On the Phylogeny of the Subtribe Carduinae (Tribe Cardueae, Compositae)

A comparative morphological study of the subtribe Carduinae, tribe Cardueae, Compositae, on genus level was performed in order to reconstruct intergeneric relationships in a cladistic analysis. The Carduinae, which are the largest subtribe of the Cardueae, comprise about 1600 species, many of which are known as thistles and have ecological and economic significance, especially as weeds. The recognition of monophyletic groups within the Carduinae and the relationship between the Carduinae and the closely related subtribe Centaureinae are important aims of the present study. 52 characters, which are phylogenetically informative on the respective taxonomic level, are identified, corresponding to 66 character state transitions. Several new characters are described. Among the most important are the relative length, structure and symmetry of the pappus bristles, the shape and distribution of sclerenchyma elements in the pericarp, the wall reinforcements in the testa epidermis cells, and the shape of the cell walls in the dorsal corolla lobe epidermis. Ontogenetic studies in the achenes have helped to clarify the nature of structures such as the pappus base or the cupula of the Jurinea pappus. Cladistic analysis of 37 ingroup and three outgroup taxa using the program PAUP yields 48 most parsimonious trees. The results support the monophyly of the Carduinae+Centaureinae (= Cardueae s. str.). Berardia, which has been regarded as a genus of uncertain affinities, is morphologically closest to the hypothetical common ancestor of the Carduinae+Centaureinae in the cladogram. Within the ingroup consisting of Carduinae+Centaureinae, several well-supported groups of genera could be identified: the Centaureinae, the Cousinia group, the Jurinea group, the Saussurea group, and the Carduus-Cirsium group. The smaller genera Lamyropsis, Ptilostemon and Cynara form a predominantly Mediterranean complex together with the Carduus-Cirsium group, in which they probably represent early evolutionary lines. The basal relationships within the ingroup are characterised by a dichotomy which divides the ingroup into two large sister clades. This early split does not correspond to the Carduinae-Centaureinae subdivision. The Carduinae are paraphyletic. The sister group of the Centaureinae contains the large Carduinae complexes around the genera Cousinia, Jurinea and Saussurea, which are mentioned above. The Centaureinae and their sister group are united by morphological synapomorphies such as