From Taxonomy to Phylogenetics: Life and Work of Willi Hennig.— By Michael Schmitt.

Abstract

The work of Willi Hennig brought about a paradigm shift in systematic biology by putting forward an approach to grouping species and lineages that in principle leads to reproducible and testable results (Farris 1979; Dupuis 1984; Schmitt 2003; Hall 2007; Wheeler 2008; Mishler 2009; Wiley and Lieberman 2011). Although Hennig's approach became quantitative and objective only after the development of computer algorithms by Farris (1970; also Kluge and Farris (1969), inspired by Herb Wagner's approach to grouping species, first shown in Hardin (1957)), it was Hennig (1949; also Hennig et al. (1953)) who had the crucial idea of contrasting plesiomorphic with synapomorphic and autapomorphic characters, who realized that synapomorphies could identify sister groups, and who put forward the concept of paraphyly, so essential to his insistence that only monophyla are worth studying and naming.