Plukenetia sect. Madagascarienses Card.-McTeag. & L.J.Gillespie, 2020

Cardinal-McTeague, Warren M. & Gillespie, Lynn J., 2020, A Revised Sectional Classification of Plukenetia L. (Euphorbiaceae, Acalyphoideae) with Four New Species from South America, Systematic Botany (Basel, Switzerland) 45 (3), pp. 507-536 : 518

IV. Plukenetia sect. Madagascarienses Card.-McTeag. & L.J.Gillespie sect. nov.

TYPE: Plukenetia madagascariensis Leandri.

Lianas, stems slender to thick. Leaf venation palmate, primary veins 3(–5). Inflorescences bisexual racemes or racemose thyrses; pistillate flowers solitary at 1–2 basal-most nodes; staminate flowers 1/node or 3–5/node in lax or moderately condensed cymules with conspicuous and irregularly branched cyme axes. Staminate flowers: receptacle ellipsoid, oblong-cylindrical, or ovoid-conical; nectaries absent; stamens 15–60, densely or loosely packed; filaments absent; pollen P = 28–41 m m, E = 35 –51 m m, tectum foveolate. Pistillate flowers: styles entirely connate into an obconic or obovoid column, 3.5–5.5 mm long, or 55–60% connate into a cylindrical column, 8–16 mm long, free style arms slender and tapered. Fruits 4- lobed capsules, dry, dehiscent, 2.3–4 cm in diam. Seeds broadly ellipsoid or subglobose, 13.1–18 ˟ 11.1–17 ˟ 11.2–17 mm (“large” sensu Cardinal-McTeague et al. 2019a).

The species in this section are distributed in Madagascar.

Etymology —The sectional epithet is derived from the combination of Madagascar and - ensis (Latin, of a place), which reflects that all the species in the section are endemic to Madagascar.

Discussion —Section Madagascarienses refers to a strongly supported clade within subclade P5 ( Fig. 1 ) and includes three species endemic to Madagascar. This section was originally defined as the Madagascan species group ( Gillespie 2007) and was noted for exhibiting sessile anthers similar to the pinnately veined clade. Style morphology is variable in the section, including both partly ( P. decidua , P. madagascariensis ) and entirely connate ( P. ankaranensis ) styles ( Fig. 3N–O ). Section Madagascarienses is differentiated by having sessile anthers on a prominently elongated receptacle ( Fig. 2L ), larger dry dehiscent fruits, “large” seeds, and by being endemic to Madagascar. All three species occur in seasonally dry environments, either dry forest on tsingy limestone ( P. ankaranensis , P. madagascariensis ) or in dry scrub ( P. decidua ).

Figures

FIG.1. Summary cladogram of the relationships recovered by Bayesian analysis of combined and partitioned ETS,ITS, KEA1 introns 11 and 17, TEB exon 17, matK, and ndhF DNA sequence data of Plukenetia and Romanoa (modified from Cardinal-McTeague et al. 2019a), highlighting our revised sectional classification of Plukenetia. Maximum parsimony bootstrap percentage (MPBP) and Bayesian posterior probability (BPP) support values> 50% are indicated on each branch. Branches in bold indicate strong support ($ 85 MPBP and $ 0.95 BPP). Subclade numbering system (P1–P5) follows Cardinal-McTeague and Gillespie (2016). Sections in the pinnately veined clade (P1 + P2) are indicated by light grey boxes,sections in the palmately veined clade (P3–P5) by dark grey boxes; new species are indicated in bold. A–B. Leaf clearings demonstrating leaf architecture (images from Gillespie 1993). A. P. stipellata, Gillespie 413 US. B.P. supraglandulosa, Granville 3626 CAY.C–D. Scanning electron micrographs demonstrating pollen tectum morphology (images from Gillespie 1994). C. P. stipellata, Gillespie 418 DAV. D. P. loretensis, Maguire & Politi 27371 US.

FIG. 3. Representative pistillate flower diversity of Plukenetia and its sister genus Romanoa. A. Romanoa tamnoides (Krapovickas & Schinini 36265 MO), styles 70–80% connate into a cylindrical column.B.P.sect. Fragariopsis: P.serrata (Davidse et al.10480 MO), styles entirely connate into an obovoid column.C–F.P.sect. Penninerviae: C. P.brachybotrya (Fuentes et al.5398 MO) and D. P.verrucosa (Prance et al.11255 DAV), styles entirely connate into a globose column; E. P.loretensis (Silva et al. 4750 MO), styles entirely connate into a slender-cylindrical column, dilated at the apex; F. P. penninervia (Wallnöfer et al. 5996 MO), styles entirely connateinto a stout-cylindrical column.G–K.P.sect.Plukenetia: G.P.polyadenia (Aulestia & Grefa 230 MO),H.P.stipellata (Cardinal-McTeague 8 CAN),I.P.volubilis (Wurdack s.n. US), and J. P. sylvestris (Woykowski 6670 MO), styles 70–95% connate into a cylindrical column; K. P. lehmanniana (Rangel et al. 5734 MO), styles 20–25% connate into a cylindrical column,free style arms 2-fid nearthe tips.L.P.sect.Angostylidium: P.conophora(Thomas 5455 MO),styles 75–(90)% connate into a funnel-shaped column,free style arms conspicuously dilated and spreading.M.P. sect.Hedraiostylus: P. corniculata (Brink 5771 L), styles entirely connate into a depressed-globose column with cross-shaped stigmas. N–O. P. sect. Madagascarienses: N. P. ankaranensis (Gillespie 4076 CAN), styles entirely connate into an obconic or obovoid column; O. P. madagascariensis (Andrianjafy et al. 1648 MO), styles 55–60% connate into a cylindrical column, free style arms slender and tapered. Photos A–C, E–H, J–L by W. Cardinal-McTeague, I by K. Wurdack, N by L. Gillespie, O by P. Phillipson. Line drawings: D by Cathy Pasquale, K by Anita Walsmit Sachs, used with permission from Naturalis Biodiversity Center, Leiden, Netherlands. (Scale bars = 1 mm).

FIG. 2. Representative staminate flower diversity of Plukenetia and its sister genus Romanoa. A. Romanoa tamnoides (Krapovickas & Schinini 36265 MO), stamens with slender-cylindrical filaments.B.P.sect.Fragariopsis:P.serrata(Davidse etal.10480 MO),anthers sessileand looselypackedon alarge globosereceptacle.C–E.P.sect.Penninerviae: C.P.loretensis (Freitas et al.155 MO),anthers sessile and densely packed on a small globose receptacle;D.P.penninervia (vander Werff et al.3173 MO),and E.P.supraglandulosa (Granville 3626CAY,US),mostanthers sessile and densely packedon a smallglobose receptacle,witha dimorphicouter whorl of;4 stamenswith filaments,and often witha 4-lobed annular nectary. F–I. P. sect.Plukenetia: F. P. polyadenia (Croat et al.20285 MO), stamens with slender-cylindrical filaments and ligulate interstaminal nectaries; G. P. stipellata (Cardinal-McTeague 8 CAN),stamens withslender-cylindrical filaments and small irregularlyshaped interstaminal nectary segments;H.P.sylvestris (Woytkowski 6670 MO), stamens with slender filaments and large irregularly shaped interstaminal nectary segments;I. P. volubilis (Wurdack s.n.US), stamens with short-conical filaments.J.P. sect.Angostylidium: P.conophora (Avio et al.1621 MO), stamens with short-conical filaments and slender-cylindrical interstaminal nectaries (in pink). K. P.sect.Hedraiostylus: P.corniculata(ChinSee Chung 2712L),stamenswith short-conicalfilaments (sometimes appearingsessile).L.P.sect.Madagascarienses:P.madagascariensis(Villiers et al.4889 MO), anthers more or less sessile,denselyto somewhatloosely packedon an elongatereceptacle.PhotosA–D,F–H,J,Lby W.Cardinal-McTeague;IbyK.Wurdack.Line drawings: E by Alice Tangerini,K byAnitaWalsmit Sachs,used with permissionfrom the NaturalisBiodiversity Center,Leiden,Netherlands.(Abbreviations:an =annularnectary;d= dimorphic filamentous stamens; in = interstaminal nectaries; r = receptacle. Scale bars = 1 mm).