The morphological, developmental and molecular landscape of Grateloupia qingdaoensis Li et Ding

The rhodophyte marine algal genus Grateloupia (Halymeniaceae, Halymeniales) is distributed worldwide, including in offshore southeastern China. Here, we investigated morphology, carpospore development, ecological habits, and molecular analyses of a rarely studied species, Grateloupia qingdaoensis . The carpogonial branch ampullae and auxiliary cell ampullae were the typical Grateloupia type (6cpb-5auxb type) and the type of spore development was “mediate discal type”. The life history included homotypic gametophytes (haploid), carposporophytes (diploid), and tetrasporophytes (diploid) and showed a typical isomorphic alternation of generations. By using single-factor and orthogonal experiments, we explored the effects of temperature, irradiance and seawater salinity on the early development of G. qingdaoensis. Each ecological factor showed distinct effect on the early development of G. qingdaoensis. Additionally, we found a significant interactive effect between temperature and irradiance on discord crust growth. The optimum conditions for the early growth of discoid crust and upright thalli were 20 °C, 80 μmol photons m −2 s −1 irradiance and 30‰ seawater salinity. To clarify its taxonomical status, we constructed the phylogenetic tree of rbc L gene sequences. Results showed that there was no pairwise divergence between G. qingdaoensis and G. asiatica from China. Our findings indicate that previous records without precise and comprehensive comparison and molecular analyses need to be re-examined to clarify the global distribution of this species.