Evidence of thermal selection from experimental evolution in the arboviral vector Aedes albopictus

The extent to which phenotypic plasticity and adaptation are coupled during ectotherm thermal evolution is poorly understood. We carried out thermal experimental evolution for 20 generations in the arboviral vector Aedes albopictus, an efficient invasive species that has newly conquered climatically diverse regions in the past few decades. During acclimation (one generation of evolution) we saw accelerated development and increased reproduction that traded off against survival. After only another 10 generations, we saw adaptation in the form of major changes in mosquito fitness, metabolism and gene expression, revealing the consolidation of a temperature-dependent trade-off between reproduction and longevity. These shifts demonstrate that Ae. albopictuscan adapt at the pace of warming. When selection was relaxed, most of the thermally shifted phenotypes reverted to control levels, revealing the importance of plasticity after prolonged evolution. Furthermore, 250 warm evolution-altered genes did not return to control levels. These genes exhibited significant negative correlation between mean and variance in warm-evolved mosquitoes, but a two-fold variance reduction without mean change in relaxed-selection mosquitoes. Both signals are consistent with the action of selection operating on a polygenic trait architecture. Ecological modelling identified egg-to-adult viability as the primary driver of thermal reproductive success, highlighting juvenile stages as a crucial control target under continued warming.