Effects of climate change on the distribution of ecologically interacting species: butterflies and their main food plants in Spain

Global climatic change exerts a generalised impact on species ranges, which could be problematic if ecologically-related species differ in their geographical response to climate change. Therefore, a combination of distribution modelling protocols is required to predict the future impacts of global warming on sets of different ecologically-dependent species. We test the extent to which the predicted future distributions of Spanish monophagous butterfly species, as estimated on the basis of climatic and physiographic variables, would differ depending on whether the geographic distribution of their larval food plants was taken into account or not. Using the favourability function as the modelling tool and fuzzy logic to combine butterfly and plant models, we extrapolated climatic favourability models for the butterfly, the plant and the butterfly–plant combination to the periods 2011–2040, 2041–2070, 2071–2100. All the models obtained were significant and the predicted butterfly–plant interactions indicated that larval food plants will represent in the future a greater constraint on butterfly species distributions. Climatic favourability for butterflies was expected to increase in the future more than the climatic favourability for the food plants. The plant data had relevant effects on the predicted future ranges of butterflies, which were generally expected to contract due to the effect of climate change on the plant. This highlights the view that opposite to recent results stating that climate is the primary driving force of butterfly distributions in Europe, variables other than those directly related to climate may exert a leading role in the near future. These include direct biotic interactions such as dependence on host plants, at least for highly specialised (monophagous) species of phytophagous insects.