Habitat complexity is an important mediator of processes spanning levels of biological organization from organisms to ecosystems (Shumway et al. 2007, Soukup et al. 2022). This complexity, which can be biogenic (e.g., foundation species; Bracken et al. 2007, Ellison 2019) or abiotic (e.g., substrate rugosity; Kovalenko et al. 2012), shapes processes ranging from individual foraging behavior (Michel and Adams 2009) to species’ interactions to food-web structure and biogeochemical rates (Langellotto and Denno 2006, Larsen et al. 2021, Soukup et al. 2022). For example, in the presence of simulated aquatic vegetation, predatory diving beetle larvae shift from active foraging to sit-and-wait predation, reducing activity and prey encounter rates (Michel and Adams 2009).

In this contribution, Edeline et al. (2023) present a detailed perspective on the role of habitat complexity in shaping populations of a freshwater fish (medaka, Oryzias latipes, Adrianichthyidae), including survival, age-class diversity, population growth rate, and density-dependence in the stock-recruitment relationship associated with changes in carrying capacity. Importantly, changes in these population demographic attributes and rates were associated with the role of habitat complexity in mitigating cannibalism – consumption of juvenile O. latipes by conspecific adults. Whereas this is not unexpected – Langelotto and Denno (2006) showed that habitat complexity reduces cannibalism in wolf spiders – the careful work of Edeline et al. (2023) to link changes in habitat complexity to multiple population-level attributes provides a uniquely detailed description of the role of submerged aquatic vegetation in mediating population diversity (e.g., higher age-class diversity) and productivity (e.g., population growth rate).

In many ways, this work by Edeline et al. (2023) provides population-level parallels to perspectives on the role of habitat complexity in determining community-level diversity and productivity. Structurally complex habitats, such as those provided by foundation species (Bracken et al. 2007, Ellison 2019) and substrate heterogeneity (Fairchild et al. 2024), are associated with higher species diversity and abundance at the community level. Edeline et al. (2023) extend these perspectives to the population level, highlighting the importance of habitat complexity across levels of biological organization. Their work highlights within-population diversity and interactions, including cannibalism and competition, illustrating often-neglected aspects of food-web complexity (Polis and Strong 1996).

References

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Eric Edeline, Yoann Bennevault, David Rozen-Rechels (2023) Habitat structural complexity increases age-class coexistence and population growth rate through relaxed cannibalism in a freshwater fish. bioRxiv, ver.4 peer-reviewed and recommended by PCI Ecology https://www.biorxiv.org/content/10.1101/2023.07.18.549540v4

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