Phylogenetic relationships in the species-rich Irano-Turanian genus Alcea (Malvaceae)

The genus Alcea (Malvaceae) includes approximately 50 species of mainly Irano-Turanian distribution and is considered one of the most challenging genera of the Middle East, due to its uniformity and pronounced plasticity in morphological traits. Here, using three molecular markers (nrDNA ITS and the plastid spacers psbA-trnH and trnL-trnF), we present a phylogeny of Alcea and test previous infrageneric taxonomic hypotheses as well as its monophyly with respect to Althaea, a genus with which it has often been merged. We additionally discuss morphological variation and the utility of morphological characters as predictors of phylogenetic relationships. Our results show that while molecular data unambiguously support the circumscription of Alcea inferred from morphology, they prove to be of limited utility in resolving interspecific relationships, suggesting that Alcea's high species diversity is due to rapid and recent radiation. Our work provides the first phylogeny of Alcea and aims to set the scene for the study of processes underlying species radiation in the Irano-Turanian region, a main centre of species diversity for many medium-sized to large genera that remains greatly understudied.