THE LATITUDINAL COMPENSATION HYPOTHESIS: GROWTH DATA AND A MODEL OF LATITUDINAL GROWTH DIFFERENTIATION BASED UPON ENERGY BUDGETS. I. INTERSPECIFIC COMPARISON OF OPHRYOTROCHA (POLYCHAETA: DORVILLEIDAE).

A northern (North Carolina) sibling species of Ophryotrocha grew more rapidly than a southern sibling species (Florida); this presumed advantage, however, diminished to zero as temperature increased from 15 to 30°C. Survival of the northern sibling species was low at 30°C. The differential response probably had a genetic basis since both species had been reared for 2-3 generations under the same conditions. The effect lasted in laboratory populations reared for a year in the laboratory at 25°C (ca. 10 generations). My results are consistent with a graphical model that suggests an evolutionary shift of metabolism-temperature curves and feeding efficiency curves for the two sibling species. These shifts predict a changing advantage of growth of one species relative to the other as temperature increases.