BIOLOGISCHE UND SYSTEMATISCHE BEDEUTUNG VON CHEMISCHEN RASSEN

Abstract

The concept of chemical races (or chemodemes) is discussed from the botanical point of view. Chemodemes are defined as chemically distinct populations within a species. Chemodemes may – but need not – be simultaneously morphologically and (or) cytologically distinct. Very often chemodemes represent ecodemes ( = ecotypes) or topodemes (= topotypes). If we are predominantly interested in plant constituents chemically distinct populations within a species or aggregate species may adequately be called „chemical races” (or chemodemes). The race concept, however, is distinct from local polymorphism, i.e. genetically controlled chemical variation within a local population.

The importance of chemical polymorphism for plant breeding and biological and taxonomic aspects of chemical polytypism (species with several chemodemes) are discussed and illustrated by a number of examples.