Abstract
The geographic mosaic of coevolution predicts reciprocal selection, the first step in coevolution, to vary with changing biotic and abiotic environmental conditions. Studying how temperature affects reciprocal selection is essential to connect effects of global warming on the microevolutionary patterns of coevolution to the ecological processes underlying them. In this study, we investigated whether temperature influenced reciprocal selection between a plant ( Brassica rapa ) and its pollinating butterfly herbivore ( Pieris rapae ). In two temperature environments (ambient and hot), we measured the phenotypes of plants and butterflies, their interactions and fitness, which we used to calculate reciprocal selection. We found a variety of traits involved in reciprocal selection in the ambient environment, but none in the hot environment. We provide experimental evidence that elevated temperature weakens reciprocal selection, which will help better predict the consequences of global warming for coevolution.