Strengthening of negative density dependence mediates population decline at high temperatures.

While temperature is well known to affect many life history traits of ectothermic organisms, any attempt to scale up these individual-level processes to population-level consequences must assume a relationship between temperature and the strength of per capita density dependence. Yet, theory has made contrasting predictions about this relationship, and we still need clear experimental tests to determine which relationship is realized in natural systems, especially in heterotrophs. Here, we experimentally isolated and quantified the thermal response of density dependence from the population dynamics of the herbivore Daphnia pulex.