October 22, 2013
Ecological Impacts Linked To Poorly Camouflaged Walking Sticks
redOrbit Staff & Wire Reports - Your Universe Online
Researchers studying the evolution of a California walking stick into two separate, distinct forms have found that such rapid changes in a creature’s appearance can set off a chain of ecological impacts.
Investigators from the Univeristy of Colorado at Boulder and the University of Helsinki report that the evolution of the species Timema cristinae resulted in two unique individuals – one that is all green in color and well camouflaged among broad leaves, and one with a white stripe down its back that is better suited to hiding within needle-like leaves.
As the study authors explain in the journal Current Biology, when either type of these walking sticks are mismatched with the type of plant they hide best in, it can have a far-reaching impact on the ecological community.
When thee mismatch happens, the flightless insect is more likely to be eaten by birds, and those birds are also more likely to dine on caterpillars, ants, spiders and other small prey living on the same plant. With fewer bugs living on it, the plant in turn is less likely to be attacked by sap-feeding insects, they explained.
“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,” stated Tim Farkas, who served as lead author of the study while serving as a doctoral student in ecology and evolutionary biology at CU-Boulder. “It's intuitive, but also really surprising.”
Farkas, who studied under assistant professor Patrik Nosil at CU-Boulder and has since accompanied him to the University of Sheffield in the UK, and his colleagues analyzed the walking sticks living on two types of shrub -- chamise, which has narrow, needle-like leaves, and greenbark ceanothus, which has broad, oval-shaped leaves.
They cataloged the walking sticks living on chamise and greenbark ceanothus in 186 research patches, and found that, as expected, the striped ones were more likely to live on the former and vice versa. They then intentionally stocked the chamise with the broad-leaf type of walking stick and found that, over the course of a month, fewer of those insects survived than their white-striped counterparts.
Farkas and his associates also noticed that the chamise plants populated with striped walking sticks were home to an increased number and variety of arthropods than those stocked with the un-striped variation, and that more leaves were damaged by hungry bugs on those shrubs stocked with the striped type of insect. They surmised that the differences were caused by birds such as the scrub jay that typically feed on walking sticks.
“A group of easy-to-spot walking sticks could attract birds, which might then feed on other arthropods as well,” the Colorado-based University explained. “To test their idea, the researchers repeated the experiment, but in this case, they caged some of the shrubs to keep the birds from feeding. As they expected, the caged chamise stocked with un-striped walking sticks did not have the same drop in numbers as they did when the bushes were not caged.”
“Studies of how rapid evolution can affect the ecology of populations, communities and ecosystems are difficult to accomplish and therefore rare,” said Farkas. “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.”