Ecology shapes metabolic and life history scalings in termites

Abstract

1. Metabolic rate (B) is a fundamental property of organisms, and scales with body mass (M) as B = αMβ. There has been much debate on whether scaling parameters should be viewed as constants or variables. However, there is increasing evidence that ecological differentiation can affect both α and β. 2. In colonial organisms such as social insects, individual metabolism is integrated at the colony level. Theory and data suggest that whole-colony metabolism partly reflects individual-level metabolic and life-history scalings, but whether these have been affected by ecological diversification is little known. 3. Here, this issue was addressed using termites. Data from the literature were assembled to assess the interspecific scalings of individual metabolic rate with individual mass, and of individual mass with colony mass. Concurrently, it was tested whether such scalings were affected by two key ecological traits: lifestyle and diet. 4. Individual-level metabolic scaling was affected by diet, with β = 1.02 in wood feeders and 0.60 in soil feeders. However, there was no difference in α. Further, individual mass scaled to the 0.25 power with colony mass, but forager species had larger colonies and smaller individuals relative to wood-dwelling, sedentary ones, thus producing a grade shift. 5. Our results show that ecological diversification has affected fundamental metabolic and life-history scalings in termites. Thus, theory on the energetics and evolution of colonial life should account for this variability.