Animals or plants? Evolutionary branching of sessile versus mobile cognitive agents in noisy environments

Abstract

The evolution of complex cognition has been tied to movement and the need to locate resources in uncertain environments. Plants present a striking contrast: despite sophisticated environmental responses, their sessile lifestyle involves predictable energy capture and growth-mediated foraging. What ecological conditions could separate these alternative strategies? We address this question using spatially explicit individual-based simulations and Adaptive Dynamics models in which evolving agents allocate resources between harvesting a stable energy source (light) and exploiting patchy, fluctuating resources through costly sensing and movement. Starting from intermediate generalists, evolution repeatedly produces two contrasting specialist lineages: sessile, light-dependent agents that abandon sensing and locomotion, and mobile foragers that sacrifice light harvesting while investing in active resource search. Spatial gradients promote divergence through niche partitioning, but specialization also emerges in homogeneous environments through frequency-dependent ecological feedbacks, showing that environmental heterogeneity is not required. Under linear or convex returns, intermediate strategies can be disadvantaged because they bear the costs of both resource-acquisition systems without fully exploiting either; under sufficiently concave returns, intermediate strategies may instead be favored. These results suggest that plant- and animal-based organizations can emerge as alternative evolutionary solutions to a common foraging problem. More broadly, they support the idea that the evolution of costly cognitive machinery depends critically on the statistical structure of the resources that organisms must find and exploit.