Phylogenetic analysis of the Sonneratiaceae and its relationship to Lythraceae based on ITS sequences of nrDNA

Phylogenetic analyses were conducted using seven species in two genera of Sonneratiaceae, seven species in five genera of the related Lythraceae and 2 outgroups based on DNA sequences of the internal transcribed spacer (ITS) and the 5.8S coding region of the nuclear ribosomal DNA to determine the proper systematic placement of the Sonneratiaceae. Paraphyly of the traditional Lythraceae was shown with the genus Lagerstroemia nested within the Sonneratiaceae. The Sonneratiaceae occurred within the Lythraceae with high bootstrap value support(96%). The two traditional genera constituting Sonneratiaceae were in different well-supported clades. Duabanga (Sonneratiaceae) is sister to the clade of Lagerstroemia (Lythraceae) (82%). The mangrove genus Sonneratia (100%)formed the other monophyletic group. It was located terminally within the Lythraceae clade and comprised two clades: one consisting of S. apetala, S. alba, S. ovata, and S. hainanensis; the other including S. caseolaris and S. paracaseolaris. The results indicated that species previously placed in two different sections (Sect. Sonneratia and Sect. Pseudosonneratia) of Sonneratia occurred within the same clade, and the taxonomic classification was not supported by the molecular analysis of the TTS region sequences. Based on the phylogenetic analyses of the TTS regions, the Sonneratiaceae were shown to be nested within the family Lythraceae. Therefore, the sequence data presented here do not support the recognition of the Sonneratiaceae as a distinct family, but instead support the inclusion of Sonneratiaceae in the Lythraceae proposed by other authors.