A 'chemotype' (sometimes 'chemovar') is a chemically distinct entity in a
plant or
microorganism, with differences in the composition of the
secondary metabolites. Minor
genetic and
epigenetic changes with little or no effect on morphology may produce large changes in the chemical
phenotype.
A good example of a plant with many chemotypes is ''
Thymus vulgaris''. While largely indistinguishable in appearance, specimens of ''T. vulgaris'' may be assigned to one of six different chemotypes, depending on whether the primary component of the
essential oil is
thymol,
carvacrol,
linalool,
geraniol,
thujanol-4 or
terpineol. Such chemotypes may be indicated as ''Thymus vulgaris'' ct. thymol (red thyme), or ''Thymus vulgaris'' ct. geraniol (sweet thyme), etc. Such an indication has no taxonomic standing, also see
ecotype.