Poorly Camouflaged Insects Bring Cascade of Effects to Local Ecosystems

We've all heard of the butterfly effect -- where one small act leads to a chain of events that effects a much larger sphere -- but new research suggests there might also be a walking stick insect effect, or at least something like it, at play in ecosystems in California.

Researchers have documented a type of walking stick insect that has evolved to give birth to two distinct types of young -- one that camouflages well within all-green surroundings and one that bares a white stripe down its back and tends to blend in best with needle-like leaves.

But scientists from University of Colorado Boulder suggest that the walking stick insects have evolved their camouflage scheme so quickly that when it fails, it can set off a cascade of effects on the flora and fauna also living in the surrounding ecosystem.

If the walking stick bug's camouflage does not match it's surroundings, researchers have documented far-reaching effects on the ecosystem, namely an increased predation of many types of insect that also dwell within the area.

A poorly camouflaged walking stick bug is more likely to be eaten by birds, and in turn, those birds are more likely to feast on spiders, caterpillars, plant hoppers, ants and other insects in the vicinity. That increased predation of insects living on and around plants goes on to affect the plants themselves.

"Our study shows that the evolution of poor camouflage in one species can affect all the other species living there and affect the plant as well," said Tim Farkas, lead author of the study published in the journal Current Biology. "It's intuitive, but also really surprising."

Farkas and his colleagues suggest their research offers some of the most comprehensive evidence yet that evolution can drive ecological changes.

"We have combined both experimental and observational data with mathematical modeling to show that evolution causes ecological effects and that it does so under natural conditions," Farkas said. "We also focused simultaneously on multiple evolutionary processes-including natural selection and gene flow-rather than just one, which affords us some unique insights."

The research was centered around the walking stick insect Timema cristinae, which lives in California. The walking stick primarily lives on two shrubs, chamise, which has narrow, needle-like leaves, and the greenbark ceanothus, which has broad, green, oval-shaped leaves.

Striped walking sticks are better camouflaged against the chamise, whereas ones without stripes blend in better amid the green leaves of the greenbark ceanothus. An analysis of shrubs within 186 research locations revealed that the insects are generally found on the plant that matches their camouflage most suitably. But when when the researchers artificially stocked the needle-leaved chamise with un-striped walking sticks, they noted increased predation of all insects on the plants.

"Studies of how rapid evolution can affect the ecology of populations, communities and ecosystems are difficult to accomplish and therefore rare," Farkas said. "We're hoping our research helps biologists to appreciate the extent of dynamic interplay between ecology and evolution, and that it can be used by applied scientists to combat emerging threats to biodiversity, ecosystem services, and food security."