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Tuesday, October 16, 2012

Ants, the Unlikely Pollinators

© Beatriz Moisset

Ants are seen visiting flowers with great frequency. People often ask me: Do ants pollinate? I answer with another question: What do you think? Are ants capable of pollinating flowers? Do they have what it takes to carry pollen from one flower to another, preferably of another plant?

Ants stealing nectar from the spur of a jewelweed. © Beatriz Moisset
Most pollinators can fly from plant to plant. Ants, lacking wings, don't go very far. Moreover, ants may be coated in some sort of antibiotics which may be detrimental to pollen. In some cases ants steal nectar from flowers, causing damage and reducing the likelihood of later pollinators' visits. Some plants resort to extrafloral nectaries, nectar-producing glands located in other plant parts, to keep the ants and other nectar robbers away from the valuable treasure reserved for legitimate pollinators.

Ants pollinating wood spurge. © Beatriz Moisset
Despite all these drawbacks, there are instances in which ants are pollinators. One case is that of spurge, or Euphorbia. This plant grows very low near the ground and tends to intertwine its runners with those of nearby plants. This increases the chances of ants going from the flowers of one plant to those of another without the need to fly. Perhaps the pollen of spurge is more resistant to the chemicals on an ant's body. So, ants pollinate spurge; although, there are also small bees that perform this job just as well.

A few other plants, also low-growing, are pollinated by ants. Finally, there are some interesting cases of orchids pollinated by ants in Australia in a highly specialized way. So, yes, ants join the ranks of pollinators. They may even be the pollinators of choice for some plants in harsh, dry climates.

Ant on Queen-Anne-lace. © Beatriz Moisset

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© Beatriz Moisset. 2012 

8 comments:

  1. Interesting observation. You probably saw ants visiting the pumpkin flowers and perhaps they were capable of carrying pollen from male to female flowers. However, to prove that pollination took place, additional observations are required. If flowers were pollinated after all other pollinators were excluded and only ants were allowed to visit the flowers, that would be solid evidence.

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  2. We moved into a house with an apple tree that produced a large crop in autumn. We noticed however that there was an ant colony living at the foot of the tree, with hundreds of ants trooping up and down the trunk to the branches, and we chose to have the colony destroyed (this was the ants=bad mindset). The next Autumn there was no crop, just a few small apples. For five years there were no or few apples. Then the ants came back and when they started going up and down the tree again the crop returned - dozens of red-green apples. Maybe they weren't pollinating, but they were doing something that made the tree happy. Now I'm of the ants=good mindset as long as they stay out of the house.

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    1. Thanks for the interesting story. The ants may be performing a beneficial role and helping indirectly with pollination. However, I can assure you that they could not pollinate the apple tree. See: apple blossoms can only be pollinated by the pollen from trees with different genetic makeup, not the same tree and not by closely related trees. Apple growers know this and alternate plants of different varieties to ensure pollination.

      What may have happened in your case is something rather intriguing. Ants are known to be helpful to certain trees by attacking any pest that comes near. They tolerate pollinators, though. I don't know if this is the case of apple trees, but it is possible that the ants were helping pollinators indirectly by keeping other insects away.

      I will ask around about this and look at apple trees and ants more closely. It would be an interesting project for a graduate student or a citizen scientist group. Thanks again for your observations.

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  3. Dear Beatriz,

    I am from India and very interested to learn about plant-animal interaction. I found your blog post very interesting and have spent a lot of time reading about interaction between ants and plants. Actually I have been looking for information with regards to an incident I came across a year back. I was looking for bats near a Crecentia cujete tree which was blooming. I didnt see any bats for the no. of visits that I made to that tree but I used to see ants in each flower. The ants were feeding on the nectar and everytime an ant would go inside the flower and come out its abdomen was full with nectar. In this case what would call it- nectar thievery or honey-pot ants (I dont know if we get honey pot ants in India). Are female and male flowers located on the same tree trunk (in case of Crecentia cujete).

    Looking forward from your reply.

    Thanks

    Mittal Gala

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  4. Thanks for telling us about your interesting observation. I am sorry I can't help you with your question as I am not familiar with the flora of your country.

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  5. I have a chirimoya tree and it needs manual pollenization because the insect that does the work, does not exist in California, I have noticed that a friend of mine has the same tree, and lots of fruits, by looking at the tree, it seems she placed at the trunk of the tree, vegetable food waste like banana, oranges, more like a fertilizer. What I noticed was that the ants where all over on the tree, and probably doing the work of pollenization.

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    Replies
    1. An interesting observation. I know that ants are possible pollinators of mangos. So, why not cherimoyas? Thanks for the comment.

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