Affinities of freshwater “Chantransia” stage algae (Rhodophyta) from China based on molecular and morphological analyses

Thorea baiyunensis sp. nov. (Thoreales, Rhodophyta) and T. okadae, a new record from China

“… pygmaea ” so far. It is clear that the morphological characteristics of the “ Chantransia ” stages cannot be used to determine the identity individual species ( Necchi and Oliveira 2011 ; Han et al 2021 ). However, how genetic information and environmental factors regulate the morphological expression of “ Chantransia ” stages remain unclear.…”

“…With the widespread application of molecular data in the taxonomy of freshwater red algae, the view that morphologically simple organisms have considerable genetic diversity and species richness has been widely recognized ( Johnston et al 2018 ; Han et al 2020 , 2021 ). In the past few years, several new species of the Batrachospermales and Thoreales were proposed based on the “ Chantransia ” sporophyte generation, such as T. quisqueyana , Sheathia shimenxiaensis J.-F.Han, F.-R.Nan et S.-L.Xie, S. jiugongshanensis J.-F.Han, F.-R.Nan et S.L.Xie, and S. qinyuanensis J.-F.Han, F.-R.Nan et S.L.Xie ( Johnston et al 2018 ; Han et al 2020 , 2021 ). In this article, based on the rbc L and COI-5P sequences, all five samples utilized in this study were unquestionably proved to be the “ Chantransia ” stages of two species of genus Thorea , whose gametophytes have never been reported in China before.…”

“…Furthermore, the molecular phylogeny based on the rbc L, COI-5P and the plastid 23S rRNA (UPA) genes unequivocally demonstrated that a sample morphologically similar to A. macrospora (Wood) Sheath & Burkholder represented the “ Chantransia ” phase of T. hispida ( Han et al 2021 ).…”

“…Like other sexually reproductive species of freshwater red algae, Thorea species have a triphasic life history, including gametophyte, carposporophyte, and a diminutive diploid sporophyte termed “ Chantransia ” stage. Recently, several studies have focused on the phylogenetic affinities of the “ Chantransia ” stages of Thorea and the relationship between the isolates in this stage and a phylogenetically distant genus Audouinella Bory ( Necchi and Oliveira 2011 ; Han et al 2021 ). Based on these studies, new species were proposed, new distributions were found, and higher Thorea species diversity was revealed ( Johnston et al 2018 ; Han et al 2021 ).…”

“…Recently, several studies have focused on the phylogenetic affinities of the “ Chantransia ” stages of Thorea and the relationship between the isolates in this stage and a phylogenetically distant genus Audouinella Bory ( Necchi and Oliveira 2011 ; Han et al 2021 ). Based on these studies, new species were proposed, new distributions were found, and higher Thorea species diversity was revealed ( Johnston et al 2018 ; Han et al 2021 ). In terms of morphological characters, the “ Chantransia ” stages of the Thoreales are very similar to those of Audouinella taxa, although some studies have indicated that thallus color can be used as a reliable character ( Zucchi and Necchi 2003 ) to distinguish true Audouinella (reddish) from “ Chantransia ” (bluish).…”