Temperature is a critical factor that influences the behavior, physiology, and development of ectothermic organisms. This has become even more important as acute temperature stress associated with global climate change becomes the new norm. Using the invasive fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), we assessed its physiological and ecological responses following acute heat stress, synonymous to heat waves associated with recent climate change. Specifically, we measured the effects of short‐term exposure (for 2 h) to heat shock (at 32, 35, and 38 °C) on physiological responses, such as critical thermal minima (CTmin) and maxima (CTmax), and life‐history traits, such as reproductive success (fecundity and hatching success) and longevity, using virgin adults. Our results showed that prior acute heat shock compromised cold tolerance (CTmin) while enhancing heat tolerance (CTmax). In addition, heat shock reduced fecundity and hatching success and had dramatic effects on adult longevity. We conclude that acute heat stress associated with shifting environmental conditions may generally offset key physiological traits, affect reproduction and thus population persistence, and simultaneously have complex effects on adult lifespan.
In this era of global climate change, intrinsic rapid and evolutionary responses of invasive agricultural pests to thermal variability are of concern given the potential implications on their biogeography and dire consequences on human food security. For insects, chill coma recovery time (CCRT) and critical thermal minima (CTmin), the point at which neuromuscular coordination is lost following cold exposure, remain good indices for cold tolerance. Using laboratory-reared Spodoptera frugiperda (Lepidoptera: Noctuidae), we explored cold tolerance repeated exposure across life stages of this invasive insect pest. Specifically, we measured their CTmin and CCRT across four consecutive assays, each 24 h apart. In addition, we assessed body water content (BWC) and body lipid content (BLC) of the life stages. Our results showed that CTmin improved with repeated exposure in 5th instar larvae, virgin males and females while CCRT improved in 4th, 5th and 6th instar larvae following repeated cold exposure. In addition, the results revealed evidence of cold hardening in this invasive insect pest. However, there was no correlation between cold tolerance and BWC as well as BLC. Our results show capacity for cold hardening and population persistence of S. frugiperda in cooler environments. This suggests potential of fall armyworm (FAW) to withstand considerable harsh winter environments typical of its recently invaded geographic range in sub-Saharan Africa.
Thermal adaptation is a key facet safeguarding organismal function among ectothermic organisms. In this era of rapidly changing environments, understanding the diverse mechanisms mediating organismal climate stress resistance have become a priority given contrasting effects on organisms, vis declines in keystone species and an increase in invasive pest species. Here, we review mechanisms and patterns of thermal adaptation among shifting climates, specifically focusing on Lepidoptera, an economically significant insect order owing to its importance in agriculture and conservation. Lepidoptera are highly distinct, comprising species of diverse and unique morphology, ontogenetic development, habitat types and diets. Similarly, the diversity of adaptive responses ensuring survival under diverse thermal niches is equally remarkable. We therefore outline the mechanisms underpinning the success of Lepidoptera, mainly focusing on the important families and species which have quite attracted research attention in that order. We conclude by highlighting future studies for better understanding of lepidopteran species thermal adaptation under climate change. Understanding such adaptation will assist in accurate predictions and management of pest insect species and help conservation efforts in keystone species of the order Lepidoptera.
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