EVOLUTION, DEVELOPMENTAL INSTABILITY AND THE THEORY OF ACQUISITION

Despite major advances in the study of molecular and morphological evo lution a substantial rift still exists between these two fields of end eavor. Phenotypic alteration through evolution results from a realloca tion of resources which has as its origin the interplay between the pr oduction capability of the genes on the one side and the acquisitional need of the phenotype on the other. This process of allocation is coo rdinated through the environmental arena and is subject to mechanical, biological and economical constraints. Differences in the rates of mo rphological change at any level (molecular, cellular, organismal or po pulation) depend on the level of environmental challenge, on the avail ability of variability and on the economics of supply and demand. Shor t run changes in response to severe environmental stress will be sudde n and energetically expensive and will rely on stress-induced unmaskin g of genetic variability and loss of canalization. Long run changes wi ll be gradual, energetically less costly and less dependent on genetic correlations.