Warren H. Wagner Jr. (August 29, 1920 - January 8, 2000) was an eminent American botanist who lived in Michigan. A longtime faculty member at the University of Michigan (Ann Arbor), he developed, in the early 1960s, the first algorithm for discerning phylogenetic relationships among species based upon their respective character states observed over a set of characters. This work was honored by James Farris and Arnold Kluge in their later appellation of related algorithms as "Wagner parsimony." Wagner specialized in the ferns, especially the Botrychiaceae. The standard botanical author abbreviation W.H.Wagner is applied to species he described. Apparently among modern phylogenetic systematists, Wagner is alone in having been mentioned in a Hollywood film (A New Leaf, starring Elaine May and Walter Matthau). Note: not to be confused with the American botanist Warren L. Wagner (1950- ).
