Temperature-related variation in growth rate, size, maturation, and lifespan in a marine herbivorous fish over a latitudinal gradient

1. In ectotherms, growth rate, body size, and maturation rate co-vary with temperature, with the direction and magnitude of variation predicted by the Temperature-Size Rule (TSR). Nutritional quality or availability of food, however, may vary over latitudinal gradients, resulting in ambiguous effects on body size and maturation rate. The Temperature-Constraint Hypothesis (TCH) predicts that marine herbivorous ectotherms are nutritionally compromised at latitudes exceeding 30o. This provides an opportunity to resolve the contrasting demographic responses of ectotherms to variation in temperature and nutritional status over latitudinal gradients. 2. This study uses analysis of demographic rates to evaluate the predictions of the TSR in a marine herbivorous ectotherm sampled over a significant latitudinal gradient. 3. The direction and magnitude of demographic variation was established in the marine herbivorous fish, Odax pullus (the butterfish), and compared with that of a phylogeneticall...