Mismatch in microbial food webs: predators but not prey perform better in their local biotic and abiotic conditions

Abstract

Understanding how trophic levels respond to changes in abiotic and biotic conditions is key for predicting how food webs will react to environmental perturbations. Different trophic levels may respond disproportionately to change, with lower levels more likely to react faster, as they typically consist of smaller‐bodied species with higher reproductive rates. This response could cause a mismatch between trophic levels, in which predators and prey will respond differently to changing abiotic or biotic conditions. This mismatch between trophic levels could result in altered top‐down and bottom‐up control and changes in interaction strength. To determine the possibility of a mismatch, we conducted a reciprocal‐transplant experiment involving Sarracenia purpurea food webs consisting of bacterial communities as prey and a subset of six morphologically similar protozoans as predators. We used a factorial design with four temperatures, four bacteria and protozoan biogeographic origins, replicated four times. This design allowed us to determine how predator and prey dynamics were altered by abiotic (temperature) conditions and biotic (predators paired with prey from either their local or non‐local biogeographic origin) conditions. We found that prey reached higher densities in warmer temperature regardless of their temperature of origin. Conversely, predators achieved higher densities in the temperature condition and with the prey from their origin. These results confirm that predators perform better in abiotic and biotic conditions of their origin while their prey do not. This mismatch between trophic levels may be especially significant under climate change, potentially disrupting ecosystem functioning by disproportionately affecting top‐down and bottom‐up control.

The effects of temperature and dispersal on species diversity in natural microbial metacommunities

“…As a basal food resource, we added 500 µL of an autoclaved Tetramin fish food solution (concentration of 2 mg of solid fish food in 1 mL of DI water) into each tube [following protocols used for the S. purpurea system by terHorst 36 and modified by Parain et al . 37 ]. This resource is consumed by the bacteria in the system, which are then consumed by the protists and rotifers.…”

Environment–host–microbial interactions shape the Sarraceniapurpurea microbiome at the continental scale

“…Indeed, the presence of a keystone predator (Wyeomyia smithii) can increase bacterial richness in S. purpurea pitchers (Peterson et al 2008), and this response may be dependent on climate as bacterial thermal tolerances can differ from that of bacterivorous consumers (Parain et al 2016). As a result, this theory would support an indirect impact of climate through food-web-associated factors on microbial diversity (Fig.…”

Disentangling how climate change can affect an aquatic food web by combining multiple experimental approaches

“…Environmental conditions play major roles in shaping species interactions (Finstad et al, 2011;Hein, Ohlund, & Englund, 2013), and indirect effects of climate change can arise when altered climatic conditions alter species interactions. Asymmetric responses of trophic levels to climate change, for instance, result in trophic mismatches that can disrupt ecosystem functioning by altering top-down or bottom-up processes (Parain, Gravel, Rohr, Bersier, & Gray, 2016;Winder & Schindler, 2004). Alternatively, interaction strengths of predators can be modified by climate change if abiotic conditions alter their functional responses (Ewald, Hartley, & Stewart, 2013;Hassell, 1978).…”

“…However, simply observing community turnover along altitudinal gradients does not permit mechanistic insights, and simultaneous experimental manipulations of abiotic and biotic components are necessary to disentangle the various mechanisms by which climate affects composition and phenotype (Dunne et al, 2004;Liancourt et al, 2013). Community transplant experiments in combination with manipulations of species interactions (Ariza & Tielbörger, 2011;Parain et al, 2016) and common garden experiments (Alexander, Diez, & Levine, 2015;De Block, Pauwels, Van Den Broeck, De Meester, & Stoks, 2013) are required to unravel the effects of altered environmental conditions, species interactions, and the potential of species to adjust to the altered climate. However, we are not aware of any studies of animal communities that manipulated in a single experiment more than one climatic stressor, species interactions, and prior exposure of species to future climatic conditions.…”