brachionus plicatilis
    Brachionus plicatilis
    Brachionus plicatilis is a euryhaline rotifer in the Family Brachionidae, and is possibly the only commercially important rotifer, being raised in the aquaculture industry as food for fish larvae. It has a broad distribution in salt lakes around the world and has become a model system for studies...

    complex (at least 14 species)
  • Common Bush-tanager
    Common Bush-Tanager
    The Common Bush-tanager is a small passerine bird. It is a resident breeder in the highlands from central Mexico south to Bolivia and northwest Argentina. C. ophthalmicus in the loose sense is a notorious cryptic species complex, and several of the up to 25 subspecies recognized in recent times...

     (several species suspected)
  • Golden/Mangrove/Yellow Warblers
    Yellow Warbler
    Dendroica petechia is a New World warbler species or superspecies; the subspecies group around D. aestiva is increasingly treated as good species Dendroica aestiva again. The name for the entire cryptic species complex is Mangrove Warbler, and another group of subspecies is known as Golden Warbler...

     (at least two species suspected)
  • Flax Tortrix complex (more than 5 species)
  • Grey-cheeked Thrush and Bicknell's Thrush
    Bicknell's Thrush
    The Bicknell's Thrush, Catharus bicknelli, is a medium-sized thrush, at 17.5 cm and 28 g . It was named after Eugene Bicknell, an American amateur ornithologist, who discovered the species on Slide Mountain in the Catskills in the late 19th century.Adults are olive-brown on the upperparts,...

  • Leopard frog
    Leopard frog
    Leopard frogs, also called meadow frogs, are the archetypal "grass frogs" of North America, a collection of about 14 species within the true frog genus Rana. They are generally very similar, green with prominent black spotting...

  • Mouse lemur
    Mouse lemur
    The mouse lemurs are nocturnal lemurs of the genus Microcebus. Like all lemurs, mouse lemurs are native to Madagascar.Mouse lemurs have a combined head, body and tail length of less than , making them the smallest primates ; however, their weight fluctuates in response to daylight duration.Mouse...

    s (16 species)
  • "Placidochromis
    Placidochromis is a genus of cichlids endemic to Lake Malawi in Eastern Africa. They are part of the haplochromine lineage of Lake Malawi's cichlid taxa. Most Placidochromis species live in the open or sandy regions of the lake.-Species:...

    (over 30 species described in 2004)
  • Pogonomyrmex barbatus and P. rugosus (at least six lineages within the two morphospecies)
  • Red-legged frog
    Red-legged Frog
    The Red-legged Frog, a threatened native species in Oregon, is a common name for a particular kind of frog of the west coast of North America. The Red-legged Frog requires stream side, woodland environments for survival...

  • Rhacophorus
    Rhacophorus is a genus of frogs in the moss frog family which together with the related Hylidae makes up the true tree frogs. They live in India, Japan, Madagascar, Africa, and Southeast Asia...

    flying frog
    Flying frog
    A "flying" frog is a frog that has the ability to glide. That is, it can descend at an angle of less than 45° relative to the horizontal. Arboreal frogs can also descend vertically, but only at angles greater than 45°, which is referred to as parachuting...

    s (several cases suspected)
  • Scytalopus
    Scytalopus is a genus of small passerine birds belonging to the tapaculo group. They are found in South and Central America from Tierra del Fuego to Costa Rica, but are absent from the Amazon Basin. They inhabit dense vegetation at or near ground-level and are mainly found in mountainous regions,...

    The tapaculos are a group of small suboscine passeriform birds with numerous species, found mainly in South America and with the highest diversity in the Andean regions...

  • Two-barred Flasher (suspected)
  • Trichoplax adhaerens (multiple species suspected)
  • White-tailed Eagle
    White-tailed Eagle
    The White-tailed Eagle , also known as the Sea Eagle, Erne , or White-tailed Sea-eagle, is a large bird of prey in the family Accipitridae which includes other raptors such as hawks, kites, and harriers...

     and Bald Eagle
    Bald Eagle
    The Bald Eagle is a bird of prey found in North America. It is the national bird and symbol of the United States of America. This sea eagle has two known sub-species and forms a species pair with the White-tailed Eagle...

  • Armillaria mellea
    Armillaria mellea
    Armillaria mellea is a plant pathogen and a species of Honey fungus. It causes Armillaria root rot in many plant species. The mushrooms are edible but some people may be intolerant to them. The fungus produces mushrooms around the base of trees it has infected...

    (turned out to include 10+ species)

Consequences for biological studies

It has been suggested that cryptic species complexes are very common in the marine environment. Although this suggestion predated the detailed analysis of many systems using DNA sequence data, it has been proven correct. The increased use of DNA sequence in the investigation of organismal diversity (also called Phylogeography
Phylogeography is the study of the historical processes that may be responsible for the contemporary geographic distributions of individuals. This is accomplished by considering the geographic distribution of individuals in light of the patterns associated with a gene genealogy.This term was...

 and DNA barcoding
DNA barcoding
DNA barcoding is a taxonomic method that uses a short genetic marker in an organism's DNA to identify it as belonging to a particular species. It differs from molecular phylogeny in that the main goal is not to determine classification but to identify an unknown sample in terms of a known...

) has led to the discovery of a great many cryptic species complexes in all habitats. In the marine bryozoan Celleporella hyalina, detailed morphological analyses and mating compatibility tests between the isolates identified by DNA sequence analysis were used to confirm that these groups consisted of more than 10 ecologically distinct species that had been diverging for many million years.

Evidence from the identification of cryptic species has led some to conclude that current estimates of global species richness are too low. For example, mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...

 research published in January 2008 suggests that there are at least 11 genetically distinct populations of giraffe
The giraffe is an African even-toed ungulate mammal, the tallest of all extant land-living animal species, and the largest ruminant...

s. Similar methods also found that the Amazonian frog Eleutherodactylus ockendeni is actually at least 3 different species that diverged over 5 million years ago.

External links

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