Taxonomic transfer of Gongrosira burmanica Skuja (Chaetophorales, Chlorophyceae) to Ulvella P. Crouan et H. Crouan (Ulvales, Ulvophyceae) based on morphological observation and phylogenetic analyses

: Two green algal specimens, newly recorded from China, were identified as Gongrosira burmanica Skuja based on their distinctive morphology. The thallus of these specimens appeared hemispherical, forming cushion-like masses with calcification, and featured erect filaments that were pseudodichotomously branched and partially merged with each other, radiating from the base. Ultrastructural investigation, particularly the observation of pyrenoids penetrated by thylakoid membranes and the absence of plasmodesmata in adjacent cells, provided confirmation that Gongrosira burmanica Skuja should be excluded from the order Chaetophorales. Phylogenetic evidence, based on nucleus (18S rDNA) and chloroplast (tufA, rbcL) sequences, clearly indicated that Gongrosira burmanica Skuja should be reclassified within the Ulvales (Ulvophyceae) as a new combination species of the genus Ulvella P. Crouan et H. Crouan, rather than the Chaetophorales (Chlorophyceae). Further evaluation of the genus Gongrosira KĂźtzing is necessary, especially by examining additional specimens, including the type species. It should be noted that the diversity of the Ulvales has been underestimated.