Direct and community-driven selection jointly drive body size evolution in harvested predator-prey systems

Abstract

Fisheries-induced evolution (FIE) affects multiple life-history traits, most notably body size. This evolutionary response is often examined at the single-species level and attributed to direct size-selective harvesting. However, fishing also targets other community members, reshaping trophic interactions and thereby modifying evolutionary constraints due to community changes. Here, we disentangle two forms of fishing-induced selection on body size - direct, arising from size-selective harvesting within species individuals, and indirect, emerging from fishing-induced changes in community structure - and investigate how their interplay shapes evolutionary trajectories. Using an adaptive dynamics framework within a predator-prey model, we show that (i) community destructuring can either amplify or dampen the effects of intraspecific size-selectivity on body-size evolution, (ii) predator evolution is primarily driven by direct selection, whereas prey evolution is mostly constrained indirectly by community structure. We then extend our analysis using a stochastic framework and show that (iii) prey evolution allows the evolutionary rescue of predators, underscoring the importance of community context. Our results demonstrate that eco-evolutionary feedbacks can profoundly alter both community structure and fishery yields, strengthening calls to incorporate evolution into ecosystem-based fisheries management.