Reevaluating the taxonomic status of Ceriops australis (Rhizophoraceae) based on morphological and molecular evidence

Ceriops australis (White) Ballment, Smith & Stoddart, a member of the mangrove family Rhizophoraceae, was originally recognized as C. tagal var. australis White but was raised to species rank based solely on isozyme features and the only distinctive morphological feature of the hypocotyl. Therefore, it was considered a sibling species of C. tagal (Perr.) C. B. Rob. The goal of this study was to test the previous assessment that C. australis and C. tagal differ consistently only in hypocotyl morphology, in order to reevaluate the taxonomic status and to establish its geographic range. Principal components analysis was employed to analyze 29 morphological characters of herbarium specimens from Australia, Madagascar, and Sumatra tentatively identified as C. australis and C. tagal, and two well differentiated distinct taxa were recognized. In addition, both of the detailed morphological features based on fresh and herbarium materials and the intron sequences of trnL gene from plastid DNA support this conclusion. This finding disagrees with previous assessment and supports the current taxonomic status of C. australis. Here, a key to these two species is provided, and a revised distribution range of C. australis is established. This is the initial report of C. australis’ occurrence in a part of Indonesia, in addition to areas of Australia and Papua New Guinea.