Thermal Plasticity is Regulated by a Key MicroRNA During Range Expansion of an Invasive Fruit Fly.

Understanding the mechanisms that enable invasive species to expand into novel thermal environments is key to predict their future distribution range under climate change. Plasticity is a key driver behind range expansion during invasion, yet the post-transcriptional regulatory mechanism underlying plasticity during range expansion remains less explored. Here, we performed an integr analysis of phenotypic, transcriptomic, and microRNA (miRNA) changes in a range-expanding invasive insect, Bactrocera dorsalis, under heat and cold acclimation. We found that populations at the invasive front exhibited reduced plasticity in fitness-related traits that were corroborated by genetic assimilation of frontloaded genes. Weighted Gene Co-expression Network Analysis uncovered important modules associated with acute cold tolerance of B. dorsalis and indicated thw gene as a critical network component. Furthermore, thw was found to be regulated by a key miRNA, miR-276b, with its function verified by our dual-luciferase reporter assay and RNAi-mediated knockdown experiment. Our findings suggested that miRNA-mediated regulation of plasticity might be key to allow invasive species to expand into novel thermal environments.