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Project Noah Nature School
This is a small-thorned species of Swollen Thorn Acacia. These plants have an ancient and strong symbiotic relationship with ants of the genus Pseudomyrmex. In the first picture you can see an ant feeding at a nectary that the plant makes only to provide a sugary nectar for the ants. Also visible are the tiny yellow-orange Beltian Bodies that the plant also makes only as a lipid protein food source for the ant larvae. These are produced at the tips of the newly forming leaves and have no other known purpose. The ants live inside the thorns, making an entrance and exit hole at the tip of the thorn. It is fun to tap on a bush branch and watch the ants swarm out of the thorns and follow the vibrations to attack whatever is tapping on their home.
In heavy shrubbery along the highway between San Cristobal de Las Casas and Tuxtla Gutierrez, km 11.5, 865 meters.
The swollen-thorn acacias are native to Mexico and Central America. In its native habitat, colonies of stinging ants (Pseudomyrmex app.) occupy the hollowed-out thorns and fiercely defend the tree against ravaging insects, browsing mammals and epiphytic vines. In return, the host supplies its little guardian ants with yellow protein-lipid Beltian bodies from its leaflet tips and carbohydrate-rich nectar from glands on its leaf stalk (pit-shaped structure at the base of the leaf stalks). There is no known function for the Beltian bodies, other than to provide food for the symbiotic ants. These species of Central American swollen-thorn acacias lack the chemical defenses of most other acacias to deal with their predators and competition. Without bitter alkaloids, ravaging insects and browsing mammals eat the leaves and branches, slowing the growth of the acacias and allowing fast-growing, competing vegetation to shade them out. Symbiotic ants have taken over this vital defense role, protecting the acacia from hungry herbivores and pruning away competing plants. The ants live inside the inflated thorns at the base of leaves.
Spotted on Aug 12, 2013
Submitted on Aug 27, 2013
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