Diversity of Phyllanthaceae Plants

Abstract

Euphorbiaceae, one of the major components of tropical flora worldwide, has long been considered a heterogeneous group (Webster 1994; Radcliffe-Smith 2001). Recent molecular phylogenetic analyses have clearly shown that Euphorbiaceae is nonmonophyletic, and consequently, Pandaceae, Phyllanthaceae, Picrodendraceae, Putranjivaceae, Peraceae, and Centroplacaceae have been removed from it, although these families all belong to the order Malpighiales together with the updated Euphorbiaceae (Euphorbiaceae s. str.; Angiosperm Phylogeny Group III 2009). Thus, the small unisexual flowers and trilocular capsule that characterize the plants of the former Euphorbiaceae are plesiomorphic or convergent characters. For example, Rafflesiaceae, the family with the world’s largest, unisexual but unilocular flowers, is embedded in the former Euphorbiaceae (Davis et al. 2007); the clade sister to Rafflesiaceae is now Euphorbiaceae s. str., and the lineage sister to (Rafflesiaceae + Euphorbiaceae s. str.) is split as Peraceae (Fig. 4.1). Of the seven former Euphorbiaceae families, Euphorbiaceae s. str. and Phyllanthaceae are by far the largest, with the former containing about 300 genera and about 7500 species, and the latter 54 genera and about 2000 species (Table 4.1). Webster (1994) noted an important morphological feature of Phyllanthaceae that clearly distinguishes them from Euphorbiaceae s. str.; the former has two ovules per locule whereas the latter only has one ovule per locule.