HOUSTON -- (May 15, 2014) -- A first-of-its-kind study this week suggests that the genomes of new species may evolve in a similar, repeatable fashion -- even in cases where populations are evolving in parallel at separate locations. The research is featured on the cover of the May 16 issue of Science.
A team of evolutionary biologists at Rice University, the University of Sheffield and eight other universities used a combination of ecological fieldwork and genomic assays to see how natural selection is playing out across the genome of a Southern California stick insect that is in the process of evolving into two unique species.
"Speciation is the evolutionary process that gives rise to new species, and it occurs when barriers prevent two groups of populations from exchanging genes," said Rice co-author Scott Egan. "One way to study how speciation occurs is to look for examples where partial reproductive barriers exist but where genes are still exchanged."
The stick insect Timema cristinae is one such example. Timema are closely related to "walking sticks," plant-eating insects that look like twigs. Timema's shape and color act as natural camouflage and help them avoid being eaten by predators, such as birds. More than a dozen unique species of Timema have evolved to feed on specific plants in California and northern Mexico.
One of these, T. cristinae, is found in two distinct varieties. One variety, or ecotype, feeds on the thin, needle-like leaves of a shrub called Adenastoma and features a distinct white stripe on its back that serves as camouflage. The other ecotype has no stripe and feeds on Ceanothus, a plant with wide green leaves where the stripe would stand out.
"Populations of T. cristinae on the two host plants have evolved many differences in their physical form while still exchanging genes," said Egan, a Huxley Faculty Fellow in Ecology an
|Contact: Jade Boyd|