Sunday, September 12, 2021

Camouflage in Plain Sight

wood sorrel

I taught ecology for years. The text books feature dramatic examples of ecological principles--camouflage illustrated with a big green katydids shaped like a leaf, mimicry illustrated by a nonvenomous snake banded like a coral snake, or an example of mutualism with an orchid and exotic bee--almost always tropical. Which tended to make you think that to see biology you should go to the tropics. In fact, though, those basic principles--camouflage, mimicry, mutualism--and all the other pillars of ecology--predation, parasitism, competition--are everywhere. 

camouflaged preying mantis
camouflaged 3" preying mantis
in Costa Rica

I can list examples from prairies and North America forests. So perhaps "we just don't go out into wild places ("nature") much any more." 

But, I found camouflage in my yard! Which shouldn't be such a surprise. Cities and suburbs are "nature" with wild organisms and ecological interactions. We walk by without looking, never thinking about the ongoing evolution of all those organisms to their current environment. 

I have a flagstone path with reddish stone. The base was covered in reddish crushed rock (Breeze) to hold the flagstones, so the whole is a nice rusty shade. I pull plants out of the spaces between the stones in the path. The path circles my house, but I use the north side more than the south. Consequently, I glance south and, when I see weeds, get a basket and clean up the path. 

flagstone path
red flagstone path

A month ago, basket in hand, I discovered that a wood sorrel (probably Oxalis stricta, yellow wood sorrel, an international weed, wood sorrel family Oxalidaceae) was growing in the cracks, and was about 2" high. BUT it had red-brown leaves and was very much less visible than the dandelion leaves that drew my attention. It was the third or so time that I went after dandelions to discover an abundance of wood sorrel. That it wasn't chance; the wood sorrel was camouflaged against the path. 

wood sorrel, Oxalis
wood sorrel, Oxalis, probably yellow wood sorrel, Oxalis stricta

And it was working. They had been there long enough to mature fruits, while I caught the dandelions while they were just a cluster of leaves.

Here, in the photo below, see how much more the green mallow leaves stand out? (The plant to the right is a shrub, Daphne, the photo is looking down on the path.)

green and brown plants in the path
See how much more visible the green leaves are?

Consequently I went looking for other cases, in which leaves were camouflaged in my own back yard.

On my "to consider" list are the sandmats. These little spurges (genus Chamaesyce, spurge family Euphorbiaceae) have red stems and green leaves, and the inconspicuous flowers and fruit sit on the midline, breaking up the shape. However they do it, I find there are more of them than I think, when I stop to pull out one. Here is how it looks close up:

sandmat, Chamaesyce,
probably thymeleaf sandmat, Chamaesyce serpyllifolia

Here's sandmat in the backyard path. It is the plant in the bottom half of the photo.

weeds in the path
Is the sandmat camouflaged?

Smalls stones, called pea gravel, are a great surface for plants in Colorado, because, among other things, they retard evaporation. Look for the purslane (Portulaca oleracea, purslane family, Portulcaceae), the round leaves, in the photo below. I think they are camouflaged by the pebbles. Not as great as wood sorrel on the path, but they got pretty big before I went "wow! look at all those purslanes taking water from my desert four o'clocks!"

purslane on gravel
purslane on gravel 

So, in my yard, camouflage happens. It protects plants from being weeded out. Humans are a major force determining plant survival today, and we are almost entirely visual in locating plants. Hiding from grasshoppers or rabbits might require not having a distinctive smell. And then, a bad taste will put off grasshoppers and rabbits, but it has no effect on me weeding. 

The composition of plant communities changes in response to the reproduction and death of plants. I kill a lot of weeds so, in my yard, eluding me is very important. The plants in the paths are largely annuals--especially when I check carefully and pull all I find, leaving only seeds--therefore, each spring the seeds are likely to be those of plants that got off the most seeds before I spotted them. Those that better matched the paving stones were likely to be among those success stories. In that case, the camouflage will get better and better.

I suppose I could test my hypothesis by treating weeds in two parts of the walk differently, but I lack the consistency to carry that through the next several years. So this will remain an untested hypothesis. But look around in your everyday activities; there's camouflage there. Of course, camouflage is hrd to spot. Good luck. 

Comments and corrections welcome.

Post script: a very quick list of examples of important ecological interations in the garden: mimicry: bee flies can't sting you but they look at a glance like bees; mutualism: flowers shaped to accommodate some pollinating insects but not all--flat for bees and flies, tubular for hummingbirds and moths etc.; competition is the reason for weeding, because plants compete for resources; predation is finding a slug eating my lovely tomato; parasitism is represented by the worm in the juicy apple... 

hawk moth
hovering hawkmoth on tubular flowers
This one was seen in Washington, D.C.,
 but they visit catmint (Nepeta x fassenii) in my yard

 Kathy Keeler, A Wandering Botanist




    1. Thanks so much for the links! I knew there were heavily- collected Asian plants, but not that the plants were adapting with camouflage. Wow!