<p>Species facing environmental heterogeneity can persist either by adapting to local conditions or by dispersing to more suitable habitats. We evaluated how species’ adaptive capacity, dispersal rate, and dispersal mode (passive versus fitness-dependent) interact to shape biodiversity in multitrophic metacommunities across thermally heterogeneous landscapes. Using simulations of a novel spatially explicit model in which species adjust their thermal optima, we found that biodiversity responded unimodally to both adaptation and dispersal, with diversity peaking at intermediate levels of each process. Greater environmental heterogeneity shifted diversity maxima toward higher adaptation rates, while fitness-dependent dispersal shifted them toward higher dispersal rates and partly buffered the homogenizing effects of movement on community composition. We also found that biodiversity in multitrophic systems was more responsive to adaptation than in competitive communities. Together, these results show that the maintenance of biodiversity in heterogeneous landscapes depends not only on how fast species move or adapt, but also on how dispersal decisions are made. Our study calls for a stronger integration of evolutionary and behavioral processes into metacommunity theory.</p>