© Jörg Ochsmann 2000 

Centaurea species of the sections Acrolophus, Phalolepis and Willkommia are found from Central and Southern Europe to SW Asia. This group contains several taxa of uncertain taxonomic status that are very difficult to distinguish morphologically. 
Our investigations concentrated on the Centaurea stoebe group, which contains the following closely related taxa: Centaurea stoebe L. s.str., C. maculosa LAM., C. muretii JORD. and C. vallesiaca (DC.) JORD. As possible outgroup taxa the following species were included in the research program: C. alba L., C. cristata BARTL., C. paniculata L., C. leucophaea JORD., C. aplolepa MORETTI, C. diffusa LAM., C. sagredoi BLANCA and some more distantly related species from SW Asia (i.e. C. aggregata FISCH. & C.A. MEY. ex DC.).

Because of the lack of good morphological characters we started molecular analyses to reconstruct the phylogeny of the Centaurea stoebe group. The established phylogenetic markers as rDNA ITS (Internal Transcribed Spacer of the ribosomal genes of nuclear DNA) or cpDNA (Chloroplast DNA) markers showed no good results (OCHSMANN, unpublished data). To get better resolution of the phylogenetic relations, parts of the rDNA IGS (Intergenic Spacer) between the 25S and the 18S gene were established as a molecular marker for low taxonomic levels (OCHSMANN & HELLWIG, in preparation). In addition we used RAPD (Random Amplified Polymorphic DNA) analysis on population level and for detection of hybrids.

The results of morphological and molecular studies were combined to reconstruct the phylogeny of the Centaurea stoebe group. From molecular data it has become obvious that the separation of Sect. Acrolophus and Phalolepis has to be discarded as indicated by WAGENITZ [Flora 187: 341-351 (1989)]. As a consequence of molecular investigations the taxonomic rank of several taxa of the Centaurea stoebe group has to be changed. Moreover it seems apparent that the distribution of the taxa in the southern Alps corresponds with the history of glaciation.

This project is supported by the Deutsche Forschungsgemeinschaft.