Physiological and life-history tradeoffs may result from local adaptation of populations across wide environmental gradients, and facilitate inferences of the ecological consequences of climate change. For example, local adaptation to warmer thermal habitats may increase heat tolerance to the detriment of metabolism, movement and lifetime fitness. Though theoretically accepted, there remains scant empirical evidence for tradeoffs from local adaptation to temperature. To assess the physiological link among physiological and life history traits, genotypes from > 200 populations of the freshwater crustacean Daphnia magna from across the northern hemisphere were used to measure oxygen consumption, swimming rates and life-history traits (body size, age and fecundity at maturation). Those phenotypes were then related to previously determined thermal tolerance levels for each genotype. Routine metabolic rates (RMR) were measured using PreSens SDR 1-ml vial respirometers, and routine swimming velocities (RSV) were measured using a video tracking system. RMR positively correlates to RSV, and both traits positively correlate to thermal tolerance, while they negatively correlate to body size. Fecundity and body size at maturation are positively correlated with age at maturity. Our results support the tradeoff hypothesis in that enhanced thermal tolerance is correlated with low fitness in life-history traits. Because our populations originate from a wide range of habitats (e.g. size of water body, elevation, climate, water chemistry, seasonal phenology) a broad range of conditions are represented, allowing for further inferences about local adaptation and the possible response to changing environments.