Cladistics (from Greek κλάδος ‘branch’ and the suffix -istic from Greek -ιστικός) is "a method of classification that groups taxa hierarchically into discrete sets and subsets. Cladistics can be used to organize any comparative data (e.g. linguistics) but its greatest application has been in the field of biological systematics. Cladistics methods were made explicit by the German entomologist Willi Hennig (1950), and became widely known to English speakers in 1965 and 1966 under the name 'phylogenetic systematics'. (...) The aim of cladistic analysis is to hypothesize the sister-group hierarchy and express the results in terms of branching diagrams. These diagrams are called cladograms, a reference to the fact that | they purport to express genealogical units or clades." (Kitching et al. 1998, 1-2).
Strictly speaking, the cladistic method implies a clear distinction between apomorphic and plesiomorphic characters or character states (characters can be molecular, but also morphological, physiological, etc.). This distinction is not necessarily made in other types of phylogenetic methods, which often rely on big data taken from molecular biology. Therefore, cladograms that result from such an analysis do not necessarily show genealogical relationships, but rather groups based on mere similarities.
– Kitching, Ian J., Peter L. Forey, Christopher J. Humphries, and David M. Williams. 1998. Cladistics: The Theory and Practice of Parsimony Analysis. 2nd ed. Oxford: Oxford University Press.
– Lipscomb, Diana. 1998. Basics of Cladistic Analysis. Washington DC: George Washington University. http://www.gwu.edu/~clade/faculty/lipscomb/Cladistics.pdf. Accessed 28 October 2015.
– Schmitt, Michael. 2013. From Taxonomy to Phylogenetics: Life and Work of Willi Hennig. Leiden: Brill.
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