Molecular Entomology, 2025, Vol.16, No.1, 28-38 http://emtoscipublisher.com/index.php/me 33 adaptive changes. On the one hand, bees may evolve stronger preferences and efficient utilization capabilities for the flowers of major crops. On the other hand, for general pollinators (such as bees and bumblebees), long-term nutritional imbalance caused by monoculture may promote changes in their nutritional physiology. In addition to nutrient utilization, the evolutionary adjustment of foraging behavior is also worthy of attention. In an environment with monotonous flower sources, bees may reduce the motivation to explore new flower sources and focus on familiar crop flowers; or evolve synchronized reproduction and activity rhythms with the annual crop flowering cycle. 4.3 Landscape structure changes and genetic diversity of honey bee populations Changes in agricultural landscapes, including habitat fragmentation, farmland expansion, and contiguous monoculture, have had a profound impact on the genetic structure of honey bee populations. Habitat fragmentation limits gene flow between honey bee populations. Wild bees (such as solitary bees and bumblebees) often need semi-natural habitats to nest and reproduce. When these habitats are divided into isolated islands, the population becomes isolated and the probability of inbreeding increases. Large-scale monoculture and frequent migration of bee colonies have changed the genetic composition of honey bees. In order to meet pollination needs, the beekeeping industry often transports bee colonies across regions, resulting in gene exchange between bee populations from different regions. This increases the surface diversity of bees in certain areas at the artificial level, but it may also cause global genetic homogeneity. The homogenization of agricultural landscapes also reduces the opportunities for gene exchange between pollinator species. For social insects such as honey bees, their gene exchange mainly depends on the nuptial flight of queen bees and drones. Tanasković et al. (2021) analyzed the mitochondrial DNA of Serbian bees and found that the genetic diversity of local bees has declined in recent decades, which is attributed to changes in the gene pool caused by human introduction and management methods. Landscape changes also affect the retention and loss of bee adaptive genes. Local bee colonies in natural environments often accumulate unique disease resistance or climate adaptation genes through long-term selection, but in an agricultural context, these genes may be at risk of loss due to genetic mixing or changes in selection pressure. 5 Specific Case Analysis of Pesticides on the Evolutionary Adaptation of Bees 5.1 The impact of neonicotinoids on the adaptive evolution of bee populations Neonicotinoids are one of the most widely used pesticides in the world in the past two decades, and their potential impact on bees has attracted much attention from researchers. These pesticides act on the nicotinic acetylcholine receptors in the insect central nervous system, causing nerve signal disorders and death. Bees are not target pests for neonicotinoids, but they are exposed to them when they feed on treated pollen, nectar or drink medicated dew. Tsvetkov et al. (2023) selected bee strains that were sensitive and tolerant to chlorothiazide for comparison and found that the survival rate of worker bees in the tolerant strain was significantly higher after exposure, accompanied by specific mutations in the CYP9Q detoxification gene (Figure 2). This shows that in areas of high-intensity use, neonicotinoids may act as a selection pressure to screen out bee individuals carrying favorable mutations, increasing their proportion in the population. In addition to genetic variation, bees may also reduce the toxicity of neonicotinoids by regulating their behavior. For example, experiments have shown that after multiple exposures to sublethal doses, worker bees will reduce their desire to feed on the smell (flowers treated with pesticides) and show a certain degree of learning to avoid it. This behavior essentially increases the chance of survival. 5.2 The impact of organic farming practices on the evolution of bee populations Organic farming creates a relatively friendly living environment for pollinators by not using chemical synthetic pesticides and fertilizers and promoting biodiversity. For bee populations, this not only reduces toxicological pressure but also increases nutritional sources, which is believed to contribute to the recovery and stability of bee populations. Pluta et al. (2024) conducted comparative experiments at 16 sites in Germany. The results showed that in areas with a higher proportion of organic farming, the parasitism rate of Varroa mites in bee colonies was lower, and the reproduction rate and group strength indicators of bee colonies were significantly improved. This
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