Body temperature, rate of biosynthesis, and evolution of genome size.

An optimality model relating the rate of biosynthesis to body temperature and gene duplication is presented to account for several observed patterns of genome size variation. The model predicts (1) that poikilotherms living in a warm climate should have a smaller genome than poikilotherms 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 should favor the evolution of poikilotherms with a large genome and that warm geological periods should do the opposite, and (4) that poikilotherms with a small genome should be more sensitive to changes in temperature 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 volume. Relevant empirical evidence is summarized to support these predictions.