Neotropical Icacinaceae

Rodrigo Duno de Stefano

Centro de Investigacion Cientifica de Yucatan, Merida, México. 

Description

Trees, shrubs, or lianas; generally all parts pubescent or glabrous, the pubescence persistent or deciduous, rarely with lepidote stellate hairs or clustered hairs. Large tubers rarely present. Leaves alternate, simple, exstipulate; petioles canaliculate; blades coriaceous to sub-coriaceous, rarely membranaceous; apex long acuminate to obtuse, rarely mucronate or emarginate; base acute or attenuate, rarely cordate; the margins entire, slightly revolute, or the juvenile leaves spinose-tipped or -margined; pore-cavities rarely present in the abaxial surface; the secondary veins joined together in a series of marginal loops, free or indistinct, alternate, rarely opposite. Inflorescences axillary, extra-axillary, terminal or cauliflorus, cymose or racemose; 1--3 bracts, rarely ebracteate; pedicels generally articulated near the end.  Flowers actinomorphic, rarely zygomorphic, bisexual, rarely unisexual; hypogynous. Calyx (4-)5-lobed or -toothed, campanulate, fleshy, pubescent without, imbricate. Petals (4--)5(--6), free, rarely united, pubescent or glabrous, valvate, reflexed; the apex acute, inflexed, sometimes extended in an appendage. Stamens (4--)5(--6), alternate with the petals; filaments fleshy, filiform or broad and flattened, occasionally with an adaxial appendage and covered with claviform hairs; anthers 2(-4)-locular, dorsi- or basifixed, longitudinally dehiscent, introrse or lateral; connective expanded, sometimes extended into an appendage. Disk present or absent, basal, free, sometimes reniform or a differentiated fleshy sterile ring at the base of the ovary. Pistil with the ovary  pubescent or glabrous, 1--(-2--3)-locular, rarely pubescent inside, rudimentary in staminate flowers; ovules 2 per locule, pendulous from near the apex, collateral or superposed; style 1, terminal or rarely excentric, rarely incurved, additional rudiments sometimes present; stigma capitate or papillose. Fruit a drupe, ovoid, oblong, globose or rarely flattened and with a large oblong fleshy appendage whitish on concave side; endocarp sometimes with ribs. Seed 1; embryo commonly minute; endosperm copious, non-ruminate.

Notes on delimitation

  • Recent molecular phylogenetic work on Icacinaceae (Kårehed, 2001) has demonstrated that the family should be split into four families: Icacinaceae s. str. (Garryales), Pennantiaceae (a member of order Apiales), Cardiopteridaceae, and Stemonuraceae (both members of order Aquifoliales).
  • The family Cardiopteridaceae includes three genera from the Old World, and Citronella D. Don, and possibly Dendrobangia Rusby from the New World. The family Stemonuraceae includes eleven genera from the Old World (e.g. Gomphandra Wall. ex Lindl., Stemonurus Blume, and Codiocarpus R. A. Howard) and Discophora Miers from the New World.
  • Finally, Icacinaceae s. str. includes nine Neotropical genera. Metteniusa H. Karst. have historically generated considerable systematic dispute but a recent phylogenetic analysis based on a combined dataset of three genes demonstrated that the genus must be considered a different monogeneric family: Metteniusaceae. This family is included in the lamiids clade but as an isolated taxon in the base of a clade including Boraginaceae, Vahliaceae, Gentianales, Lamiales, and Solanales (González et al., 2007). Garryales and the family Icacinaceae form another clade in the lamiids.
  • See also separate family webpages for Cardiopteridaceae and Stemonuraceae.

Distribution in the Neotropics

  • Calatola Standl., South Mexico, Central America, and South America (mainly Andes). 7 species.
  • Casimirella Hassl., 6 species in South America to Paraguay, with a diversity center in SW Brazil and Paraguay.
  • Citronella D. Don, 21 species in Malaysia, Pacific and the New World (8-10 spp in Mexico to Chile and Argentina).
  • Dendrobangia Rusby, 2 species in Central America to South America.
  • Discophora Miers., 2 species in Central America and South America.
  • Emmotum Desv. in Ham., 13 species in South America, mainly the Venezuelan Guayana and the Amazon Basin.
  • Leretia Vell., Monotypic in Costa Rica to Panama, South America to Brazil, and Bolivia.
  • Mappia Jacq., 5 species from Mexico to Panama, and the Great Antilles (Cuba, the Hispaniola, and Puerto Rico).
  • Oecopetalum Greenm. & C.H. Thomps., Two species from South Mexico to Costa Rica.
  • Ottoschulzia Urb., 3 species in the Great Antilles (Cuba, the Hispaniola, and Puerto Rico) and South of Mexico, Belize, and Guatemala.
  • Pleurisanthes Baill., 5 species in South America to Brazil, and Bolivia.
  • Poraqueiba Aubl., 3 species in South America to Peru, Brazil, and Bolivia.

Distinguishing characters (always present)

Icacinaceae is a medium-size family of woody, mostly tropical and subtropical plants. Vegetatively it is not easily recognizable:

  • Trees and lianas.
  • Simple, alternate and exstipulate leaves.
  • Flower articulated at the base (not in Pleurisanthes Baill.).
  • Unilocular ovary (multilocular in Emmotum Desv. in Ham.) with two pendulous ovules.

Other important characters

  • Icacinaceae are mostly trees or vines, sometimes shrubs with scandent branches.The most conspicuous character of the family is the ovary: 1-locular, rarely 2-3-locular with two ovules, apical, pendulous, anatropous and unitegmic.
  • Small domatia are found in the abaxial surface of Citronella and Mappia.
  • Indumentation is very common and variable in the family. Heintzelmann & Howard (1948) found at least 10 types of hairs in that family.
  • The inflorescence is generally axillary, sometimes terminal or opposite to the leaves (Citronella); it is variable, ranging from one or two flowers for extreme reduction as in Ottoschultzia, to a raceme, thyrse or cyme, sometimes very modified as a pseudo-spike in female plants of Calatola or as a spiciform raceme in Pleurisanthes.
  • Flowers are very small and the pedicel is generally articulated at the base of the flower (not in Pleurisanthes). They are generally bisexual, and less commonly completely unisexual bearing only stamens or pistil, as in Calatola.
  • A typical bisexual flower generally has 5 parts, rarely four (as in Calatola).
  • The sepals are small, connate into a tube, or with small imbricate lobes, rarely valvate, rarely accrescent as in Oecopetalum
  • Petals are generally free or connate below to various degree, the tip is inflexed.
  • The stamens are as many as the petals and are free and alternate to the petals.
  • The fruit is mostly subglobose or globose drupe, sometimes laterally compressed as in Discophora.
  • The epicarp is usually thin and often colored; the mesocarp is variably fleshy and sometimes rich in oils.
  • The inner layer of the fruit is hard.
  • Seed is solitary, exarillate, generally with abundant endosperm.
  • Embryo straight and the cotyledon foliaceous or not.

Key differences from similar families

  • Vegetatively not easily distinguished from many tropical families with simple, alternate exstipulate leaves (e.g. some Euphorbiaceae, Flacourtiaceae, Metteniusaceae, and Olacaceae).
  • The genus Metteniusa with seven species distributed through Costa Rica, Panama, Colombia, Venezuela, Ecuador and Peru has cymose inflorescences with large flowers and long sagittate, moniliform stamens.

Number of genera

  • Calatola Standl.
  • Casimirella Hassl.
  • Citronella D. Don
  • Dendrobangia Rusby
  • Discophora Miers.
  • Emmotum Desv. in Ham.
  • Leretia Vell.
  • Mappia Jacq.
  • Oecopetalum Greenm. & C.H. Thomps.
  • Ottoschulzia Urb.
  • Pleurisanthes Baill.
  • Poraqueiba Aubl.

Useful tips for generic identification

Citronella and Dendrobangia (which may be considered as members of the family Cardiopteridaceae) can be differentiated in the first case by:

Dendrobangia:

Discophora (which may be considered a member of the family Stemonuraceae) can be easily identified by:

Notable genera and distinguishing features

  • Emmotum is the biggest genus with 13 species found in the Guayana Shield and the Amazon basin. It is a unique genus with multilocular ovary.
  • Citronella with 8-10 species, still has many problems for recognition at specific level.

Status

  • Icacinaceae genera are mostly endemic to major phytogeographical realms. One exception is Citronella, which is shared by America, Asia and Oceania. Twelve genera and approximately 50 species occur naturally in the New World.  Most New World Icacinaceae genera are found within the tropics, a few species occur in subtropical regions, and one species outside of these (Citronella mucronata at 45° S). Most New World genera are widespread in the region, but Oecopetalum is confined to Southern Mexico and Central America, and Mappia and Ottoschultzia to Southern Mexico, Mesoamerica and the Caribbean region.
  • In America only two species are economically important. Poraqueiba sericea has a fleshy fruit rich in oil that is eaten fresh, also seeds that can provide flour. The fruit is widely traded throughout the  Amazon basin. Also Casimirella ampla produces a tuber weighing 5-20 kilos, rich in starch that is edible after washing out the bitter-tasting compounds.

General notes

  • Most Neotropical genera of the family Icacinaceae s. str. were not included in the molecular analysis of Kårehed (2001) and their position within the lamiid clade needs to be confirmed.

Important literature

Duno de Stefano, R. 2007. El género Dendrobangia Rusby (Cardiopteridaceae o Icacinaceae) en el Neotrópico. Candollea 62(1): 91-103.

Duno de Stefano, R. 2003. Icacinaceae. In: Flowering Plants of the World (N. P. Smith, S. A. Mori, A. Henderson, D. Wm. Stevenson, S. V. Heald, eds.). Princeton University Press, New Jersey; USA 616 pp.

González, F., J. Betancur, O. Maurin, J. V. Freudenstein & Mark W. Chase. 2007. Metteniusaceae, an early-diverging family in the lamiid clade. Taxon 56(3): 795-800.

Heintzelmann & R.A. Howard. 1948. The Comparative Morphology of the Icacinaceae. V. The Pubescence and the Crystal. Amer. J. Bot. 35: 42-52.

Howard, R. A. 1942a. Studies of the Icacinaceae, II. Humirianthera, Leretia, Mappia and Nothapodytes, valid genera of the Icacinaceae. J. Arnold Arbor. 23: 55-78.

Howard, R. A. 1942b. Studies of the Icacinaceae V. A revision of the genus Citronella D. Don. Contr. Gray Herb. 142: 60-89.

Howard, R. A. 1992. A revision of Casimirella, including Humirianthera (Icacinaceae). Brittonia 44: 166- 172.

Howard, R. A. & R. Duno de Stefano. 1999. Icacinaceae. In: Flora of the Venezuelan Guayana (Berry, P. et al., eds.) vol. 5. Missouri Botanical Garden.

Kärehed, J. 2001. Multiple origins of the tropical forest tree family Icacinaceae. Amer. J. Bot. 88(12):2259-2274.

Sleumer, H. 1971. Icacinaceae. In Flora Malesiana, serie I, vol 7 (1): 1-87.

How to cite

Duno de Stefano, R. (2009). Neotropical Icacinaceae. 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/Icacinaceae.htm.