Molecular phylogenetic studies on Trigonella section Ellipticae (Trifolieae, Fabaceae) from India utilising nrDNA (ITS) and cpDNA (trnL–trnF & petL–psbE)

Abstract

This study highlights the critical importance of species delimitation in biodiversity conservation, focusing on the poorly understood Indian Trigonella species, with focus on T. sect. Ellipticae. Despite their ecological and socio-economic significance, these species, primarily found in the northwest Himalayas, have been inadequately catalogued and preserved. Adapted to harsh, dry environments, T. sect. Ellipticae exhibits morphological traits that complicate traditional species delimitation due to significant overlap among species boundaries. To address these challenges, we integrated molecular sequence data (nrDNA ITS and cpDNA (trnL–trnF & petL–psbE)) with morphological analysis, confirming the monophyly of Trigonella and revealing distinct evolutionary lineages within T. sect. Ellipticae. While nrDNA ITS sequences alone proved insufficient for resolving species relationships, phylogenetic investigations utilizing plastid data identified three distinct clades, enhancing taxonomic clarity. The study also suggests that observed morphological variations in T. cachemiriana may be due to phenotypic plasticity rather than distinct evolutionary lineages. We propose a new combination, T. emodi var. gracilis, to better represent the diversity within this group. Overall, this research underscores the necessity of combining molecular and morphological approaches for effective species delimitation, contributing to broader biodiversity conservation efforts in India, where many species remain inadequately catalogued. As the urgency for conservation increases, refining taxonomic frameworks is essential for ensuring that conservation strategies are based on accurate biological data.