Phylogenetic position of Jaoa, a green algal genus endemic to China Huan Zhu, 1,2 Shuang Xia, 1,2 Qi Zhang, 1,2 Guo-Xiang Liu 1 * and Zheng-Yu Hu 1 1 Key Laboratory of Algal Biology, Institute of Hydrobiology, the Chinese Academy of Sciences, Wuhan, and 2 University of Chinese Academy of Science, Beijing, China SUMMARY Jaoa prasina, a freshwater green alga endemic to China, was collected from a stream in Hubei province, China. Unialgal cultivation, morphological observation, and phylogenetic analyses of small subunit ribosomal DNA and RuBisCO large subunit sequences were performed. When cultured on agar medium, the alga was irregularly filamentous, similar to marine species of Acrochaete. Aplanospores were observed on solid medium. A vesicular-like thallus without rhizoids developed in liquid medium, similar to specimen development in natural habitats. Molecular phylogenetic analyses revealed that Jaoa was closely related to the marine genera Acrochaete Pringsheim and Ulvella Crouan & Crouan. The results suggested the genus Jaoa is a member of the family Ulvellaceae (Ulvophyceae), which contains mostly marine algae. The family name Jaoaceae should be abandoned. We speculate that Jaoa may have evolved from a marine Ulvellaceae ancestor. Key words: Acrochaete, Jaoa, phylogeny, Ulvellaceae, Ulvophyceae. INTRODUCTION The green algal family Jaoaceae (Chlorophyta) contain- ing a single genus with two species, Jaoa prasina (Jao) Fan and Jaoa bullata (Jao) Fan, has only been docu- mented in China (Jao 1941; Wang et al. 1988; Li & Hu 2003; Shi et al. 2004). Jaoa Fan has a wide distribu- tion from Xinglong County, Hebei province, northern China to Menglun County, Yunnan province, southern China (Jao 1941; Wang et al. 1988; Li & Hu 2003; Shi et al. 2003, 2004). The young fronds of Jaoa are spherical or ellipsoidal, grass-green or olive in color, with a surface being more or less uneven; the mature plants are disc-shaped, vesicular, olive or dark-green, hollow with stout folds on the surface, and attached to substrata by rhizoids (Jao 1941). The thalli of Jaoa clearly have a distromatic (Jaoa prasina) or trilaminar (Jaoa bullata) structure, which is the traditional species-level delimiter in the genus. Cells coalesce to produce pseudoparenchymatous masses. The globular inner cells are larger than the outer cells, which are ellipsoidal and flask-shaped in outline. Often several outer cells are attached to an inner cell in the pseu- doparenchymatous masses (Li & Bi 1998). Viewpoints on the taxonomic position of Jaoa in the Chlorophyta have been changing. Jaoa was first identi- fied by Jao in Chongqing in 1941 and established as a new family, Coelodiscaceae, comprising a single new genus, Coelodiscus Jao (Jao 1941). In 1964 Fan changed the genus name from Coelodiscus to Jaoa because Coelodiscus Jao 1941 was a later synonym of Coelodiscus Baillon 1858, a flowering plant genus (Euphorbiaceae), and hence illegitimate according to the rules of the International Code of Botanical Nomen- clature. Similarly, the name Coelodiscaceae was changed to Jaoaceae. The family was placed in the Ulotrichales (Fan 1964). Li and Bi (1998) placed the family in Chaetophorales in Flora Algarum Sinicarum Aquae Dulcis. Both Printz (1964) and Silva (1982) considered Jaoaceae lacking in wide acceptance, and moreover argued that Jaoa prasina and Jaoa bullata were not distinct species. Printz (1964) classified Jaoa (Jao) Fan in the Chaetophoraceae. Wang et al. (1988), and Li and Hu (2003) observed the ultrastructure of Jaoa, and the former reported that the ultrastructure of the chloroplast of Jaoa was similar to members of the Ulvaceae. Overall, the diversity and species-level delimitation of this genus has been surrounded by con- siderable uncertainty. The predominant focus on mor- phology in previous taxonomic studies has contributed to the uncertainty. We examined Jaoa obtained from Xianning County, Hubei province (China), in March and identified it as Jaoa prasina. We observed the vegetative morphology both in natural habitat and in laboratory culture condi- tions, and also reassessed the taxonomic position based on phylogenetic analyses of small subunit ribosomal DNA (SSU rDNA) and RuBisCO large subunit (rbcL) sequences. *To whom correspondence should be addressed. Email: liugx@ihb.ac.cn Communicating editor: O. De Clerck. Received 10 August 2012; accepted 1 April 2013. doi: 10.1111/pre.12021 Phycological Research 2013 © 2013 Japanese Society of Phycology