Tropical Storms Make Spiders More Aggressive | Science

By Kelly MayesAugust 19, 2019, 11:40

After Tropical Storm Florence flooded North and South Carolina in September 2018, Jonathan Pruitt traveled the US east coast looking for warning signs of damage. But he was not looking for destroyed houses; he was looking for nests of spiders and spiders that had survived the storm. What the behavioral ecologist and his colleagues at the University of California (UC), Santa Barbara, discovered was provocative: aggressive spiders survived the storm – and the like – better than their docile counterparts, which has led to future neater colonies.

"This [study] Of course, it's fantastic because it's very complicated and very risky, "says Eric Ameca, conservation biologist at the University of Veracruz in Xalapa, Mexico, who did not participate in the work. Studies on the ecological effects of tropical cyclones are rare, he says, because of the dangers of storm debris and the forecast of the landing for such storms is a tricky but necessary part of collecting basic data. In addition, most storm studies focus only on human survivors. But, says Ameca, "we do not really know the consequences for wildlife."

To find out how tropical storms affect biodiversity, Alexander Little, a postdoc at Santa Barbara University, spent the summer following the survival rate of aggressive and docile patches of legged spiders on the eastern coast of the United States. United. When unforeseen circumstances prevented him from going to the field, Pruitt, his adviser, took over. On board his van and listening to Robert Jordan's fantasy novels, Wheel of Time, Pruitt traveled hundreds of miles to track storms and collect data.

Spiders in the study, Anelosimus studiosus, is a type of spider with comb legs well known for its two very different behaviors: aggressive and docile. Aggressive spiders attack their prey immediately and in large numbers, while docile spiders take longer to approach their careers. These behavioral traits affect entire colonies and are transmitted from generation to generation. As spiders rarely move – they tend to build their houses on low branches above water – they were ideal for studying the potential impact of tropical storms on behavior, says Pruitt.

In 2018, Pruitt, Little and his colleagues visited 240 colonies in seven states, including North Carolina, Florida, and Louisiana. They collected data on the aggression of the colonies by placing a small piece of paper, attached to an electric toothbrush, on each veil. When they lit the toothbrush to vibrate a part of the canvas without damaging it, they classified the spiders that ran towards the "aggressive" disturbance and the spiders that were waiting before appearing "docile" . The researchers also examined how many times each colony had been hit by a tropical storm or cyclone over the past 100 years. They found that the sites most damaged by cyclones contained more aggressive spider colonies.

Then they waited. The 2018 season was a good season for their research: first, Tropical Storm Alberto swept Florida and Alabama in May; Hurricane Florence then invaded the Carolinas in September, before Hurricane Michael roared across the panhandle of Florida in mid-October.

The researchers went back to see the spider colonies that survived each place affected by the storms. They found that most surviving colonies were aggressive. Because the colonies with the genetic trait of this behavior have survived, the discovery suggests that aggressive traits are passed on to the next generation, they report today in Nature Ecology & Evolution.

Researchers still do not know why aggressive colonies surpass docile colonies after a tropical storm. But Lisa Taylor, an arachnologist at the University of Florida in Gainesville, said the evidence obtained by comb spiders gives a striking insight into the future of biodiversity as climate change worsens and tropical storms become more frequent.

According to Taylor, the study "really documents the effect of these rare events on populations." She hopes that the work – though difficult – may inspire similar studies among other animals.