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 (ndh)F and 27 morphological characters. We find strong evidence for the non–monophyly of Melaleuca, with all other currently recognized genera of Melaleuceae (Beaufortia, Calothamnus, 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 the M. 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.

Interpreting the modern distribution of Myrtaceae using a dated molecular phylogeny

“…New Caledonian Melaleuca species are nested deep within Melaleuceae (Cook et al, 2008;Edwards et al, 2010) and the estimated crown age of this tribe (c. 26.5-45.0 Ma) means that the divergences between Australian and New Caledonian taxa are too recent to have been caused by vicariance. Interestingly, Melaleuceae and its monotypic sister tribe Osbornieae had an inferred divergence age of 56 Ma and the monotypic Osbornia is the sole member of Myrtaceae to occur in mangroves, while many Melaleuca species occur in swamps or along creek or river banks.…”

New combinations and names in Melaleuca (Myrtaceae)

“…Melaleuca punicea, as anomalous in Melaleuca on account of its androecium, gynoecium and seed as it was in Regelia where it was placed by Barlow (1987), was placed by Craven (1999) in the new genus Petraeomyrtus. On morphological evidence, the New Caledonian Callistemon species were transferred to Melaleuca by Craven & Dawson (1998) and the accepted Australian species of Callistemon were later transferred to that genus by Craven (2006Craven ( , 2009 (Edwards & al., 2010). Their results showed there were three major clades, each of which contained species of Melaleuca s.str.…”

An Expanded <I>Metrosideros</I> (Myrtaceae) to Include <I>Carpolepis</I> and <I>Tepualia</I> Based on Nuclear Genes

“…Recent molecular phylogenetic studies at the family level have delimited a number of tribes (Wilson et al 2005;Biffin et al 2010;Wilson 2011) that allow more targeted follow-up studies at the tribal level to assess generic limits. Such approaches have already been applied to tribe Syzygieae (Biffin et al 2006), Myrteae ), Melaleuceae (Edwards et al 2010) and Backhousieae (Harrington et al 2012), leading to changes in generic boundaries, often broadening some genera to include other smaller ones.…”