Neotropical Peraceae

Hans-Joachim Esser

Botanische Staatssammlung München, Munich, Germany. 

Description

Trees or shrubs, usually evergreen, lacking latex (rarely yellowish watery exudate reported), without extrafloral nectaries.  Leaves alternate (rarely opposite), simple, margin entire, petiole present, quite short, eglandular, stipules present and scaly to large or (nearly) absent to invisible; indumentum of simple, T-shaped, stellate or lepidote hairs; venation pinnate, veinlets reticulate to percurrent. Inflorescences unisexual (rarely bisexual), dioecious (rarely monoecious), axillary, fasciculate-glomerulate, sometimes surrounded by two fused spathaceous bracts, or elongate raceme -like to paniculate; bracts otherwise small, inconspicuous. Flowers actinomorphic, pedicellate to subsessile, with imbricate, free to mostly fused sepals or without, petals free or absent. Staminate flowers with 4-6 free sepals or calyx fused with 2-4(-6) lobes, or without, with 5 free petals or without, stamens (2-)5-20, filaments free or connate at base, anthers dorsifixed or basifixed, extrorse to introrse, bilocular, opening with longitudinal slits, pollen 3-colporate, tectate to perforate-tectate, exine rugulose to psilate, disc consisting of separate glands, fused, or absent, pistillode present, sometimes surrounding staminate flowers and therefore then being a reduced flower itself.  Pistillate flowers with 4-6 free sepals or without, with 5 free petals or without, without staminodes, disc entire to cupular or absent, ovary hypogynous, syncarpous, with 3 locules, glabrous to pubescent and sometimes echinate-spiny, ovules 1 per locule, placentation axile, anatropous, bitegmic, style short to absent, stigmas 3, bilobed and fimbriate or peltate-discoid. Fruits septicidally dehiscent schizocarps with 3 seeds, echinate-spiny or smooth. Seeds ellipsoid to ovoid, smooth and conspicuously shiny black, anatropous, carunculate, without sarcotesta, endosperm copious, embryo with flat cotyledons broader than radicle. Chromosome numbers not reported.

Notes on delimitation

  • The family had been accepted as distinct by a few authors in the past, and was then treated as part of Euphorbiaceae for a long time.  It has been re-established mainly by recent molecular phylogenies, but is also supported by some unusual characters of the fruits and seeds (APG III). Peraceae are therefore sufficiently well defined as a taxon; the status as separate family or as a basal part of Euphorbiaceae is still viewed differently by some authors.  Characters of, among others, wood anatomy and pollen agree mostly with Euphorbiaceae.

Distribution in the Neotropics

Peraceae are pantropical with 5 genera and ca. 120-130 species. Of these, 3 genera and ca. 50 species are Neotropical, mostly occurring in tropical lowland evergreen rainforests.

  • Chaetocarpus Thwaites: pantropical with ca. 15 species, 9 of which are Neotropical in the Antilles and from Venezuela to Bolivia.
  • Pera Mutis: ca. 40 species from S Mexico to the Antilles and Bolivia, with numerous endemics in particular on Cuba.
  • Pogonophora Miers ex Benth.: one species (P. schomburgkiana Miers ex Benth.) in the rainforests of the N Amazon (Colombia to the Guianas), two species of somewhat doubtful affinity in W Africa.

Distinguishing characters (always present)

  • Dioecious woody plants (very rarely reported as monoecious).
  • Leaves simple, entire and completely eglandular.
  • Small unisexual flowers in axillary inflorescences.
  • 3-locular ovaries with one anatropous ovule per carpel.
  • Fruits with 3 conspicuously shiny black seeds, the mericarps splitting regularly from the top but often remaining attached at the base.
  • Testa of the seeds with a tracheoidal exotegmen.

Other important characters

Key differences from similar families

  • Peraceae share simple leaves, small unisexual flowers and 3-locular septicidal schizocarps with several families. They differ in the following characters from:
  • Euphorbiaceae - leaves completely eglandular, fruits dehiscent but often not dehiscing completely, seeds conspicuously shiny and black.
  • Phyllanthaceae -  fruits with one seed per carpel, seeds conspicuously shiny and black.
  • Putranjivaceae - plants without glucosinolates, leaf base not oblique, fruits dehiscent with 3 seeds, seeds conspicuously shiny and black.

Number of genera

  • See under Notable genera.

Notable genera and distinguishing features

  • Chaetocarpus - hairs always simple, flowers apetalous, stamens with the filaments fused at base, ovaries and fruits echinate -spinose.
  • Pera - hairs stellate-lepidote, inflorescences with spathaceous connate bracts completely enclosing the buds, flowers apetalous, stamens with the filaments fused at base, ovaries and fruits smooth to wrinkled but never echinate.
  • Pogonophora - hairs simple and T-shaped, flowers with regular calyx and corolla, stamens free, fruits smooth.

Status

  • Native - Chaetocarpus Thwaites, Pera Mutis, Pogonophora Miers ex Benth. (the latter two being endemic).

Important literature

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

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

Secco, R. 1990. Revisão dos gêneros Anomalocalyx Ducke, Dodecastigma Ducke, Pausandra Radlk., Pogonophora Miers ex Benth. e Sagotia Baill. (Euphorbiaceae -Crotonoideae) para a America do Sul. Belém: Museu Paraense 'Emilio Goeldi'.

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. & Davis, C.C. 2009. Malpighiales phylogenetics: Gaining ground on one of the most recalcitrant clades in the angiosperm tree of life. Amer. J. Bot. 96(8): 1551-1570.

How to cite

Esser, H.-J. (2009). Neotropical Peraceae. 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/Peraceae.htm.