Aim Maintenance of ecosystem function under climate change may depend on variation in the way species within functional guilds and individuals within species respond to changes in temperature. What level of variation among and within species do we need to understand, and is it predictable from distribution and trait data? Location Northern California, USA.Methods We used a mesocosm experiment and a set of feeding trials to test the ability of a guild of marine invertebrate grazers to control benthic algal blooms along a local temperature gradient. We investigate links between the locally disjunct distributions of these species, their temperature tolerance traits and the temperature dependence of their population growth and grazing rates. Results We found that the effect of increased temperature on population growth rates is independent of species interactions, but strongly species specific. This variation among herbivores is only partly predictable from differences in species distributions and traits, but translated into large differences in their ability to control macroalgae. Further, these species effects were amplified at warmer temperatures. Finally, we found evidence for a strong response to temperature in the feeding rates of the most important consumer over the course of the experiment, resulting in almost as much variation in grazing rates within one species as the average difference between species.Main conclusions These results illustrate the importance of understanding the variation in responses to temperature among species within a trophic level, among populations within key species and potentially within populations over time. However, this variation is not easily predicted. Further research is needed to uncover links between individuals' thermal optima and their current and future temperature niche.