Abstract:

Aims: The red imported fire ant (RIFA), Solenopsis invicta, is one of the world’s worst invasive species, both environmentally and ecologically. In this study, we aim to analyze the spatial pattern of RIFA and the interactive mechanism of driving factors of its population density in island cities.
Methods: We used the Haitan Island as an example, the biggest island in Fujian Province, to analyze the spatial pattern of RIFA populations using Kernel density estimation and spatial autocorrelation models. We also used geographical detector to elucidate the individual and interactive effects of both environmental factors (8 types) and socio-economic factors (10 types) on RIFA prevalence.
Results: The spatial density of RIFA populations in the study area was characterized by uneven distribution, with the highest population density occurring in farmland (high-high aggregation), followed by landscaping and greening land (high-low and low-low aggregation), and the lowest density around residential areas. There were positive spatial autocorrelations within the population range. The q value for the interpretation of 18 impact factors on the spatial differentiation ranged from 0.014 to 0.278. Overall, there were differences between the effects of the two types of factors on RIFA occurrence, and the mean q value of the socio-economic factors were higher than those of the environmental factors. The socio-economic factors that had the greatest impact on RIFA occurrence were rural population size (q = 0.278) and township area (q = 0.268). The soil classification (q = 0.172) and average annual precipitation (q = 0.149) were stronger than other environmental factors. The interaction between township area and distance to nearby scenic spot, and average annual precipitation and distance to nearby scenic spot, had the greatest impact on the occurance of RIFA (q = 0.466). The combined effect of environmental and socio-economic factors positively enhanced the occurance of RIFA.
Conclusion: Our study indicates that agricultural cultivation, seedling introduction in urban greening construction, and transportation significantly affect the spatial pattern of RIFA prevalence in island cities. As far as its prevention and control strategy is concerned, we should not only implement strict plant quarantine regulations on imported seedlings and cargo, but also take locally-appropriate measures to effectively reduce the population size and prevent the spread of RIFA.

Key words: Solenopsis invicta, island cities, spatial pattern, geographic detector, Haitan Island