Summary of “Quanta Magazine”

Researchers in ecology and evolution had wrestled with it for decades as one possible answer to a major question in their field: How does so much biodiversity survive in nature? But even aside from its scientific history, the strategy is better known as a game used by children around the world to settle playground squabbles.
The game is rock-paper-scissors, “a classic game in game theory and evolutionary theory,” said the mathematical biologist Barry Sinervo of the University of California, Santa Cruz, whose field studies on side-blotched lizards helped to establish its relevance to ecosystems.
The rules of the game are easy: Rock beats scissors, scissors beat paper, and paper beats rock.
Biologists studying rock-paper-scissors have modeled how the game plays out with scores or even hundreds of species.
If simplistic competition were the only evolutionary force, then after billions of years, only a handful of highly competitive species should be left.
The number of species for which Earth is home is almost impossible to estimate; one recent attempt pegged it at about 2 billion, but earlier efforts ranged from under 10 million to 1 trillion.
The lowland Amazon rainforests alone are home to more than 6,700 tree species and 7,300 other seed plant species – numbers that don’t begin to account for the accompanying insects, mammals, fungi and microbes.
Later mathematicians extended their work to show that these intransitive relationships could involve a nearly infinite number of species.

The orginal article.