Temperature effects on prey and basal resources exceed that of predators in an experimental community.

ABSTRACT

Climate warming alters the structure of ecological communities by modifying species interactions at different trophic levels. Yet, the consequences of warming-led modifications in biotic interactions at higher trophic levels on lower trophic groups are lesser known. Here, we test the effects of multiple predator species on prey population size and traits and subsequent effects on basal resources along an experimental temperature gradient (12-15°C, 17-20°C, and 22-25°C). We experimentally assembled food web modules with two congeneric predatory mites (Hypoaspis miles and Hypoaspis aculeifer) and two Collembola prey species (Folsomia candida and Proisotoma minuta) on a litter and yeast mixture as the basal resources. We hypothesized that warming would modify interactions within and between predator species, and that these alterations would cascade to basal resources via changes in the density and traits (body size and lipid protein ratio) of the prey species. The presence of congeners constrained the growth of the predatory species independent of warming despite warming increased predator density in their respective monocultures. We found that warming effects on both prey and basal resources were greater than the effects of predator communities. Our results further showed opposite effects of warming on predator (increase) and prey densities (decrease), indicating a warming-induced trophic mismatch, which are likely to alter food web structures. We highlight that warmer environments can restructure food webs by its direct effects on lower trophic groups even without modifying top-down effects.