Phylogenetic relationship of genus Kumanoa based on chloroplast Psaa and psba genes

Kumanoa intorta (former Batrachospermum intortum) and K. curvata (former B. curvatum) are two species of genus Kumanoa originally from China. In this study we amplified and sequenced the chloroplast psaA and psbA genes of these two species and of other six freshwater Rhodophyta species. We aligned their sequences with related groups from GenBank, and constructed phylogenetic trees of both single gene and combined genes by using the methods of Bayesian analysis, maximum likelihood and neighbor-joining. The trees generated with three different methods showed similar topologies and thus inferred consistent phylogenetic relationships. The two species from genus Kumanoa could form one clade with high supportive values but should be separated from genus Batrachospermum. The analysis above supported our report about a new genus Kumanoa. The molecular biological study of Kumanoa species originally from China revealed similar results with those originally from South America and Australia, indicating wide geographical areas of this genus. The phylogenetic tree demonstrated a close relationship between genus Kumanoa and Batrachospermum. According to the characteristics of the carpogonial branch, we deducted that the evolution of genus Kumanoa was later than that of Batrachospermum, but earlier than that of Acrochaetiales and Thoreales. B. gelatinosum should be separated from other section Batrachospermum species and be classified as an independent section. The construction of the order Thoreales could be supported by the fact that Thoreales and Batrachospermales should be separated. Furthermore, our study suggested that psaA and psbA genes could be used as molecular markers in the study of the phylogenetic relationships of Rhodophyta.