The systematic position of <i>Cubanthus</i> and other shrubby endemic species of <i>Euphorbia</i> (Euphorbiaceae) in Cuba

Abstract

Cubanthus (Euphorbiaceae) has traditionally been recognized as a small genus of three similar species restricted to Cuba and Hispaniola. In this study we used DNA sequence data from the nuclear ITS and chloroplast ndhF gene regions to investigate its systematic position and the position of four other shrubby Euphorbia species endemic to Cuba: E. cubensis, E. helenae, E. munizii, and E. podocarpifolia. The results demonstrate that all of these taxa belong to a well-supported Antillean clade nested within Euphorbia that also includes E. punicea and E. gymnonota. For that reason, we treat Cubanthus as a section of Euphorbia instead of a separate genus. Euphorbia sect. Adenorima is relegated to a synonym of sect. Cubanthus. New names are proposed for Cubanthus brittonii and Cubanthus linearifolius (Euphorbia millspaughii and E. scutiformis, respectively), and a new combination is made for Cubanthus umbelliformis (Euphorbia umbelliformis). Section Cubanthus belongs to clade C of Euphorbia and is part of a New World assemblage that includes members of sections Euphorbiastrum, Pteroneurae, Portulacastrum, Stachydium, and the former genus Pedilanthus. Based on both the molecular results and morphological differences, two subsections are proposed: subsect. Cubanthus and subsect. Moa. The molecular phylogeny supports the hypothesis that section Cubanthus radiated entirely within the Antilles and the nearby Bahamian archipelago.

Euphorbiaceae

“…are either paraphyletic or polyphyletic. Further work (Steinmann 2003;Bruyns et al 2006;Steinmann et al 2007;Zimmermann et al 2010;Horn et al 2012) confirmed and extended these findings, and led to the broadly construed generic concept of Euphorbia that is gaining increasing acceptance. Steinmann and Porter (2002) also recovered four major lineages within Euphorbia, designated as clades A-D; with one exception, these do not correspond to any previously known taxon but are composed of various sections or subgenera of Euphorbia; only a single clade, by and large, is congruent with subg.…”

880. Euphorbia Tuckeyana

“…Macaronesicae and occur in the Antilles and the Bahamas [ Euphorbia subgenus Euphorbia section Cubanthus ; see Steinmann et al . () and Dorsey et al . ()], Malesia‐Melanesia‐Australia [ E. plumerioides , placed in Euphorbia subgenus Euphorbia section Pacificae ; see Forster () and Dorsey et al .…”

“…These other groups are phylogenetically distant from subsect. Macaronesicae and occur in the Antilles and the Bahamas [Euphorbia subgenus Euphorbia section Cubanthus; see Steinmann et al (2007) and Dorsey et al (2013) Chevalier (1935), Carter et al (1984), Brochmann & Rustan (1987), Brochmann et al (1997), Gomes et al (1995), and Duarte & Moreira (2002). The species occurs throughout Cabo Verde except on the island of Maio and the islets of Branco and Raso (Fig.…”

An up-to-date familial and suprafamilial classification of succulent plants

“…Euphorbia. Likewise, Pedilanthus (Steinmann, 2002;Park & Jansen, 2007) and Cubanthus (Steinmann et al, 2007) should also be included in Euphorbia s.l. The alternative to the sinking of all these well-established segregates (each conforming to a more or less monophyletic clade) would be to break up Euphorbia s.l.…”