Systematic and molecular biological study of Sambucus L. (Caprifoliaceae) in Iran

Sambucus is a medicinal plant with approximately 25 accepted taxa in the world from which two are present in Iran, S. nigra and S. ebulus. In order to evaluate the affinities and relationships in Sambucus and resurrect subspecies or verities in these two species, the micro-morphological, anatomical and molecular properties of Sambucus species of Iran have been studied. Pollen and seed surfaces of two species were examined with scanning electron microscope. In micro-morphological studies, the pollen shape is prolate-spheroidal in S. nigra but subprolate in S. ebulus. The exine sculpture is microperforate in S. nigra and is reticulate-microechinate in S. ebulus. The surface of the seed in S. nigra is smooth, not elongated and no clear organizational pattern is discernable and the anticlinal walls are shallowly undulate. In S. ebulus, the seeds have a microperforate surface and the anticlinal walls are observed deeply undulate. Petiole anatomical studies show that vascular bundles and existence of druse crystals are diagnostic characters in studied species. Using nuclear (nrDNA ITS) marker, we reconstructed phylogenetic relationships within two species of Sambucus. The ITS dataset was analyzed by phylogenetic methods including Bayesian inference, maximum likelihood and maximum parsimony. In phylogenetic analyses, all members of this genus form a well-supported clade (PP = 1, ML/BS = 100/100). The Sambucus clade is composed of two clades. Clade I includes the populations of S. nigra and the clade II comprises the rest of the species of Sambucus (S. ebulus). NeighborNet diagram demonstrated separation of the studied populations. In general, molecular studies supported micro-morphological findings. Pollen, seed-coat characters and molecular phylogeny support the separation of S. nigra and S. ebulus.