First Record of Sirodotia assamica (Batrachospermales, Rhodophyta) from the Western Ghats, India

The Western Ghats, a renowned biodiversity hotspot, have emerged as a critical region for discovering freshwater red algae, including numerous endemic and novel taxa. Sirodotia assamica Necchi, Rossignolo, Yasmin, West & Ganesan, a freshwater red alga of the family Batrachospermaceae, was originally described from Assam in northeastern India. This study documents its first occurrence in the Western Ghats of southern India, significantly extending its known geographical range. Specimens collected from a forest stream in Kerala were identified through comprehensive morphological analyses and molecular phylogenetic studies using rbcL and COI-5P gene sequences. Phylogenetic analyses using Maximum Likelihood and Bayesian inference confirmed the specimen's placement within S. assamica. Morphological observations revealed distinct deviations from the Assam populations, including variations in spermatangial arrangement and other structural features, suggesting possible regional adaptations or intraspecific variability. This study highlights the value of combining morphological and molecular approaches for accurate taxonomic identification. The discovery of S. assamica in the Western Ghats highlights the region's potential for expanding knowledge of freshwater red algal diversity.