Following tropical cyclones, spider colonies with a more aggressive behavior have higher rates of survival and reproduction that those that are more docile, according to a new study. This suggests that extreme weather events could influence animal behavior.
Natural habitats can be severely altered by tropical cyclones but studying their ecological effects can be challenging, as it requires a comparison of habitats both before and after a storm strikes land.
“This is particularly concerning given we are witnessing increasingly frequent and intense extreme climatic events but are unable to accurately predict how they may influence selection pressures, population persistence or extinction,” the authors said in the paper, published in Nature Ecology & Evolution.
Alexander Little and colleagues sampled colonies of the group-living spider Anelosimus studiosus before and after three tropical cyclones hit the Gulf and Atlantic coasts of the United States in 2018.
By anticipating the trajectory of the tropical cyclones, the authors assessed the size of colonies in the projected path and tested how aggressively each colony responded to simulated prey.
The authors vibrated the spiders’ web and counted the number of spiders that subsequently attacked. They then returned 48 hours after the cyclone to see which colonies had survived, and on two later occasions to count how many eggs had been produced and how many spiderlings hatched.
According to the research, colonies that were more aggressive before a cyclone had higher rates of reproduction and juvenile spider survival following a storm strike. In regions unaffected by the tropical cyclones, more docile colonies were favored.
“By studying the impacts of tropical cyclones with spatiotemporal replications and control sites, they show that selectivity for more aggressive colonies of Anelosimus studiosus is a robust evolutionary response to cyclone- induced disturbance,” said Eric Ameca, a conservational biologist.
The authors then follow-up on these findings through a retrospective analysis of colony aggressiveness in sites with historical impacts of cyclones. Using cyclone track data, the authors identified a positive correlation between variation in colony aggressiveness and cyclone disturbance events within the past 100 years.
Looking ahead, it remains to be answered why aggressive colonies of A. studiosus outperform docile colonies when subject to cyclone exposure. At the same time, examining how variations in cyclone exposure shape the strength of selection pressures.
“The effect of inland zonation and habitat quality and composition may become more evident as cyclones grow in intensity and duration. In this regard, the adaptive capacity of historically exposed populations will be crucial to confront the most severe tropical cyclones,” said Ameca.
The study was published in Nature Ecology & Evolution.