Trait-dependent plasticity erodes rapidly with repeated intergenerational acclimation in an invasive agricultural pest

Abstract

Climate change is associated with increased mean temperatures and amplitudes manifesting both acutely and chronically, triggering organism stress responses that confer fitness costs and/or benefits. The larger grain borer (LGB), Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) is an invasive postharvest agricultural pest. While host shift is its well-known potential invasive mechanism, how repeated intergenerational stress environments may influence offspring phenotypes is largely unknown. We thus evaluated physiological and ecological performance of LGB following repeated intergenerational acute heat acclimation to insinuate its likely responses to projected increased bouts of heat stress associated with climate change. Parental colonies were acutely heat-acclimated separately at 35°C and 38°C; 80% RH for 2 h in climate chambers and released onto sterilized maize grain at optimal conditions (32°C, 80% RH). The F₁ progenies were, respectively, acclimated at the same conditions and incubated to F₂ generation. We then evaluated physiological and ecological performance under optimal conditions across parental, F₁ and F₂ generations. Our results showed that plasticity was highly trait dependent, and that acclimation did not affect F₁ and F₂ critical thermal maxima, but did improve critical thermal minima. However, while acclimation improved heat knockdown time at F₁, repeated acclimation significantly reduced heat knockdown times at F₂, suggesting plasticity erosion with generational repeated acclimations. Acute acclimation negatively affected ecological performance of F₁ generations although this was restored with repeated acclimation in F₂ populations. Our results suggest that the LGB may inflict more economic damage with repeated heat stress due to generational adaptation to temperature stress. The results contribute to knowledge on pest forecasting modelling under changing climates and provides a framework for phytosanitary adjustments in heat treatment protocols for international grain trade.