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Tropical storms make these spiders aggressive science



Aggressive combed foot spiders are better storm survivors, according to a new study.

Judy Gallagher / Wikimedia Commons (CC BY)

9, 2019, 11:40 AM

After Tropical Storm flooded Florence North and South Carolina in September 2018, Jonathan Pruitt paced the East Coast of the US, searching for treacherous ones Signs of damage. But he did not look for ruined houses. He searched for spider nests – and for spiders who had survived the storm. What the behavioral ecologist and his colleagues at the University of California (UC), Santa Barbara, found challenging: Aggressive spiders survived the storm – and others like him – better than their docile colleagues and led to bolder future colonies.

The [study] is fantastic, of course, because it's actually very tricky and risky, "says Eric Ameca, a conservation biologist at the University of Veracruz in Xalapa, Mexico, who was not involved in the work. Studies on the environmental impact of tropical cyclones are rare, as there is a risk of storm debris and forecasting the landing for such storms is a difficult but necessary part of capturing basic data. In addition, most storm-related studies focus only on human survivors. But Ameca says, "We do not really know the consequences for wildlife."

In order to find out how tropical storms affect biodiversity, Alexander Little, a postdoctoral fellow at UC Santa Barbara, spent a summer monitoring the survival rates of aggressive and Inhabit the trapped colonies of comb spiders along the US East Coast. When unexpected circumstances meant that he could not make it into the field, Pruitt, his advisor, took the lead. Pruitt drove hundreds of miles with his pickup and listened to Robert Jordan's fantasy novel "Wheel of Time" to track incoming storms and gather data.

The Spiders in the Study, Anelosimus studiosus are a species of comb spider that is known to exhibit one of two completely different behaviors: aggressive and docile. Aggressive spiders attack prey immediately and in large numbers, whereas docile spiders need more time to approach their quarry. These behaviors affect entire colonies and are passed from one generation to the next. Because spiders rarely move – they usually build their houses on low-hanging branches above the water – they were ideal for studying how tropical storms could affect behavior, Pruitt says.

In 2018, Pruitt, Little, and colleagues visited 240 colonies in seven states, including North Carolina, Florida, and Louisiana. They collected data on colonial aggression by putting a small piece of paper attached to an electric toothbrush on each lane. When they switched on the toothbrush to vibrate part of the tissue without damaging it, they classified spiders that were "aggressive" to the disorder and spiders that had been waiting before they came out "docile." The researchers also looked at how many times each colony had been hit by a tropical storm or cyclone over the last 100 years. They found that the sites with more historical cyclone damage contained more aggressive spider colonies.

Then they waited. The 2018 season was good for their research: first, Tropical Storm Alberto moved through Florida and Alabama in May; then Hurricane Florence wiped out the Carolinas in September, before Hurricane Michael roared through Florida's panhandle in mid-October.

For each site hit by the storms, the researchers went back to see which spider colonies survived. They found that most of the surviving colonies were aggressive. Since the colonies with the genetic trait for this behavior have survived, the finding suggests that the aggressive traits are passed on to the next generation, they report today in Nature Ecology & Evolution .

The researchers do not yet know why aggressive colonies outperform docile colonies after a tropical storm. Lisa Taylor, an arachnologist at the University of Florida at Gainesville, says that the evidence of comb spiders gives an impressive insight into the future of biodiversity as climate change increases and tropical storms become more prevalent.

The study, says Taylor, "actually documents the impact of these rare events on the populations. "She hopes that the work, while not easy, can stimulate similar studies in other animals.


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