Canadian Forest Service Publications

Earlier springs enable high-Arctic wolf spiders to produce a second clutch. 2020. Høye, T.T.; Kresse, JC.; Koltz, A.M.; Bowden, J.J. Proceedings of the Royal Society B: Biological Sciences 287 (1929)

Year: 2020

Issued by: Atlantic Forestry Centre

Catalog ID: 40596

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1098/rspb.2020.0982

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Spiders at southern latitudes commonly produce multiple clutches, but this has not been observed at high latitudes where activity seasons are much shorter. Yet the timing of snowmelt is advancing in the Arctic, which may allow some species to produce an additional clutch. To determine if this is already happening, we used specimens of the wolf spider Pardosa glacialis caught by pitfall traps from the long-term (1996–2014) monitoring programme at Zackenberg, NE Greenland. We dissected individual egg sacs and counted the number of eggs and partially developed juveniles, and measured carapace width of the mothers. Upon the discovery of a bimodal frequency distribution of clutch sizes, as is typical for wolf spiders at lower latitudes producing a second clutch, we assigned egg sacs to being a first or second clutch depending on clutch size. We tested whether the median capture date differed among first and second clutches, whether clutch size was correlated to female size, and whether the proportion of second clutches produced within a season was related to climate. We found that assigned second clutches appeared significantly later in the season than first clutches. In years with earlier snowmelt, first clutches occurred earlier and the proportion of second clutches produced was larger. Likely, females produce their first clutch earlier in those years which allow them time to produce another clutch. Clutch size for first clutches was correlated to female size, while this was not the case for second clutches. Our results provide the first evidence for Arctic invertebrates producing additional clutches in response to warming. This could be a common but overlooked phenomenon due to the challenges associated with long-term collection of life-history data in the Arctic. Moreover, given that wolf spiders are a widely distributed, important tundra predator, we may expect to see population and food web consequences of their increased reproductive rates.

Plain Language Summary

Climate change has had significant impacts on the biology of organisms, practically at high latitudes where the change is occurring more rapidly than other areas of the earth. Specifically, springs are occurring earlier and warming is occurring at a rapid rate. Terrestrial arthropods, such as insects and spiders are really canaries in the coalmine for climate changes as the have short life cycles and their physiology is dictated by the external environment. With a dataset of wolf-spider egg clutches over 18 years from the high-Arctic, we show that earlier-warmer springs enabled females the time in the season to lay second egg clutches. It is unclear whether these later juveniles are recruited into the population, but could have knock-on implications for these generalist predators and the local food-web. This appears to be the first evidence of a climate change induced shift in the number of clutches produced by Arctic invertebrates.