Natural Delineation, Molecular Phylogeny and Floral Evolution in Campanula

The circumscription and infrageneric classification of Campanula is highly controversial. Independent and combined data from nuclear and chloroplast sequences (trnL–trnF, ITS) were analyzed with Bayesian and parsimony methods to elucidate the phylogenetic relationships of Campanula and allied genera, and explore the biological processes that occurred during the evolution of this genus. The main sections and subgenera of Campanula and related genera were sampled extensively. Chromosome numbers, corolla types, habit and capsule dehiscence were mapped on the trees to search for evolutionary patterns. The phylogenetic analyses revealed that Campanula, as currently circumscribed, is not monophyletic. This genus is divided into two main clades: a large core of Campanula species that includes related genera (Adenophora, Asyneuma, Azorina, Campanulastrum, Diosphaera, Edraianthus, Githopsis, Hanabusaya, Heterocodon, Legousia, Michauxia, Petromarula, Physoplexis, Phyteuma, Trachelium, and Triodanis), and a clade constituted by Musschia plus two Campanula species. The large core of Campanula is divided into two main groups, a rapunculoid and a campanuloid group. Both Bayesian and Parsimony analyses indicate that the main morphological characters used in classifications, such as flower shape and capsule dehiscence, have arisen in parallel. Strong selective pressures from pollinators are suggested to explain floral convergence. We put forward two different proposals in order to accomplish a classification of Campanula that more accurately reflects the evolution of this genus.