Enterolobium Cyclocarpum - Ecology

Ecology

Guanacaste trees appear to delay the onset of fruit development - some nine months - so that seed maturation will coincide with the start of the rainy season. This adaptive behavior presumably is designed to give germinating seedlings as much time as possible to establish root systems before the start of the next dry season. Both Jatobá (Hymenaea courbaril) and Cenizaro (Albizia saman) exhibit similar reproductive strategies. Of course, Guanacaste trees - like all deciduous and semi-deciduous species in this part of the world - share in the water conserving benefits of dry season leaflessness.

Guanacaste flowers are heavily visited by bees - insects that probably are responsible for pollination as well. Guanacaste seed pods, however, are completely ignored by native fauna and they accumulate on the forest floor underneath parent trees. The seeds are not eaten by any animals currently native where the tree occurs. Perhaps Guanacaste pods were among the foods exploited by certain species of Pleistocene megafauna that became extinct some 10,000 years ago (e.g. giant ground sloths, giant bison). Under this scenario, the tree remains today without an effective seed-dispersing vector - except humans, that is.

As discussed above, the tough-coated Guanacaste seeds do not begin to grow unless their protective covers are punctured in some way. This may be an adaptation designed to keep the seeds from germinating while still in the pods at the start of the rainy season - and very likely still underneath the parent tree after having fallen from its crown. With more time to find them, foraging ground sloths (and other extinct mammals) could eat the pods and transport the seeds to a new site. The resulting mastication and digestion of the fruits would induce seed coat abrasion, which would help seed germination.

An insect pest, common to Guanacaste trees of the Costa Rican Central Valley, produces spherical green galls of 1.5 cm diameter on new shoots in February and March. Similar parasitism seems to occur on Guanacaste trees of the wet, southwestern lowlands (around Palmar Sur).