Melaleuca revisited: cpDNA and morphological data confirm that Melaleuca L. (Myrtaceae) is not monophyletic

Abstract

With about 335 species, the tribe Melaleuceae comprises a major lineage within the Australian Myrtaceae. Here we investigate relationships within Melaleuceae using cpDNA sequences (ndhF) and 27 morphological characters. We find strong evidence for the non-monophyly of Melaleuca, with all other currently recognized genera of Melaleuceae (Beaufortia, Calo-thamnus, Conothamnus, Eremaea, Lamarchea, Petraeomyrtus, Phymatocarpus, Regelia) falling within that genus. Our findings are broadly consistent with previous studies using nuclear ITS DNA sequence data; however, the cpDNA phylogeny estimate is more resolved and has higher support for major nodes. Melaleuceae is found to comprise three major clades, each containing species of Melaleuca and each with good support. The M. leucadendra (broad-leaf paper-barks), M. uncinata, M. pungens and M. acacioides groups, New Caledonian callistemons, and all other currently recognized genera of Melaleuceae form one clade. Australian Callistemon species, which have been synonymised recently with Melaleuca, cluster within a second clade of Melaleuca that includes the M. fulgens, M. laxiflora and M. ordinifolia groups, and some members of the M. lanceolata and M. cuticularis groups. A third clade includes other members of the M. lanceolata and M. cuticularis groups, M. foliolosa and theM. huegelii group. No morphological support or diagnostic synapomorphies are identified for any of these clades. Together with previous studies, our findings indicate that the circumscription of Melaleuca, and the generic status of other genera within Melaleuceae, is poorly supported, and we propose that all genera within the Melaleuceae are synonymised with Melaleuca.