Solving taxonomic species complexes of Stevia (Eupatorieae, Asteraceae) in southern central Andes: a morphometric and statistical approach

Abstract

The South American central Andes have a great richness of Asteraceae, where the genus Stevia (Eupatorieae, Piqueriinae) is also especially diverse. The taxonomy of Stevia species in thesouthern part of the central Andes pose a challenge because of the unclear delimitationamong the species and overlap of morphological characters. Two species complexes wereidentified for the region comprising north Argentina and southern Bolivia. In this study, ourobjectives were to employ morphometric analyses to assess the delimitation of taxa within theStevia alpina Griseb. and Stevia chamaedrys Griseb. complexes. We aimed to identify informativemorphological characters and gain insight into the identity of species in each group. To accomplishthis, we utilised cluster analysis, principal-component analysis, non-metric multidimensionalscaling and univariate analyses to evaluate 37 morphological traits. In total, 200 specimens wereexamined, covering the entire geographic distribution of each species complex. We foundsupport for the recognition of nine species: Stevia alpina, S. breviaristata Hook. & Arn.,S. chamaedrys, S. mandonii Sch.Bip., S. mercedensis Hieron., S. minor Griseb., S. potrerensisHieron., S. procumbens Hieron. and S. vaga Griseb. A new combination and status is proposedfor S. tarijensis Hieron., incorporating it as a variety of S. mandonii, and S. centinelae Cabrera andS. crassicephala Cabrera are merged as synonyms under the name S. alpina. Two neotypes aredesignated for the names S. mercedensis and S. potrerensis.