Further experiments demonstrated that the sterility trait is caused by more than one genetic change. "I think there are many genes--4 or 5 probably, maybe many more," Reed predicted.

Now that the researchers are hot on the trail of a set of "speciation genes," their next task will be to identify them. To help toward that endeavor, they plan to take advantage of the newly begun D. mojavensis genome sequencing project, which will provide a complete roadmap of every gene in the species.

Reed reflects upon the implications of the findings. "There's a huge amount of biodiversity out there, and we don't know where it comes from. Evolutionary biologists are excited to figure out what causes what we see out there--the relative forces of selection and drift--whether things are adapting to their environment or variation is random.

"Another important component to that is how that variation is partitioned into separate species. Once you're a separate species, you have an independent evolutionary trajectory to some other species--an independent set of tools, or genetic potential, relative to other species. So this partitioning of genomes is an important cause of the variation we see in nature."

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7-Jun-2004