Natural selection can thwart the formation of new species

Stick insects, one of the most peculiar insects found on earth, have intrigued scientists by exhibiting how the process of natural selection can prevent the formation of new species. A team of researchers from the University of Sheffield in England and the University of Colorado Boulder studied a plant-eating stick insect species from California called Timema cristinae. It is known for its cryptic camouflage that allows it to hide from hungry birds. There are many types in T. cristinae, such as the one which is green in color and the one that is green with a white vertical stripe. These two types could have formed new species. However, the team discovered a brown variety of T. cristinae, which they inspected using field investigations, laboratory genetics, modern genome sequencing and computer simulations. They observed that the brown version of T. cristinae “carries genes back and forth between the green populations, acting as a genetic bridge that causes a slowdown in divergence.” Thus, it was preventing the other two varieties from developing into new species. Moreover, it was also favored by natural selection as it had a slight advantage in mate selection and a stronger resistance to fungal infections than its green counterparts. The researchers believe this to be an evidence of how natural selection sometimes supports whereas at other times hinders the formation of new species.

Read more in Science Daily.