Current and future potential geographical distribution of Bactericera cockerelli: an invasive pest of increasing global importance

Due to ongoing climate change and the spread of invasive pests, understanding and predicting climatic suitability for invasive insect species has shown growing demand from government and industry biosecurity managers. The invasive pest Bactericera cockerelli, (Šulc) (Hemiptera: Triozidae), commonly known as tomato potato psyllid (TPP), is native to North America and has recently invaded Australasia. TPP is also the vector of the bacterial plant pathogen Candidatus Liberibacter solanacearum (CLso), which has caused severe economic losses for potato growers worldwide. We used the niche modelling software CLIMEX to predict the potential geographical distribution of TPP in Australasia and worldwide under current and future climatic scenarios. Our model prediction of the current climate conditions closely agrees with all the known distributions of TPP. In its native range (North America), TPP is predicted to expand its current geographical range in semi‐arid, temperate, and continental climates. Within Australia, along with the known occurrence of TPP in Western Australia, potential expansion into South Australia, Victoria, New South Wales and Queensland is predicted. The predicted distribution closely matches all the known records with higher climatic suitability in New Zealand. Globally, the model projected that the pest‐free countries in Europe and East Asia are climatically more suitable for TPP. Predictions under the future climate change scenarios (A1B, CSIRO Mk 3.0 for 2090) showed a significant reduction of the known geographical range of TPP with a possible expansion towards higher latitudes. Areas in North America and Australia are projected to be less climatically suitable for the survival of TPP in future climates. However, our model suggested that Europe and New Zealand will remain unchanged or will become more favourable in the future. These CLIMEX projections for current and future climatic distribution provide valuable information for existing and future biosecurity preparedness and management programmes, which may prove helpful in risk assessments and identifying potential areas that are likely to be susceptible to a TPP invasion.

TPP damages crops by feeding on the phloem, causing psyllid yellows.This condition is characterised by leaf curling or cupping, chlorosis, stunting and falling of flowers, and production of small or deformed fruits (Liefting et al. 2009;Munyaneza 2012).In addition, this psyllid pest is also the primary vector of Candidatus Liberibacter solanacearum (CLso), a bacterial pathogen that is indirectly transmitted during feeding on host plants, causing 'Zebra chip disease' on potatoes (Mora et al. 2021;Munyaneza 2012;Munyaneza et al. 2013;Munyaneza, Crosslin, & Upton 2007;Secor et al. 2009).Potato cultivation that is affected by psyllid yellows and Zebra chip disease can result in significant yield losses, plant mortality and decreased quality of potato crops (Munyaneza 2015).
TPP is considered one of the most destructive pest species in the western hemisphere and has caused severe damage to potato crops worldwide (CABI 2020).Economic losses of US$ 2 million per annum have been reported in Texas, USA, due to Zebra chip disease, where over 35%-40% of the potato crop in the affected area was estimated to be vulnerable to the disease (CNAS 2009).Greenway and Rondon (2018) estimated that US$ 9.2 million were spent on purchasing pesticides, while additional application costs totalled approximately US$ 11 million in Idaho, Oregon and Washington in the United States.In New Zealand, CLso disease caused NZ$1 million in crop losses within commercial glasshouse tomatoes in Auckland in 2008 (Liefting et al. 2009).Pest management activities against TPP in New Zealand, after only 4 years since its arrival, have had a significant impact on the New Zealand export market that includes Pacific Islands, Japan and Australia (Teulon et al. 2009).In 2008, export orders lost by the capsicum industry were estimated to be around NZ$ 5.22 million, while the greenhouse tomato industry lost export orders valued at around NZ$ 3 million (Teulon et al. 2009).Ogden (2011) reviewed the impact of TPP and CLso on cultivation industries and research programmes in New Zealand, estimating that tomato and capsicum industries associated with TPP and CLso costed NZ$ 5 million in pest surveillance and disease control.Additionally, the potato industry spent NZ$ 120 million on crop reduction, pest management, losses in processing and seed industries and research-related costs.
Prediction and prevention are the key approaches in invasive pest management (Venette & Hutchison 2021).The impact of climate change has posed a significant threat to current biosecurity and pest risk, with the shifting of pest range (Stephens, Kriticos, & Leriche 2007).Consequently, the demand for the estimate and visualise potential risk areas as an effective means of communication has accelerated.Due to its invasive nature and broad host range, TPP has excellent potential to expand its distribution into new geographical regions.This highlights the importance of understanding and estimating the potential geographical range of this pest, which will inform risk assessments and contribute to biosecurity preparedness activities for TPP.The use of ecological niche/ bioclimatic models has become increasingly common in predicting suitable habitats for pests, with several modelling software, such as BIOCLIM, DOMAIN, GRAP, HABITAT, MaxEnt and CLIMEX, being available for this purpose (Avila & Charles 2018;Kriticos et al. 2021).
This study aims to develop a bioclimatic model to predict the current and future distribution of TPP using CLI-MEX (Sutherst, Maywald, & Kriticos 2007), integrating species-specific biological data and dynamic climatic variables in the modelling process (Avila & Charles 2018;Kriticos et al. 2015).CLIMEX, being a process-based mechanistic niche modelling software, offers the advantage of incorporating species' biological traits and physiological tolerances into the modelling process, distinguishing it from correlative niche models.Our niche model for the TPP was developed by integrating published data on its developmental biology and all available distribution records.This comprehensive approach enabled us to predict the potential geographical distribution of TPP under current global climate conditions as well as future climate change scenarios; published data on the developmental biology of TPP and all known distribution records were combined to develop and validate our niche model and predict TPP's potential geographical distribution under the current global climate and future climate change scenarios.

CLIMEX model
CLIMEX v3.0 was used for modelling.CLIMEX is a bioclimatic modelling software package that integrates climatic information and physiological data of a species to model population growth in response to climatic conditions.CLIMEX generate ecoclimatic index (EI)-based maps where it integrates the weekly responses to climate and calculates a series of annual indices to simulate the favourable conditions needed for population growth and combine various environmental stresses (Sutherst, Maywald, & Kriticos 2007).
The ecoclimatic index (EI), which describes how favourable the climate of a location is for a particular species to survive and develop, is expressed by The annual growth index (GI A ) is calculated as a function of temperature and soil moisture to estimate population growth, which is calculated with the following equation: where w is the week of the year, TI W is the temperature index for week w and MI W is the moisture index for week w.The stress index (SI) and their interactions (SX) (hot, cold, dry, wet and their various combinations) are also calculated to estimate the species' response to unfavourable conditions that could limit their distribution as described by Sutherst, Maywald, & Kriticos (2007).
The EI varies between 0 and 100.An EI value of 0 is entirely unsuitable, and an EI value of 100 is optimal for survival.However, an EI value of 100 is unlikely and only occurs in very stable or artificially simulated environments (Kriticos et al. 2015).Generally, an EI value greater than 20 indicates the suitability of a species to establish a substantial population.(Kriticos et al. 2015;Sutherst, Maywald, & Kriticos 2007).Hence, this study classifies EI values into five categories; EI = 0 as unsuitable, EI = 1-5 as marginal suitability, EI = 6-10 as moderate suitability, EI = 11-25 as high suitability, and EI ≥ 25 as optimal suitability.
CLIMEX also includes a mechanism for defining the minimum annual developmental heat sum (degree days above the base temperature) during the growing season necessary for population persistence (PDD).This parameter is used to calculate the potential number of generations per year that a population can produce and may also act as a limiting condition when a minimum of one generation needs to be completed for the species to survive in a given location.The species must reach the number of degree days set for PDD to complete a generation (Sutherst, Maywald, & Kriticos 2007).

Climate data
The CliMond v1.2 global 10-min gridded climate dataset for 30 years from 1961 to 1990 for CLIMEX modelling was used for simulating present climate scenario (https://www.climond.org).This dataset included average monthly values of minimum and maximum relative air humidity recorded at 9:00 AM and 3:00 PM and monthly totals of precipitation combined with Köppen Geiger climate classification (Köppen 1936Kriticos et al. 2012).CLIMEX 5-min gridded Had_CM3 dataset for 'CLIMEX models and projections for New Zealand' (http://www.b3.net.nz/climenz/) was used for mapping predictions for New Zealand.

CLIMEX model parameters
The parameter values (Table 1) for the 'Compare Locations' module were determined through two approaches.Firstly, we extracted data on the thermal requirements of the TPP from relevant literature sources, specifically Tran et al. (2012).Secondly, we fine-tuned the projected distribution by aligning it with known observations of this species in their native home range in North America and other regions where this pest has been reported successfully established (e.g., New Zealand).

Temperature index
The lower, optimum and maximum temperature thresholds for the development of TPP were initially estimated based on experimental data on thermal development reported by Tran et al. (2012).The authors estimated the lower temperature threshold for development to be 7.1 C by fitting a linear model whereas the optimum temperature range for development was estimated to vary from 26 C to 27 C using nonlinear models.Additionally, they claimed that TPP was able to survive at 31 C in a laboratory study.For our model, these parameters were iterated to match the known distribution of TPP in North America and Mexico.
The limiting lower temperature threshold (DV0) was set to 7 C.The lower optimum temperature (DV1) and upper optimum temperature (DV2) were set to 20 C and 26 C, respectively.The upper-temperature threshold (DV3) was set to 32 C.

Moisture index
The moisture index was set to reflect the moisture availability in the soil.It assumed that soil moisture content is the key factor determining the moisture levels in vegetation and, thereby the microclimate CLIMEX (Sutherst, Maywald, & Kriticos 2007).The native and invasive ranges of TPP overlay the semi-arid to temperate climates according to the Köppen climate classification (Köppen 1936).Hence, the lower soil moisture parameter (SM0) was set to 0.1 to reflect the permanent wilting point of plants (Kriticos et al. 2015), as well as the lowest humidity levels observed in the United States and Mexico (native distribution).The lower optimum soil moisture (SM1), upper optimum soil moisture (SM2) and upper soil moisture (SM3) thresholds were set to 0.5, 1 and 1.5 respectively.

Cold stress
TPP has been observed to be highly cold-tolerant, and nymphs have been observed to tolerate subfreezing temperatures of À15 C in Texas, USA (Henne et al. 2010;Horton et al. 2015).Accordingly, the cold temperature threshold (TTCS) was set to À15 C, and the stress accumulation rate (THCS) was iteratively adjusted to cover the known distribution in the coldest locations in the United States.

Heat stress
Previous thermal development studies of TPP estimated high mortality rates at temperatures above 32 C (Tran et al. 2012;Yang & Liu 2009).Therefore, the heat stress temperature threshold (TTHS) and stress accumulation rate (THHS) were set to 32 C and 0.0003 per week.

Dry stress
The dry stress parameter (SMDS) was set to 0.1, and its accumulation rate (HDS) was adjusted to match the model with semi-arid regions in the United States and Mexico.

Wet stress
The wet stress threshold (SMWS) was set to 1.5 and its accumulation rate (HWS) set to match the wettest areas in the United States and Mexico.

PDD
The minimum annual developmental heat sum for TPP to complete a generation was estimated to be 358 C degree days, based on thermal development studies conducted by Tran et al. (2012).

Irrigation scenario
Irrigation scenario was applied improve the model as irrigation has significant impact for potential distribution of invasive pest (Yonow et al. 2017).This is particularly useful to reflect the presence of species in agricultural and urban lands as a result of irrigation (Sutherst, Maywald, & Kriticos 2007).Therefore, to capture the risk posed by TPP in areas where cropping could be sustained by irrigation practices (i.e., some drier regions of the world), a top-up irrigation of 2.5 mm/day (i.e., to increase the effective rainfall to the set amount) through the year was applied to the model.The composite potential distribution model was built based on an updated version of global irrigation areas reported by Siebert et al. (2013).If a location was irrigated, the EI accounting for irrigation was used; otherwise, the EI accounting only for natural rainfall was used.

Model validation
After setting all the parameters to fit the model to available records within the native region (the United States and Mexico), the model was validated by overlaying the CLIMEX distribution model obtained and known occurrences that were not used to fit the model in the invaded regions (37 occurrences in New Zealand and only 1 known occurrence in Australia).The species geographical distribution locations used in this model are provided as Supporting information.

Climate change scenario
After the CLIMEX parameters were fitted under the current climate conditions and validated, the potential distribution of TPP under future climate change scenarios was simulated worldwide (10-min grid resolution) and for New Zealand (5-min grid resolution).We have selected CSIRO Mark 3.0 general circular model (GCM) model (Gordon et al. 2002), a global climate model as the future climate data.The A1B climate change scenario (a balanced emphasis on all energy sources) was chosen to reflect future climatic conditions (IPCC 2000).The future climate scenario dataset is available in CliMond described by Kriticos et al. (2012) for CSIRO Mark 3 (Gordon et al. 2002) under the A1B emission scenario for the year 2090 was used for this simulation.

RESULTS
The projected potential global distribution of TPP resulting from the parameters described in Table 1 covers 94% of the current global distribution records for this species in its native range (i.e., 372 points out of 394 points), and all known distributions in adventive region fell within the predicted potential.Broadly, semiarid, temperate, continental and oceanic climates were predicted to be climatically suitable for the development of TPP.In contrast, tropical rainforest and monsoon, desert, polar and alpine climates were not.The addition of an irrigation scenario (i.e., non-climatic factor) into our model resulted in a better predicted distribution in the native region than the model considering only natural rainfall (Figure 1a,b).Hence, all model projections (i.e., under current and future climates) in this section are presented based on the simulation of natural rainfall including irrigation.

Native range
The predicted potential distribution of TPP is consistent with most of its known distribution in North and Central America (Figure 2).TPP is predicted to have moderate to optimum climatic suitability for establishment in California, Arizona, Oregon, Texas, and Montana in the USA.In addition, considerable areas of Florida, Georgia, North Carolina, South Carolina, Virginia, Washington DC and New York were also expected to have optimal climatic suitability for TPP.The EI values mostly ranged from moderately suitable (EI = 5-10), highly suitable (EI = 10-25), to optimal suitability (EI ≥ 25) categories in this region (Figure 2).Furthermore, the model predicted that the geographical distribution of TPP could expand to Midwest USA (Ohio, Iowa and Illinois), where the pest is absent at present but where optimum climatic suitability exists.Apart from the known occurrences in Alberta in Canada, the model also estimated that British Columbia was climatically suitable for establishing TPP.In Mexico, our model predicted all the known distribution records to be in highly climatic suitable areas for the establishment of TPP (Figure 2).Similarly, the current model predicted all known distribution records in Guatemala, Honduras, Nicaragua and El Salvador as climatically suitable for establishing TPP (Figure 2).Munyaneza, Crosslin and Buchman (2009) and Butler and Trumble (2012a) have reported restricted distribution for TPP in these countries, also reflected in our model showing areas predicted have an optimal to marginal climatic suitability.

Invasive range
Australasia has recently been identified as a region of invasion by TPP, and current CLIMEX model parameters matched all observed non-native occurrences in this region (Figures 3 and 4).
In Australia, TPP is predicted to expand its current distribution from Western Australia to South Australia, Victoria, New South Wales and Queensland (except far North Queensland).This predicted distribution in Australia ranges from optimal (e.g., Victoria, Tasmania and New South Wales) to marginal (South Australia) climatic suitability categories (Figure 3).
In New Zealand, most areas in the North Island (i.e., Northland, Auckland, Hawkes Bay, Gisborne and Manawatu-Wanganui) and most of the northern, eastern and central regions of the South Island (i.e., Nelson, Marlborough and Canterbury) were predicted to be climatically suitable for the survival of TPP.Climatically suitable areas mostly ranged from moderate to high climatic suitability (Figure 4).

South America
Apart from confirming a recent pest record in Ecuador by this model, it also predicted a larger region of South America to be suitable for establishing TPP (Figure 1).Most western and southern countries in South America are predicted to be climatically suitable for establishing TPP, mainly ranging from optimum to high climatic suitability.

Europe
Europe is currently free of TPP, but the model suggested that this region has high climatic suitability for the potential establishment of TPP.As per model predictions, regions with a temperate-dry summer climate (in western, central and southern Europe) fall under the optimum to higher climatic suitability classes.North and Eastern Europe with temperate-hot summer climates are marginally suitable for TPP survival (Figure 1).

Asia
The current model suggests that most temperate climates in Asia are climatically suitable for TPP.Consequently, Eastern Asia (China, Korea, and Japan) matched optimum and higher suitable climatic classes, while some areas in central Asia showed moderate to marginal suitability (Figure 1).Overall, tropical rainforest and monsoon climates in South and Southeast Asia do not provide an environment suitable for the pest.Africa Some temperate climates in Africa are projected to be climatically suitable for establishing TPP.A narrow region in North Africa and Southern Africa is suggested to be more suitable for TPP with optimum and moderate climate suitability categories.In contrast, arid desert, tropical monsoon and savannah climates were not favourable for TPP in this region (Figure 1).

Model projections under a future climate change scenario
The climate change scenario simulated with A1B emission for the year 2090 showed an overall contraction in the TPP's predicted distribution compared with the current climate, alongside a considerable poleward distribution expansion of the pest (Figure 5).
Within its native North and Central American region, future climate change scenarios suggest TPP would decrease in range and shift towards higher latitudes and areas that are currently too cold for this species.In particular, regions of its range where the pest was initially discovered, in the Rocky Mountains, Colorado, and northern and central Mexico, diminished in size and became moderately suitable or unsuitable for the pest.The USA's midwest, northeast and southeast states exist in the same range.Still, suitability ranges are predicted to shift from optimum to high suitability under the modelled climate change scenario (Figure 6a).Conversely, poleward expansion in Alaska (USA), covering Southeast, Southcentral, Southwest Alaska, and Western Alaska, is highlighted as overlapping with moderate to high suitability categories.Similarly, the Canadian region will expand in size, covering the Canadian shield, Atlantic region (Newfoundland and Labrador), central (Quebec and Ontario) Prairie provinces (Manitoba, Saskatchewan, Alberta), and the west coast of Canada (British Columbia).
Significant contraction in the potential range of TPP was observed in Australia in a future climate change scenario.A dramatic range contraction is projected towards the coastal margins of New South Wales, Victoria, South Australia, South-Western Australia and Tasmania in Australia (Figure 6b).
The model confirmed that warm temperate oceanic climates in New Zealand would remain climatically suitable for the population persistence of TPP in a future climate change scenario (Figure 7).This model suggested that future climatic conditions would be more favourable for TPP in all regions except for the South Island's Tasman, West Coast, and Southland regions.In contrast, expansion of optimum climatic suitability in the North Island (Northland to Auckland and Hawkes Bay to Gisborne) was predicted.In the South Island, the Canterbury region would remain a climatically optimum region for TPP.
In addition to geographical distribution predictions in the native and invasive regions, the future CLIMEX model also suggested striking changes in the predicted distribution for the rest of the world.In South America, climatic suitability was expected to be more restricted to the southern parts of the continent (e.g., Argentina, Chile, Uruguay and Paraguay), which have optimum and moderate climatic suitability categories (Figure 5).
The extent in the European region with suitable climate conditions remains unchanged under the future climate change scenario.Still, a shift of climatic suitability categories from optimum to high and moderate was predicted.Expansion in TPP's potential range towards northern Europe, covering Norway, Sweden and Finland, was also predicted (Figure 5).In Asia, countries in Central, Southern and South-Eastern Asia were deemed unsuitable for a possible invasion.Nevertheless, Eastern Asia persists with favourable climate suitability, but climatic suitability classes are predicted to change from high to moderate climatic category in 2090 (Figure 5).

DISCUSSION
The CLIMEX model developed for TPP provides essential information about the directions and likely changes in the pest's potential climatic suitability under current and future climate changes.TPP is projected to persist well in a range of climatic conditions, including hot and cold semi-arid, Mediterranean, temperate savannah, tropical savannah, continental and oceanic climates.Under current climate models, heat stress and wet stress are the major limiting factors preventing the potential establishment of this species in the tropical rainforest or hot-wet climates, while cold stress limits their survival in subarctic climates.Our model matches well with the current known distribution of TPP in its native (USA and Mexico, Guatemala and Honduras) and invasive (El Salvador, New Zealand and Australia) ranges.Additionally, the model suggests that TPP has the potential to expand into other continents such as South America, Europe, Asia and Africa.Our results closely agree with potential distribution projections made by Wan et al. 2020 using MaxEnt.Both MaxEnt and CLIMEX are widely used ecological niche modelling tools to predict species distributions effectively (Byeon, Jung, & Lee 2018;Huang et al. 2019;Liu & Shi 2020).The MaxEnt software is a correlative model used to find the maximum entropy distribution probability to predict potential distributions considering the primary climate variables that affect the target species.MaxEnt primary uses information on sampling locations of the target species and environment variables (Phillips, Anderson, & Schapire 2006) whereas CLIMEX does not necessarily rely on species occurrence data but uses species climatic requirements and tolerances.CLIMEX provides more opportunities to use species-specific biological data for the model and climatic variables at dynamic daily and weekly intervals (Sutherst, Maywald, & Kriticos 2007).However, potential distribution maps are similar in their coverage of geographical range, and both niche modelling tools have identified Eurasia, North and South America, Africa and Australasia as climatically suitable regions.However, there are substantial differences in climatic suitability classes predicted by the two models due to variation in modelling algorithms, their assumptions and limitations used in defining particular aspects of suitability.The differences in spatial resolutions, as well as the type and time of climate datasets utilised could also be contributing factors that influence this outcome.Max-Ent use WorldClim climatic data with 5 arcmin resolution whereas CLIMEX uses CliMond climatic data with 10-or 30-min resolutions (Kumar, Neven, & Yee 2014).
A climate change scenario simulated for the year 2090 showed an overall significant contraction of the potential distribution of TPP and changing suitability classes from higher to lower climatic categories.Shifts in the known distribution of species are expected to result from climate change (Harrington, Fleming, & Woiwod 2001;Van der Putten, Macel, & Visser 2010;Walther et al. 2002;Yukawa et al. 2007).Our model projections in a climate change scenario showed apparent poleward range shifts, which match predicted hot-summer continental climates at higher latitudes in the future (Bebber, Ramotowski, & Gurr 2013).However, TPP's distribution in the Mediterranean and oceanic climates will remain relatively unchanged in the future with climate warming, including in the United Kingdom, France, Switzerland, the Netherlands, Germany, Poland and Italy.
The effect of climate change on invasive species can be double-edged, with both positive and negative consequences depending on species interactions with the environment (Skendži c et al. 2021).For instance, under the future climate change scenario used in our study (i.e., CSIRO Mark 3 under the A1B emission scenario for the year 2090), New Zealand is predicted to be more climatically suitable for TPP's survival, while Australia is predicted to be less climatically suitable.
Both of our CLIMEX models (i.e., current and future climate scenarios) will provide valuable information to develop or improve the current management strategies for TPP.Our model showed that the world's largest-scale potato producers (i.e., China, Russia, Ukraine, Germany, France, Poland and the Netherlands (FAOSTAT 2021)), which are currently free of TPP, are expected to have optimal and high climatic suitability for TPP under current climatic conditions.Therefore, the information provided from our model's predictions can assist biosecurity authorities in developing appropriate strategies to manage the risk posed by this invasive species.Authorities in high-risk countries may evaluate options to strengthen biosecurity measurements to prevent pest entry.Whereas New Zealand, for example, could use the model predictions to develop future pest management strategies as TPP is an injurious pest to control with current management practices (Vereijssen 2020).
It is paramount to have a thorough understanding of all variables that may define the geographical distributions of invasive species when attempting to predict their current potential range and future dispersal (Taylor & Kumar 2013).For example, host availability, dispersal capacity, competition, the effect of natural enemies, habitat preferences and landscape can have significant roles in defining the new geographical range of invasive species once they have arrived in a new environment (Patrick & Olckers 2014).
CLIMEX and other niche modelling software have some restrictions because they only use climate-related features and meteorological data and do not incorporate non-climatic factors, such as dispersal capacity and host availability when modelling predictions (Baker et al. 2000;Kriticos et al. 2015;Saavedra et al. 2015).The spatial scale and resolution are also critical factors to consider when assessing risk and predicting potential distribution of species using niche modelling software (Xie et al. 2022).
Nevertheless, the models presented in this study have provided valuable information on the potential and future geographical distribution of TPP globally.This information can be used to assist biosecurity programmes such as identifying high-risk areas and potential entry pathways, designing a grid for detection traps, field surveys and monitoring.Climate change implications for biosecurity are also important with the shifting ); Munyaneza, Crosslin and Upton (2007); Munyaneza, Crosslin and Buchman (2009); Munyaneza et al. (2013); Olaniyan et al. (2020); Teulon et al. (2009); Thomas et al. (2011); Wan et al. (2020) were also considered.
T A B L E 1 CLIMEX parameters used for modelling the potential distribution of tomato potato psyllid (TPP), Bactericera cockerelli.heat sum/PDD Number of degree-days above DV0 necessary to complete one generation 358 C

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I G U R E 1 Predicted global climatic suitability (ecoclimatic index) for tomato potato psyllid (TPP; Bactericera cockerelli under current climatic conditions using the adjusted parameters given in Table1under (a) natural rainfall and (b) as composite of natural rainfall and irrigation based on areas identified bySiebert et al. (2013).The known global distributions are denoted by green colour dots.

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I G U R E 2 Predicted global climatic suitability for tomato potato psyllid (TPP; Bactericera cockerelli) under current climatic conditions in its native region in North America.The known global distributions are denoted by green colour dots.

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I G U R E 3 Predicted climatic suitability for tomato potato psyllid (TPP; Bactericera cockerelli) under current climatic conditions in Australia current climatic conditions.The known global distributions are denoted by green colour dots.

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I G U R E 4 Predicted climatic suitability for tomato potato psyllid (TPP; Bactericera cockerelli) under current climatic conditions in New Zealand under current climatic conditions.The known global distributions are denoted by green colour dots.

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I G U R E 5 Predicted global climatic suitability for tomato potato psyllid (TPP; Bactericera cockerelli) under a future climate change scenario predicted to the year 2090 in CLIMEX using the general circular model (GCM) CSIRO Mark 3.0, run with the A1B emissions scenario.F I G U R E 6 Predicted future climatic suitability for tomato potato psyllid (TPP; Bactericera cockerelli) in (a) its native range in North America, and (b) its invasive regions in Australia under a future climate change scenario predicted to the year 2090 in CLIMEX using the general circular model (GCM) CSIRO Mark 3.0, run with the A1B emissions scenario the known global distributions denoted by green colour dots.ofpest ranges.Our study contributes to raising the awareness of the potential distribution of TPP and CLSo and thereby may assist regulatory agencies in prioritising actions that may minimise the possible threat of TPP to global agriculture.We further suggest the importance of long-term monitoring to validate and update the model's continuously, ensuring its accuracy and effectiveness over time.

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I G U R E 7 Predicted future climatic suitability for tomato potato psyllid (TPP; Bactericera cockerelli) in New Zealand under a future climate change scenario predicted to the year 2090 in CLIMEX using the general circular model (GCM) CSIRO Mark 3.0, run with the A1B emissions scenario.The known global distributions denoted by green colour dots.