A Phylogeny of Mallotus (Euphorbiaceae) Based on Morphology: Indications for a Pioneer Origin of Macaranga

Abstract

A phylogenetic parsimony analysis based on 76 morphological characters of 43 Mallotus ,3 Macaranga ,1 Claoxylon ,1 Cleidion ,1 Sampantaea ,a nd 1Wetria species, resulted in 314 trees of length 602 (CI 5 0.600, RI 5 0.685), which could be summarized in a well resolved consensus cladogram. This consensus cladogram indicates that the genus Mallotus is possibly polyphyletic and that sections Hancea and Oliganthae should probably be excluded from Mallotus. It is proposed to refer to Mallotus as either Mallotus sensu lato (with the sections Hancea and Oliganthae )o rMallotus sensu stricto (excluding the sections Hancea and Oligantae). The genus Macaranga forms a monophyletic group within Mallotus s.s. The traditional section delimitations within Mallotus s.s. do not circumscribe monophyletic clades of species with the exception of section Polyadenii. It is suggested that sections Stylanthus, Rottlera, Mallotus, and the genus Macaranga should form one monophyletic clade. Sections Axenfeldia and Rottleropsis remain unresolved, but are probably closely related. The position of Macaranga within Mallotus suggests that Macaranga evolved from pioneer ancestors that lived in open, scrub-like vegetation. It is hy- pothesised that Macaranga originated relatively recently in South East Asia during the Oligocene or early Miocene (between 38 and 15 million years ago). Macaranga Thou. (ca. 250 species) and Mallotus Lour. (c. 150 species) are two large genera in the Euphorbi- aceae (Webster 1994). They mainly occur in (sub-)trop- ical Asia and the Pacific with only a few species in tropical Africa. They can be found in a large variety of habitats, ranging from the forest understory to com- pletely open scrub vegetation, from dry to swampy or even inundated terrains, and from sandy-loam to lime- stone soils (Pax and Hoffmann 1914; Airy Shaw 1975; Whitmore 1975; Slik et al. 2000). They also show a large variety of life-histories, with typical shade-pre- ferring forest understory species as well as typical shade-avoiding pioneer species (Primack and Lee 1991;