I had been following an army ant raid for half an hour through dense tropical forest when the trees unexpectedly parted to reveal a small clearing. Sun broke through the canopy and fell on a low tangle of furry plants. It was a monoculture, looking as though planted by a reclusive sort of gardener.
I had stumbled into a Devil’s Garden.
Local lore holds that malevolent forest spirits create these unnatural crop circles, but the truth is just as weird. Devil’s Gardens are made by ants.
The plant species that compose these gardens- mostly in the genera Tococa, Clidemia, and Duroia– sport swollen structures filled by the nests of tiny Myrmelachista ants* no more than 3 millimeters long. The ants are meticulous about caring for their hosts, removing pesty herbivores and injecting formic acid into the saplings of competing plants.
Over time, the systematic removal of non-host species leads to a dense garden composed of nothing but the ant-plants. As the ant colonies are spawned by thousands of continually replaced queens, the gardens are potentially immortal. One Duroia garden in Peru was recently estimated to be 800 years old.
I had never seen a Devil’s Garden. Finding this one was one of these delightful surprises of tropical ecology- what a treat! I abandoned my planned photo session with the army ants to spend an afternoon shooting the furry little ant plants and their quirky ant partners.
More photos here.
Sources:
- Frederickson, M. E., Greene, M. J., Gordon, D. M. 2005. Ecology: ‘Devil’s gardens’ bedevilled by ants. Nature 437: 495-496.
- Renner, S.S., and Ricklefs, R. E. 1998. Herbicidal Activity of Domatia-Inhabiting Ants in Patches of Tococa guianensis and Clidemia heterophylla. Biotropica 30: 324-327.
*Myrmelachista is an extraordinarily poorly known group of ants. Most species are probably undescribed. Given their ecologically fascinating habits, though, big discoveries certainly await those with the patience to work with these small insects.
This is so amazing. Ants and people seem to be similarly sophisticated in their approaches to agriculture. I’d love learning more about this topic; maybe it could be the theme of the next theme week?
wow, I totally wanna be out in the field!!
Fascinating!
Ants are so amazing!
I find the mealybug thing interesting – I wonder if this is one of those complex cases where a parasitism becomes part of a mutualism! It would be interesting to see if the fitness of the garden overall improves or diminishes when the mealybugs are removed. This may be similar to the coffee agroecosystem in Mexico that Dr. Perfecto and Dr. Vandermeer study, where the presence of Azteca ants, which help scale insects, in localized areas of the ecosystem actually helps the overall fitness of the coffee population, as the scale insects provide food for spiders which then act as natural pesticides in the rest of the areas of the ecosystem that lack the ants. But this may not work in a devil’s garden, as I would think the ants are ubiquitous throughout the plant population.
I was thinking along the same lines. I appreciate your idea about why the two situations may be different.
VERY cool. I’ve always been fascinated by ant-plant relationships.
I find the mealybugs interesting too. I see it as a sort of bribe similar to those of plants that offer nectar through extrafloral glands…only that these glands are six-legged, wax-coated parasites! It’s demanding to pay your security forces literally with your own blood, but when you are growing in a flourishing monoculture with close relatives or clones of yourself and without the pressures of competition with other plants, you can easily sustain a burden of ant-boosting mealybugs.
Also interesting is the fact that Clidemia hirta, which I don’t think is an ant plant, is a rampant weed in Hawaii, smothering native vegetation.
This is perhaps more plausible. I always thought that these ant-plants provided food in addition to shelter, in which case it would be like a plant giving an extrafloral nectary plus sacrificing extra “blood”. But I actually don’t know if the plants provide food!
when you opened the domatia, did the ants come out looking for a fight like Azteca ants?
These guys are actually pretty timid. So, they wandered about and half-heartedly tried a nip here and there, but nothing so impressive as Azteca in full defensive mode.
In the first picture you almost look like you need a lawn mower.
How common were these patches and did you notice any of the host plants growing outside the garden?
Single host plants are far, far more common and often house other species of ants (Pheidole, for instance). I only saw a couple of these patches, with this one being the largest.
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