Molecular and morphological systematic investigation of Chondrophycus minutus sp. nov. (Ceramiales, Rhodophyta) from India

We describe a new species from Tamil Nadu, India, Chondrophycus minutus sp. nov. based on molecular and morphological data. Chondrophycus minutus is characterized by 1) a small, terete, cartilaginous thallus up to 0.6 cm in height, 2) an alternate branching pattern, 3) thick-walled and obconical cortical cells, 4) appearing polygonal to irregularly angular in surface view, 5) lacking secondary pit connections, 6) tetrasporangia with right-angle arrangement. Molecular phylogenetic analyses confirmed our C. minutus as a distinct species, showing sequence divergences from other Chondrophycus species ranging from 5.3–9.6% for rbcL gene and 7.4–10.9% for COI-5P. Chondrophycus minutus sp. nov. is distinguished from two species known to occur in India, C. brandenii and C. ceylanicus. It differs from C. brandenii, which has terete to partially compressed thalli, irregular radial branching, and thin-walled medullary cells, and from C. ceylanicus, which is characterized by a compressed thallus with palisade-arranged, elongated cortical cells. This study identifies Chondrophycus minutus as a newly described species in the Indian macroalgal flora, supported by molecular and morphological evidence.