Integrative morphological and DNA barcode insights into Suaeda species: Untangling phenotypic plasticity and taxonomic challenges of Suaeda maritima

Suaeda, a true halophytic genus comprising over 100 species, are distributed across salt marshes worldwide. It is rich in polyphenolic compounds and widely used in traditional medicine, food, and animal feed. However, its taxonomy remains challenging due to phenotypic plasticity, parallel evolution, and adaptations to diverse environmental conditions. Among the three Suaeda species reported in Sri Lanka, accurate identification of S. maritima was challenged by the presence of distinct morphotypes. Further, there is a severe dearth of information on both morphometrics and DNA barcodes in Suaeda species in South Asia. In the present study, a thorough analysis of morphological information along with DNA barcode data was conducted for all the Suaeda species and morphotypes found in Sri Lanka. BLASTn results and floral traits revealed that S. maritima exhibits a drastic phenotypic plasticity in Sri Lanka. In the phylogenetic analysis using ITS sequences, multiple species association was observed with S. maritima . Additionally, unweighted pair group method with arithmetic mean (UPGMA), hierarchical cluster analysis (HCA), and principal component analysis (PCA) analysis based on start codon targeted (SCoT) markers, indicated that S. maritima morphotypes did not form distinct clusters, further confirming its phenotypic plasticity.