Molecular Entomology, 2025, Vol.16, No.1, 39-49 http://emtoscipublisher.com/index.php/me 41 Figure 1 Chemical mechanisms of plant-insect interactions (Adopted from Dofuor et al., 2024) Image caption: 1) Herbivore are able to distinguish host plants from background signals thus avoiding non-host plants, 2) Herbivore uses host derived signals to locate suitable site for oviposition and feeding (below and above ground); It may be able to distinguish between enantiomer (R or S) in selecting a suitable host, 3) Plant under herbivore feeding indirectly defend itself by emitting volatile compounds that are attractive to natural enemies of the feeding herbivore; Signals from herbivore fed plants can at the same time prime neighboring plants for possible attack; The primed plant emits volatile signals that are attractive to natural enemies (below and above ground), 4) Herbivore fed leaf of a plant can prime neighboring leaves to start emitting biotic stress signals that are capable of recruiting natural enemies, 5) Volatile of certain uninfected plants such as desmodium emit background signals that are able to prime neighboring plant of different species to emit stress related signals for the recruitment of natural enemies (below and above ground) (Adopted from Dofuor et al., 2024) 2.3 Basic concepts of ecological adaptation of herbivorous insects Adaptive evolution refers to the process in which the frequency of favorable traits in biological populations increases under environmental selection pressure on the basis of genetic variation, thereby improving survival and reproductive success. In the context of agricultural ecosystems, herbivorous insects face special selection pressures, including the combined effects of human factors (pesticides, farming systems, insect-resistant varieties) and environmental factors (single field landscape, irrigation and fertilization patterns, etc.) (Gould et al., 2018). Therefore, their adaptive evolution exhibits some unique characteristics. The first is the rapid adaptation speed. Many studies have shown that the evolutionary response of pests to new environments and new resistance measures can occur in dozens of generations or even shorter (Crossley et al., 2021). The second is the diversity of adaptation mechanisms. The adaptation of herbivorous insects is not limited to a single pathway, but often involves multiple levels of physiology, biochemistry and behavior. In addition, the periodicity of disturbance in agricultural ecosystems also shapes the adaptation pattern of pests. For example, agricultural measures such as crop rotation and fallow will interrupt the continuous host source of pests, which requires pests to have adaptations such as migration or dormancy to survive unfavorable seasons or find new hosts (Lawton et al., 2022). 3 Evolutionary Adaptation Mechanisms of Herbivorous Insects 3.1 Nutritional adaptation evolution Herbivorous insects can feed on a variety of plant tissues and digest the nutrients in them, which is an important manifestation of their nutritional adaptive evolution. There are significant differences in the utilization strategies of host nutritional resources among different insects, which is largely attributed to evolutionary nutritional adaptation. Insects' tolerance and utilization of plant secondary compounds is one of the core of nutritional adaptation (Crossley et al., 2021). In order to defend against herbivores, many plants synthesize a variety of secondary metabolites (such as alkaloids, phenols, protease inhibitors, etc.) with anti-nutritional or toxic effects. In the process of co-evolution, herbivorous insects have evolved corresponding detoxification and tolerance mechanisms (Skidmore and Hansen, 2017; Salem et al., 2025).
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