AFLP Phylogeny of 36 Erythroxylum Species

Four taxa of the plant genus Erythroxylum; Erythroxylum coca var. coca (Ecc), Erythroxylum coca var. ipadu (Eci), Erythroxylum novogranatense var. novogranatense (Enn) and Erythroxylum novogranatense var. truxillense (Ent) are cultivated primarily for the illicit extraction and processing of cocaine. Despite their economic and medical importance, the evolutionary history of these species remains unknown in a modern phylogenetic framework. The aims of this study were to: (a) investigate the relationship among the cultivated and a select number of non-cultivated taxa, and (b) test Plowman??s (Journal of Psychodelic Drugs 11:103?C117, 1979b) linear progression hypothesis of the cultivated Erythroxylum taxa versus Johnson??s et al. (Annals of Botany 95:601?C608, 2005) hypothesis that Ec and En are sister species. AFLP phylogeny was used to compare the relationships among 36 Erythroxylum species (133 accessions) spanning the geographic distribution of the genus. A Maximum Parsimony tree revealed both geographic and taxonomic partitioning into clades representing species from Africa, Asia-Pacific and the New World (Tropical Americas). Ec and En formed distinct clades, indicating they are sister species and a cluster of non-cultivated species were the most closely related to the cultivated species. Multivariate ordination analysis was used to evaluate the relationship between cultivated and non-cultivated Erythroxylum taxa from the Tropical Americas. Our results support the hypothesis that the cultivated species are more closely related to each other than to any other species of Erythroxylum, but refute the hypothesis that Ent (and Enn) descended from Ecc. Instead our data suggest an independent, non-linear evolutionary relationship between Ec and En. Finally, the AFLP analyses identified significantly different genetic groups within Erythroxylum suggesting that the current intrageneric classification of this genus be revised.