Progeny from populations that are distinguishable with one or more heritable characters is a weak yet sufficient definition of hybrid (Harrison, 1990) and used here. “Species are groups of interbreeding natural populations which are reproductively isolated from all other such groups” according to Mayr (1959). This is the biological species concept and used here. Descent from an origin is vertical, whereas mutation to create the same phenotype is horizontal. The approaches of Stebbens (1950), Grant (1981) and Rieseberg (1997) to hybridization are variously influenced by preDarwin Linnaean taxonomy which is currently changing to evolutionary or phylogenetic classification, emphasizing tree topologies. For discussion of macromutation, see Charlesworth (1990). How often do adaptations involve the fixation of macromutations?