Potential Geographic Distribution and Suitable Area of Three Species of Diabrotica (Coleoptera: Chrysomelidae) Beetles in Corn-Planting Regions of China

Corn rootworms of <i>Diabrotica virgifera virgifera</i> Le Conte, 1868; <i>Diabrotica undecimpunctata howardi</i> Barber, 1947, and <i>Diabrotica barberi</i> R.F. Smith & Lawrence, 1967 are important pests of corn crops that natively occur in America and have a potential risk of spreading into China through natural spreading or anthropogenic invasion. In this study, the potential geographic distribution and suitable area of these three <i>Diabrotica</i> species based on their global distribution samples and relevant bioclimatic variables were estimated, and an overlay analysis was further carried out in combination with the actual distribution of corn-growing regions, especially in China, in order to assess the potential invasion risks of these <i>Diabrotica</i> beetles, especially in the corn-planting regions of China. The results indicated that six bioclimatic variables (i.e., bio2 (mean diurnal range), bio4 (temperature seasonality), bio5 (max temperature of the warmest month), bio6 (min temperature of coldest month), bio13 (precipitation of wettest month), and bio14 (precipitation of driest month)) were selected for the analysis of the potential geographic distribution and suitable areas of these <i>Diabrotica</i> beetles. The suitable area ranges of <i>D. undecimpunctata</i> and <i>D. virgifera virgifera</i> are relatively large in China, i.e., 21.01-48.46° N and 74.01-131.26° E for <i>D. undecimpunctata</i> and 21.58-41.42° N and 78.71-124.43° E for <i>D. virgifera virgifera</i>, respectively, while <i>D. barberi</i> occupies only a small area in China, i.e., 34.21-46.81° N and 108.80-133.75° E. Based on the overlay analysis of the potential geographic distribution of these three <i>Diabrotica</i> species and the actual distribution of corn-growing regions in China, <i>D. undecimpunctata</i> and <i>D. virgifera virgifera</i> have the largest potential geographic distribution areas, totaling 2.618 × 10⁷ ha and 1.814 × 10⁷ ha in 22 and 20 provinces respectively, while <i>D. barberi</i> has the lowest potential geographic distribution area just in 8 provinces, totaling 44.37 × 10⁴ ha, indicating a low-suitability area. Moreover, under the four climate scenarios (i.e., SSP1_2.6, SSP2_4.5, SSP3_7.0, and SSP5_8.5) in the 2030s and 2050s, these <i>Diabrotica</i> beetles have the potential for sporadic increases or decreases surrounding the potential suitable areas under the current scenario. However, it is worth noting that the high-suitability areas of <i>D. undecimpunctata</i> and <i>D. virgifera virgifera</i> decreased, and their medium- and low-suitability areas increased accordingly. It is presumed that <i>Diabrotica</i> beetles, especially <i>D. virgifera virgifera</i> and <i>D. undecimpunctata</i>, have a high risk of potential invasion into China because there is a large potentially suitable area distribution for their possible occurrence in the maize-planting regions of China.