To find out whether this was the case, Egan and a dozen co-authors led by University of Sheffield biologist Patrik Nosil conducted four years of detailed genomic and ecological tests. They first had to sequence the genome for T. cristinae and identify which portions of the genome corresponded to particular biological functions. They then collected about 160 T. cristinae from the wild. Samples were collected at several geographic locations and were equally split between the ecotypes on the two host plants.
"We resequenced the genome of each individual that we collected and looked at which genes were differentiated between populations adapted to different host plants," Nosil said. "Because we also conducted an experiment in the field measuring evolution in real time, we gained information on how natural selection is pulling these populations apart."
For example, the team found that many of the genetic differences were reated to the biochemical function of metal ion binding, and metals are known to influence differences in pigmentation and mandible shape between the two T. cristinae ecotypes.
Previous ecological studies have shown that Timema do not migrate long distances. Because of this, the team expected to find evidence of localized gene flow among individuals collected at specific geographic locations. The genomic tests confirmed this, but they also revealed a pattern in the way that natural selection was playing out at each of the localities.
"In particular, we found that there were regions of the genome that exhibited significant differ
|Contact: Jade Boyd|