Patterns that Organisms Create

[lpetrich]

A Mathematician Who Decodes the Patterns Stamped Out by Life | Quanta Magazine
About mathematician Corina Tarnita and her moving into biology. In particular, how organisms make patterns.

Of all the patterns Tarnita explores, one of the most enchantingly enigmatic are fairy circles: barren round patches that dot the grasslands of Namibia like pepperoni slices on a pizza. They can persist as long as 75 years, but their cause has been hotly debated. Some scientists argue that termite colonies build and maintain the bare circles, while others blame them on plants battling for water across the arid landscape. In January, Tarnita and her colleagues published an article in Nature that suggested a compromise: that both processes together, acting on different scales, could imprint the observed pattern on the ecosystem.

Then an interview with her.

She described how she has worked with a certain Bob Pringle on the spacing of termite mounds in Kenya. They are spaced out because the groups of termites don't want to get too close to each other, because they'd be competing for resources if they did. They thus form a roughly hexagonal pattern, because a hexagonal pattern is the best possible circle packing in 2 dimensions.

She speculates that this could be useful in diagnosing the health of ecosystems:

Do you know about Alan Turing? Turing was obsessed with morphological patterns. Why do tigers have stripes, why do leopards have spots, and so on. He created what’s called an activator-inhibitor system, and it’s a very elegant system that people had employed for vegetation as well.

The Turing-type pattern says that when I have a lot of rainfall, the world should look like my well-watered lawn. As I start to lose precipitation I start to lose biomass, but the way I lose biomass is in a very predictable manner. The first thing I should see is something that looks like regular gaps of vegetation. As you keep decreasing the precipitation, those gaps start to form this maze-like pattern that looks like a beautiful labyrinth. As you keep decreasing the precipitation even further, those gaps stretch even more into spots.

And immediately after you’ve gotten to the spots-like stage, if you keep losing precipitation, the very next thing you should see is desert. You have what’s called catastrophic collapse. You just immediately lose everything.

At least if the individual ground-cover plants need some neighbors to survive.