If you don't like spiders, you won't be happy to hear this - climate change will likely make them much more warlike. How can that happen?
The answer, say a team of scientists, lies in selective evolutionary pressures. In the face of more frequent extreme weather events like tropical cyclones that can wreak havoc on forests, spiders that are naturally more aggressive will likely survive at the expense of more docile specimens.
Extreme events select more aggressive colony phenotypes in the group-living spider, Anelosimus studiosus, ”explains a team of researchers from McMaster University in Canada in a new study. "This selection is large enough to drive regional variation in colony phenotypes, despite the fact that tropical cyclone attacks are irregular and occur only every few years, even in particularly prone regions."
The scientists examined female colonies of Anelosimus studiosus spiders, which live along the Gulf and Atlantic coasts of the United States and Mexico. They inhabit storm-prone areas that are regularly hit by tropical cyclones between May and November.
The researchers sampled 240 spider colonies by examining them before a storm made landfall and then re-observing them to see how the spiders had fared and what traits allowed them to best survive. Females that were more aggressive when attacking prey, were more territorial against other females, and had a greater tendency to cannibalize males appeared to do better.
These aggressive traits can be harmful in times of plenty because they make spiders fight each other more, but they can benefit Anelosimus studiosus in times of food shortage, such as after devastating storms.
"Tropical cyclones likely affect both stressors by altering the number of flying prey and increasing sun exposure from a more open canopy layer," says Jonathan Pruitt, evolutionary biologist in McMaster's Department of Psychology, Neuroscience and Behavior, author. principal of the study.
"Aggression is transmitted from generation to generation in these colonies, from father to daughter, and is an important factor in their survival and reproductive capacity," he adds.
Knowing how animals will respond to climate change will help us understand changes in the natural world. "As sea levels rise, the incidence of tropical storms will only increase," says Pruitt. "Now more than ever we have to deal with the ecological and evolutionary impacts of these storms on non-human animals," he closed.