BioConcepts

sister groupSchwestergruppe (ger.)

• A species or higher monophyletic taxon that is hypothesized to be the closest genealogical relative of a given taxon. Sister taxa are derived from an ancestral species not shared by any other taxon. Graphically, sister groups appear on a cladogram as lineages that arise as branches from a single divergence node. (Oxford Dict. of Genetics 2007)
  category systematics see also adelphotaxon

  1950

  man [wird] wohl annehmen müssen, daß die Arten der „Gattung“ Endonepenthia mit einigen Arten der Gattung Megaselia […] näher verwandt sind als mit anderen […], daß Endonepenthia also eine apomorphe und apooeke Teilgruppe, keine koordinierbare Schwestergruppe der Gattung Megaselia ist.

  Hennig, W. (1950). Grundzüge einer Theorie der phylogenetischen Systematik: 208.

  1953

  Keine als monophyletisch erkannte Tiergruppe kann ihren Platz im System zugewiesen erhalten, ehe nicht ihre Schwestergruppe bekannt ist.

  Hennig, W. (1953). Kritische Bemerkungen zum phylogenetischen System der Insekten. Beitr. Entom. 3, Sonderheft, 1-85: 9.

  1967

  The essence of that system is that, if certain attributes can be accurately categorised as “plesiomorphic” (primitive) and paired with corresponding “apomorphic” (derived) attributes, two taxa showing respectively the plesiomorphic and apomorphic members of such a pair indicate a dichotomy in a phylogenetic “tree”; in Hennig’s term, they are “sister-groups.” If then two taxa share an apomorphic attribute, they together constitute the sister-group of any third taxon (or group of taxa) that exhibits the corresponding plesiomorphic attribute; and, thus, the whole tree is reconstructed.

  Colless, D.H. (1967). The phylogenetic fallacy. Systematic Zoology 16, 289-295: 291.
  

  1982

  sister groups The two monophyletic groups produced by a single dichotomy; each is the other's nearest relative; sister species-groups.

  Lincoln, R.J., Boxshall, G.A. & Clark, P.F. (1982). A Dictionary of Ecology, Evolution and Systematics: 228.