Ants and Spurge Part 1: Planting Seeds

Yesterday’s general post about seed dispersal by ants reminded me of a specific example in my own yard.

These tiny seedlings started to germinate in the soil around a Solenopsis xyloni nest.

It didn’t take too long to figure out the plants were ground spurge, Chamaesyce prostrata. Another common name is sandmat. Ground spurge is a native annual that is usually considered to be a weed.

Why are seedlings growing on ant pilings significant?

The seeds of spurges are known to have elaiosomes, and in fact the elaiosomes are given a different name. The special structures on seeds that serves as food for ants in spurges are called caruncles. It’s easy to remember if you realize it comes from the Latin caruncula, which means wart.

A spurge seed with caruncle – Illustration from Wikipedia

Alex Wild has an excellent series of photographs of Formica ants with the seeds of the invasive spurge, leafy spurge.

It turns out that ants are known to disperse and accidentally plant the seeds of a number of different species of spurge. In fact, ants may have another close association with spurges, but let’s save that one for the next post.

For more information:

Robert W. Pemberton and Delilah W. Irving. (1990). Elaiosomes on Weed Seeds and the Potential for Myrmecochory in Naturalized Plants. Weed Science. 38(6): 615-619.

John Eastman also talks about spurges in Book of Field & Roadside: Open-Country Weeds, Trees, and Wildflowers of Eastern North America.

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4 Replies to “Ants and Spurge Part 1: Planting Seeds”

  1. This is a particularly interesting case of ant plant relationship, in that these mat-like plants appear tailor-made to be pollinated by ground foraging ants, and ants are the most frequent insect visitors at the flowers.

  2. I’m a little new to seriously studying ants. I have noted in the last 15 years how a very specific species of ant seems to almost always have nest openings under spurge (sand mat) in out yard. These ants seem to be everywhere and especially love moist soil. They swarm and sting painfully. They have a variety of worker sizes, 2-5mm. They also tend aphids which seem to really like dill plants. I am assuming they are solenopsis xyloni. The ones we have a mostly black although the large workers will have a reddish tinge to the head and thorax, but the gaster is black.

  3. Bill,

    What you describe sounds does sound like our local Southern fire ant. They are very common here and behave as you describe.

    If you’d like to learn more, this site is a great one to get started learning the ants of Arizona:

    Good luck!

  4. Bill,

    By the way, I hope you don’t mind, but I removed your location information to help ensure your privacy.

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