Jordan's rule

Jordan's rule (sense 1) is an ecogeographical rule that describes the inverse relationship between water temperature and meristic characteristics in various species of fish. The most commonly observed relationship is that fin ray, vertebrae, or scale numbers increase with decreasing temperature. The rule is named after David Starr Jordan (1851–1931), the father of American ichthyology.^[1]

Jordan's law (or rule) (sense 2) is also an ecogeographical rule (named after the same scientist) that states: "‘[g]iven any species in any region, the nearest related species is not likely to be found in the same region nor in a remote region, but in a neighbouring district separated from the first by a barrier of some sort’^[2] This "rule" is frequently violated (see discussion in Fitzpatrick & Turelli 2007^[3]), but when patterns are consistent with Jordan's rule (sense 2), this suggests an important role for allopatric speciation in the diversification of the clade in question.^[4][5] Jordan himself wrote: "To this generalization Dr. Allen, in a late number of Science, gives the name of 'Jordan's Law.' The present writer makes no claim to the discovery of this law. The language above quoted is his, but the idea is familiar to all students of geographical distribution and goes back to the master in that field, Moritz Wagner."^[6][7] Thus, Jordan's law is an example of Stigler's law.

See also

• Allen's rule
• Allopatric speciation
• Bergman's rule
• Jordan's Principle

References

1. McDowall, R. M. (March 2008). "Jordan's and other ecogeographical rules, and the vertebral number in fishes". Journal of Biogeography. 35 (3): 501–508. Bibcode:2008JBiog..35..501M. doi:10.1111/j.1365-2699.2007.01823.x.
2. Jordan, David Starr (1908-02-01). "The Law of Geminate Species". The American Naturalist. 42 (494): 73–80. doi:10.1086/278905. ISSN 0003-0147.
3. Fitzpatrick, Benjamin M.; Turelli, Michael (2006). "The Geography of Mammalian Speciation: Mixed Signals from Phylogenies and Range Maps". Evolution. 60 (3): 601–615. doi:10.1111/j.0014-3820.2006.tb01140.x. ISSN 1558-5646. PMID 16637504. S2CID 32663278.
4. Mayr, Ernst, 1904-2005. (1963). Animal species and evolution. Cambridge: Belknap Press of Harvard University Press. ISBN 0-674-03750-2. OCLC 551391.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
5. Barraclough, Timothy G. (20 June 2019). The evolutionary biology of species (First ed.). Oxford. ISBN 978-0-19-106665-8. OCLC 1104724041.{{cite book}}: CS1 maint: location missing publisher (link)
6. Jordan, David Starr (February 1908). "The Law of Geminate Species". The American Naturalist. 42 (494): 73–80. doi:10.1086/278905. ISSN 0003-0147.
7. Allen, J. A. (October 1907). "Mutations and the Geographic Distribution of Nearly Related Species in Plants and Animals". The American Naturalist. 41 (490): 653–655. doi:10.1086/278852. ISSN 0003-0147.