Myrtales and Myrtaceae: a phylogenetic analysis

Phylogenetic analysis of 19 families or quasi-families of the Myrtales is carried out by CLAX, a new numerical technique, as well as by other methods, the comparative merits of which are discussed. The results establish some phylads as reliable, in particular Psiloxylaceae-Heteropyxidaceae-Myrtaceae and the Lythraceae sensu lato (including Punica, Duabanga, and Sonneratia). Onagraceae are very distinct, but may have an early link with Trapaceae. Memecylaceae and Crypteroniaceae are separated from Melastomataceae sensu stricto, a family Alzateaceae is recognized, and the new unigeneric family Rhynchocalycaceae is described. The earlier suggestion of the separate order Lythrales is not supported. Scenarios of phylogeny are given, with attention to phytogeography; the order seems to have originated and largely radiated (except for the predominantly Australasian Myrtaceae sensu stricto) in West Gondwana. Similar analysis of Myrtaceae depends particularly on features of androecium, trichomes, and wood anatomy; a complex set of changes in the androecium is hypothesized. The analysis implies a considerably altered picture of tribal and generic relationships; the formerly recognized subfamilies Myrtoideae and Leptospermoideae must be abandoned. The subfamily Chamelaucioideae, previously discarded by us, is shown to be a polyphyletic grade taxon, and cannot be sustained as an integrated suballiance, much less as a subfamily. Consideration is given to the status of Kjellbergiodendron, the (possibly combined) Eucalyptopsis and Eucalyptus alliances, the Acmena alliance, and Osbornia.