Thermal buffering by termite mounds maintains safety margins while worker traits track climate

Understanding how environmental conditions influence organismal performance requires linking physiological limits with the microclimates actually experienced by individuals. In mound-building termites, nest architecture can modify thermal exposure, yet its consequences for physiological and functional variation remain poorly understood. We combined experimental measurements of critical thermal maximum (CT max ), field measurements of mound microclimate, mechanistic estimates of operative body temperature, and analyses of morphological, enzymatic, and gut bacterial traits to examine responses of Cornitermes cumulans across a climatic gradient. At the Campinas site, mound interiors showed markedly lower thermal variation than ambient conditions, while modelled operative temperatures indicated positive thermal safety margins across the broader climatic gradient. Nevertheless, CT max remained associated with regional climate, increasing with annual precipitation and decreasing with mean diurnal temperature range. Worker morphology also varied strongly with climatic conditions, while β-glucanase activity and gut bacterial richness were associated with different climatic drivers. Future projections indicated substantial reductions in thermal safety margins under SSP2–4.5 and SSP5–8.5 scenarios, with greater losses at lower latitudes and progressively smaller reductions toward higher latitudes. These findings suggest that mound-mediated buffering reduces direct exposure to thermal extremes without eliminating climatic effects on physiological and functional traits. Architectural niche construction may therefore generate a Bogert-like effect in which thermal buffering maintains current safety margins but does not fully protect colonies from future warming, particularly at lower latitudes.