Morphology and phylogenetic position of Stomatochroon reniformis var. chinensis var. nov. (Trentepohliales, Ulvophyceae), a rare endobiotic alga from China

Specimens of the genus Stomatochroon (Trentepohliales, Ulvophyceae) were found in leaf stomata of the fruit tree Syzygium samarangense (Myrtaceae). Phylogenetic analysis based on 18S rDNA sequences showed that Stomatochroon was closely related to Cephaleuros. The specimens were identified as Stomatochroon reniformis based on the branched internal filamentous and ovoid gametangia. However, our specimens differed from the type by having larger basal and clavate cells, a noticeable stalked gametangium, and secondary growth of the sporangiate-laterals. Consequently our taxon was described as a new variety, S. reniformis var. chinensis var. nov. We found no physiological dysfunction or host tissue hyperplasia was caused by the algal infection. The waterlogged and dead host tissue was probably caused by plugged host stomata that resulted from growth of this alga. This interpretation means this alga was an endophyte, not a parasite.