Anorak News | Aggressive spiders will conquer the world

Aggressive spiders will conquer the world

by | 22nd, August 2019

Things climate change is responsible for: angrier spiders. The Sun says this “maybe” true. As for labelling spiders angry in the fist place, well, who knew?

The paper picks up on a report in Nature Ecology & Evolution. Scientists at Canada’s McMaster University in Canada watched spiders before and after tropical storms along the Gulf and Atlantic coasts of the United States and Mexico. “It is tremendously important to understand the environmental impacts of these ‘black swan’ weather events on evolution and natural selection,” says Jonathan Pruitt, lead author of the study. “As sea levels rise, the incidence of tropical storms will only increase. Now more than ever we need to contend with what the ecological and evolutionary impacts of these storms will be for non-human animals.”

Aggressiveness of the spiders was measured in the speed, the number of attackers that respond to prey entering the web, how likely the female spiders were to cannibalize males and their own offspring, as well as how vulnerable they were to being infiltrated by predatory foreign spiders.

Maybe they’re, you know, hungrier?

Adds Pruit: “Tropical cyclones likely impact both of these stressors by altering the numbers of flying prey and increasing sun exposure from a more open canopy layer. 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.”

And then the jump: “There is, therefore, a possibility that this could happen to more spider populations if weather around the world gets more extreme due to climate change.”

Back in 2013:

Pruitt performed personality tests on dozens of A. studiosus spiders and then arranged them into 90 couples consisting of an aggressive pair, a docile pair, or an aggressive spider matched with a docile one. The arachnids’ personalities are heritable, so a docile pair produces almost exclusively docile offspring, aggressive mates mainly make aggressive offspring, and mixed pairs produce a combination of docile and aggressive babies. After 1 week in the lab, each of the pairs had created small webs, or nests, on chicken wire within separate containers.

Pruitt returned to the Tennessee woods where he originally collected the spiders and wired each of the 90 nests onto trees and shrubs. For the next 5 years, he removed other species of spiders from the territory surrounding half of the webs. These 45 webs served as a control to test the hypothesis that disposition matters when hungry, solitary spiders abound in nature. The colonies in these well-maintained territories faired roughly the same as one another between 2007 and 2012, no matter the personality of their founders.

In contrast, colonies in the areas that were open to invaders differed from one another over time as solitary spiders began to infest the webs.

Colonies founded by aggressive spiders successfully fought the intruders off, but produced fewer offspring because of the continuous conflict.

Eventually the docile colonies died out.

Posted: 22nd, August 2019 | In: Strange But True Comment | TrackBack | Permalink