Morphological and phylogenetic relationships within Viola sect. Sclerosium (Violaceae) in Iran

Viola sect. Sclerosium contains up to seven taxa distributed from northeastern Africa to western India. Here we used morphometry and Bayesian phylogenetic analyses of a low-copy nuclear gene (NRPD2a) to investigate the systematics of its three taxa occurring in Iran, i.e., V. behboudiana, V. cinerea, and V. stocksii. Features of stipules, and indument of peduncle, ovary and capsule were found to be important in separating the taxa morphologically. Divergence times, estimated using a relaxed molecular clock, suggest a crown node age of 4.1-10.1 million years (Ma) for sect. Sclerosium, coinciding in time with the intensification of the Indian monsoon. Ancestral (meso-) tetraploidy was inferred for V. stocksii and (neo-) allooctoploidy for V. behboudiana and V. cinerea, both of which were inferred to be alloploids of the V. stocksii lineage and another, unsampled lineage within sect. Sclerosium.