Global warming has become a major climate change issue during the last century (Stocker et al., 2013). These changes have affected the distribution patterns of organisms, leading to changes in the suitable areas of species and biodiversity reduction. The impact of climate change on insects is particularly important, and climate change can directly or indirectly affect the distribution and number of insects (for example, by changing the emergence of species and hosts), so simulating how climate change affects invasive pests and their natural enemies can provide important information for controlling and managing the spread of these pests and introducing natural enemies (Wei et al., 2020). Economic globalization has also accelerated the spread of invasive species, resulting in serious economic losses. The Colorado potato beetle (CPB), scientifically known as Leptinotarsa decemlineata Say, is a destructive quarantine pest whose main hosts are the Solanaceae species such as potato (Solanum tuberosum L.) (Guo et al., 2010).

CPB has strong autonomous diffusion (Casagrande, 1985, 2014) and adaptability abilities (Weber, 2003, Jiao, 2016). It was first identified in the Rocky Mountains of North America while feeding on the wild plant Solanum rostratum D. CPB mostly spreads out with potato as its host plant because it is widely planted as an important economic crop (Jacques, 1985; Casagrande, 2014). CPB has gradually spread from North America to more than 40 countries across Europe, Asia, and Africa in the past century. CPB can have 1–4 generations in 1 year depending on the geographic distribution (Hare, 1990). The adults overwintered at 10–60 cm below the soil and mostly at 10–30 cm. The overwintering depth was related to the soil texture and deeper in sandy loam (Tuerxun et al., 2010). After overwintering, adults feed, mate and lay eggs on the back of host plant leaves. The egg period is 5 for 7 days, and then the larvae and the overwintering adults feed heavily on the leaves of the host crops (mainly potato), which can cause great harm to the crop hosts in spring (Pulatov et al., 2016). CPB can reduce potato yield by 20–100%, resulting in serious economic losses (Caprio, 1987; Casagrande, 2014). CPB control includes plant quarantine, agricultural, physical, biological, and chemical control, though chemical control remains the main method (Wang, 2017). However, the effect of chemicals has been significantly reduced by the over-dependence on chemicals and the strong adaptability of CPB (Cutler et al., 2005; Malekmohammadi et al., 2012; Rinkevich et al., 2012; Szendrei et al., 2012). Numerous studies postulate that CPB has developed resistance to most registered insecticides (Li, 2014). It is thus necessary to actively develop new technologies that can partially replace chemical control or complement chemical control technologies in CPB control (Li, 2014). Numerous studies focusing on biological control technologies have been carried out in China and abroad, mainly on utilizing natural enemy resources. This study explored the biological prevention of CPB using a modeling approach to assess the distribution of CPB and its natural enemy, Picromerus bidens (P. bidens).

Picromerus bidens L. is a predatory insect belonging to the family Pentatomidae in the order Hemiptera. It mainly preys on the larvae of insects in the order Lepidoptera, Hymenoptera, and Coleoptera, and sometimes on their pupae and adults. It is widely distributed in the western parts of the Palearctic, including Europe, China, and North Africa (Ahmad and Önder, 1990; Legaspi et al., 1996; De Clercq, 2000). It likes fresh, cool and humid areas (Larivière and Larochelle, 1989), mainly growing in moist bushes and forests more than 2 m above the ground (Čokl et al., 2011). Adjacent fresh vegetation is important for the successful development of nymphs and adults, as well as for reproductive activities (Mahdian et al., 2008). The P. bidens has univoltine (one brood per year) life cycle with obligate embryonic diapause and overwinters primarily at the egg stage (Ganyukova et al., 2020). Nymphs hatch in spring. During the I-age, the nymphs live closely together and gather together, and the size varies with the number of eggs in each batch. Ii-instar nymphs also tend to live in groups, living in groups of 3–56 individuals, and the activity and mobility of nymphs increase from iii to v-age (Cianferoni and Dioli, 2019). The I-instar nymph does not eat, but only absorbs water (De Clercq, 2000) or absorbs liquids from plant diversity. Second or third instar nymphs begin to prey (Cianferoni and Dioli, 2019). P. bidens is long known as an active predator for caterpillars and other insects with soft cover (Mayné and Breny, 1948). The P. bidens has been studied as suitable as agents of biological control of CPB since 1997 (Volkov et al., 2013). Volkov et al. (2013) in laboratory and field researches the ability of P. bidens to reduce the number of CPB larvae on potato plants was established.

Species Distribution Models (SDMs), also called Ecological Niche Models (ENMs use species distribution data and related environmental variables to infer the current ecological needs of the species through differential algorithms. These models are projected to the research area set at different times and spaces to obtain the species’ potential distribution area in the study area (Elith et al., 2006). Currently, SDMs are widely used in various disciplines, such as ecology, biological invasion, and conservation biology. The MaxEnt software has become more popular because of its stable performance and user-friendly interface (Liu et al., 2020) compared to other models. It has been widely used in predicting the potential distribution areas of plants, animals, and microorganisms.

This study predicted the potential distribution areas of CPB and P. bidens using the distribution data and environmental variables to explore the possibility of P. bidens being a natural enemy of CPB. It also comparatively analyzed the diffusion dynamics in the suitable zone of CPB and P. bidens under different climatic scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5) for the future (2021–2100 years). This study provides a theoretical basis and data support for early warning, monitoring, and control of the CPB spread.

Colorado potato beetle, a worldwide quarantine pest (Wang et al., 2011; Hou et al., 2020), has invaded many countries and regions (Wang, 2018). P. bidens is a kind of polyphagous insect, which can prey on many kinds of pests such as CPB and can be used to control CPB (Mahdian et al., 2006; Tang, 2020). Therefore, predicting the potential distribution areas of CPB and P. bidens can facilitate the monitoring, early warning and control of CPB all over the world. This study predicted the potential distribution areas of CPB and P. bidens and their changes under different climatic scenarios using the MaxEnt model based on their distribution data and environmental variables. Their possible introduction routes were subsequently predicted by combining the distribution points of the large airports and ports. The AUC of the MaxEnt model was more than 0.8 (Figure 3), demonstrating good performance in predicting the potential distribution area of CPB and P. bidens.

CPB was distributed in six continents except Antarctica based on the prediction of the current potential distribution of CPB. Europe, North America, the southeast coastal areas of Oceania, and Oakland as the primary highly suitable areas. The middle and low suitable growth areas are distributed in almost six continents, including South America and Oceania (Figure 4). According to the records so far, CPB is distributed in Europe, Asia, and North America between 15 and 55°N in the American continent and 33 and 60°N in Eurasia. It is also distributed in many regions in northern Africa (Guo et al., 2014; Wang, 2018). Notably, the modeling results are consistent with the actual distribution of CPB in Europe and North America. Although South America and Oceania have not found the distribution of CPB at present, as the suitable growth area of CPB, we should focus on preventing and controlling the invasion of CPB. Moreover, strict precautions should be taken in large airports and ports because they are the primary introduction routes (Figure 10). The current distribution prediction of P. bidens suggested that it is mainly distributed in the southeast coastal areas of Eurasia, North America and Oceania, and Oakland (Figure 4). After comparing the suitable growth areas of P. bidens and CPB, it was found that under the current climatic conditions, the overlap accounted for 76.21% of the suitable growing areas of P. bidens (Figure 9). In the future climate, the overlap reaches more than 80% of the suitable growth area of the P. bidens (Supplementary Figures 7–10). Therefore, according to the range of suitable growth area of P. bidens (Figure 9), we can judge whether P. bidens can be introduced into the area where CPB is seriously harmful. At the same time, combined with the predicted introduction path (Figure 11) and suitable growth area (Figure 9), the introduction path and release location of P. bidens can be determined to achieve the maximum effect of controlling CPB.

It has been reported that climate change will lead to the expansion, transfer or contraction of the distribution of species, which will greatly affect the distribution of species (Biber-Freudenberger et al., 2016; Wei et al., 2018, 2020). The results of this study show that the change in the suitable growth areas of CPB from 2021 to 2100 under different climate scenarios was very small and mostly insignificant, accounting for 0.31–0.34 of the study areas. The expansion area accounted for 0.01–0.05 of the study areas, while the contraction area accounted for 0.01–0.04. The area change of the total suitable growth area is shown in Figure 7. Under the climatic scenario of ssp126, the suitable habitat area of CPB showed a decreasing trend from 2021 to 2100, but it increased compared with the current suitable habitat area before 2080, and decreased only during the period of 2081–2100. Under the climatic scenario of ssp245, the suitable habitat area of potato beetle was only from 2041 to 2060, which decreased compared with the current suitable habitat, and increased at other times. Under the climatic scenario of ssp370, it showed an increasing trend from 2021 to 2100, but from 2021 to 2040, the suitable habitat area of potato beetle decreased compared with the current suitable habitat area, and increased compared with the current suitable habitat area after 2040. In the ssp585 climate scenario, there was little change in 2021–2040, only a slight increase, a small decrease in 2041–2060, and a growing trend in 2061–2100.

This phenomenon was attributed to the strong adaptability of CPB, which has made it a globally invasive pest (Wang, 2018). But that doesn’t mean the CPB has stopped its expansion. According to the forecast, most of the suitable areas of CPB have not been invaded by CPB, such as South America, Oceania and the Central Plains of China. These areas still need to focus on monitoring, prevention and control on possible path of introduction.

The predicted distribution areas of P. bidens showed a decrease under different climatic scenarios, with a significantly larger shrinking area (purple part) than that of CPB (Figures 7, 8). The expansion area accounted for 0.001–0.03, the contraction area accounted for 0.05–0.09, while the unchanged area accounted for 0.12–0.15 of the study areas. The area change of the total suitable growth area is shown in Figure 7. Under the climatic scenario of ssp126, the suitable habitat area decreased sharply from 2021 to 2040, increased from 2041 to 2060, and decreased slightly from 2061 to 2100. Under the climatic scenario of ssp245, it showed a downward trend from 2021 to 2060, and increased slightly from 2061 to 2080, but after 2081, it showed a downward trend. Under the climate scenario of ssp370, the trend is roughly the same as that of ssp245; under the climate scenario of ssp585, it shows an increasing trend from 2041 to 2100, but the area of suitable habitat is still decreasing compared with the current one.

These findings suggest that global warming will reduce the suitable areas of P. bidens. P. bidens is a predatory insect that can be used as a natural enemy to control pests belonging to the orders Coleoptera, Lepidoptera, and Hymenoptera (Mahdian et al., 2006; Tang, 2020). A reduction of its suitable habitats may cause a decrease in its population density, leading to a lack of effective and timely prevention and control of invasive pests. Active measures should thus be enacted to minimize global warming and protect biodiversity.

The centroid movement is drawn as a vector, which represents the size and direction of the movement in the predicted distribution range (Hannah et al., 2019). Centroid movement can reflect the spatial variation of the distribution of eco-environmental vulnerability index in the study area (Luck and Wu, 2002). In this study, the centroid of the potential distribution area of CPB migrated to the northwest and southeast between 2021 and 2100. However, the migration range was not large, indicating that climate change had insignificant effects on CPB during the period. In contrast, the centroid of the potential distribution area of P. bidens migrated westward under different climatic scenarios. The migration range was smallest in the SSP126 scenario between 2021 and 2040 and largest in the SSP370 scenario between 2081 and 2100. This phenomenon may be attributed to the decrease of forest area under the SSP370 climate scenario.

Invasive insect species, such as CPB, are a major threat to the ecosystem functions and indigenous biodiversity globally. Their invasion is strengthened by climate change and economic globalization. Notably, they have natural enemies, such as P. bidens, which can control them. This study provides a current prediction of the potential distribution areas of CPB and its natural enemy P. bidens. Further, it analyzes the diffusion dynamics of their suitable areas under different future climate change scenarios. It also highlights the airports and ports as the primary introduction routes of CPB and P. bidens by intersecting their positions with the binary potential distribution map. This study provides a theoretical basis and data support for early warning, monitoring, and control of the CPB spread.

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author/s.

JW, QZ, and HZ contributed conception and design of the study and funding. XG conducted analysis and wrote the first draft of the manuscript. All authors contributed to manuscript revision and read and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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