Tropical-subtropical divergence in <i>Halophila beccarii</i> functional traits: environmental filtering and conservation implications in coastal China

We studied the relationships between functional traits of Halophila beccarii (shoot density, seed bank density, number of blades, above-ground biomass, below-ground biomass, leaf length, leaf width, and petiole length) and environmental factors (pH, salinity, temperature, physical disturbance by humans, and algal coverage) in eight populations along the coast of China. There were statistically significant differences in the functional traits of H . beccarii between tropical and subtropical regions. Traits such as shoot density, seed bank density, and biomass were notably higher in tropical populations, whereas leaf dimensions showed greater variability across regions. Further analysis using a linear mixed-effects model revealed that water temperature and salinity positively influenced shoot density, seed bank density, and biomass. Conversely, salinity negatively impacted traits such as leaf length, leaf width, and petiole length. Additionally, physical disturbance by humans and algal coverage demonstrated statistically significant negative correlations with shoot density and biomass. These findings provide insights into the environmental adaptability and conservation needs of this vulnerable seagrass species.