Earlier springs enable high-Arctic wolf spiders to produce a second clutch

Abstract

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.

Nonlinear trends in abundance and diversity and complex responses to climate change in Arctic arthropods

“…This habitat also exhibited a rather different set of relationships between abundance and climate variables. However, the negative impact of spring temperatures on overall abundance in this habitat warrants close monitoring, particularly as spring snowmelt timing is considered to be a key driver of population dynamics (47).…”

Rapid shifts in Arctic tundra species' distributions and inter‐specific range overlap under future climate change

“…The impacts of climate change are believed to be particularly pronounced for cold‐adapted species residing in the Arctic, an area disproportionally affected by climate change relative to most other regions in the world (Gilg et al., 2012; Post et al., 2009). While the ecology and evolution of some resident Arctic species are already being affected by a warming climate (Gilg et al., 2012; Taylor et al., 2020), most of the evidence is based on marine (Clairbaux et al., 2019; Kovacs et al., 2011; Neukermans et al., 2018) and invertebrate (Høye et al., 2020; Nielsen & Wall, 2013) species. Projections of distributional range changes by an assemblage of vertebrate species found on the Arctic tundra and possible implications for inter‐specific overlap are currently lacking.…”

Biogeographic position and body size jointly set lower thermal limits of wandering spiders

“…A weakened subnivean shelter could negatively influence northern populations and even more so for the rare D. plantarius which is less cold resistant. Another impact of the increased length of the snow free season could be a second clutch in northern Dolomedes, as reported in the arctic Lycosidae Pardosa glacialis (Høye et al, 2020).…”