Integrating Morphological, Molecular, and Climatic Evidence to Distinguish Two Cryptic Rice Leaf Folder Species and Assess Their Potential Distributions

The larvae and damage symptoms of <i>Cnaphalocrocis medinalis</i> and <i>Cnaphalocrocis patnalis</i> exhibit a high degree of similarity, which often leads to confusion between the two species. This has posed challenges for research on their population dynamics and the development of effective control measures. To better understand their morphological and damage characteristics, population dynamics, species identification based on <i>COI</i> gene fragments, and potential future distribution, a searchlight trap monitoring program was conducted for <i>C. medinalis</i> and its closely related species <i>C. patnalis</i> across four sites in Longhua, Haitang, and Yazhou districts in Hainan Province from 2021 to 2023. The MaxEnt model was utilized to predict the potential global distribution of both species, incorporating known occurrence points and climate variables. The trapping results revealed that both species reached peak abundance between April and June, with a maximum of 1500 individuals captured in May at Beishan Village, Haitang District. Interannual population fluctuations of both species generally followed a unimodal pattern. Genetic analyses revealed distinct differences in the mitochondrial <i>COI</i> gene fragment, confirming that <i>C. medinalis</i> and <i>C. patnalis</i> are closely related yet distinct species. The population peak of <i>C. patnalis</i> occurred slightly earlier than that of <i>C. medinalis</i>, and its field damage was more severe. Infestations during the booting to heading stages of rice significantly reduced seed-setting rates and overall yield. Model predictions indicated that large areas of southern Eurasia are suitable for the survival of both species, with precipitation during the wettest month identified as the primary environmental factor shaping their potential distributions. At present, moderately and highly suitable habitats for <i>C. medinalis</i> account for 2.50% and 2.27% of the global land area, respectively, whereas those for <i>C. patnalis</i> account for 2.85% and 1.19%. These results highlight that climate change is likely to exacerbate the damage caused by both rice leaf-roller pests, particularly the emerging threat posed by <i>C. patnalis</i>. Overall, this study provides a scientific basis for invasion risk assessment and the development of integrated management strategies targeting the combined impacts of <i>C. medinalis</i> and <i>C. patnalis</i>.