Variability in prickly sow-thistle (Sonchus asper) from western Mediterranean region

Abstract

We studied the morphological variability of Sonchus asper (L.) Hill in the western Mediterranean region by means of multivariate analysis. A two-step clustering method indicated that selection of a two-cluster model was optimal, with anther length and ligule length as the main characters contributing to cluster delimitation. These variables presented a general bimodal pattern of frequency distribution, denoting the presence of two floral morphotypes in the complex that, although partially sympatric, seem to show distinct geographical ranges and important differences in their reproductive systems. In addition, a preliminary karyological analysis yielded differences in chromosome morphology between the two morphs. Possible taxonomic implications of this variability are discussed. We propose the segregation of plants showing different flower morphotype as different taxa at specific level: large-flowered plants should be designated as Sonchus nymanni Tineo & Guss. in Guss., while small-flowered plants correspond to Sonchus asper (L.) Hill.