You can't have it all. It's a cliché, but it's also a powerful principle in biology. Now, a set of new computer models reveal how evolutionary compromises ("trade-offs") drive the diversity of life.

"Biologists have long known that when species compete for limited resources such as food, they are pressured to diversify," explains Chris Adami, a Michigan State University professor of microbiology and molecular genetics. "But what we found through computer simulation is that trade-offs are the main driver of diversification when resources are scarce. The stronger the trade-offs, the more diversification will occur." However, there is price to pay when diversifying. Organisms cannot optimize all traits. In other words, they can't have it all.

The MSU researchers created an animation of Chester the Winged Cat (above) to demonstrate the principle. Watch as the virtual feline's descendants branch off into different species—each one developing a specialized trait, such as larger whiskers and ears, but at the price of losing other traits., such as their eyes.

We've seen evidence of this among living animals. In Madagascar, lemurs have evolved to eat different things, which ensures that there is enough food for all. Some lemur species eat fruit, but due to trade-offs, cannot eat leaves because their digestive tracts have become too short and cannot process the fiber. Other lemurs have long digestive tracts and can eat leaves, but they get sick from eating fruit because it ferments from staying in their guts too long. So to preserve the supply and demand of food, a compromise evolved between fruit- and leaf-eating lemurs—they are biologically prevented from eating each other's food.

"We did not know until now just how essential such trade-offs were in driving diversification among species," explained Bjorn Ostman, one of the MSU researchers. "The computer simulations allowed us to remove other possible factors that influence speciation, such as geographical barriers."

[Note: MSU assures the public that "no virtual cats were evolved (or harmed)" in the making of their video.]