The systematic position of Centaurea ensiformis and Centaurea isaurica from Turkey and the evolution of some characters in Centaurea

The systematic affinities of Centaurea ensiformis and Centaurea isaurica, two rare Turkish endemics, were difficult to establish on the basis of morphological characters. Their systematic position was recently unraveled by DNA sequence analyses, and they appear to be related to sect. Cheirolepis. We have carried out a detailed study of the main morphological characters that are used for the sectional classification of Centaurea, the appendages of the bracts and the achenes, in a wide sample of sect. Cheirolepis. The main conclusion is that the extremes of diversity in the shape of the appendages can be connected by intermediate forms, and a hypothesis of the evolution of the appendages is offered. This hypothesis, together with some cases of parallel evolution, would explain why there are so many examples of misclassifications based on this character alone. Regarding achenes, our conclusion is that they are important for the species level, but not useful for sectional classification of this group. Finally, the closely related sect. Plumosipappus, described mainly on microcharacters of the pappus, must be merged into Cheirolepis.