Parental heat stress has transgenerational physiological- but not ecological-progeny fitness advantage in the larger grain borer

Abstract

Climate change forecasts predict that global temperature and variability will continue rising owing to anthropogenic activities. This poses significant stress on ectotherms, whose bodily function depends on ambient temperatures. The ability of species to adapt within and/or across generations through phenotypic plasticity is thus a critical ecological topic. We investigated transgenerational thermal plasticity of the larger grain borer, Prostephanus truncatus, a devastating postharvest maize pest. Specifically, we tested the effects of parental exposure to sublethal heat stress (35 and 38 °C for 2 h; 80 % RH) on progeny thermal— and ecological—performance. Following acclimation, the colonies were separately maintained on shelled maize at optimum conditions of 32 °C at 65 ± 10 % RH. After 21 d, adult beetles were removed and the emerging progeny respectively labelled as F1 treatments (F1_35 °C and F1_38 °C). Subcultures from these 2 × F1 treatments were sampled in the same manner to obtain F2 (F2_35 °C and F2_38 °C) and subsequently F3 (F3_35 °C and F3_38 °C) generations which were then evaluated against parental (control) cultures maintained at optimal conditions 32 °C (P_32 °C). Our results showed that parental heat acclimation: (i) had transgenerational physiological— but not ecological-progeny fitness advantage; (ii) decreased critical thermal limit ranges; (iii) had cross-protection improvement in cold tolerance; and (iv) had transgenerational physiological responses that may last generations. Transgenerational plastic responses may help in understanding how species and ecosystems adapt to environmental temperature changes. This is the first report documenting transgenerational heat tolerance plasticity in P. truncatus.

HIGHLIGHTS • Parental heat acclimation had transgenerational physiological- but not ecological-progeny fitness advantage. • Parental heat acclimation decreased progeny critical thermal limit ranges. • Parental heat acclimation had cross protective improvement in progeny cold tolerance. • Transgenerational physiological responses may last generations.