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Intraspecific diversity in Atlantic cod drives divergent trophic cascades across a coastal food web

Hocevar, Sara1; Perälä, Tommi1; Kuparinen, Anna1

Published Jan 29, 2026 on Dryad. https://doi.org/10.5061/dryad.tqjq2bw6c

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Abstract

Intraspecific diversity can profoundly shape ecological interactions, yet its role within complex food webs remains challenging to quantify. We explored how eco-evolutionary divergence within Atlantic cod (Gadus morhua), specifically between the resident Fjord and migratory North Sea ecotypes, influences food web structure and function in a coastal marine ecosystem. Using key trait differences, including growth rate, age, and size at maturation, reproductive investment, and ontogenetic dietary shifts, we parameterized an allometric trophic network (ATN) model with empirical data from the Norwegian Skagerrak. The high-resolution network comprised 148 trophic guilds and 2054 feeding links, permitting resolution of ecotype-specific interactions. We found pronounced intraspecific divergence: North Sea cod reached higher trophic position earlier, exerting greater interspecific influence, whereas Fjord cod retained higher early-stage biomass, intensifying intraspecific competition between ecotypes. Together, these complementary roles indicate that variation within a single species can both dampen and amplify food web interactions across life stages, enhancing ecosystem connectivity, and triggering cascading ecological effects. To sustain this natural buffer, conservation and management must move beyond species-level metrics and actively protect intraspecific diversity.