Cryptic species complex

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This article is about groups of species that appear very similar. For the principles of hiding, a means of Camouflage, see Crypsis.
"Cryptic species" redirects here, not to be confused with Cryptid, a supposed or imagined creature whose existence is not scientifically recognised.
Cryptic species are extremely similar, such as these two Trimma goby species.[1]

In scientific classification, a cryptic species complex is a group of organisms that are typically very closely related yet their precise classification and relationships cannot be easily determined.

The component species of a cryptic species complex may be parapatric, are frequently sympatric, and are sometimes allopatric. Cryptic species complexes are not the same as populations undergoing speciation: they typically represent a situation where speciation has already broken the gene flow between populations, but where evolution has not progressed to a point where easily recognizable adaptations have taken place.

Cryptic species 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. A famous example are the Eurasian Treecreeper and Short-toed Treecreeper. These birds were perhaps the first cryptic species to be recognized as such (by Christian Ludwig Brehm 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, while the Short-toed Treecreeper is probably the sister species of the North American Brown Creeper. Cryptic species are also common in certain families of insects such as Chironomidae.[2][3]

Definition and related concepts[edit]

The members of a cryptic species might or might not constitute a superspecies; in other words, they might appear very similar but not be very closely related.

Recognition of cryptic species[edit]

Usually, when a cryptic species complex has been discovered, the individual species within the complex are separated by analysing data from multiple sources, such as by comparing polytene chromosomes, DNA sequence analyses, bioacoustics and thorough life history studies.

Examples of cryptic species
An adult and a young elephant bathing in a waterhole.
The African forest elephant was recognized as distinct from the African bush elephant through molecular phylogenetics.[4] 
An individual of a black, yellow spotted salamander.
Salamandra corsica is one of four fire salamander species recognized as distinct through molecular analysis.[5] 
A mosquito sitting on the tip of a finger.
The malaria-carrying mosquito Anopheles gambiae conceals several nearly identical species. 
Picture showing two mushrooms with red caps on a meadow.
The fly agaric mushroom comprises several genetically distinct species.[6] 
Leaves and fruits of blackberry (Rubus fruticosus).
Blackberries are a complex of species difficult to delineate due to hybridization and apomixis.[7] 

Evolutionary and ecological interpretation[edit]

Cryptic species have typically diverged very recently from eachother, allowing in some cases to retrace the process of speciation.[citation needed]

Where cryptic species coexist in sympatry, it is often a particular challenge to understand how these similar species persist without outcompeting each other. Niche partitioning is one mechanism invoked to explain this. Studies in some species complexes indeed suggest that species divergence went in par with ecological differentiation, with species now preferring different microhabitats.[citation needed]

Practical implications[edit]

Biodiversity estimates[edit]

It has been suggested that cryptic species complexes are very common in the marine environment.[8] Although this suggestion came before the detailed analysis of many systems using DNA sequence data, it has been proven correct.[9] The increased use of DNA sequence in the investigation of organismal diversity (also called Phylogeography and DNA barcoding) has led to the discovery of a great many cryptic species complexes in all habitats. In the marine bryozoan Celleporella hyalina,[10] 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[who?] to conclude that current estimates of global species richness are too low. For example, mitochondrial DNA research published in January 2008 suggests that there are at least 11 genetically distinct populations of giraffes.[11][12] Similar methods also found that the Amazonian frog Eleutherodactylus ockendeni is actually at least 3 different species that diverged over 5 million years ago.[13]

Conservation biology[edit]

When a species is found to comprise in fact several phylogenetically distinct species, each of these typically have smaller distribution ranges and population sizes than reckoned before.[citation needed]

Disease and pathogen control[edit]

Pests, species causing diseases, and their vectors, have direct importance for humans. When they are found to be cryptic species complexes, the ecology and virulence of each of these species needs to be reevaluated to devise appopriate control strategies.[citation needed] An example are cryptic species in the malaria vector Anopheles, or the fungi causing cryptococcosis.

See also[edit]

References[edit]

  1. ^ Winterbottom R, Hanner RH, Burridge M, Zur M. (2014). "A cornucopia of cryptic species - a DNA barcode analysis of the gobiid fish genus Trimma (Percomorpha, Gobiiformes)" (PDF). Zookeys 381: 79–111. doi:10.3897/zookeys.381.6445. 
  2. ^ Int Panis L, Kiknadze I, Bervoets L, Aimanova A (1994). "Karyological identification of some species of the genus Chironomus Meigen, 1803 from Belgium". Bulletin et Annales de la Societé Royale Belge d'Entomologie (Belgium) 130: 135–142. 
  3. ^ Кикнадзе ИИ, Михайлова П, Истомина АГ, Голыгина ВВ, Инт Панис Л, Крастанов Б (2006). "Хромосомный полиморфизм и дивергенция популяций у Chironomus nuditarsis Str. (Diptera, Chironomidae) [The chromosomal polymorphism and divergence of populations in Chironomus nuditarsis Str. (Diptera, Chironomidae]". Tsitologia (in Russian) 48: 595–609. 
  4. ^ Roca AL, Georgiadis N, Pecon-Slattery J, O'Brien SJ. (2001). "Genetic evidence for two species of elephant in Africa". Science 293 (5534): 1473–1477. doi:10.1126/science.1059936. PMID 11520983. 
  5. ^ Steinfartz S, Veith M, Tautz D. (2000). "Mitochondrial sequence analysis of Salamandra taxa suggests old splits of major lineages and postglacial recolonizations of Central Europe from distinct source populations of Salamandra salamandra". Molecular Ecology 9 (4): 397–410. doi:10.1046/j.1365-294x.2000.00870.x. 
  6. ^ Geml J, Tulloss RE, Laursen GA, Sasanova NA, Taylor DL. (2008). "Evidence for strong inter- and intracontinental phylogeographic structure in Amanita muscaria, a wind-dispersed ectomycorrhizal basidiomycete". Molecular Phylogenetics and Evolution 48 (2): 694–701. doi:10.1016/j.ympev.2008.04.029. PMID 18547823. 
  7. ^ Salvini D, Fineschi S, Pastorelli R, Sebastiani F, Vendramin GG. (2006). "Absence of geographic structure in European populations of Rubus fruticosus L. complex using chloroplast DNA microsatellites". Journal of the American Society for Horticultural Science 131 (5): 616–621.  open access publication - free to read
  8. ^ Knowlton N (1993). "Sibling species in the sea". Annual Review of Ecology and Systematics 24 (1): 189–216. doi:10.1146/annurev.es.24.110193.001201. ISSN 0066-4162. 
  9. ^ Knowlton N. (February 2000). "Molecular genetic analyses of species boundaries in the sea". Hydrobiologia 420 (1): 73–90. doi:10.1023/A:1003933603879. ISSN 0018-8158. 
  10. ^ Gómez A, Wright PJ, Lunt DH, Cancino JM, Carvalho GR, Hughes RN. (2007). "Mating trials validate the use of DNA barcoding to reveal cryptic speciation of a marine bryozoan taxon". Proceedings of the Royal Society B 274 (1607): 199–207. doi:10.1098/rspb.2006.3718. ISSN 0962-8452. PMC 1685843. PMID 17035167. 
  11. ^ "Giraffes and frogs provide more evidence of new species hidden in plain sight". Science Daily. January 2008. 
  12. ^ Brown D, Brenneman R, Koepfli K-P, Pollinger J, Mila B, Georgiadis N, Louis E, Grether G, Jacobs D, Wayne R. (2007). "Extensive population genetic structure in the giraffe". BMC Biology 5: 57. doi:10.1186/1741-7007-5-57. ISSN 1741-7007. PMC 2254591. PMID 18154651. 
  13. ^ Elmer K, Davila J, Lougheed S. (2007). "Cryptic diversity and deep divergence in an upper Amazonian leaflitter frog, Eleutherodactylus ockendeni". BMC Evolutionary Biology 7: 247. doi:10.1186/1471-2148-7-247. ISSN 1471-2148. PMC 2254618. PMID 18154647. 

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