Evolution,developmental instability and the theory of acquisition

Despite major advances in the study of molecular and morphological evolution a substantial rift still exists between these two fields of endeavour. Phenotypic alteration through evolution results from a reallocation of resources which has as its origin the interplay between the production capability of the genes on the one side and the acquisitional need of the phenotype on the other. This process of allocation is coordinated through the environmental arena and is subject to mechanical, biological and economical constraints. Differences in the rates of morphological change at any level (molecular, cellular, organismal or population) depend on the level of environmental challenge, on the availability of variability and on the economics of supply and demand. Short run changes in response to severe environmental stress will be sudden and energetically expensive and will rely on stress-induced unmasking of genetic variability and loss of canalization. Long run changes will be gradual, energetically less costly and less dependent on genetic correlations.