The Corotú and the Gomphothere

The corotú is one of the largest and most beautiful of the trees of the savanna (left photo, below). It is known in Costa Rica as the guanacaste and is the national tree of that country. It is also known as false mahogany, the earlobe tree, and the elephant ear tree, among other names.

The gomphothere is an extinct large mammal, with four tusks and some elephant-like features. The illustration at right below is from Fossil Treasures of Florida, used by permission.

Tree Of The Ears Gomphotheres

How the corotú and the gomphothere are related is a fascinating story uncovered by Janzen and Martin while working in Costa Rica, and we’ll get to it shortly.

How to recognize the corotú

The corotú is an intriguing tree in its own right. As a member of the Fabaceae (bean) family, it has alternating, compound leaves and produces pods filled with beans.

Leaves2 Pods In Tree

The tree itself may grow to 35 meters (about 115 ft) and its trunk may exceed 1 meter (3.2 ft) in diameter. The trunk of this particular roadside tree is covered with woody vines, nearly hiding its light gray color and dark, reddish brown vertical fissures.

Corotu Trunk

But the sure-fire key to recognizing the corotú lies in its distinctive pods.

Pod-1

The pods give the corotú, Enterolobium cyclocarpum, its scientific name:

  • Enterolobium [1] = within (entero-) lobes (lobium) [Dave's Botanary]
  • Enterolobium [2] = relating to the intestine (entero-) [American Heritage Dictionary]
  • cyclocarpum = circle (cyclos) fruit (carpos) [Dictionary of Botanical Epithets]

It is a fruit in the shape of a circle; it has lobes that make it look like a section of intestines.

Humans have found uses for these pods. When I brought one home to show our then worker, he immediately broke it in two and  took it over to the standpipe, where he held it under water for a bit. Then he rubbed his thumbs on the pulp and gradually worked up a lather! Panamanians clearly know how to use these pods as a source for soap, and it has been documented that some indigenous people in Mexico have used this soap especially for washing woolen clothes.

The pulp that lathers is on the above left and the protected seed in its cavity is on the right. And what a seed it is! Stone hard and beautiful. It needs to be scored before it will germinate.

When the pods of the corotú ripen, they fall to the ground and accumulate directly under the parent tree. Since the seeds can’t germinate without having been scored, they simply sit there. How, then, does the corotú ever expand its range, or does it?

Gompotheres to the rescue

Nearly 20 years ago, Janzen and Miller asked this question not only of the corotú, or guanacaste, but also of several other trees and plants that produced large fruits and that had no obvious way to disperse their seeds: the jobo or hog plum (Spondias sps.), the anona or custard apple (Annona reticulata), the naranjillo (Zizyphus guatemalensis), the jicaro or Mexican calabash (Crescentia alata), the trompillo (Albertia edulis), and many more. They suggested that large herbivores that lived during the pre-Pleistocene eras but that are now extinct distributed the seeds of at least 37 different species of trees found in Costa Rica. Large herbivores that lived in Central America at that time included the giant ground sloth, the giant armadillo, the native horse, and the gomphothere. These herbivores could have eaten the fruits and thereby could have carried the seeds to distant places before defecating.

Fruits in the American Northern Hemisphere may also have had their seeds distributed by large, now extinct, herbivores – fruits such as the osage orange (Maclura pomifera), pawpaw (Asimina sp.), and the Kentucky coffee bean (Gymnocladus dioica). [Janzen and Miller] Connie Barlow has written about these possibilities in Anachronistic Fruits and the Ghosts Who Haunt Them, a very good read.

Horses and cattle

Janzen and Miller also suggested that the introduced cattle and the re-introduced horses in Central America may today be dispersing at least some of the seeds formerly moved around by the extinct large herbivores. They have a picture in their paper of a horse eating, apparently with relish, a jicaro gourd (Crescentia alata), something we humans find inedible, or at the very least, extremely boring.

Here in the western province of Chiriqui, in Panama, the corotú is more widely distributed than you might think, for a tree that dumps all its fruits directly beneath its canopy. But here in Chiriqui, also, many Panamanians ride their horses as their main way of getting around. And where are the corotú trees found? Often along the roadside. It’s easy to imagine a horse tethered in the fine shade of a corotú, eating the fruits right at her feet. Then, as the horse is ridden home, somewhere along the way or more probably in a day or so, it defecates the corotú seeds, now nicely corroded by horse intestines and ready to germinate.

Note: Special thanks to Sarcozona of Gravity’s Rainbow for sharing with me her copy of the Janzen & Martin paper, which enabled me to understand a little of  pre-Pleistocene ecology.

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14 Responses to The Corotú and the Gomphothere

  1. Carla says:

    Mary,

    What a great story! Incredible that any species have survived without their intended dispersers. What were the seeds like of the plants that didn’t make the transition? I suppose we’ll have to ponder that buck-toothed gomphothere and imagine what it did that a horse can’t. Now that I think of it, something else was keeping the corotu spread around during the long gap between the epochs of these two animals.

    Fun to think about!
    Carla

  2. This is a similar story to the large trunk spines of honey locust (Gleditsia triacanthos), which I have heard (and it seems reasonable to me) evolved to protect the tree from predations by mastodons. The mastodons are gone, but the thorns remain (at least for the short geologic moment afterwards).

  3. mary says:

    Carla,
    Yes, it is fun to think about. Janzen did discuss how the ranges of many of these trees contracted between the Pleistocene and now, and that some survived because they were good at cloning – sending out runners and shoots. With the reintroduction of horses and also the introduction of cattle, some of the trees appear to have begun expanding their range. Barlow’s paper on similar trees is easily available on the web (link provided in the post) and if you have time to read it, you might find food for further thought.
    Mary

  4. mary says:

    Yes, it certainly is a similar story, Ted. Both Janzen and Barlow mentioned the honey locust – and Janzen also mentioned a few other species that had thorns presumably to protect themselves from large herbivores. For my part, I’ll never look at a custard apple or an osage orange or for that matter a honey locust pod without thinking of those extinct creatures. Mary

  5. Hugh says:

    Great post, Mary. So much of zoology/botany is also history. These fructal mysteries and the possible explanations give one pause. They make me sort of happy and sad at the same time.

  6. Greg Laden says:

    I love this story. There are many plant-animal cases where the animal is gone and the plant’s ecology is now… different, in some cases threatened.

  7. Greg Laden says:

    This post has been included in the latest edition of the Berry Go Round web carnival. Please visit the carnival and let other people know about it, click on the links, read everything, and help promote plant blogging! The plants can not do this themselves, people!

  8. mary says:

    I love the story, too, Greg. It has opened my mind to all the possibilities you suggested – and how many plants have already died out, for instance, simply because their pollinator is gone?

    And Hugh, no wonder you feel both sad and happy at such a story. It has both drama and pathos. I greatly admire Janzen and Martin for thinking through the issue of uneaten fruits!

  9. Joy K. says:

    So the Osage Orange trees in the woods are like links to the past. Ours, at least, have their seeds dispersed by the neighbor’s dogs, who like to use the fruits as fetching toys until they fall apart.

  10. mary says:

    Joy K. – Yes! Dogs as seed-dispersers. Kids, too, I guess. I certainly remember tossing a lot of hedge-apples around when I was young. :-) Mary

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  12. Pat says:

    “Entero” in this case will be in its sense as gut or intestine, I would think. Those seed pods are quite similar to a section of gut.

  13. mary says:

    You’re right, Pat. I used the more general sense of entero to mean within. It does also mean intestine or gut, which is within animal bodies, and that more specific use is appropriate here. I will modify my definition to reflect this more accurate meaning.

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