Predictions of potential geographical distribution of Diaphorina citri (Kuwayama) in China under climate change scenarios

Potential distribution prediction of Ceracris kiangsu Tsai in China

Ceracris kiangsu Tsai (C. kiangs) is a kind of forest pest, which can harm nearly 100 kinds of weeds and crops. In this study, based on 314 species distribution points of C. kiangsu which were obtained from Chinese herbaria, literatures and investigation, and data of three future climate scenarios presented by CMIP6, two niche models (Garp, Maxent) were used to predict the suitable area of C. kiangsu in China. The result shows that the main environmental factors affecting the distribution of C. kiangsu are precipitation of driest month (bio14) and min temperature of coldest month (bio6). No matter now and future, the potential distribution areas of C. kiangsu in China are mainly in the south of Qinling-Huaihe River. Under current scenarios, the areas of the total, highly, moderately and poorly suitable of C. kiangsu in China are 160.65 × 104 km2, 31.70 × 104 km2, 60.36 × 104 km2 and 68.59 × 104 km2 respectively. The southern Hubei, western Jiangxi and eastern Hunan are highly-suitable areas. Under SSP1-2.6 and SSP2-4.5 scenarios, both the total suitable area and the highly suitable show a decreasing tread in 2050s. Compared to the 2050s, the total suitable area will coninue to decease in 2090s under SSP1-2.6, while it will increase under SSP2-4.5. The highly suitable area will increase in both scenarios, and the increased percentage under SSP2-4.5 is greater than that under SSP1-2.6. Under SSP5-8.5 scenarios, the total suitable area will increase by 1.83% in the 2050s, and decrease by 1.17% in the 2090s. The highly suitable area in the 2050s and 2090s under this scenarios is larger than under current scenarios. No matter what the scenario, the southern part of Yunnan, the southeast of Sichuan and the southwest of Chongqing will become highly-suitable areas as the climate continues to warm and should be monitored more cosely.

Risk of spread of the Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) in Ghana

The impact of invasive species on biodiversity, food security and economy is increasingly noticeable in various regions of the globe as a consequence of climate change. Yet, there is limited research on how climate change affects the distribution of the invasive Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera:Liviidae) in Ghana. Using maxnet package to fit the Maxent model in R software, we answered the following questions; (i) what are the main drivers for D. citri distribution, (ii) what are the D. citri-specific habitat requirements and (iii) how well do the risk maps fit with what we know to be correctly based on the available evidence?. We found that temperature seasonality (Bio04), mean temperature of warmest quarter (Bio10), precipitation of driest quarter (Bio17), moderate resolution imaging spectroradiometer land cover and precipitation seasonality (Bio15), were the most important drivers of D. citri distribution. The results follow the known distribution records of the pest with potential expansion of habitat suitability in the future. Because many invasive species, including D. citri, can adapt to the changing climates, our findings can serve as a guide for surveillance, tracking and prevention of D. citri spread in Ghana.

Effect of tree height and spraying methods on Diaphorina citri kuwayama endosymbionts in the context of Huanglongbing disease management in citrus orchards

BACKGROUND

Huanglongbing (HLB) (caused by Candidatus Liberibacter asiaticus) is the most damaging disease of citrus around the world. This study investigated the effects of citrus tree height on Diaphorina citri Kuwayama mortality, endosymbiont responses, and HLB distribution.

RESULTS

The results reveal that the age of citrus trees plays a significant role in psyllid mortality. Interestingly, the cumulative mean mortality (%) of psyllids over the seven-day observation period was higher (31.50±0.03) when four-year-old (501A1, 502A2, 501A3) citrus trees were sprayed with a US-SMART mechanical sprayer. In contrast, the psyllids mortality was 0.09±0.23 for the 13-year-old citrus trees (104A2, 104A3, 104C1) sprayed with a US-SMART mechanical sprayer and 9.10±0.05 for 13-year-old (502A2, 502B2, 502D1) citrus trees sprayed with a fixed US-SMART mechanical sprayer. Our findings also revealed that psyllids from both four- and 13-year-old citrus trees carried Candidatus Carsonella ruddii species and Wolbachia, the primary and secondary endosymbionts, respectively. Surprisingly, infection rates of these endosymbionts remained consistent across different age groups, as confirmed by quantitative polymerase chain reaction analysis. Furthermore, our study highlights the significance of tree height as a proxy for tree age in influencing HLB occurrence. Specifically, four-year-old citrus trees subjected to the US-SMART mechanical sprayer for citrus psyllid control demonstrated effective disease management compared to 13-year-old (104A2, 104A3, 104C1) citrus trees sprayed with US-SMART mechanical sprayers. Additionally, the investigation explored the impact of tree height on HLB distribution. In four-year-old trees, no significant correlation between HLB disease and tree height was observed, potentially due to effective spray coverage with US-SMART mechanical sprayer. However, in 13-year-old (104A2, 104A3, 104C1) citrus tree sprayed with US-SMART mechanical sprayer, a positive correlation between tree height and HLB disease was evident.

CONCLUSION

This research provides valuable insights into the complex interaction between citrus tree age, psyllid endosymbionts responses, and HLB distribution. These results emphasize effective HLB management strategies, especially in orchards with diverse tree age populations, ultimately contributing to the long-term sustainability of citrus cultivation. © 2023 Society of Chemical Industry.

Geographical distribution of two major quarantine fruit flies (Bactrocera minax Enderlein and Bactrocera dorsalis Hendel) in Sichuan Basin based on four SDMs

Both Bactrocera minax and Bactrocera dorsalis are phytophagous insects, and their larvae are latent feeders, which cause great damage and economic losses to agriculture production and trade. This study aimed to provide a scientific reference for researching and developing the feasible countermeasures against these two pests. Based on the distribution data of B. minax and B. dorsalis in China, obtained from the Chinese herbaria, investigation and literature. Four niche models (Garp, Bioclim, Domain, and Maxent) were used to analyze the key environmental factors affecting the distribution of both pests and to build prediction models of the potential distribution in Sichuan Basin. Combined with two statistical standards, area under the receiver operating characteristic curve (AUC) and Kappa, the validity of prediction models were analyzed and compared. The results show that: the average AUC values of the four models are all above 0.90, and the average Kappa values are all above 0.75, indicating that the four models are suitable for predicting the potential distribution area of B. minax and B. dorsalis. The annual range of temperature, the mean temperature in the driest quarter, the mean temperature in the warmest quarter, the annual precipitation, and the precipitation in driest month are the key environmental factors affecting the distribution of B. minax, while the mean diurnal temperature range, the mean temperature in the driest quarter, the seasonal temperature variations and the precipitation in driest month affect the potential distribution of B. dorsalis. The suitable areas for B. minax are mainly concentrated in the eastern of Sichuan Basin, while the suitable areas for B. dorsalis are concentrated in the southeastern. Except for the Bioclim model, the highly-suitable area for both pests predicted by the other three models are all greater than 15.94 × 104 km2 and the moderately-suitable areas are greater than 13.57 × 104 km2. In conclusion, the suitable areas for both pests in Sichuan Basin are quite wide. Therefore, the relevant authorities should be given strengthened monitoring of both pests, especially in areas with high incursion rates.

Host-Parasitoid Phenology, Distribution, and Biological Control under Climate Change

Climate change raises a serious threat to global entomofauna-the foundation of many ecosystems-by threatening species preservation and the ecosystem services they provide. Already, changes in climate-warming-are causing (i) sharp phenological mismatches among host-parasitoid systems by reducing the window of host susceptibility, leading to early emergence of either the host or its associated parasitoid and affecting mismatched species' fitness and abundance; (ii) shifting arthropods' expansion range towards higher altitudes, and therefore migratory pest infestations are more likely; and (iii) reducing biological control effectiveness by natural enemies, leading to potential pest outbreaks. Here, we provided an overview of the warming consequences on biodiversity and functionality of agroecosystems, highlighting the vital role that phenology plays in ecology. Also, we discussed how phenological mismatches would affect biological control efficacy, since an accurate description of stage differentiation (metamorphosis) of a pest and its associated natural enemy is crucial in order to know the exact time of the host susceptibility/suitability or stage when the parasitoids are able to optimize their parasitization or performance. Campaigns regarding landscape structure/heterogeneity, reduction of pesticides, and modelling approaches are urgently needed in order to safeguard populations of natural enemies in a future warmer world.

Future habitat changes of Bactrocera minax Enderlein along the Yangtze River Basin using the optimal MaxEnt model

Background

Bactrocera minax (Enderlein, 1920) (Diptera: Tephritidae) is a destructive citrus pest. It is mainly distributed throughout Shaanxi, Sichuan, Chongqing, Guizhou, Yunnan, Hubei, Hunan, and Guangxi in China and is considered to be a second-class pest that is prohibited from entering that country. Climate change, new farming techniques, and increased international trade has caused the habitable area of this pest to gradually expand. Understanding the suitable habitats of B. minax under future climate scenarios may be crucial to reveal the expansion pattern of the insect and develop corresponding prevention strategies in China.

Methods

Using on the current 199 distribution points and 11 environmental variables for B. minax, we chose the optimal MaxEnt model to screen the dominant factors that affect the distribution of B. minax and to predict the potential future distribution of B. minax in China under two shared socio-economic pathways (SSP1-2.6, SSP5-8.5).

Results

The current habitat of B. minax is located at 24.1-34.6°N and 101.1-122.9°E, which encompasses the provinces of Guizhou, Sichuan, Hubei, Hunan, Chongqing, and Yunnan (21.64 × 104 km2). Under future climate scenarios, the potential suitable habitat for B. minax may expand significantly toward the lower-middle reaches of the Yangtze River. The land coverage of highly suitable habitats may increase from 21.64 × 104 km2 to 26.35 × 104 × 104 km2 (2050s, SSP5-8.5) ~ 33.51 × 104 km2 (2090s, SSP5-8.5). This expansion area accounts for 29% (2050s, SSP1-2.6) to 34.83% (2090s, SSP1-2.6) of the current habitat. The center of the suitable habitat was predicted to expand towards the northeast, and the scenario with a stronger radiative force corresponded to a more marked movement of the center toward higher latitudes. A jackknife test showed that the dominant variables affecting the distribution of B. minax were the mean temperature of the driest quarter (bio9), the annual precipitation (bio12), the mean diurnal range (bio2), the temperature annual range (bio7), and the altitude (alt).

Discussion

Currently, it is possible for B. minax to expand its damaging presence. Regions with appropriate climate conditions and distribution of host plants may become potential habitats for the insects, and local authorities should strengthen their detection and prevention strategies. Climate changes in the future may promote the survival and expansion of B. minax species in China, which is represented by the significant increase of suitable habitats toward regions of high altitudes and latitudes across all directions but with some shrinkage in the east and west sides.

Impacts of Climate Changes on Geographic Distribution of Primula filchnerae, an Endangered Herb in China

Primula filchnerae, an endangered plant endemic to China, has drawn people's attention in recent years due to its ornamental value in flower. It was rarely recorded since being described in 1902, but it was rediscovered in 2009 and is now known from a limited number of sites located in Hubei and Shaanxi Provinces. Since the species is still poorly known, a number of unanswered questions arise related to it: How has P. filchnerae responded to past climate change and how might it respond in the future? Why was P. filchmerae so rarely collected during the past century? We assembled geographic coordinates for P. filchnerae through the field surveys and website searches, and then used a maximum entropy model (MaxEnt) to simulate its potential suitable distribution in six periods with varied carbon emission levels by combining bioclimatic and environmental factors. MaxEnt showed that Min Temperature of the Coldest Month (bio6) and Precipitation of the Coldest Quarter (bio19) affected P. filchnerae's distribution most, with an aggregate contribution >60% and suitable ranges above -5 °C and below 40 mm, respectively. We also analyzed potential habitat distribution in various periods with differing impacts of climate change compared to today's suitable habitats, and in most cases, Shaanxi and Sichuan remained the most stable areas and with possible expansion to the north under various carbon emission scenarios, but the 2050s SSP5-8.5 scenario may be an exception. Moreover, we used MaxEnt to evaluate population shifts, with various scenarios indicating that geometric center would be concentrated in Sichuan Province in China. Finally, conservation strategies are suggested, including the creation of protected areas, long-term monitoring, raising public awareness of plant conservation, situ conservation measures, assisted migration, and species introduction. This study demonstrates how P. filchnerae may have adapted to changes in different periods and provides a scientific basis for germplasm conservation and management.

Modeling climate change impacts on potential global distribution of Tamarixia radiata Waterston (Hymenoptera: Eulophidae)

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is an efficient vector of "Candidatus Liberibacter" species, the causative agents implicated in citrus greening or huanglongbing (HLB). HLB is the most devastating citrus disease and has killed millions of citrus trees worldwide. Classical biological control using Tamarixia radiata Waterston (Hymenoptera: Eulophidae) against ACP has been successful in some regions. Climatic conditions are critical in determining suitable areas for the geographical distribution of T. radiata. However, paucity of information on climate change impacts on the global spread of T. radiata restricts international efforts to manage ACP with T. radiata. We investigated the potential global distribution of T. radiata using 317 native and non-native occurrence records and 20 environmental data sets (with correlation coefficients (|r| > 0.7)). Using the Maximum Entropy model, these data were analyzed for two shared socioeconomic pathways (SSPs) and two time periods (2030s and 2050s). We showed that habitat suitability for T. radiata occurred in all continents except Antarctica. However, the highly suitable areas for T. radiata were found in parts of the Americas, Asia, Africa and Oceania. The climate suitable areas would increase until the 2050s. The predictions showed that mean temperature of coldest quarter and precipitation of warmest quarter were the most important environmental variables that influenced the distribution of T. radiata. The model reliably predicted habitat suitability for T. radiata, which can be adapted in classical biological control programs to effectively manage ACP in an environmentally friendly manner.

Prediction of the Potential Distributions of Prunus salicina Lindl., Monilinia fructicola, and Their Overlap in China Using MaxEnt

Prunus salicina Lindl. (P. salicina) is an essential cash crop in China, and brown rot (BR) is one of its most important diseases. In this study, we collected geographic location information on P. salicina and Monilinia fructicola (G. Winter) Honey (M. fructicola), one of the BR pathogenic species, and applied the MaxEnt model to simulate its potential suitable distribution in China. There have been discussions about the dominant environmental variables restricting its geographical distribution and their overlap. The results showed that the mean temperature of the coldest quarter, precipitation of the warmest quarter, precipitation in July, and minimum temperatures in January and November were the main climatic variables affecting the potential distribution of P. salicina, while the coldest quarter, precipitation of the driest month, precipitation of March, precipitation of October, maximum temperatures of February, October, and November, and minimum temperature of January were related to the location of M. fructicola. Southern China had suitable conditions for both P. salicina and M. fructicola. Notably, the overlap area of P. salicina and M. fructicola was primarily located southeast of 91°48' E 27°38' N to 126°47' E 41°45' N. The potential overlap area predicted by our research provided theoretical evidence for the prevention of BR during plum planting.

Citrus Huanglongbing correlated with incidence of Diaphorina citri carrying Candidatus Liberibacter asiaticus and citrus phyllosphere microbiome

In China, citrus Huanglongbing (HLB) disease is caused by the Candidatus Liberibacter asiaticus bacterium, which is carried by the Asian citrus psyllid Diaphorina citri Kuwayama. It was hypothesized that the epidemic of the HLB may related with the rate of bacterium presence in the insect vector and bacterium content in plant tissues, as well as the phyllosphere microbe communities changes. This study systematically analyzed the presence or absence of Ca. L. asiaticus in citrus tree leaves and in the insect vector D. citri over a 6-year period using real-time PCR. In addition, changes in the number of bacteria carried by D. citri over 12 months were quantified, as well as the relationship between the proportion of D. citri carrying Ca. L. asiaticus and the proportion of plants infected with Ca. L. asiaticus were analyzed. Results showed that the proportion of D. citri carrying bacteria was stable and relatively low from January to September. The bacteria in citrus leaves relatively low in spring and summer, then peaked in December. The proportion of D. citri carrying bacteria gradually declined from 2014 to 2019. The proportion of D. citri carrying Ca. L. asiaticus showed a significant positive correlation with the proportion of diseased citrus. The phyllosphere bacterial and fungal communities on the healthy citrus leaf were significantly different with the disease leaf in April and December. Pathogenic invasions change the citrus phyllosphere microbial community structure. It could be summarized that citrus Huanglongbing correlated with incidence of Diaphorina citri carrying Candidatus Liberibacter asiaticus and citrus phyllosphere microbiome.

Using MaxEnt to Predict the Potential Distribution of the Little Fire Ant (Wasmannia auropunctata) in China

Invasive ants are some of the most destructive species in ecosystems and can have serious ecological and socioeconomic impacts. The little fire ant, Wasmannia auropunctata, is native to Central and South America and was listed as one of the 100 most threatening major invasive organisms in the world by the International Union for Conservation of Nature (IUCN). The presence of W. auropunctata was first reported on the Chinese mainland in January 2022, but its distribution in China is still unclear. In this study, MaxEnt was used to predict the potential distribution of W. auropunctata in China based on known distribution points and climatic variables. The prediction results showed that most of the area south of the Yangtze River is potentially suitable for W. auropunctata, and temperature is the main factor affecting its distribution. The contemporary total suitable living area of W. auropunctata is 1,954,300 km², accounting for 20.36% of China's total land area. Further attention should be given to the potential impact of W. auropunctata invasions, and effective measures should be taken to eliminate the introduced population in China.

Determining the potential distribution of Oryctes monoceros and Oryctes rhinoceros by combining machine-learning with high-dimensional multidisciplinary environmental variables

The African coconut beetle Oryctes monoceros and Asiatic rhinoceros beetle O. rhinoceros have been associated with economic losses to plantations worldwide. Despite the amount of effort put in determining the potential geographic extent of these pests, their environmental suitability maps have not yet been well established. Using MaxEnt model, the potential distribution of the pests has been defined on a global scale. The results show that large areas of the globe, important for production of palms, are suitable for and potentially susceptible to these pests. The main determinants for O. monoceros distribution were; temperature annual range, followed by land cover, and precipitation seasonality. The major determinants for O. rhinoceros were; temperature annual range, followed by precipitation of wettest month, and elevation. The area under the curve values of 0.976 and 0.975, and True skill statistic values of 0.90 and 0.88, were obtained for O. monoceros and O. rhinoceros, respectively. The global simulated areas for O. rhinoceros (1279.00 × 10⁴ km²) were more than that of O. monoceros (610.72 × 10⁴ km²). Our findings inform decision-making and the development of quarantine measures against the two most important pests of palms.