Common Name: Oil Bean Tree
Latin Name: Pentaclethra marcoloba

Family: Fabaceae

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Range:

P. macrolobacan be found from Nicaragua sown to Amazonia, including some of the West Indian Islands. There are currently three major populations: the largest found in Amazonian lowlands on the Atlantic coast, the second in western Columbia and the third in the humid lowlands from Nicaragua through Costa Rica down into Panama [1].

Abundance:

It is a very common emergent tree in humid tropical forests. It is often found near areas of moderate slope near the coast [2]. It is the most abundant tree in the wet lowlands of Costa Rica, such as La Selva, where is has twice the basal area of the next most abundant species [4]. It is found primarily from 0 to 600 meters elevation.

Coloration and Morphology:

reaches 30-35 meters high and 1.3 meters as a fully grown tree. It has smooth bark that is a grayish-brown color and long shiny green leaves [1]. The leaves are biparipannate (having two leaflets one either side) and up to 30 cm long giving it a feather-like appearance. In commonly flooded areas the base of the tree may develop small buttresses.

Reproductive cycle:

The species blooms from April until August. They make numerous flowers, but produce few developed fruits. The flowers are bisexual and monomorphic. The main fruit crop is from August to Spetember with a minor crop season in November – December and the fruit is a woody pod approximately 20-50 cm long containing 3-8 seeds inside [2]. DSCN0168.JPG The seeds can germinate well under different light conditions as shown by Oberbauer et. Al (1985), so juveniles can easily survive, although their growth is slow in the first 2 years [3].





Habitat:

It is commonly found near rivers creeks and seasonally flooded zones as DSCN0303.JPG well as near the coast [2]. Its habitat is in generally infertile soils [4], and it reaches the canopy of the forest. The canopy receives the most sunlight so this tree has to be adapted to live in such sunlight rich areas. It lives in areas where the temperature ranges from 24°-35°C and average annual rainfall is more than 3500mm [2].


Ecology:

P. marcolobais a shade tolerant species and therefore can grow easily all over the forest without the need for forest gaps. Because of this, the species is, as well as its nitrogen fixing root nodules, it is considered a great species for natural forest regeneration and forest management [1,2]. The seeds are toxic so monkeys and birds avoid eating them; they are usually dispersed and pollinated by small insects [1]. Predators of P. morcoloba include man and moth as well as other insects that feed on their seeds. The moth (Carmenta surinamensis) is a parasite to the seeds of this tree. Larvae enter the seed and grow inside of it until the larvae become full grown moths. They feed on the seed as larvae and then on the leaves as moths [5]. A study by McKenna et Al. showed that this herbivory from the moth negatively affected the germination, seedling growth, survival, and all mearsures of adult growth such as number of leaves, height, and mass. This is one of few predators known for this tree. The other important predator is man. The wood of the tree has been used in Central America for many years to make telephone poles as well as act as a sunstitue for mahogany in the making of furniture, floors, railroad ties, and bridge decking [2]. This is no longer done in the areas of Costa Rica that are protected. The tree is also well known for its oil, which is used industrially in lubricants and soaps.

Interactions with other Species:

P. macroloba was found by Bennet et al (1985) to be weakly associated to the giant tropical ant species Paraponera clavata. In their study they found that 35.7 percent of the P. clavata nests were located at the base of these trees. They hypothesize that the ants may have this nest site preference due to the nesting habitat in the buttresses of the trees or that they nest at the base of these trees because they provide extrafloral nectarines as a food source to the ants [4].

Personal Experience:

While in La Selva I saw Pentaclethra marcoloba all over the arboretum where I did most of my research. The area was relatively cleared understory so it was easy to spot the trees and notice that there were almost never any animals or insects on the tree, which follows with the research I had read beforehand.

References:

  1. Dorthe, J., Salazar, Rodolfo. Pentaclethra macroloba (Willd.), Seed Leaflet No. 35, Spetember 2000.
  2. Flores, E.M., Pentaclethra macroloba (Willd.), Acedemia Nacional De Ciencias de Costa Rica, September 2000.
  3. Oberbauer, Steven and Strain, Boyd. Effects of Light Regime on the Growth and Physiology of Pentaclethra macroloba in Costa Rica, Journal of Tropical Ecology Vol. 1 No. 4 November 1985 pp. 303-320
  4. Bennet, Beth and Breed, Michael. On the Association Between Pentaclethra macroloba and Paraponera clavata Colonies, Biotropica Vol. 17 No. 3 September 1985 pp. 254-255
  5. McKenna, Duane and McKenna, Katherine. Sesiid Moths Reduce Germination, Seedling Growth, and Suvivorship in Pentaclethra macroloba a Locally Dominant Lowland Tropical Tree, Biotropica Vol. 38 No. 4 July 2006 pp. 508-513