Why so much diversity?

Why does one hectare of rainforest have more tree species than Canada and the US combined? 

A single hectare of tropical rainforest can contain a staggering 650 tree species. Why this is the case has baffled biologists for decades.

Recent research may have finally shed light on the answer – a biological arms race.

Scientists believe that evolutionary changes may be driven by an arms race between plants and plant-eaters. When a plant-eater finds a new way to attack a plant, the plant must evolve to fight the plant-eater.

Through many generations these changes force the formation of new species, leading to the diversity that is characteristic of tropical forest. 

The leaves of a single tropical tree can contain hundreds of different chemical compounds that stop attack by almost all plant-eating species. An infinite number of defensive combinations are possible, with each combination vulnerable only to a small group of specialised herbivores.

This explanation is known as the Red Queen hypothesis, which gets its name from Lewis Carroll’s ‘Through the Looking-Glass’ when the Queen says to Alice, “Now, here, you see, it takes all the running you can do, to keep in the same place.”

Source: Science