The short Arctic summer is getting longer and longer and now sometimes gives wolf spiders enough time to produce not one but two broods.

This is evident from research carried out near a research station in northeast Greenland. For over twenty years, researchers have been catching spiders belonging to the species Pardosa glacialis here . These wolf spiders are common on the Arctic tundra and are at the top of the invertebrate food chain. The spiders take a long time to reach maturity and, once they do – unlike their southern counterparts – normally produce one brood per year. But as their habitat changes, the habits of these spiders also change. And researchers have now discovered that in warm years they can also produce two broods.

Egg sac
The researchers draw this conclusion after they have examined the egg sacs that the wolf spiders carry and in which they store their eggs. The researchers counted the number of eggs in these egg shops and noted the date on which they counted the eggs. And soon those datasets indicated that the wolf spiders gave birth to more cubs than they were used to here in the Arctic. “In warmer areas on Earth, wolf spiders typically produce more than one brood,” researcher Toke Høye explains to . “And each extra brood usually contains fewer eggs than the first and is also produced later in the season. We discovered this same pattern among Arctic wolf spiders and the pattern was strongest in the years when the growing season was the longest. ”

It has been known for a long time that the Arctic is subject to considerable change. The area is warming up faster than the rest of the Earth (in the north-east of Greenland, where Høye and colleagues caught and studied the wolf spiders, temperatures are rising twice as fast as the average worldwide). And previous studies have already shown that this causes some plants to flower earlier in the growing season and cold-loving species are forced to move north or higher. But now it has been shown that global warming also affects invertebrate species. “The massive amounts of data allow us to show how small animals in the Arctic change their life histories in response to climate change,” said Høye.

The enormous dataset that the researchers focused on further shows that the disappearance of the snow has a major influence on the reproductive behavior of the wolf spiders. The sooner the snow disappears, the more female wolf spiders take on a second laying car. It’s probably simply because the early melting of the snow gives the wolf spiders more time to reproduce, the researchers write. “It is known that larger female wolf spiders have more chicks and our results confirm this for the first brood. However, we could find no evidence that larger females were more likely than smaller females to produce a second brood or that larger females also produced larger second broods. This suggests that the link between the production of the second brood and the disappearance of the ice is not due to females having more food at their disposal and thereby increasing. Instead, an early meltdown of the snow seems to allow the females to produce their first brood earlier, and then have more time to produce a second brood before the end of the season. ”

Follow-up research
Since wolf spiders play an important role in their ecosystem, researchers are naturally very curious about what the baby boom means for that ecosystem. However, a great deal of research still needs to be done to find out, because determining the impact of a given development on an ecosystem is not so easy. “I would assume that spiders are becoming more abundant (in Greenland, ed.),” Says Høye. “But food chains are complicated and are often regulated by feedback mechanisms. For example, through cannibalism, whereby spiders increasingly eat their own kind. ”

If it is up to Høye, the wolf spider and the ways in which it adapts to a warmer Arctic can quickly become more important. For example, one should observe the spider and other invertebrates for a long time and use experiments to interpret the observations. “For now, we can only speculate about how ecosystems are changing, but what we can be sure of now is that changes in species reproduction are an important factor to consider if we want to understand how Arctic ecosystems respond to the rising temperatures. ”

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