A multivariate approach to assess the taxonomic utility of morphometric characters inDoronicum (Asteraceae, Senecioneae)

Abstract

A multivariate morphometric study based on 22 characters was carried out on samples of the 26 accepted species of the Eurasian and north-African genusDoronicum, to assess whether quantitative, mainly continuous, characters were of use in suggesting, delimiting and structuring natural groups. The study concentrated on three-medium sized to small groups: Mediterranean (D. plantagineum group), European (D. grandiflorum group), and central Asian. Two questions were addressed for each of these groups: species delimitation within them and the inclusion/exclusion of species of uncertain, but putative close affinities. Principal components analysis and discriminant analysis (canonical variates analysis), gave moderately satisfactory results. The addition of doubtfully-related species to presumably natural groups increased cohesiveness of the groups because the between-species differences were minimized when placed in a broader more diverse context. The relative status of the uncertain species, either as outliers or true members, was appropriately depicted by the scatterplots, but more convincingly solved when the species turned out to be outliers. Discrimination between species, which belong to cohesive groups was effective in some cases at least when using discriminant analysis, and the exceptions involved particularly problematic taxa. It was concluded that morphometric characters are a useful complementary source of information in groups where qualitative (in particular, shared) characters are scarce as is the case inDoronicum.