This blog post on ‘Complex interactions and foodwebs’ is part of the BES ‘Key Concepts in Ecology’ series, designed to help ecologists in learning the key topics in ecology! Take a look at the full blog series for a list of key topics you might typically find in an ecology textbook, each providing a quick introduction to the topic, and a list of suggested papers for students to refer to.  

Ecological networks emerge from interactions within and between species and describe the interconnected nature of biodiversity. For example, a foodweb describes the network of who-eats-whom in an ecological community. Body size is a key organismal trait that influences foodweb interactions through its effects on an individual’s metabolism (Williams et al., 2020) and trophic position (Melguizo-Ruiz et al., 2020). Understanding the processes that determine the strength and organization of interactions in food webs (Pinheiro et al., 2022; Saravia et al., 2022) and other ecological networks (Picoche & Barraquand, 2020; Smith & Pinter-Wollman, 2021) is critical for anticipating how populations, communities, and ecosystems will respond to environmental change (Barbour & Gibert, 2021; Yacine et al., 2020).  

Indirect interactions occur when the effect of one species on another is mediated by a third species. For example, ‘exploitative competition’ occurs when two species negatively affect each other’s abundance through feeding on a shared resource (Browett et al., 2023), while ‘apparent competition’ occurs through predation by a shared natural enemy (Miller et al., 2021). Another common type of indirect interaction is when the presence of a top predator initiates a trophic cascade by suppressing the abundance or altering the behavior of an intermediate consumer (e.g., herbivore), resulting in an increase in the abundance of lower trophic levels (e.g., plants) (Lundgren et al., 2022). The strength of trophic cascades and other indirect interactions may be unaffected or modified by changes in the abiotic environment, such as temperature and water availability (Antiqueira et al., 2022, Melguizo-Ruiz et al., 2020; Nowicki et al., 2021). 

Introduction written by Matt Barbour (Associate Editor, Journal of Animal Ecology). Reading list curated by the BES journal Editors. 

References and suggested reading 

• Antiqueira P.A.P. et al. (2022). Warming and top predator loss drive direct and indirect effects on multiple trophic groups within and across ecosystems. Journal of Animal Ecology, 91; 428–442.  
  
• Barbour, M. A. et al. (2021). Genetic and plastic rewiring of food webs under climate change. Journal of Animal Ecology, 90; 1814–1830.
  
• Browett, S. S. et al. (2023). Resource competition drives an invasion-replacement event among shrew species on an island. Journal of Animal Ecology, 92; 698–709.
  
• Lundgren, E. J. et al. (2022). A novel trophic cascade between cougars and feral donkeys shapes desert wetlands. Journal of Animal Ecology, 91; 2348–2357.
  
• Melguizo-Ruiz, N. et al. (2020). Field exclusion of large soil predators impacts lower trophic levels and decreases leaf-litter decomposition in dry forests. Journal of Animal Ecology, 89; 334–346.
  
• Miller, K. E. et al. (2021). Land-use intensity affects the potential for apparent competition within and between habitats. Journal of Animal Ecology, 90; 1891–1905.
  
• Nowicki, R. J. et al. (2021). Loss of predation risk from apex predators can exacerbate marine tropicalization caused by extreme climatic events. Journal of Animal Ecology, 90; 2041–2052.
  
• Picoche, C. et al. (2020). Strong self‐regulation and widespread facilitative interactions in phytoplankton communities. Journal of Ecology, 108; 2232–2242.
  
• Pinheiro, R. B. P. et al. (2022). Hierarchical compound topology uncovers complex structure of species interaction networks. Journal of Animal Ecology, 91; 2248–2260.
  
• Saravia, L. A. et al. (2022). Ecological network assembly: How the regional metaweb influences local food webs. Journal of Animal Ecology, 91; 630–642.
  
• Smith, J. E. et al. (2021). Observing the unwatchable: Integrating automated sensing, naturalistic observations and animal social network analysis in the age of big data. Journal of Animal Ecology, 90; 62–75.
  
• Williams, T. M. et al. (2020). Hunters versus hunted: New perspectives on the energetic costs of survival at the top of the food chain. Functional Ecology, 34; 2015–2029.
  
• Yacine, Y. et al. (2020). Collapse and rescue of evolutionary food webs under global warming. Journal of Animal Ecology, 90; 710–722.