Predicting potential distribution areas of wheat stem sawfly (Cephus pygmeus (L.) (hymenoptera: cephidae) under climate change

Wheat stem sawfly Cephus pygmeus (L.) is a significant pest exerting adverse impacts on wheat yields globally. Global climate changes are mediating changes in the distribution of different pest species resulting in complex pest problems. Predicting the changes in the distribution of pest species through species distribution models and adopting precautionary measures could help in the maangement of range-shifting species. This study predicted the global habitat suitability of wheat stem sawfly (WSS) using maximum entropy (MaxEnt) model. Global occurrence records of the species were gathered from GBIF and various other sources and cleaned resulting in a dataset of 641 occurrence records. The values of 19 bioclim variables were extracted to the final occurrence records and Pearson correlation was computed among the extracted values. The variables with correlation scores >0.70 were eliminated. However, the variables with higher contribution towards the model and correlation coefficient >0.70 were retained. A total of 10 variables (i.e., bio3, bio4, bio5, bio6, bio8, bio11, bio13, bio14, bio16 and bio19) were used to predict the habitat suitability of WSS under current and future climatic conditions. The future habitat suitability of WSS was predicted under two climate change scenarios, i.e., SSP1-2.6 (moderate climate change scenario) and SSP5-8.5 (severe climate change scenario). The model was trained on 70% of the data and tested on the remaining 30%. The results revealed that model predicted the habitat suitability of WSS with high accuracy (ROC = 0.97). The model predicted that Europe (Germany, France, Netherlands, and Belgium), United Kingdom, Turkey and Kazakhstan had the highest suitable areas for the species under current and future climatic conditions. The model indicated that habitat suitability of WSS would be decreased by 6.20%, 17.61%, 3.28%, and 20.56% during 2021-2040, 2041-2060, 2061-2080, and 2081-2100, respectively under moderate climate change scenario. Similarly, habitat suitability will observe a decline by 31.70% during 2021-2040 and 27.97% duing 2061-2080 under severe climate change scenario. Contrastingly, the suitable habitat will observe an increase of 2.10% during 2041-2060 and 3.09% during 2081-2100 under severe climate change scenario. The model predicted that suitable habitat will be contracted globally, while there will be rare niche shifts. The southeastern side of Turkey will have the highest suitable habitat under current and future climatic conditions of the country. The model revealed that the species would not experience dramatic niche shifts. Therefore, management strategies should be concentrated in the areas having the highest suitable habitat.