![]() ![]() Egg sacs are conspicuous, being blue-gray or silver in color and large compared to a female's body ( Figure 1A). During this incubation time, eggs develop into juvenile spiders and ultimately leave the egg sac. Female wolf spiders display maternal care by tethering their egg sacs to their abdomens for one to several weeks. Additionally, wolf spiders themselves are preyed upon by a variety of vertebrates (e.g., birds, Wirta et al., 2015) and parasitic wasps, including egg predators and egg parasitoids which target their egg sacs (both generally referred to here as parasitoids Bowden and Buddle, 2012a). They commonly prey upon decomposers and thereby indirectly affect decomposition rates and nutrient cycling in the tundra ( Koltz et al., 2018b) and elsewhere ( Lawrence and Wise, 2000 Lensing and Wise, 2006). Wolf spiders inhabit nearly all terrestrial ecosystems and are dominant predators in the Arctic ( Wyant et al., 2011 Bowden et al., 2018 Koltz et al., 2018a). Here, we compare the strength of host-parasite interactions in one of the most abundant arctic arthropod groups for two sites in Greenland. Addressing this important gap in our knowledge of arctic natural history is critical because arthropods represent the most biodiverse group of multi-cellular organisms in this region, and as herbivores, detritivores, pollinators, and predators, arthropods play important roles in maintaining the health and functioning of arctic ecosystems ( Høye and Culler, 2018). Unfortunately, while vertebrate host-parasite dynamics are relatively well-described in the Arctic (e.g., Moerschel, 1999 Hagemoen and Reimers, 2002 Kutz et al., 2002), little is currently known about parasitism among arctic arthropods ( Kukal and Kevan, 1987 Bowden and Buddle, 2012a, but see Avery and Post, 2013 Ernst et al., 2016). Parasite impacts on arthropod hosts may even increase in the future, because parasitoids are disproportionately benefitting from rapidly warming temperatures relative to other arthropod groups ( Koltz et al., 2018c). Host-parasite interactions may play a particularly important role in food web dynamics in the Arctic, where arthropod communities exhibit a high diversity of parasitoids relative to overall arthropod diversity ( Stahlhut et al., 2013). ![]() The surprising lack of parasitism in the north suggests that populations of this widespread spider species have different eco-evolutionary histories and may respond differentially to climate change. While up to 13% of egg sacs were parasitized annually in the low-arctic site, we found no evidence of it at the high-arctic site despite the presence of congeneric parasitoid species at both locations. ![]() We investigated potential changes in egg sac parasitism rates at two rapidly warming sites in Greenland: a high-arctic site (18 years of data, 1,088 egg sacs) and a low-arctic site (5 years of data, 538 egg sacs). ![]() Wolf spiders are dominant and ecologically important arctic predators that experience high rates of egg sac parasitism by wasps. In the Arctic, a high diversity of parasitoids relative to potential hosts suggests that parasitoids may exert strong selection pressure on arthropods, but the extent to which these interspecific linkages drive arthropod population dynamics remains unclear. Parasitoids can affect host population dynamics with community-level consequences. 7Department of Bioscience Kalø, Aarhus University, Aarhus, Denmark.6Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, Davis, CA, United States.5Arctic Research Centre, Aarhus University, Aarhus, Denmark.4Canadian Forest Service-Atlantic Forestry Centre, Corner Brook, NL, Canada.3Institute of Arctic Studies, Dartmouth College, Hanover, NH, United States.2Environmental Studies Program, Dartmouth College, Hanover, NH, United States.1Department of Biology, Washington University in St. ![]()
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