Species Diversity Not Caused By Environment
By Annalee Newitz, 2:31 PM on Fri Jul 17 2009, 11,274 views

Accepted scientific wisdom holds that new species arise because of geographic separation - the same bird evolves differently on two different islands. But a new study overturns this idea, challenging the importance of environment as a driver of evolution.

Published this week in Nature, the new study shows that even when a group of creatures is not separated by mountain ranges, and isn't forced to find a niche in the ecosystem via natural selection, new species will evolve over hundreds of generations. The researchers created a mathematical model of speciation, when one species evolves into many, which tracks emergence of species over 2,000 generations. The model was based on scientific observation of how new species have evolved all over the Earth.


Above, you can see the model, showing how species transform over time. Each color represents a species. What begins as a uniform single-color group slowly evolves into several distinct species. But this occurs via mutation and sexual selection, not from the creatures growing distant from each other geographically. And not from competing for different niches in the environment. In this model, there are no niches and no geographical boundaries.

So what's the big deal? In short, it means that new species can arise without competion for environmental resources. Sexual selection alone is enough to produce species diversity.

According to the New England Complex Systems Institute, which funded the study:

The study found that over generations the genetic distance between organisms in different regions increases, and groups of organisms spontaneously form groups that can no longer mate, causing a patchwork of species across the area. The number of species increases rapidly until it reaches a relatively steady state.
"One can think about the creation of species on the genetic level in the same way we think about the appearance of many patterns, including traffic jams," said [researcher] Yaneer Bar-Yam. "While the spatial environment may vary, specific physical barriers aren't necessary. Just as traffic jams can form from the flow of traffic itself without an accident, the formation of many species can occur as generations evolve across the organisms' spatial habitat."

The study authors are not claiming that enviroment is unimportant. They are simply saying that under some circumstances, it is not a necessary ingredient for evolutionary transformation.

Nevertheless, this study overturns the typical view of evolution. It turns out that we don't need adaptation to a hostile natural environment to evolve new forms of life. We can do it just by having offspring and mutating over time.

Sexual selection alone is enough to produce species diversity.