Neotropical Burseraceae

Douglas C. Daly

The New York Botanical Garden. 

Description

Habit: trees, less often shrubs, rarely epiphytes; resin present, often aromatic and smelling like turpentine. Bark thin and smooth to thick and fissured, shedding as flakes, variously sized plates, or papery sheets (some Bursera), often lenticellate, sometimes hooped, sometimes red or yellowish (some Bursera). Stipules absent. Leaves alternate, imparipinnately compound, less often unifoliolate; pulvinulus present (most Protieae and Canarieae) at distal end of terminal petiolule and often lateral petiolules; rachis winged (some Bursera and Commiphora); lateral leaflets opposite. Inflorescences axillary to subterminal, indeterminate panicles of racemes, laxly branched or variously reduced, sometimes short and fasciculate, secondary axes can be pseudospicate (some Protium). Flowers actinomorphic, 3-5(6)-parted, unisexual (plants dioecious, or polygamodioecious in some Bursera and Commiphora) or bisexual (some Dacryodes), small; calyx valvate, synsepalous, usually lobed, sometimes irregulary split at anthesis (Tetragastris and some Dacryodes); corolla induplicate-valvate, apopetalous to partly sympetalous, usually pale green to greenish-yellow, sometimes wine-red (some Dacryodes and Trattinnickia). Staminate flowers: androecium diplostemonous or rarely isostemonous, sometimes didynamous, often series difficult to distinguish,  filaments distinct, less often connate basally, inserted at base of disc; disc intrastaminal, annular, nectariferous; reduced pistillode usually present, sometimes ontogenetically fused with disc to form conical or discoid "ovariodisc", sometimes reduced locules and ovules present, stigmas absent. Pistillate flowers:  staminodes present, reduced, anthers devoid of pollen; gynoecium syncarpous, ovary superior, carpels and locules 2-5, style solitary, apical, sometimes with as many short branches as locules, stigma(s) 1 or as many as locules, capitate to discoid; placentation axile, ovules 2 per locule, collateral, pendulous, epitropous. Fruits compound drupes or pseudocapsules, pyrenes dehiscent or remaining fused together. Seeds 1 per locule (or aborted), usually fewer than locules, exalbuminous, testa thin or, in some Protium, irregularly thickened and infolded with cotyledons; embryo minute, straight.

Notes on delimitation

  • The monophyly of the Burseraceae has been repeatedly confirmed.  Recently derived phylogenies place the Burseraceae and Anacardiaceae as sister clades nested within the Sapindales, sister to the Sapindaceae.

Distribution in the Neotropics

  • Beiselia Forman :  restricted to Michoacán, Mexico.
  • Bursera Jacq. Ex L.:  SW United States, Mexico, Central America, Caribbean, Colombia, Ecuador, N Peru, N Venezuela, extreme N Brazil.
  • Commiphora Jacq.:  Orinoco basin and Brazil (NE, Central).
  • Dacryodes Vahl.:  Caribbean, Costa Rica south to N South America.
  • Protium Burm.f.:  Mexico, Caribbean, Central America, N South America south to Paraguay.
  • Tetragastris Gaertn.:  Hispaniola, Puerto Rico, Belize and Honduras south to Bolivia and SE Brazil.

Distinguishing characters (always present)

  • For all species, virtually all vascularized tissues with resin ducts. Consistenty imparipinnate leaves with opposite leaflets (when not unifoliolate).  

Other important characters

  • The fruit in most Neotropical taxa is somewhat fleshy and dehisces by valves, exposing one or more pyrenes at least partially covered by a fleshy or spongy arillate structure; in the remainder the fruit is a plurilocular drupe with connate carpels.
  • In most Protieae, pulvinulus present at least at apex of terminal leaflet.
  • In many Bursereae the bark is shed in papery sheets.
  • Virtually all vascularized tissues of Burseraceae contain resin canals. The resin may be clear, drying as a white to yellow or blackish crystalline powder or mass, or milky and drying in yellowish globules. The resin of some taxa is flammable.
  • All of the Protieae and the vast majority of species in the other two tribes possess hypogynous flowers. Perigynous flowers, with the disc adnate to the receptacle, occur in some species of Bursera and Commiphora.
  • There are five fruit types, three dehiscent and two indehiscent. In all of them at most one fertilized ovule develops per locule. The dehiscent fruits have as many valves as developed locules; the valves fall away via acropetal septicidal dehiscence, leaving a columellate structure in the taxa in which more than pyrene develops.
  • In the fleshy dehiscent fruits the exposed pyrenes (stones) are partially to almost completely covered by a pseudaril. In the Protieae, the pyrenes are attached apically to the columella and suspended from it after dehiscence; the pseudaril is spongy, sweet, and usually white; and the pyrene is (thinly) cartilaginous to bony. In the Bursereae-Burseriinae, when the valves fall away, the pyrene remains attached basally, and the pseudaril is fleshy, proteinaceous, and red or yellow. The Bursereae-Boswelliinae have dry, pseudocapsular fruits and flattened, usually winged pyrenes.
  • The indehiscent fruit of the Canarieae consists of a single 2-3-locular compound drupe with a thin exocarp, oily mesocarp (in many cases edible when ripe), and cartilaginous to bony endocarp.
  • In the tribe Protieae the cotyledons are entire and plano-convex (these sometimes uncinately curved) or lobed and contortuplicate, less often transversely twice-folded (Protium sect. Icicopsis). The tribe Bursereae have palmatifid cotyledons. Those of tribe Canarieae may be palamtifid or trifoliolate, and contortuplicate or folded.
  • Germination is epigeal or hypogeal, cryptocotylar or phanerocotylar, the eophylls opposite or alternate, simple, trifoliate, or pinnately compound.

Key differences from similar families

Number of genera

7 genera:

  • Beiselia
  • Bursera
  • Commiphora
  • Dacryodes
  • Protium
  • Tetragastris
  • Trattinnickia

Useful tips for generic identification

Key to genera of Neotropical Burseraceae

1.  Branches and trunk armed with laterally compressed, acutely pointed protuberances formed by the persistent swollen petiole bases; secondary leaflet venation craspedodromous, tertiary veins freely ramified but opposing tertiaries meeting at higher ranks; fruit a pseudocapsule with 10(-12) narrow valves dehiscing to release as many pyrenes separated by a columella, the pyrenes compressed and distally winged, the wings parallel to radii of the fruit axis; endemic to Michoacán, Mexico … Beiselia
1.  Trunk unarmed except sometimes with spiny short shoots (Commiphora); secondary leaflet venation diverse but almost never craspedodromous; fruit drupaceous or, if a pseudocapsule, 1-5-valved, and the pyrenes not notably flattened and at least partially covered with an arillate structure; tropics … 2

2.  Flowers 3-merous; filaments less than twice as long as anthers; fruit indehiscent, with a single 2- or 3-locular pyrene, 1 or 3 locules developing (tribe Canarieae) … 3
2.  Flowers 3-5(6)-merous, when 3-merous either filaments at least twice as long as anthers (Bursera pro parte) or petals cucullate (Protium section Sarcoprotium); fruit dehiscent, with 1-5 unilocular pyrenes … 4

3.  Leaflets usually somewhat asperous on at least one side; flowers 3-5 mm long; petals partially connate, (sub)erect, fleshy, with retrorse hairs; fruit globose to umbonate, the endocarp 2-3-lobed, bony, tuberculateTrattinnickia
3.  Leaflets not asperous (except Dacryodes cuspidata), flowers 1-3 mm long; petals free, spreading, membranaceous, pubescence not retrorse; fruit ellipsoid to ovoid (rarely globose), the endocarp cartilaginous, not lobed, smooth … Dacryodes

4.  Plants usually deciduous; petiolules all without a pulvinulus; carpels 2 or 3; pyrenes 1(2 or 3), provided with a fleshy, brightly colored arillate structure (tribe Bursereae) … 5
4.  Plants usually evergreen; terminal petiolules and usually lateral ones with a pulvinulus or, if pulvinuli lacking altogether, all vegetative organs invested with snail-shaped glandular trichomes (Crepidospermum); carpels 4 or 5; pyrenes 1-5, with a spongy white arillate structure usually covering each pyrene almost entirely (tribe Protieae) … 6

5.  Calyx saucer-shaped to shallowly cupular, lobes open in bud; antepetalous stamens same length as antesepalous ones or nearly so (anthers overlappping); arillate structure, when not covering pyrene entirely, with arms on sutures but never on faces … Bursera
5.  Calyx cupular to bell-shaped, lobes closed in bud; antepetalous stamens usually much shorter than antesepalous ones; arillate structure rarely covering pyrene entirely, and arms, lobes, or teeth (when present) on sutures as well as on 1 or both faces … Commiphora

6.  Lateral petiolules with a pulvinulus (absent in Protium pilosum, then the acumen serrulate), petals free (rarely basally connate) … Protium (most of the genus)
6.  Lateral petiolules without a pulvinulus; petals free or connate … 7

7.  Leaflets entire … 8
7.  Leaflets serrate or serrulate … 9

8.  Petals connate at least 1/2 their length; anthers continuous with the filaments (bases entire, not sagittate) on stamens and sometimes staminodes; disk glabrous; in staminate flowers the disk and pistillode fused to form a parenchymatous ovariodisk; fruits glabrous; resin clear … Tetragastris
8.  Petals free; anthers sagittate on stamens and staminodes (some of these usually persisting in fruit); disk usually pubescent; in staminate flowers the disk and pistillode distinct; fruits often pubescent; resin milky … Protium (some of section Pepeanthos and of P. subserratum group)

9.  Leaflets uniformly serr(ul)ate to almost crenate; terminal pulvinulus absent; petals only papillate adaxially, usually strongly reflexed at anthesis; pyrene cartilaginous; resin clear … Crepidospermum
9.  Leaflets irregularly serr(ul)ate; terminal pulvinulus present; petals adaxially with dense long trichomes, (sub)erect at anthesis; pyrene bony; resin milky … Protium (most P. subserratum group)

Notable genera and distinguishing features

  • Protium and Bursera are the most conspicuous Neotropical genera in terms of both diversity and ecological importance.
  • Bursera dominates many of Mexico's dry forests in these terms.  On dehiscence of the fruit, the valves fall away to reveal a basifixed stone (usually) partially enveloped in a fleshy pulp that is red, orange, or yellow.  One of its two subgenera has a characteristic peeling bark that is often red or yellow. 
  • Protium is highly important in relative density, relative diversity or both in many of northern South America's moist to wet forests, particularly in central Amazonia. It usually has a relatively smooth, grayish bark, the lateral petiolules almost always have a distal pulvinulus, and on dehiscence of the fruit the valves fall away and the 1-5 stones, each enveloped in a sweet, white (rarely red) pulp, are suspended from the apex of the fruit by an inverted V-shaped structure.

Status

  • Given existing generic circumscription, Beiselia, Bursera, Tetragastris, and Trattinnickia endemic to Neotropics; Commiphora, Dacryodes, and Protium native but also present in Paleotropics.

Important literature

Cuatrecasas, J.  1957a.  Burseraceae.  Prima Flora Colombiana. Webbia 12 (2): 375-437.

Cuatrecasas, J.  1957b.  The American species of Dacryodes.  Trop. Woods 106: 46-65.

Daly, D. C.  2007.  A new section of Protium Burm. f. from the Neotropics.  Studies in neotropical Burseraceae XIV.  Brittonia 59: 1-24

Daly, D. C.  1999.  Notes on Trattinnickia, including a synopsis in eastern Brazil's Atlantic forest complex.  Studies in neotropical Burseraceae IX.  Kew Bulletin 54 (1): 129-137.

Daly, D. C.  2002.  Burseraceae.  In:  S. A. Mori, G. Cremers, C. Gracie, J.-J. de Granville, M. Hoff, & J. D. Mitchell, eds.  Guide to the Vascular Plants of Central French Guiana.  Part 2.  Dicotyledons.  Mem. New York Bot. Gard. 76(2): 151-165.

Daly, D. C.  1989.  Studies in neotropical Burseraceae II.  Generic limits in Neotropical Protieae and Canarieae.  Brittonia 41: 17 27.

Daly, D. C.  1987.  A Taxonomic Revision of Protium Burm.f. (Burseraceae) in Eastern Amazonia and the Guianas.  Ph.D. dissertation, City University of New York.

Daly, D. C.  1992.  New taxa and combinations in Protium Burm.f.  Studies in neotropical Burseraceae VI.  Brittonia 44: 280 299.

Daly, D. C.  1997.  Burseraceae.  Pages 688-728.  In: J. Steyermark, P. E. Berry, & B. Holst, eds.  Flora of the Venezuelan Guayana.  Vol. 3.  Timber Press, Portland

Daly, D. C.  2003.   Burseraceae; Erythroxylaceae; Flacourtiaceae; Lacistemataceae; Peridiscaceae.  Pages 67-70, 143-145, 158-161, 200-201, 290-291.  In:  N. P. Smith, S. A. Mori, A. Henderson,  D. W. Stevenson, & S. V. Heald, eds.  Flowering Plant Families of the  American Tropics.  Princeton University Press/New York Botanical Garden.

Engler, A.  1883.  Burseraceae.  D. C. Mon. Phan. 4: 1 169.

Fine, P. V. A., D. C. Daly, F. G. Villa M., I. Mesones A., & K. M. Cameron  2005.  The contribution of edaphic heterogeneity to the evolution and diversity of Burseraceae trees in the Western Amazon.  Evolution 29: 1464-1478.

Harley, M. M. & D. C. Daly  1996.  Burseraceae-Protieae.  World Pollen and Spore Flora 20: 1-44.

McVaugh, R. & J. Rzedowski  1965.  Synopsis of the genus Bursera L. in western Mexico, with notes on the material of Bursera collected by Sessé & Mociño.  Kew Bull. 18: 317-382.

Pell, S. K.  2004.  Molecular Systematics of the Cashew Family (Anacardiaceae).  Doctoral Dissertation, Louisiana State University, Baton Rouge.

Ribeiro et al. 1999.  Flora da Reserva Ducke. Guia de identificaçao das plantas vasculares de uma floresta de terra-firme na Amazonia Central.  INPA, Manaus.

Rzedowski, J. & F. Guevara-Féfer  1992.  Burseraceae.  Flora del Bajío y de Regiones Adyacentes 3: 1-46.

Rzedowski, J., R. Medina Lemos & G. Calderón de Rzedowski  2004.  Las especies de Bursera (Burseraceae) en la cuenca superior del río Papaloapan (México).  Acta Bot. Mex. 66: 23-151.

Rzedowski, J., R. M. Lemos & G. Calderón de Rzedowski  2005.  Inventario del conocimiento taxonómico, así como de la diversidad y del endemismo regionales de las espcies mexicanas de Bursera (Burseraceae).  Acta Bot. Mex. 70: 85-111.

Savolainen, V., M. W. Chase, S. B. Hoot, C. M. Morton, D. E. Soltis, C. Bayer, M. F. Fay, A. Y. de Bruijn, S. Sulllivan & Y.-L. Qiu  2000. Phylogenetics of flowering plants based on combined analysis of plastid atpB and rbcL sequences.  Systematic Biology 49: 306-362.

Swart, J. J.  1942.  A monograph of the genus Protium and some allied genera (Burseraceae).  Drukkerij Koch en Knuttel, Gouda.

Weeks, A., D. C. Daly & B. B. Simpson  2005.  The phylogenetic history and historical biogeography of the frankincense and myrrh family (Burseraceae) based on nuclear and chloroplast sequence data.  Molecular Phylogenetics and Evolution 35:  85-101.

How to cite

Daly, D.C. (2010). Neotropical Burseraceae. 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/Burseraceae.htm.