Molecular phylogeny of Sonneratia

Abstract

Among the mangrove members grown in Okinawa Prefecture, Japan, Sonneratia alba Sm. placed in the family Sonneratiaceae has a specific character of yellowish green colored calyx, while the same species grown in Pan Yi River, Phang-naga, Thailand has the same species but have reddish colored calyx. To pinpoint whether they belong to different species, we conducted molecular phylogenetic study on the genus Sonneratia using DNA sequence information of chloroplast ribosomal protein L9 gene (rpL9) and nuclear cysteine proteinase inhibitor gene (cpi). Our results show that S. alba, S. apetala, S. griffithii, S. ovate, and S. caseolaris are distinct species, but S. lanceolata is a form of S. caseolaris. Sonneratia apetala is very closely related to S. griffithii and S. caseolaris is a diverse species showing considerable genetic differentiation. The Japanese populations or Thai populations of S. alba do not form a monophyletic lineage, suggesting that these populations belong to the same species. Natural hybridizations between S. alba and S. grifithii in Thailand were confirmed again and the hybrid is suggested to be given a name S. ×albo-griffithii. Either rpL9 or cpi or both can serve as DNA barcodes of Sonneratia.