BODY-TEMPERATURE, RATE OF BIOSYNTHESIS, AND EVOLUTION OF GENOME SIZE

An optimality model relating the rate of biosynthesis to body temperat ure and gene duplication is presented to account for several observed patterns of genome size variation. The model predicts (1) that poikilo therms living in a warm climate should have a smaller genome than poik ilotherms living in a cold climate, (2) that homeotherms should have a small genome as well as a small variation in genome size relative to their poikilothermic ancestors, (3) that cold geological periods shoul d favor the evolution of poikilotherms with a large genome and that wa rm geological periods should do the opposite, and (4) that poikilother ms with a small genome should be more sensitive to changes in temperat ure than poikilotherms with a large genome. The model also offers two explanations for the empirically documented trend that organisms with a large cell volume have larger genomes than those with a small cell v olume. Relevant empirical evidence is summarized to support these pred ictions.