9407049 Blackstone Much of the theory and data of modern evolutionary biology converges on two related subjects: the evolution of development and the evolution of life history. Curiously, these subjects have remained conceptually and operationally distinct-studies of the former focus on evolutionary changes in the timing of organismal development and on the morphological manifestations of this process (e.g., size, presence of juvenilized, adult or derived features), while studies of the later focus on the organism's allocation of energy into various life history traits (e.g., size, timing of reproduction, number of offspring). To unite studies of life history and the evolution of development conceptually, it is necessary to elucidate a mechanistic link between energy allocation and the timing of development. In particular, efforts must be made to identify an appropriate organismal system which can illuminate the withinorganism mechanisms mediating the connection between energy allocation and the timing of developmental and life history traits. This system must show correlations (1) in natural populations between variation of the putative mechanism and the observed variation of life history and development, and (2) in laboratory populations between experimental perturbation of the putative mechanism and variation which mimics the naturally occurring variation. Recent studies of colonial marine hydroids suggest that within-colony circulation serves as a mechanism by which energy allocation mediates the timing of morphological and life history traits. The PI proposes to initiate a research program which will establish, for the first time, how ecological variation in life histories is linked to evolutionary changes in the timing of development. ***
