The Pieris climate accords: how climate change shapes molecular interactions between the butterfly Pieris rapae (Lepidoptera: Pieridae) and its host plant Arabidopsis thaliana (Brassicales: Brassicaceae).

Global temperatures are projected to rise by approximately 1.5 °C between 2030 and 2050, driven by increasing atmospheric carbon dioxide (CO2) levels. Such rapid climate change is predicted to drive correspondingly rapid change in animals and plants, particularly those that humans depend on for food and security. Here, we investigated how increased temperature and CO2 may affect herbivore-host plant interactions using controlled experiments with a widespread agricultural pest, the cabbage white butterfly Pieris rapae, and a model host plant, Arabidopsis thaliana. Pieris rapae and A. thaliana were reared at varying levels of temperature (22.7 °C to 27.7 °C) and CO2 (400 ppm to 850 ppm) to assess how climate change affects phenotypic variation and gene expression in this herbivore-host system. Phenotypic analysis indicated heat stress causes leaf surface area to decrease in A. thaliana, larval mass in P. rapae to remain consistent, and egg laying to increase. Heat stress appeared to severely affect the pair of organisms when they were interacting. Transcriptomic analyses revealed a suite of genes that responded specifically to climate change conditions and herbivore-host plant interactions in each species. These findings highlight genetic pathways responsive to both species interactions and intensified climate change, offering valuable insights into how climate change may reshape this ecologically and economically important interaction.