Extreme weather conditions, such as hurricanes and tropical cyclones can drive spiders to evolve into more aggressive, found a team of researchers at McMaster University. These conditions can make spider colonies into cannibals and let them pass on their aggressive traits to their offsprings. The reason behind this, according to scientists, is that aggressive spiders have better chances to survive in havoc-wreaking storms that go on destroying their habitats such as trees and canopies and lead them to need extreme measures for survival.
“It is tremendously important to understand the environmental impacts of these ‘black swan’ weather events on evolution and natural selection," said Jonathan Pruitt, an evolutionary biologist and lead author of the study, in a news release by McMaster University in Ontario, Canada. The research was published on August 19, 2019. The scientists studied 240 colonies of spiders living in storm-prone areas, before a storm and after a storm. They used meteorological data to predict the storms. For the study, they took a special interest in areas disrupted by the storm Alberto in 2018. To study the behaviour of the spiders, researchers categorized them into docile and aggressive. Spiders who were put into the aggressive category had a tendency to cannibalise eggs and males. They took samples of spiders just before a storm and returned within 48 hours.
Scientists found that the aggressive colonies were better at acquiring resources even when there is a scarcity of them. However, these aggressive colonies are also more prone to fight among themselves in case of food deprivation for longer periods. Increasing temperature also contributes to the tendency of infighting.
“Aggressiveness is passed down through generations in these colonies, from parent to daughter, and is a major factor in their survival and ability to reproduce," Pruitt added.
Scientists also found that spiders who used aggressive techniques to obtain resources could produce more egg cases and were able to sustain them to the forthcoming early winter.