Differential impacts of climate change on specialist butterflies and their host plants

It is increasingly acknowledged that shifts in climate may lead to mismatches in the distribution of interacting species. However, the influence of biotic interactions on the distribution of insect species in tropical biomes, and the potential for climate change to disrupt these interactions, remain largely unexplored. We investigated the impacts of climate change on the distribution of six monophagous butterfly species endemic to South America’s Atlantic Forest, one of the most species-rich Global Biodiversity Hotspots. We compiled occurrence data from museum specimens and online sources to predict the distribution of the butterflies and their respective host plants using an ensemble modelling technique. We project that five of the six butterfly species and all host plant species will experience range contractions under a pessimistic climate scenario, with range losses of up to 79% for one butterfly ( A. chalciope ). Among areas projected to be climatically suitable for both butterflies and their host plants in the future, only around half are formally protected. Additionally, land-use constraints are substantial: ~25–80% of climatically suitable areas for the butterflies and their hosts consist of converted landscapes likely unsuitable for the species. Our results show that accounting for biotic interactions and land use can substantially reduce climate-based estimates of species distributions. If these findings extend to other specialised species interactions that have not yet been surveyed, they indicate that specialist species may be at greater risk from climate change than previously thought. Our study highlights the importance of incorporating biotic interactions and habitat suitability in biogeographical, ecological and conservation research.