Adaptive life histories effected by age-specific survival and growth rate

Life history data for three unexploited populations of brook trout Salvelinus fontinalis were used to test the predictions of life history theory that, relative to juveniles, 1) high adult survival favors low reproductive effort and delayed reproduction, and 2) increased juvenile growth rate favors high effort and early reproduction. The population having the highest adult-to-juvenile survival ratio indeed expended the least effort, reproduced latest in life, and experienced the lowest survival cost of reproduction. Among populations a high juvenile-to-adult growth rate was associated with early reproduction, high reproductive effort, and high reproductive cost. Early reproduction was also associated with increased growth within populations. Empirically derived fitness functions supported the hypothesis that population and differences in life history were adaptive. Observed combinations of age-specific survival and fecundity were those that maximized fitness. -from Author