Warming reverses top-down effects of predators on belowground ecosystem function in Arctic tundra

Abstract

Predators can disproportionately impact the structure and function of ecosystems relative to their biomass. These effects may be exacerbated under warming in ecosystems like the Arctic, where the number and diversity of predators are low and small shifts in community interactions can alter carbon cycle feedbacks. Here, we show that warming alters the effects of wolf spiders, a dominant tundra predator, on belowground litter decomposition. Specifically, while high densities of wolf spiders result in faster litter decomposition under ambient temperatures, they result, instead, in slower decomposition under warming. Higher spider densities are also associated with elevated levels of available soil nitrogen, potentially benefiting plant production. Changes in decomposition rates under increased wolf spider densities are accompanied by trends toward fewer fungivorous Collembola under ambient temperatures and more Collembola under warming, suggesting that Collembola mediate the indirect effects of wolf spiders on decomposition. The unexpected reversal of wolf spider effects on Collembola and decomposition suggest that in some cases, warming does not simply alter the strength of top-down effects but, instead, induces a different trophic cascade altogether. Our results indicate that climate change-induced effects on predators can cascade through other trophic levels, alter critical ecosystem functions, and potentially lead to climate feedbacks with important global implications. Moreover, given the expected increase in wolf spider densities with climate change, our findings suggest that the observed cascading effects of this common predator on detrital processes could potentially buffer concurrent changes in decomposition rates.

Host-associated microbiomes are predicted by immune system complexity and climate

“…Bio2 explained 59.6% of the variation in external microbiome community structure (Additional file 1: Table S2) have weaker effects on microbiome diversity and structure than do the top-down processes of host physiology and immune function. Just as abiotic factors can influence or reverse top-down effects of predators on ecosystem function [80], the relative strength of host immune function may be similarly disrupted (e.g., antibiotics, immunocompromise) and have strong influences on the host microbiome ( [15,17,31]; Table 1).…”

Flexibility in a changing arctic food web: Can rough‐legged buzzards cope with changing small rodent communities?

“…The effects of climate change on ecosystems are often difficult to predict, because species are interlinked in complex interaction networks and changes in one species can have consequences for many others (Koltz, Classen, & Wright, ; Schmidt et al, ). Indirect effects of climate‐driven changes in species abundance or guild composition are often mediated by trophic interactions, and shifts in the relative abundance of species can lead to changes in interaction strength and food web dynamics (Martin, ; Mortensen, Schmidt, Høye, Damgaard, & Forchhammer, ).…”

Dominant Arctic Predator Is Free of Major Parasitoid at Northern Edge of Its Range

“…Understanding what drives wolf spider population dynamics is important because these predators comprise a large proportion of worldwide spider abundance and diversity (World Spider Catalog, 2018). In the Arctic, this endeavor is even more relevant, because wolf spiders are one of the most widespread and locally abundant arthropods (Bowden and Buddle, 2010;Wyant et al, 2011;Hansen et al, 2016a;Koltz et al, 2018b). In terms of hostparasite dynamics, the absence of parasitism in Zackenberg is especially surprising when considering that this site hosts two wasp species (Wirta et al, 2016) of a genus known to parasitize wolf spiders in North America (Bowden and Buddle, 2012a) and Kangerlussuaq (this study).…”

“…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). 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). 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).…”