Biosystematics and Evolution of Cultivated Coca (Erythroxylaceae)

Abstract

ABSTRAcr. Erythroxylum coca vars. coca and ipadu and E. novogranatense vars. novogranatense and truxillense are closely related taxa cultivated in South America for their cocaine-bearing leaves. Taxonomically they have been variously treated, ranging from one to three separate species. Erythroxylum novogranatense var. truxillense is morphologically somewhat intermediate between E. c. var. coca and E. n. var. novogranatense and has been suggested to be a hybrid between the two. Evidence from artificial hybridizations, leaf flavonoid chemistry, and breeding system studies was used to clarify the taxonomic and evolutionary relationships of these plants. This evidence suggests that E. n. var. truxillense is intermediate between E. coca and E. n. novogranatense but it is not a hybrid between them. These three taxa represent a linear evolutionary series, with E. c. var. coca the ancestral taxon, E. n. var. truxillense derived from it, and E. n. var. novogranatense derived from E. n. var. truxillense. Eythroxylum c. var. ipadu was independently derived from E. c. var. coca. All of the taxa are partially isolated genetically except E. c. var. coca and E. c. var. ipadu. The taxonomic treatment that best reflects their relationships is to regard E. novogranatense var. novogranatense and E. n. var. truxillense as varieties of a species distinct from E. coca. Only limited material of E. c. var. ipadu was available for study, but it might better be regarded as a cultivar of E. coca.