A review of the history and taxonomy of the enigmatic southern African endemic wild lettuce Lactuca dregeana DC. (Asteraceae: Lactuceae: Lactucinae)

Abstract

We review the herbarium material and taxonomic literature pertaining to Lactuca dregeana DC., a poorly understood southern African endemic species that is closely allied to and sometimes treated as conspecific with the European L. serriola L. Published molecular and karyological analyses on the species have all used cultivated accessions of undetermined origin. On the basis of morphology, historical occurrence, and ecology we conclude that L. dregeana represents a distinct genotype and should be maintained as a separate species unless analysis of appropriately documented material indicates otherwise. We lectotypify the name to fix its application and provide a complete description of the species, with illustrations, and a distribution map, as well as an identification key to the native and naturalised Lactuca species in South Africa. The paucity of recent collections of L. dregeana in herbaria suggests that the range of the species has been significantly reduced over the past century. Efforts should be made to determine its current distribution in the wild, especially given its close relationship to cultivated lettuce.