Neotropical Euphorbiaceae

Hans-Joachim Esser

Botanische Staatssammlung München, Munich, Germany. 

Description

Trees, shrubs, climbers or herbs, succulent or not, spiny or not, with white or variously coloured latex or without, usually with extrafloral nectaries. Leaves alternate (rarely subverticillate, opposite or decussate), petiole short to long (rarely absent), eglandular or glandular, stipules usually present but caducous, rarely intrapetiolar or absent, membranous to scaly, eglandular or glandular, lamina simple, palmately lobed (rarely divided) or not, rarely peltate, margins entire to variously dentate-serrate; indumentum of simple, lepidote, dendritic, T-shaped or urticating hairs or absent, venation pinnate to palmate, veinlets variable. Inflorescences unisexual or bisexual, monoecious or dioecious, axillary or terminal, usually elongate racemose, paniculate, thyrsoid, dichasial, more rarely fasciculate-glomerulate or umbel-like or (pistillate), flowers solitary, or grouped into pseudanthia such as cyathia (a female flower surrounded by several staminate ones); bracts small and inconspicuous or larger and conspicuous. Flowers unisexual, small, actinomorphic to rarely zygomorphic, pedicellate to rarely sessile, with 3-5(-8), imbricate to valvate, free to fused sepals or rarely without, petals present or absent. Staminate flowers with (1-)2-20(-90) stamens, filaments free to fused or absent, anthers dorsifixed to basifixed, extrorse to introrse, bilocular, opening with longitudinal slits, disc present or absent, variable, pollen 3(-4)-colporate, porate or inaperturate, tectate-perforate or semitectate, with or without baculae, pistillode absent or present. Pistillate flowers without staminodes, disc present or absent, variously shaped, ovary hypogynous, syncarpous, with (1-)2-3(-20) locules, smooth to spiny, ovule 1 per locule, placentation axile, anatropous, bitegmic, style present or absent, stigmas (1-)2-3(-20), usually elongate, entire, bifid or multifid or rarely bilobed. Fruits septicidally or loculicidally dehiscent schizocarps or (rarely) indehiscent drupaceous. Seeds ellipsoid to ovoid, anatropus, smooth or sculptured, ecarunculate to carunculate, dry, rarely with sarcotesta or aril, endosperm copious, embryo straight, cotyledons usually broad.

Notes on delimitation

  • The Euphorbiaceae were considered as a morphologically well defined family for a long time, based mostly on their unisexual flowers and the typical schizocarpous fruits. Recent molecular studies resulted in the recognition of several, mostly smaller families (Peraceae, Phyllanthaceae, Picrodendraceae, Putranjivaceae), that are also characterized sufficiently by morphological characters (see below). In this most recent circumscription, Euphorbiaceae are clearly monophyletic.

Distribution in the Neotropics

  • Found throughout the Neotropics, in most vegetation types except for true aquatic plants, but including, e.g. rain forest trees, weeds, and succulents. The family is poorly represented in montane grasslands with only two genera (Dysopsis, Euphorbia), and it does not include epiphytes.

Distinguishing characters (always present)

  • Flowers small, unisexual.
  • Ovaries hypogynous, syncarpous, with 1 ovule per carpel.
  • Fruits, if dehiscent, with a remaining central columella.
  • Seeds 1 per carpel, anatropous, globose-ellipsoid without sharp edges.

Other important characters

  • Leaves often simple.
  • Stipules present but caducous, small.
  • Leaves often with nectaries.
  • Ovaries and fruits often 3-carpellate.
  • Latex white or yellowish to red (but absent in subfamily Acalyphoideae).

Key differences from similar families

The Euphorbiaceae can be confused with several families with similar fruits and small flowers. The Euphorbiaceae can be distinguished as follows:

Number of genera

Euphorbiaceae are pantropical and comprise c. 230 genera and c. 5700 species. In the Neotropics they are represented by 82 genera and c. 2550 species:

Acalypha L.
Acidocroton Griseb.
Acidoton Sw.
Actinostemon Mart. ex Klotzsch
Adelia L.
Adenophaedra (Müll.Arg.) Müll.Arg.
Alchornea Sw.
Alchorneopsis Müll.Arg.
Aleurites J.R. & G.Forst.
Angostylis Benth.
Anomalocalyx Ducke
Aparisthmium Endl.
Argythamnia P.Browne
Astraea Klotzsch
Astrococcus Benth.
Bernardia Houst. ex Mill.
Bonania A.Rich.
Brasiliocroton P.E.Berry & I. Cordeiro
Caperonia A.St.-Hil.
Caryodendron H.Karst.
Chiropetalum A.Juss.
Cleidion Blume
Cnidoscolus Pohl
Codiaeum Rumph. ex A.Juss.
Colliguaja Molina
Conceveiba Aubl.
Croton L.
Dalechampia Plum. ex L.
Dalembertia Baill.
Dendrocousinsia Millsp.
Dendrothrix Esser
Ditaxis Vahl ex A.Juss.
Ditta Griseb.
Dodecastigma Ducke
Dysopsis Baill.
Enriquebeltrania Rzed.
Euphorbia L.
Gavarretia Baill.
Glycydendron Ducke
Grimmeodendron Urb.
Gymnanthes Sw.
Haematostemon (Müll.Arg.) Pax & K.Hoffm.
Hevea Aubl.
Hippomane L.
Hura L.
Jatropha L.
Lasiocroton Griseb.
Leucocroton Griseb.
Mabea Aubl.
Manihot Mill.
Maprounea Aubl.
Micrandra Benth.
Micrandropsis W.A.Rodrigues
Microstachys A.Juss.
Nealchornea Huber
Omphalea L.
Ophellantha Standl.
Ophtalmoblapton Allemão
Pachystroma Müll.Arg.
Pausandra Radlk.
Philyra Klotzsch
Platygyne P.Mercier
Pleradenophora Esser
Plukenetia L.
Polyandra Leal
Pseudosenefeldera Esser
Rhodothyrsus Esser
Ricinus L.
Romanoa Trevis.
Sandwithia Lanj.
Sapium Jacq.
Sebastiania Spreng.
Senefeldera Mart.
Senefelderopsis Steyerm.
Stillingia Garden ex L.
Tetraplandra Baill.
Tetrorchidium Poepp. & Endl.
Tragia L.
Vaupesia R.E.Schult.
Vernicia Lour.

Useful tips for generic identification

  • The flowers are very small, and in many cases it is not necessary to study their characters for generic identification. The family is very rich in extrafloral nectaries (on floral bracts, stipules and leaves), and shows a large variation in the type of hairs. The indumentum, the nectaries in particular on the leaves, leaf morphology and venation, inflorescence type, and some characters of fruits and seeds are useful for the identification of genera.

Notable genera and distinguishing features

  • Acalypha - Pantropical with c. 450 species, of which c. 400 are Neotropical; herbs to shrubs with variable hairs but not urticating, leaves simple and serrate-crenate, inflorescences simple, bracts of pistillate flowers accrescent, conspicuous and often serrate to lobed, stigmas laciniate -multifid.
  • Alchornea - Pantropical with c.. 25 Neotropical species; the leaves are often coriaceous and distinctly triplinerved and/or distinctly dentate, the infloresces usually compound; in Neotropical species the ovaries and fruits are always 2-locular with conspicuous long stigmas, in contrast to some similar Neotropical genera that have 3-locular ovaries and fruits (such as Alchorneopsis, Aparisthmium).
  • Astraea Klotzsch - Endemic with c.. 15 species; similar to Croton but usually with lobed leaves and with staminate flowers with a glabrous receptacle.
  • Caperonia - c. 30 Neotropical species of herbs to small shrubs, characterized by leaves with a typical venation, the straight side veins running directly into the serrate margin of the blade (craspedodromous).
  • Cnidoscolus - Endemic with c. 50 species; similar to Jatropha, but plants with urticating hairs or bristles, leaves biglandular at base, flowers with a petaloid perianth but without separate petals.
  • Croton - A pantropical genus with perhaps 900 Neotropical species; hairs dendritic or lepidote, leaves usually simple with a pair of basal glands, inflorescences mostly simple, staminate flowers with a pubescent receptacle and with numerous stamens inclinate in bud.
  • Dalechampia - Pantropical but with the majority of its c. 110 species Neotropical; non-stinging, twining herbs to shrubs, leaves very variable and most often palmatilobed, with a very complex pseudanthial inflorescence supported by conspicuous involucral bracts.
  • Dysopsis - Endemic with a single species, being a small herb with suborbicular crenate leaves in montane habitats.
  • Euphorbia - Cosmopolitan and with c. 2250 species one of the largest genera of plants, with less than 400 Neotropical species; herbs to shrubs or succulents, characterized by the unique pseudanthium of much-reduced flowers (cyathium); recently all cyathia-bearing species were united into one single genus (Steinmann & Porter 2002).
  • Hevea - Endemic with c. 15 species (its distribution defining the Amazonian region); hairs simple, leaves 3-foliolate, inflorescences pseudopaniculate, flowers without petals.
  • Jatropha - Pantropical with c. 100 Neotropical species; herbs to trees, sometimes succulent, often with a thick rootstock, hairs simple, leaves variously shaped but often palmately lobed, stipules often conspicuous and multifid, inflorescences dichotomous, corymbiform, flowers with distinct sepalas and petals.
  • Mabea - Endemic with c. 40 species; hairs dendritic and brownish to reddish, staminate flowers pedicellate with numerous (up to 90) stamens each, ovaries and fruits tomentose, pistillate flowers with long styles.
  • Manihot - Endemic with c. 100 species; not urticating, leaves simple to palmately lobed, often pruinose-glaucescent, eglandular but stipellate at base, inflorescences racemose-paniculate, flowers without petals.
  • Microstachys - Pantropical with c. 15 Neotropical species; herbs to small shrubs, hairs simple to dendritic but not urticating, inflorescences elongate and basically bisexual but pistillate and staminate flowers often separated on different nodes, ovaries and fruits usually with six pairs or rows of spines.
  • Plukenetia - Pantropical with most of its 15 species Neotropical; climbing vines to lianas, hairs simple, leaves simple, conspicuously glandular at base, inflorescences leaf-opposed, racemose-paniculate, flowers and fruits 4-merous (the 4-merous flowers distinguish it from several similar genera).
  • Sapium - Endemic with c. 25 woody species; leaves simple with petiolar glands, staminate flowers subsessile with 2 stamens each, seeds with a red aril.
  • Sebastiania - Endemic with c. 20 species; woody plants with simple elongate inflorescences, the staminate flowers subsessile and with 3 stamens and 3 free sepals, the fruits regular with a notably thin wall.
  • Stillingia - Pantropical with the majority of its 27 species Neotropical; similar to Sapium but with more variation in habit (subshrubs to trees or succulents), the petioles eglandular, the fruits with a characteristic woody persistent cornute base, seeds dry without an aril.
  • Tragia - Pantropical with c. 60 Neotropical species; herbs to subshrubs, often twining, indumentum of simple and urticating hairs, leaves simple and often serrate, inflorescences often leaf-opposed, racemose, staminate flowers with 2-50 stamens. Some smaller similar genera differ in minor floral characters, and the generic limits are not completely solved yet.

Status

  • Seventy-eight of the 82 genera (95%) are native; 60 of these are endemic.
  • Four, originally paleotropical, genera are cultivated with a single species each: Aleurites (candle nut), Codiaeum (garden croton), Ricinus (castor oil), Vernicia (tung oil).

Important literature

Govaerts, R., Frodin, D.G. & Radcliffe-Smith, A. 2000. World checklist and bibliography of Euphorbiaceae (with Pandaceae). London: Royal Botanic Gardens, Kew.

Radcliffe-Smith, A. 2001. Genera Euphorbiacearum. London: Royal Botanic Gardens, Kew.

Steinmann, V.W. & Porter, J.M. 2002: Phylogenetic relationships in Euphorbieae (Euphorbiaceae) based on ITS and ndhF sequence data. Ann. Missouri Bot. Gard. 89: 453-490.

Webster, G.L. 1994. Classification of the Euphorbiaceae; Synopsis of the Genera and Suprageneric taxa of Euphorbiaceae. Ann. Missouri Bot. Gard. 81(1): 3-32, 33-144.

Wurdack K.J., Hoffmann, P. & Chase, M.W. 2005. Molecular phylogenetic analysis of uniovulate Euphorbiaceae (Euphorbiaeae sensu stricto) using plastid rbcL and trnL-F DNA sequences. Amer. J. Bot. 92(8): 1397-1420.

How to cite

Esser, H.-J. (2009). Neotropical Euphorbiaceae. In: Milliken, W., Klitgård, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://www.kew.org/science/tropamerica/neotropikey/families/Euphorbiaceae.htm.

Click images to enlarge


Acalypha sticky © John Wood, Darwin Initiative Project 161/11/015.



Alchornea discolor © Denise Sasaki, Programa Flora Cristalino.



Alchornea schomburgkii © Denise Sasaki, Programa Flora Cristalino.



Alchornea triplinervia © William Milliken, RBG, Kew.



Aparisthmium cordatum © William Milliken, RBG, Kew.



Bernardia crossifolia © William Milliken, RBG, Kew.



Bernardia similis © Daniela Zappi, RBG, Kew.



Caperonia palustris © Denise Sasaki, Programa Flora Cristalino.



Cnidoscolus urens © William Milliken, RBG, Kew.



Conceveiba guianensis © Denise Sasaki, Programa Flora Cristalino.



Leaf of Conceveiba guianensis © Denise Sasaki, Programa Flora Cristalino.



Croton adamantinus © Denise Sasaki, Programa Flora Cristalino.



Croton lobatus © William Milliken, RBG, Kew.



Croton palanostigma © Gracieli Henicka, Programa Flora Cristalino.



Croton palanostigma © Denise Sasaki, Programa Flora Cristalino.



Croton campestre © Leandro Freitas, Jardim Botânico do Rio de Janeiro.



Flowers of Dalechampia sylvestris © Daniela Zappi, RBG, Kew.



Euphorbia heterophylla © Daniela Zappi, RBG,  Kew.



Glycidendron amazonicum © Denise Sasaki, Programa Flora Cristalino.



Hevea brasiliensis © William Milliken, RBG,  Kew.



Hevea brasiliensis © Denise Sasaki, Programa Flora Cristalino.



Jatropha curcas © Daniela Zappi, RBGardens, Kew.



Jatropha pegaj © John Wood, Darwin Initiative Project 161/11/015.



Mabea paniculata © Denise Sasaki, Flora Programa Cristalino.



Mabea pohliana © Denise Sasaki, Flora Programa Cristalino.



Mabea angustifolia © Sue Frisby, RBG,  Kew.



Mabea angustifolia © William Milliken, RBG, Kew.



Opening flowers of Manihot anomala © Denise Sasaki, Programa Flora Cristalino.



Manihot caerulescens © William Milliken, RBG,  Kew.



Manihot tristis © William Milliken, RBG, Kew.



Leaves of Maprounea guianensis © Nicola Biggs, RBGardens, Kew.



Microstachys bidentata © William Milliken, RBG, Kew.



Microstachys daphnoides © William Milliken, RBG, Kew.



Microstachys ditassoides © William Milliken, RBG, Kew.



Microstachys hispida © Denise Sasaki, Programa Flora Cristalino.



Plukenetia aff. brachybotrya © William Milliken, R BG, Kew.



Sapium glandulosum © Denise Sasaki, Programa Flora Cristalino.



Sapium pallidum © Nicola Biggs, RBG, Kew.



Sapium paucinervium © William Milliken, RBG, Kew.



Tragia volubilis © William Milliken, RBG, Kew.