Fig 4.

Overview of influences on growth rate (G) and development rate (D) responses to temperature, and hence their ratio and the temperature–size response. TSR, temperature–size rule. Temperature stimulates both growth rate and development rate, but the relative increase may be modulated by effects of cell size, genome size, body size, life cycle, thermoregulatory behaviour and mode of respiration. Oxygen limitation is more likely in large aquatic ectotherms with large cells, and could constrain the stimulating effects of temperature on growth rate. Consequently, animal development outpaces growth under warmer conditions, resulting in a decrease in body size (purple pathway). A large genome size may be associated with a lower thermal sensitivity of development. Consequently, development does not outpace growth under warmer conditions and the faster growth results in larger body sizes (green pathway). Due to the strong linkage between genome size and cell size, both mechanisms will operate in tandem, but the relative importance of these mechanisms may differ among animals, depending on their characteristics.