Morphological convergence or lineage sorting? The case of Cytisus purgans auct. (Leguminosae)

(ENG) Genetic distances among populations and phylogenetic hypothesis concerning origin and diversification of Cytisus purgans s.l. are inferred by analysis of the ITS and ETS regions (nrDNA) and the trnL-trnF intergenic spacer (cpDNA). Cytisus purgans s.l., a shrub of western Mediterranean mountains, consists of two evolutionary units: C. balansae (Boiss.) Ball (Morocco, Algeria, southern Spain) and C. oromediterraneus Rivas Mart. & al. (France, Portugal, Andorra, central and northern Spain). The two units are related to different Cytisus groups, in Bayesian and Maximum Parsimony analyses, and may be genetically unrelated, their morphological similarities being the result of convergence. However, the incongruence in the position of both species in the ITS tree and the ETS and trnL-trnF trees suggests an alternative explanation. Genetic differentiation could be due to lineage sorting of allelic polymorphism in the ITS region of the common ancestor, and the morphological similarities the result of morphological parallelism. Cytisus balansae conserves ITS sequences related to old Cytisus taxa; rapid radiation may have led to a western Mediterranean lineage in which C. oromediterraneus originated.