A Revised Sectional Classification of Plukenetia L. (Euphorbiaceae, Acalyphoideae) with Four New Species from South America

Abstract

Abstract—We present a phylogenetic classification for Plukenetia (Euphorbiaceae, Acalyphoideae) based on morphology and molecular phylogenetic studies using nuclear (ETS, ITS, KEA1 introns 11 and 17, TEB exon 17) and plastid (matK, ndhF, psbA-trnH) DNA data. Plukenetia comprises 25 species divided into six sections, with three new sections and four new species described here. The circumscription of Plukenetia is unaltered from recent treatments and we continue to recognize Romanoa as distinct. The sections of Plukenetia correspond with the subclade system proposed by Cardinal-McTeague and Gillespie (2016): P1 = P. sect. Fragariopsis comb. et stat. nov.; P2 = P. sect. Penninerviae sect. nov.; P3 = P. sect. Plukenetia; P4 = P. sect. Angostylidium; and P5 = P. sect. Hedraiostylus + P. sect. Madagascarienses sect. nov. The sections are distinguished by a combination of leaf venation, staminate flower morphology, pistillate flower number, style morphology, fruit type, and seed size. Additionally, we describe three new species from South America belonging to sect. Penninerviae: Plukenetia brevistyla and Plukenetia megastyla from the Amazon basin and Plukenetia chocoensis from the Chocó Biogeographic Region of Colombia. The new Amazonian species are morphologically similar to P. brachybotrya but distinguished by their style shape and size. The new Colombian species is morphologically similar to P. penninervia but distinguished by its elongate basilaminar extrafloral nectaries, presence of abaxial laminar extrafloral nectaries, and longer inflorescences. We also describe a new species from sect. Plukenetia, Plukenetia sylvestris, which is found in central and southern Peru. This species is suggested to be the wild progenitor of the cultivated P. carolis-vegae, differing by its smaller seeds/fruits and fewer stamens. Molecular data, including a new ETS phylogeny sampling P. brevistyla, support our new taxa as distinct. Keys to the sections and species of Plukenetia are provided and we designate 12 new lectotypes for Plukenetia and Romanoa.