Fabaceae: Mimosoideae

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Pea Family – Mimosoid Subfamily

For additional information see Fabaceae.

Stryphnodendron microstachyum Poepp. & Engl., a canopy tree in the Mimosoideae. Note the bipinnately compound leaves. Un árbol del dosel. Note las hojas bipinnadas.

Description: Mimosoideae can be herbs, shrubs, lianas, or trees. Except for the four lianas Acacia hayesii, A. tenuifolia, Mimosa myriadenia, M. watsonii, and the shrubs M. pudica and M. pigra, all the species at La Selva Biological Station are trees. Almost all Mimosoideae have bipinnately compound (i.e., twice divided) leaves, with glands on the rachis. The flowers of Mimosoideae typically have many exserted stamens. Ironically, the two most important groups of Mimosoideae at La Selva are atypical mimosoids. There are 22 species of Inga, which is unusual in that it is only once pinnate. All Inga species have opposite leaflets with a gland between each pair, making it an easily recognized genus. Pentaclethra macroloba, which constitutes 40% of the basal area and up to 18% of the stem density in parts of the La Selva forest, is unusual in that it lacks glands on the rachis.

Economic uses: Many mimosoids are important timber trees, and since they are nitrogen fixers many species are also used as shade trees for coffee. Several Inga species produce fruit with edible pulp around the seeds.

Descripción: Las Mimosoideae pueden ser hierbas, arbustos, bejucos, o árboles. Con la excepción de cuatro bejucos, Acacia hayesii, A. tenuifolia, Mimosa myriadenia y M. watsonii, y los arbustos M. pudica y M. pigra, todas las especies en la Estación Biológica La Selva son árboles. Casi todas las Mimosoideae tienen hojas bipinnadas (es decir, las hojas son pinnadas, pero sus foliolos, en vez de simples, son pinnados) con glándulas en el raquis. Irónicamente, los dos grupos de Mimosoideae más importantes en La Selva son atípicos. Hay 22 especies del genero Inga, un grupo un poco raro porque es simplemente pinnado. El género es fácil de identificar, porque tiene foliolos opuestos con una glándula entre cada par de foliolos. Pentaclethra macroloba, que constituye 40% del área basal y hasta 18% de los tallos leñosos en partes del bosque en La Selva, es una especie atípica porque las glándulas en el raquis estan ausentes.

Usos económicos: Muchas Mimosoideae son maderables. Al ser fijadoras de nitrógeno, muchas especies se cultivan como sombrío y fuente de nutrientes en fincas cafetaleras. Algunas especies de Inga (guabas) tienen frutos con pulpa comestible.

Genera/species at La Selva: 13/43: Lianas (bejucos): Acacia (2 of the 3), Mimosa (2 of the 4) Shrubs (arbustos): Mimosa (2 of the 4) Trees (árboles): Abarema (1), Acacia (1 of the 3), Albizia (2), Balizia (1; and no, it’s not a typo!), Cojoba (2), Dinizia (1), Entada (1), Inga (22), Leucaena (1), Pentaclethra (1), Stryphnodendron (1), Zygia (3).

FIELD MARKS – alternate, bipinnate leaves (except for Inga), generally with nectaries on rachis, leaflets small generally <1 cm wide, some with spines, conspicuous part of flower are stamens, seeds either vertically or transversely arranged within fruit

Inga – Paripinnate leaves (NOT bipinnate) with disc-shaped nectaries on rachis, rachis often winged, flowers white.

Inga.	Comparison of species of Inga with and without a winged rachis.
Trunk of Inga alba.

Pentaclethra macroloba “gavillon” – bipinnate with tiny leaflets, serial axillary buds along stem, elongated inflorescence of white showy stamens (summer). The most common tree at La Selva!

Pentaclethra macroloba tree in flower (July) at edge of forest..	Bipinnate leaves of Pentaclethra macroloba.
Inflorescence of Pentaclethra macroloba.	Close-up of flowers showing long white stringy stamens.
Fruits of Pentaclethra macroloba.	Open fruit and seeds of Pentaclethra.
Pentaclethra seedlings are common on the forest floor at La Selva.	Trunk of Pentaclethra macroloba.
Sprouting seeds of Pentaclethra.	View of the canopy showing the abundance of Pentaclethra.

Stryphnodendron microstachyum – pinnate compound leaves, rectangular-shaped leaflets, thin buttresses.

Stryphnodendron trunk showing very thin buttresses.	Closeup of thin buttresses of Stryphnodendron
Looking up into the canopy of Stryphnodendron and its feathery leaves.	Pinnate leaf of Stryphnodendron. Note the distinctive shape of the leaflets, almost rectangular with the mid-vein forming a diagonal line.

Zygia longifolia (formerly known as Pithecelobium longifolia) – unusual compound leaves that are actually bipinnate, nectaries along rachis and at base of some leaflets, common along rivers. Look for this tree from the suspension bridge at La Selva.

Zygia longifolia.	Zygia longifolia tree overhanging Rio Puerto Viejo.
Zygia bearing fruit.

Ecorefs:

• Koptur, S. (1984). Experimental evidence for defense of Inga (Mimosoideae) saplings by ants. Ecology 65: 1787-1793.
• Romero-Alvarado, Y., Soto-Pinto, L., Garcia-Barrios, L. & Barrera-Gaytan, J.F. (2002). Coffee yields and soil nutrients under the shades of Inga sp. vs. multiple species in Chiapas, Mexico. Agroforestry Systems 54: 215-224.
• Coley, P.D., Lokvam, J., Rudolph, K., Bromberg, K., Sackett, T.E., Wright, L. et al. (2005). Divergent defensive strategies of young leaves in two species of Inga. Ecology 86: 2633-2643.
• McKenna, D. D., and K. M. McKenna. 2006. Sesiid moths reduce germination, seedling growth, and survivorship in Pentaclethra macroloba (Mimosoideae), a locally dominant lowland Neotropical tree. BIOTROPICA 38(4):508-513.
• Slocum, M. G. 2001. How tree species differ as recruitment foci in a tropical pasture. Ecology 89:2547-2559. (Pentaclethra)

For additional information see Fabaceae.

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