A burrowing ecosystem engineer positively affects its microbial prey under stressful conditions

Abstract

Species that facilitate others under stressful conditions are often ecosystem engineers: organisms that modify or create physical habitat. However, the net effect of an engineering species on another depends on both the magnitude of the direct interactions (e.g., competition or predation) and the specific environmental context. We used a laboratory system to isolate the trophic and engineering impacts of a predator, the nematode Caenorhabditis remanei , on its prey, Escherichia coli under different levels of environmental stress. We predicted that under stressful surface conditions the nematodes would positively impact their prey by creating burrows which protected the bacteria. Colony plate counts of E. coli indicated that there was a stress‐induced change in the net impact of nematodes on bacteria from neutral to positive. Predator engineering in the form of burrowing allowed larger bacteria populations to survive. We conclude that even in a simple two‐species system a predator can positively impact prey via ecosystem engineering.

Ecological engineering across a spatial gradient: Sociable weaver colonies facilitate animal associations with increasing environmental harshness

“…This study provides empirical support for the SGH and complements recent research using terrestrial animal communities that found evidence of increased importance of associative or facilitative interactions in harsh environments (Bell & Cuddington, 2019;Dangles et al, 2018;García-Navas et al, 2021). Additionally, by demonstrating that some taxa associate strongly with colony trees in more arid climates, we provide support that facilitation by weaver colonies increases the realized niches of certain species (Armas et al, 2011;He & Bertness, 2014).…”

“…Additionally, by demonstrating that some taxa associate strongly with colony trees in more arid climates, we provide support that facilitation by weaver colonies increases the realized niches of certain species (Armas et al, 2011; He & Bertness, 2014). Furthermore, only one other study has extended this hypothesis to free‐ranging animals (García‐Navas et al, 2021), as many of the previous studies were tested under laboratory conditions (Bell & Cuddington, 2019; Dangles et al, 2018). Temporal variations in climatic conditions may also play a part in understanding the facilitative role of weaver colonies.…”

Phenotypes of predator individuals underpin contrasting ecosystem effects

“…Non‐consumptive effects on prey communities and ecosystem processes are particularly expected when focal organisms driving those effects are both ecosystem engineers and predators (Bell & Cuddington, 2019; Majdi et al., 2014; Romero et al., 2015). Other non‐consumptive effects that might have contributed to our results include sediment reworking resulting from the burrowing behaviour of C. boltonii (de Nadaï‐Monoury et al., 2014), as well as nutrient excretion differences among individuals (Ngai & Srivastava, 2006; Vanni, 2002).…”

“…Non-consumptive effects on prey communities and ecosystem processes are particularly expected when focal organisms driving those effects are both ecosystem engineers and predators (Bell & Cuddington, 2019;Majdi et al, 2014;Romero et al, 2015).…”