Dietary restriction and aging: comparative tests of evolutionary hypotheses.

Dietary restriction (DR) increases life span in many types of animals. The response to chronic DR may be an adaptation to environments with variable food levels. This study uses the comparative method to test evolutionary predictions about the origin of the response to DR, using data from 10 species of rotifers. Most species, but not all, responded to DR by increasing mean life span, maximum life span, reproductive life span, mortality rate doubling time, and initial mortality rate. Interspecific comparisons did not show the predicted correlations between the strength of the response to DR and either reproductive life span, age of first reproduction, or total reproduction. There was support for the idea that the response to chronic DR is associated with changes in reproductive allocation during short-term periods of starvation: species that reduced reproduction when starved increased their life spans under DR, whereas species that continued to reproduce when starved decreased their life spans under DR.