An integrated morpho-molecular study of Salicornia (Amaranthaceae-Chenopodiaceae) in Iran proves Irano-Turanian region the major center of diversity of annual glasswort species

Salicornia (Chenopodiaceae) with ca. 25-30 annual, hyperhalophytic succulent species is a taxonomically difficult sub-cosmopolitan genus. The taxonomic complexity arose from succulent shoots causing a lack of taxonomically useful characters, scarcity and variability of characters, and poor genetic differentiation. The Irano-Turanian region, a major center for several lineages of chenopod diversification, is also an important diversity center and more likely the center of origin of annual Salicornia. This paper presents long-term comprehensive morpho-molecular and cytological studies of the genus in Iran, as the most species-rich country in the Irano-Turanian region. We originally generated 250 sequences of one nuclear (ETS) and two plastid markers (atpB-rbcL spacer, intron rpl16). We analyzed a global ETS dataset including 257 sequences of putative 28 taxa using Bayesian inference and maximum likelihood analysis. In order to evaluate the application of plastid data in species taxonomy in annual Salicornia, we performed numerical morphological analysis (principal component analysis and agglomerative hierarchical clustering) of 186 Iranian accessions using 18 characters. Our results (1) confirm the efficiency of plastid sequences comparing to ETS sequences for clarifying species-level phylogeny of Salicornia; (2) identify the S. persica clade as a monophyletic Irano-Turanian endemic lineage; (3) recognize nine origins of the Irano-Turanian Salicornia based on nuclear ETS sequences; (4) approve the monophyly of tetraploid species using plastid sequences; (5) provide a synopsis and diagnostic key for 10 Iranian taxa of Salicornia; (6) describe S. turanica sp. nov.; (7) classify S. iranica at infraspecific level (S. iranica subsp. iranica, S. iranica subsp. rudshurensis comb. nov., S. iranica subsp. sinus-persica comb. & stat. nov.); (8) suggest three informal taxa to be studied in the future; and (9) discuss the threatened status of Salicornia-dominated ecosystems in Iran.

Automated summary

This study on Salicornia in Iran confirmed the efficiency of plastid sequences in clarifying the phylogeny of Salicornia at the species level, identified a unique S. persica clade in the Irano-Turanian region, recognized nine origins of Irano-Turanian Salicornia based on nuclear ETS sequences, validated the monophyly of tetraploid species using plastid sequences, and provided a synopsis and diagnostic key for 10 Iranian taxa of Salicornia.