Baby Boom For Wolf Spiders As Arctic Summers Get Warmer

The wolf spider Pardosa glacialis has been seen with two egg sacs for the first time in the Arctic. Jörg U. Hammel

Rachael Funnell 26 Jun 2020, 17:23

Concerning stats continue to emerge about warming conditions in the Arctic, but a new study has found that for one species of spider the higher temperatures have triggered a population surge. Published in the Proceedings of the Royal Society B, the research shows that predators like wolf spiders appear to have responded to the changing conditions by producing two clutches of offspring during the short Arctic summer, double the usual amount.

The warming Arctic temperatures have already been associated with booming plant populations, but this is the first time it’s been recognized in influencing the reproductive rate of invertebrates. Wolf spiders have been a species of interest for two decades, being captured by researchers armed with pitfall traps at the Zackenberg Research Station in north-eastern Greenland, as part of the monitoring program Greenland Ecosystem Monitoring.

Estimating the clutch counts of wolf spiders is reasonably simple, since they carry their eggs around in a little sac. The teams were able to count the number of eggs in the sacs of captured wolf spiders and see how these compared depending on which season they were found. It soon became apparent that the spiders captured in the short Arctic summer were carting around two egg sacs, a behavior that’s common in warmer places but had never been seen before in the Arctic.

The snow disappears earlier and earlier from the Arctic tundra and climate change therefore entails a longer growth season for Arctic plants and animals. Toke T. Høye

"We now have the longest time series of spiders collected in the Arctic. The large amount of data allows us to show how small animals in the Arctic change their life history in response to climate change," said Toke T. Høye from the Arctic Research Centre and Department of Bioscience at Aarhus University in a statement. "These changes in the life history have not been seen earlier and evidence suggests that the phenomenon plays an important role for Arctic insects and spiders."

The wolf spider Pardosa glacialis is already extremely common in the Arctic tundra, and so if this baby boom becomes a regular occurrence it could spell disaster for their prey species. A sudden surge in a predator of any kind is always a cause for concern for ecologists as the balance of an ecosystem can be tipped.

"We can only speculate about how the ecosystems change," Høye continued. "But we can now ascertain that changes in the reproduction of species are an important factor to include when we try to understand how Arctic ecosystems react to the rising temperatures on the planet.”

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