Ant Plants

April 1, 2010

Mutualism in nature has always been something that interests me, and in my eyes one of the more amazing examples would have to be the relationship between certain ants and plants. These relationships can be relatively simple, where the plant produces supplemental food, or more complex with the plant providing a home for the ants.

Plants which produce supplementary food can do so via small food nodules, or by the production of sugary secretions at extrafloral nectaries (basically, a nectary outside of a flower). These attract ants, which benefit from the easily harvested nutrient, and in turn this benefits the plant because the ants defend the food supply.

The next step up is plants which actually create an area for the ants to inhabit (domatia). These can range from simple hollow thorns, such as in Acacia sphaerocephala, to the more complex tunnel networks found in the tuber of the Myrmecodia. Now here’s a superb example of a refined mutualistic relationship. This plant gains both a defense mechanism and a food source from its association with ants. Myrmecodia are epiphytes (they live on other plants), and are somewhat unusual in appearance, as the bulk of the organism is usually made up of the tuber (some call this the caudex, which is a modified stem). Within this tuber is a network of tunnels, some with smooth walls which the ants live in, and some covered in nodules in which the ants deposit their refuse. This refuse is then used as nutrient by the plant. A variety of ant species have been found living in these plants and in Australia they include Philidris cordatus (most common inhabitant), Pheidole megacephala and Crematogaster physothorax (Huxley, 1978). Even frogs have been found using them as a temporary home!

No prizes for photography... a young Myrmecodia beccarii found on the beach.

The fact that organisms from two completely separate kingdoms have managed to co-evolve and work so efficiently together is always pretty neat.

Huxley, Camilla R. 1978. The Ant-Plants Myrmecodia and Hydnophytum (Rubiaceae), and the Relationships between their Morphology, Ant Occupants, Physiology and Ecology. New Phytologist.

As a side note… how’s this for a title!

Amador-Vargas, S. 2008. Spartan defense in the Thermopylae pass: Strategic defense by aggregations of Pseudomyrmex spinicola (Hymenoptera, Formicidae) on the trunk of Acacia collinsii (Mimosaceae). Insectes Sociaux 55 (3):241-245.

7 Responses to “Ant Plants”

  1. I had never heard of this epiphyte what an amazing example of the interdependencies that evolve in nature. My personal favorite article on ant – plant relationships is:

    T.M. Palmer, Stanton, Young, Goheen, Pringle, Karban (2008) Breakdown of an Ant-Plant Mutualism Follows the Loss of Large Herbivores from an African Savanna. Science 319:5860, 192-195

    In this study the authors fence off and thus exclude large herbivores in an area and examine the changes that occur in the ant – acacia relationship. The result of the experiment is a dramatic change in the ant community that is eventually dominated by a normally rare ant species. This species is one that does not depend on rewards from the tree and actually harms the trees health.

    • peteryeeles Says:

      That’s pretty neat. I think this is one of the appeals of ants, for me at least. Not many organisms have the capacity to single-handedly alter the local ecosystem.

  2. Are the leaves part of the host tree or the Myrmecodia plant? Very strange looking plant, indeed.

    • peteryeeles Says:

      Those are the Myrmecodia’s leaves. This one had probably been rolling around in the surf for a bit, so does look a little sad. However even a larger healthy plant will still only have a few leaves.

      When I first saw these from a car traveling at speed, I thought they were termite nests!

  3. The following page has a great cross section drawing of this cool plant.

  4. Roberta Says:

    I think mutualism is fascinating as well, and especially between ants and plants. Nice start to your new blog.

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