Analysis of phylogenetic relationships of Potamogeton and Stuckenia (Potamogetonaceae) in Iran based on morphological, anatomical and molecular data

Potamogeton and Stuckenia comprise 90 and 7 respectively accepted species worldwide. Because of a wide range of intraspecific morphological variability including extensive phenotypic plasticity and ecological diversity, Potamogeton and Stuckenia are considered notoriously difficult taxa. A total of 100 accessions representing 11 taxa of Potamogeton and three of Stuckenia were collected across Iran. An initial screening based on allele lengths of highly variable cpDNA sequences allowed considering 59 different accessions of one to eight individuals of each species for further morphological, anatomical, and molecular analyses. NrDNA ITS and three plastid regions (rbcL, matK, and trnH-psbA) were employed to reconstruct molecular phylogenies using maximum likelihood and Bayesian inferences. Analyses of nrDNA ITS sequences generated well-resolved tree topology than plastid data. There was some incongruence between nuclear data and concatenated chloroplast marker data (P=0.001). Additional testing of ISSR and SRAP markers for 48 specimens showed higher resolution in species delimitation among linear leaved taxa, though not conclusive. Anatomical features could not separate Iranian species alone and should be used in combination with morphological characters that were highly informative. The results showed that Iranian Potamogeton species contain a rich gene pool due to the specific and diverse geographical conditions of Iran.