A molecular phylogeny reveals frequent changes of growth form in Carlina (Asteraceae)

The genus Carlina, with its 28 currently accepted species, ranks among the most thoroughly studied plant genera in Europe. Previous evolutionary hypotheses rested on a priori assumptions of character change, but for this study, DNA sequence data from nuclear ETS and three chloroplast regions obtained from all but one species of Carlina were used to produce a phylogenetic hypothesis. The results reveal that early branching lineages were morphologically divergent and that growth form shifts occurred more often and in different directions than previously thought, rendering a reconstruction of character states for the common ancestor of Carlina difficult to achieve. Nonetheless, results indicate that treelets were not plesiomorphic and that they most likely evolved in parallel in two island lineages growing in Macaronesia and in the Aegean. In addition, an independent evolution of two annual species in Carlina was revealed and most of the 50 morphological, biochemical, and karyological characters plotted on the tree proved to be homoplasic. Twenty-three anatomical characters from the stem-base/hypocotyl region provided no clear evidence for secondary woodiness and only the length of libriform fibers was clearly associated with plant height, but not without exceptions.