Species

From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Species (disambiguation).
Life Domain Kingdom Phylum Class Order Family Genus Species
The hierarchy of biological classification's eight major taxonomic ranks. A genus contains one or more species. Intermediate minor rankings are not shown.

In biology, a species (abbreviated sp., with the plural form species abbreviated spp.) is the basic unit of biological classification and a taxonomic rank. A species is often defined as the largest group of organisms in which two individuals can produce fertile offspring, typically by sexual reproduction. While this definition is often adequate, looked at more closely it is often problematic. For example, in a species complex, the boundaries between closely related species become unclear or disappear altogether. Other ways of defining species include similarity of DNA, morphology, or ecological niche. The presence of locally adaptive traits may further subdivide species into infraspecific taxa such as subspecies.[a]

Species are grouped into genera (singular: genus) by taxonomists, genera are grouped into families, families into larger groups. Taxonomists use scientific hypotheses that species in the same genus have the same ancestors. The hypotheses are first based on observed similarity of physical attributes and behaviour, and where available, the DNA sequences of individuals and of species.

All species are given a two-part name, a "binomial". The first part of a binomial is the genus to which the species belongs. The second part is called the specific name (zoology) or the specific epithet (in botany, also sometimes in zoology). For example, Boa constrictor is one of four species of the Boa genus.

A usable definition of "species" and reliable methods of identifying particular species are important for stating and testing biological theories and for measuring biodiversity, though other taxonomic levels such as families can form the basis of broad-scale studies.[1] Extinct species known only from fossils are generally difficult to assign precise taxonomic rankings, which is why higher taxonomic levels such as families are often used for fossil-based studies.[1][2]

History[edit]

Classical forms[edit]

In his biology, Aristotle used the term γένος (génos) to mean a kind, such as a bird or fish, and εἶδος (eidos) to mean a specific form within a kind, such as (within the birds) the crane, eagle, crow, or sparrow.[b] A kind was distinguished by its attributes; for instance, a bird has feathers, a beak, wings, a hard-shelled egg, and warm blood. A form was distinguished by being shared by all its members, the young inheriting any variations they might have from their parents. Aristotle believed all kinds and forms to be distinct and unchanging. His approach remained influential until the Renaissance.[3]

Fixed species[edit]

John Ray believed that species breed true, and do not change.

When early modern observers began to develop systems of organization for living things, they began to place formerly isolated species into a context. Many of these early delineation schemes would now be considered whimsical and these included consanguinity based on color (all plants with yellow flowers) or behavior (snakes, scorpions and certain biting ants). John Ray (1686), an English naturalist, was the first to give a biological definition of the term "species," as follows: "... no surer criterion for determining species has occurred to me than the distinguishing features that perpetuate themselves in propagation from seed. Thus, no matter what variations occur in the individuals or the species, if they spring from the seed of one and the same plant, they are accidental variations and not such as to distinguish a species... Animals likewise that differ specifically preserve their distinct species permanently; one species never springs from the seed of another nor vice versa".[4]

Carl Linnaeus created the binomial system of naming species.

In the 18th century, the Swedish scientist Carl Linnaeus classified organisms according to shared physical characteristics, and not simply based upon differences.[5] He established the idea of a taxonomic hierarchy of classification based upon observable characteristics and intended to reflect natural relationships.[6][7]

At the time, however, it was still widely believed that there was no organic connection between species, no matter how similar they appeared. This view was influenced by European scholarly and religious education, which held that the categories of life are dictated by God, forming a hierarchy, the scala naturae or great chain of being. However, whether or not it was supposed to be fixed, the scala (a ladder) inherently implied the possibility of climbing.[8]

Species that could change[edit]

By the 19th century, naturalists understood that species could change form over time, and that the history of the planet provided enough time for major changes. Jean-Baptiste Lamarck, in his 1809 Zoological Philosophy, described the transmutation of species, proposing that a species could change over time. Textbooks ignore most of this, focusing on one aspect, that an organism could pass on an acquired trait to its offspring. They use the example[9] of the giraffe's long neck supposedly having been created by generations of giraffes stretching to reach the leaves of higher treetops.[c]

In 1859, Charles Darwin and Alfred Russel Wallace provided a compelling account of evolution and the formation of new species. Darwin argued that it was populations that evolved, not individuals, by natural selection from naturally occurring variation among individuals.[10] This required a new definition of species. Darwin concluded that species are what they appear to be: ideas, provisionally useful for naming groups of interacting individuals. "I look at the term species", he wrote, "as one arbitrarily given for the sake of convenience to a set of individuals closely resembling each other ... It does not essentially differ from the word variety, which is given to less distinct and more fluctuating forms. The term variety, again, in comparison with mere individual differences, is also applied arbitrarily, and for convenience sake."[11]

Naming[edit]

Common names[edit]

The commonly used names for plant and animal taxa sometimes correspond to species, as with lion, walrus, and camphor tree, but often they do not: for instance deer refers to a family which includes fallow deer and red deer.[12]

Abbreviations[edit]

Books and articles sometimes intentionally do not identify species fully and use the abbreviation "sp." in the singular or "spp." (standing for species pluralis, the Latin for multiple species) in the plural in place of the specific name or epithet (e.g. Canis sp.) This commonly occurs when authors are confident that some individuals belong to a particular genus but are not sure to which exact species they belong, as is common in paleontology. Authors may also use "spp." as a short way of saying that something applies to many species within a genus, but not to all. If scientists mean that something applies to all species within a genus, they use the genus name without the specific name or epithet. The names of genera and species are usually printed in italics. Abbreviations such as "sp." should not be italicized.[13]

Identification codes[edit]

Various codes have been devised for identifying particular species. For example:

Standard definition: Mayr's Biological Species Concept[edit]

Most modern textbooks use Ernst Mayr's definition, known as the Biological Species Concept (BSC). It is also called a reproductive or isolation concept. This defines a species as "groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups".[17] It can be argued that this definition is a natural consequence of the effect of sexual reproduction on the dynamics of natural selection.[18][19][20][21] Mayr's definition excludes unusual or artificial matings that result from deliberate human action, or occur only in captivity, or that involve animals capable of mating but that do not normally do so in the wild.[17]

The Species Problem[edit]

Main article: Species Problem

It is difficult to define the word "species" in a way that applies to all organisms.[22] The debate about how to define "species" is called the "Species Problem".[1][17][23][24][25][26] The problem dates to On the Origin of Species, where Darwin wrote:

No one definition has satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of a species. Generally the term includes the unknown element of a distinct act of creation.[27]

A simple textbook definition, following Mayr's BSC, works well for most multi-celled organisms, but breaks down in several situations:

  • Among organisms that reproduce asexually, as in single-celled organisms and parthenogenetic or apomictic multi-celled organisms.[28]
  • When biologists do not know whether two morphologically similar groups of organisms are capable of interbreeding.
  • When hybridization and the extent of sexual reproduction vary widely.[29]
  • In ring species, when members of adjacent populations interbreed successfully but members of some non-adjacent populations do not.[30]

Species identification is made difficult by discordance between molecular and morphological investigations; these can be categorized as two types: (i) one morphology, multiple lineages (e.g. morphological convergence, cryptic species) and (ii) one lineage, multiple morphologies (e.g. phenotypic plasticity, multiple life-cycle stages).[31] In addition, horizontal gene transfer (HGT) makes it difficult to define the term species.[32] All species definitions assume that an organism acquires its genes from one or two parents very like the "daughter" organism, but that is not what happens in HGT.[33] There is strong evidence of HGT between very dissimilar groups of prokaryotes, and at least occasionally between dissimilar groups of eukaryotes,[32] including some crustaceans and echinoderms.[34]

The evolutionary biologist James Mallet concludes that

there is no easy way to tell whether related geographic or temporal forms belong to the same or different species. Species gaps can be verified only locally and at a point of time. One is forced to admit that Darwin's insight is correct: any local reality or integrity of species is greatly reduced over large geographic ranges and time periods.[35]

Alternative definitions[edit]

Vavilov[edit]

Nikolai Vavilov developed ways to define and conceive of Linnaean species. He saw species as systems, each an integral entity consisting of closely interlinked components.[36] He emphasized the variability within species, relativity of taxonomic criteria and the accumulation of genetic variation within a species. From the evolutionary point of view he compared species to knots in evolutionary chains. Building on V.L. Komarov's aphorism: "a species is a morphological system plus geographic distinctness", Vavilov defined a "Linnaean species" as "an isolated complex dynamic morph-physiological system bound in its origin to a certain environment and area".[37]

Genetic similarity[edit]

In microbiology, genes can move freely even between distantly related bacteria, possibly extending to the whole bacterial domain. As a rule of thumb, microbiologists have assumed that kinds of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA-DNA Hybridization to decide if they belong to the same species or not.[38] This concept was narrowed in 2006 to a similarity of 98.7%.[39]

DNA-DNA hybridization results have however sometimes led to misleading conclusions about species, as with the pomarine skua – great skua.[40][41]

Typological or morphospecies[edit]

All adult Eurasian blue tits[42] share the same coloration to a high degree of fidelity, unmistakably identifying the morphospecies.[43]

A typological species is a group of organisms in which individuals conform to certain fixed properties, so that even pre-literate people often recognize the same taxon as do modern taxonomists.[44][45] The clusters of variations or phenotypes within specimens (i.e. longer or shorter tails) would differentiate the species. This method was used as a "classical" method of determining species, such as with Linnaeus early in evolutionary theory. However, different phenotypes are not necessarily different species (e.g. a four-winged Drosophila born to a 2-winged mother is not a different species). Species named in this manner are called morphospecies.[46][47]

Evolutionary species[edit]

A single evolutionary lineage of organisms within which genes can be shared, and that maintains its integrity with respect to other lineages through both time and space. At some point in the evolution of such a group, some members may diverge from the main population and evolve into a subspecies, a process that may eventually lead to the formation of a new species if isolation (geographical or ecological) is maintained. The process through which species are formed by evolution is called speciation. A species that gives rise to another species is a paraphyletic species, or paraspecies.[48]

Phylogenetic or cladistic species[edit]

A phylogenetic or cladistic species (PSC) is an evolutionarily divergent lineage, one that has maintained its hereditary integrity through time and space.[49][50][51] A PSC is the smallest group of populations that can be distinguished by a unique set of morphological or genetic traits. Molecular markers may be used to determine genetic similarities in the nuclear or mitochondrial DNA of various species.[50][52][53] For example, in a study done on fungi, studying the nucleotide characters using PSC produced the most accurate results in recognizing the numerous fungi species compared to other concepts used.[53] Unlike the popular Biological Species Concept, PSC also does not rely on reproductive isolation, thus it is independent of processes that are integral in other concepts.[52] PSC works for asexual lineages, and can detect recent divergences, which the Morphological Species Concept cannot.[50][53] However, PSC does not work in every situation, and may require more than one polymorphic locus to give an accurate result.[53] PSC may lead to splitting of existing species, for example of Bovidae, into many new ones.[54][55][56]

Ecological species[edit]

An ecological species is a set of organisms adapted to a particular set of resources, called a niche, in the environment. According to this concept, populations form the discrete phenetic clusters that we recognize as species because the ecological and evolutionary processes controlling how resources are divided up tend to produce those clusters.[57]

Genetic species[edit]

A genetic species is a set of individuals or populations with sufficiently similar DNA. Techniques to compare similarity of DNA include DNA-DNA hybridization, genetic fingerprinting and DNA barcoding. Richard Dawkins for example defined two organisms as conspecific if and only if they have the same number of chromosomes and, for each chromosome, both organisms have the same number of nucleotides.[58]

Evolutionarily significant unit[edit]

An evolutionarily significant unit (ESU) or "wildlife species"[59] is a population of organisms considered distinct for purposes of conservation.[60]

Phenetic species[edit]

A phenetic species is a set of organisms which have a similar phenotype to each other, but a different phenotype from other sets of organisms.[61]

Microspecies[edit]

A microspecies is a group of organisms with very little genetic variability, usually a part of a species aggregate reproducing by apomixis.[62]

Recognition species[edit]

A mate-recognition species is a group of sexually reproducing organisms that recognize one another as potential mates.[61] Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms; no matter whether populations can hybridize successfully, they are still distinct cohesion species if the amount of hybridization is insufficient to completely mix their respective gene pools.[35]

Lumping and splitting of taxa[edit]

Main article: Lumpers and splitters

The naming of a particular species may be regarded as a hypothesis about the evolutionary relationships and distinguishability of that group of organisms. As further information comes to hand, the hypothesis may be confirmed or refuted. Sometimes, especially in the past when communication was more difficult, taxonomists working in isolation have given two distinct names to individual organisms later identified as the same species. When two named species are discovered to be of the same species, the older species name is usually retained, and the newer species name dropped, a process called synonymization, or colloquially, as lumping. Dividing a taxon into multiple, often new, taxons is called splitting. Taxonomists are often referred to as "lumpers" or "splitters" by their colleagues, depending on their personal approach to recognizing differences or commonalities between organisms.[63][64]

See also[edit]

Notes[edit]

  1. ^ And in botany varieties, subvarieties, and formae.
  2. ^ These terms were translated into Latin as "genus" and "species", though they do not correspond to the Linnean terms thus named.[3]
  3. ^ Recent interest in inheritance of acquired characteristics centers around epigenetic processes (e.g. methylation) that do not affect DNA sequences, but instead alter expression in an inheritable manner. Thus, Neo-Lamarckism, as it is sometimes termed, is not a challenge to the theory of evolution by natural selection.

References[edit]

  1. ^ a b c Sahney, S.; Benton, M.J.; Ferry, P.A. (2010). "Links Between Global Taxonomic Diversity, Ecological Diversity and the Expansion of Vertebrates on Land". Biology Letters. 6 (4): 544–547. doi:10.1098/rsbl.2009.1024. PMC 2936204Freely accessible. PMID 20106856. open access publication - free to read
  2. ^ Sahney, S. & Benton, M.J. (2008). "Recovery from the most profound mass extinction of all time" (PDF). Proceedings of the Royal Society: Biological. 275 (1636): 759–65. doi:10.1098/rspb.2007.1370. PMC 2596898Freely accessible. PMID 18198148. open access publication - free to read
  3. ^ a b Leroi, Armand Marie (2014). The Lagoon: How Aristotle Invented Science. Bloomsbury. pp. 88–90. ISBN 978-1-4088-3622-4. 
  4. ^ Historia plantarum generalis, in the volume published in 1686, Tome I, Libr. I, Chap. XX, page 40 (Quoted in Mayr, Ernst. 1982. The growth of biological thought: diversity, evolution, and inheritance. Cambridge, Mass.: Belknap Press: 256)
  5. ^ Davis, P. H.; Heywood, V. H. (1973). Principles of Angiosperm Taxonomy. Huntington, New York: Robert E. Krieger Publishing Company. p. 17. 
  6. ^ Reveal, James L.; Pringle, James S. (1993). "7. Taxonomic Botany and Floristics". Flora of North America. New York and Oxford: Oxford University Press. pp. 160–161. ISBN 0-19-505713-9. 
  7. ^ Simpson, George Gaylord (1961). Principles of Animal Taxonomy. New York and London: Columbia University Press. pp. 56–57. 
  8. ^ Mahoney, Edward P. Mahoney. "Lovejoy and the Hierarchy of Being". Journal of the History of Ideas. 48 (2): 211–230. doi:10.2307/2709555. 
  9. ^ Ghiselin, Michael T. "The Imaginary Lamarck: A Look at Bogus "History" in Schoolbooks". The Textbook League. Retrieved 2 December 2016. 
  10. ^ Bowler, Peter J. (2003). Evolution: The History of an Idea (3rd ed.). Berkeley, CA: University of California Press. pp. 177–223 and passim. ISBN 0-520-23693-9. 
  11. ^ Menand, Louis (2001). The Metaphysical Club: A Story of Ideas in America. Farrar, Straus and Giroux. pp. 123–124. ISBN 0-374-70638-7. 
  12. ^ Bailey, L.H. (1933). How plants get their names. New York: Macmillan. ISBN 978-0-486-20796-4. [page needed]
  13. ^ Hardy, Jay (2011). Naming Conventions. Nomenclature of Microorganisms, Hardydiagnostics.com.
  14. ^ "Home – Taxonomy – NCBI". Ncbi.nlm.nih.gov. 2012-10-19. Retrieved 2012-11-25. 
  15. ^ "KEGG Organisms: Complete Genomes". Genome.jp. Retrieved 2012-11-25. 
  16. ^ "Taxonomy". Uniprot.org. Retrieved 2012-11-25. 
  17. ^ a b c de Queiroz K (2005). "Ernst Mayr and the modern concept of species". Proc. Natl. Acad. Sci. U.S.A. 102 (Suppl 1): 6600–7. doi:10.1073/pnas.0502030102. PMC 1131873Freely accessible. PMID 15851674. open access publication - free to read
  18. ^ Hopf FA, Hopf FW. (1985). The role of the Allee effect on species packing. Theor. Pop. Biol. 27, 27-50.
  19. ^ Bernstein H, Byerly HC, Hopf FA, Michod RE (December 1985). "Sex and the emergence of species". J. Theor. Biol. 117 (4): 665–90. doi:10.1016/S0022-5193(85)80246-0. PMID 4094459. 
  20. ^ Bernstein, Carol; Bernstein, Harris (1991). Aging, sex, and DNA repair. Boston: Academic Press. ISBN 0-12-092860-4. 
  21. ^ Michod, Richard E. (1995). Eros and Evolution: A Natural Philosophy of sex. Reading, Mass: Addison-Wesley Pub. Co. ISBN 0-201-44232-9. 
  22. ^ Hanage, William P. (April 2013). "Fuzzy species revisited". BMC Biology. 11 (41). Retrieved 2013-04-22. A coherent species concept that can be applied throughout the kingdoms of life is still elusive. 
  23. ^ Wilkins, John (2010-10-20). "How many species concepts are there?". London: The Guardian. Retrieved 2010-10-19. 
  24. ^ Koch, H. (2010). "Combining morphology and DNA barcoding resolves the taxonomy of Western Malagasy Liotrigona Moure, 1961" (PDF). African Invertebrates. 51 (2): 413–421. doi:10.5733/afin.051.0210. open access publication - free to read
  25. ^ De Queiroz K (2007). "Species concepts and species delimitation". Syst. Biol. 56 (6): 879–86. doi:10.1080/10635150701701083. PMID 18027281. open access publication - free to read
  26. ^ Fraser C, Alm EJ, Polz MF, Spratt BG, Hanage WP (February 2009). "The bacterial species challenge: making sense of genetic and ecological diversity". Science. 323 (5915): 741–6. doi:10.1126/science.1159388. PMID 19197054. closed access publication – behind paywall
  27. ^ "Darwin 1859 Chapter II, p. 59". Darwin-online.org.uk. Retrieved 2012-11-25. 
  28. ^ Templeton, A.R. (1989). "The meaning of species and speciation: A genetic perspective". In D. Otte; J.A. Endler. Speciation and its consequences. Sunderland: Sinauer Associates. pp. 3–27. 
  29. ^ Edward G. Reekie; Fakhri A. Bazzaz (28 October 2005). Reproductive allocation in plants. Academic Press. pp. 99–. ISBN 978-0-12-088386-8. Retrieved 4 August 2010. 
  30. ^ A closer look at a classic ring species: The work of Tom Devitt
  31. ^ Lahr D. J.; Laughinghouse H. D.; Oliverio A. M.; Gao F.; Katz L. A. (2014). "How discordant morphological and molecular evolution among microorganisms can revise our notions of biodiversity on Earth". BioEssays. 36 (10): 950–959. doi:10.1002/bies.201400056. PMID 25156897. 
  32. ^ a b Ulrich Melcher (2001) "Molecular genetics: Horizontal gene transfer," Oklahoma State University (Stillwater, Oklahoma USA)
  33. ^ Bapteste, E.; et al. (May 2005). "Do orthologous gene phylogenies really support tree-thinking?". BMC Evolutionary Biology. 5 (33). doi:10.1186/1471-2148-5-33. PMC 1156881Freely accessible. PMID 15913459. 
  34. ^ Williamson, David I. (2003). The Origins of Larvae. Kluwer. ISBN 1-4020-1514-3. 
  35. ^ a b Mallet, James. Calow, P., ed. Species, Concepts of (PDF). Encyclopaedia of Ecology and Environmental Management. Blackwell. pp. 709–711. ISBN 978-0-632-05546-3. 
  36. ^ What is a species
  37. ^ Vavilov, N.I. The Linnean species as a system// Fifth International Botanical Congress, (Cambridge, 16–23 August, 1930), report of proceedings. – Cambridge University Press, 1931. pp. 213–216. 
  38. ^ Stackebrandt E, Goebel BM (1994). "Taxonomic note: a place for DNA-DNA reassociation and 16S rRNA sequence analysis in the present species definition in bacteriology". Int. J. Syst. Bacteriol. 44 (4): 846–9. doi:10.1099/00207713-44-4-846. 
  39. ^ Stackebrandt E, Ebers J (2006). "Taxonomic parameters revisited: tarnished gold standards". Microbiol. Today. 33: 152–5. 
  40. ^ Newton, Ian (2003). Speciation and Biogeography of Birds. Academic Press. p. 69. ISBN 9780080924991. 
  41. ^ Andersson, Malte (1999). "Hybridization and skua phylogeny". Proceedings of the Royal Society B. 266 (1428): 1579–1585. doi:10.1098/rspb.1999.0818. 
  42. ^ Wright, Gill, Frank and Minturn (2006). Birds of the World: Recommended English Names (1 ed.). Princeton University Press. pp. ix + 259. ISBN 0-691-12827-8. 
  43. ^ Gooders, John (1986). Kingfisher Field Guide to the Birds of Britain and Ireland. London: Kingfisher Books. p. 246. ISBN 0 86272 139 3. 
  44. ^ Gould, Stephen Jay (1980). "A Quahog is a Quahog". In: The Panda’s Thumb: More Reflections in Natural History. New York: W.W. Norton & Company. pp. 204–213. ISBN 0-393-30023-4. 
  45. ^ Maynard Smith, John (1989). Evolutionary Genetics. Oxford: Oxford University Press. pp. 273–274. ISBN 0-19-854215-1. 
  46. ^ Michael Ruse (1969). "Definitions of Species in Biology". The British Journal for the Philosophy of Science. 20 (2): 97–119. doi:10.1093/bjps/20.2.97. JSTOR 686173. 
  47. ^ Lewin, Ralph A. (1981). "Three Species Concepts". Taxon. 30 (3): 609–613. doi:10.2307/1219942. 
  48. ^ Albert, James S.; Reis, Roberto E. (2011). Historical Biogeography of Neotropical Freshwater Fishes. ISBN 978-0-520-26868-5. 
  49. ^ Wheeler Q.D., Platnick N.I. 2000. The phylogenetic species concept (sensu Wheeler & Platnick). In: Wheeler Q.D., Meier R., editors. Species concepts and phylogenetic theory: a debate. New York: Columbia University Press. p. 55–69.
  50. ^ a b c Giraud T, Refrégier G, Le Gac M, de Vienne DM, Hood ME (2008). "Speciation in Fungi". Fungal Genetics and Biology. 45: 791–802. doi:10.1016/j.fgb.2008.02.001. 
  51. ^ Bernardo, J. 2011. A critical appraisal of the meaning and diagnosability of cryptic evolutionary diversity, and its implications for conservation in the face of climate change. Pp. 380-438 In Climate Change, Ecology and Systematics. Systematics Association Special Series (T. Hodkinson, M. Jones, S. Waldren & J. Parnell, eds). Cambridge University Press. (ISBN 9780521766098).
  52. ^ a b Nixon KC, Wheeler QD (1990). "An amplification of the phylogenetic species concept". Cladistics. 6: 211–223. doi:10.1111/j.1096-0031.1990.tb00541.x. 
  53. ^ a b c d Taylor JW, Jacobson DJ, Kroken S, Kasuga T, Geiser DM, Hibbett DS, Fisher MC (2000). "Phylogenetic species recognition and species concepts in fungi". Fungal Genetics and Biology. 31: 21–32. doi:10.1006/fgbi.2000.1228. PMID 11118132. 
  54. ^ Groves C., Grubb P. 2011. Ungulate taxonomy. Baltimore, MD: The Johns Hopkins University Press.
  55. ^ Heller R.; Frandsen P.; Lorenzen E. D.; Siegismund H. R. (2013). "Are there really twice as many bovid species as we thought?" (PDF). Systematic Biology. 62 (3): 490–493. doi:10.1093/sysbio/syt004. 
  56. ^ Cotterill F; Taylor P; Gippoliti S; et al. (2014). "'Why one century of phenetics is enough: Response to "are there really twice as many bovid species as we thought?"'". Systematic Biology. 63 (5): 819–832. doi:10.1093/sysbio/syu003. 
  57. ^ Ridley, Mark. "The Idea of Species". Evolution (2nd ed.). Cambridge, Massachusetts: Blackwell Science. p. 719. ISBN 0-86542-495-0. 
  58. ^ The Blind Watchmaker, p. 118
  59. ^ Government of Canada, COSEWIC, Committee on the Status of Endangered Wildlife in Canada. "COSEWIC's Assessment Process and Criteria". Cosepac.gc.ca. Retrieved 2015-04-07. 
  60. ^ DeWeerdt, Sarah (29 July 2002). "What Really is an Evolutionarily Significant Unit?". University of Washington. Retrieved 1 December 2016. 
  61. ^ a b "Other species concepts". University of California Berkeley. Retrieved 1 December 2016. 
  62. ^ Heywood VH. (1962). "The "species aggregate" in theory and practice". In VH Heywood; Löve Á. Symposium on Biosystematics, organized by the International Organization of Biosystematists, Montreal, October 1962. pp. 26–36. 
  63. ^ Simpson, George G. (1945). "The Principles of Classification and a Classification of Mammals". Bulletin of the AMNH. New York: American Museum of Natural History. 85: 23. 
  64. ^ Chase, Bob (Autumn 2005). "Upstart Antichrist". History Workshop Journal (60): 202–206. 

Further reading[edit]

External links[edit]

Taxonomic ranks
Magnorder Section (zoo.)
Domain/Superkingdom Superphylum/Superdivision Superclass Superorder Superfamily Supertribe
Kingdom Phylum/Division Class Legion Order Family Tribe Genus Species
Subkingdom Subphylum Subclass Cohort Suborder Subfamily Subtribe Subgenus Subspecies
Infrakingdom/Branch Infraphylum Infraclass Infraorder Section (bot.) Variety
Microphylum Parvclass Parvorder Series (bot.) Form
Retrieved from "https://en.wikipedia.org/w/index.php?title=Species&oldid=761794368"