BioConcepts

sibling speciesspecies sorores (lat.); sœur espèces (fr.); Schwesterarten (ger.)

• Distinct species that are morphologically very similar.
  category species

  1794

  ich [machte] mir zum Gesetze: Jede Art, welche die einzige aus ihrer Gattung in Oestreich gezogen zu werden scheint, wegzulassen; jene Arten aber, deren Schwester-Arten in Oestreich wild vorkommen, und die daselbst häufig gezogen werden, ohne die gewöhnliche Nummer einer Art aufzunehmen, und den Botaniker ihres Gastrechtes zu erinnern.

  Schultes, J.A. (1794). Oestreichs Flora, vol. 1: [Vorrede, p. 6-7].
  

  1819

  Schwesterarten [von Pflanzen], die sich einander wie Zwillinge gleichen

  Trattinnick, L. (1819). Die Dattelpalme, eine Bewohnerin des österreichischen Kaiserthumes. In: Sartori, F. (Hg.). Österreichs Tibur, oder Natur- und Kunstgemählde aus dem österreichischen Kaiserthume, 129-142: 139.

  1893

  Es giebt Uredineen, welche nur deshalb als verschiedene Species angesehen werden, weil einzelne Stadien derselben verschiedene Wirte haben müssen; solche Species zeigen dann keine sicheren morphologischen Unterschiede. Für sie wird der Terminus „Species sorores“ vorgeschlagen.

  Schroeter, J. (1893). Zur Entwickelungsgeschichte der Uredineen. Schles. Ges. f. vaterl. Cultur. 71 (II. b: botan. Sect.), 31-32: 31.

  1940

  Sibling species: The […] condition exists where pairs or larger groups of related species are so similar that they are generally considered as one species, or at least have in the past for a long time been mistaken for one another. Several such incompletely analyzed species groups are known from the genus Drosophila, for example, Drosophila “obscura” and “affinis.” The species of the flycatcher genus Empidonax are the closest to this situation that we find among North American birds, although this case was completely settled more than a generation ago. From Europe two pairs of exceedingly similar species of birds are known, the two chickadees (Parus atricapillus and palustris) and the two creepers (Certhia famnitiaris and brachydactyla).

  Mayr, E. (1940). Speciation phenomena in birds. Amer. Nat. 74, 249-278: 258. 

  1942

  pairs or even larger groups of related species which are so similar that they are considered as belonging to one species until a more satisfactory analysis clears up this mistake. I call such morphologically similar and closely related, but sympatric species, sibling species. This corresponds to the “dual species” of Pryer and of Hering (1935), to the “Doppel-” or “Geschwister-”Arten of some German taxonomists, or the “espèces jumelles” of Cuénot (1936: 236). The category of sibling species does not necessarily include species which are phylogenetically siblings, for example, the members of a superspecies. The term sibling species is arbitrarily limited to species which are as similar as are twins or quintuplets. The term is merely a conventional label for a not-infrequent taxonomic situation and has been adapted from the equivalent German and French terms. It is used only as a practical category, not clearly separable from other groups of similar species.

  Mayr, E. (1942). Systematics and the Origin of Species: 151.
  

  1947

  The degree of morphological difference between two species is an exceedingly unreliable measure of the number of genic differences between them. Many sibling species of Drosophila are virtually indistinguishable morphologically even though they may differ by scores, if not hundreds, of genes. This is indicated, by their cytological, ecological, and physiological differences, as well as by their partial or complete sterility. […] Many of the cases of so-called “ecological or physiological” races of the literature are nothing but sibling or cryptic species. There is no evidence that these sibling species have evolved in any other way than by geographical speciation.

  Mayr, E. (1947). Ecological factors in speciation. Evolution 1, 263-288: 278; 282.
  

  1948

  Pairs or groups of morphologically nearly or completely identical species have been termed sibling species (Mayr, 1942, p. 151). Their existence is usually revelaed only if they coexist at the same locality, and in my original definition I had therefore limited the definition to sympatric species. This is, however, not necessary since it is feasible with modern techniques to test the conspecifity of allopatric populations.

  Mayr, E. (1948). The bearing of the new systematics on genetical problems: the nature of species. Adv. Genet. 2, 205-237: 226.