Giant African snail invasion homogenizes seasonal soil biodiversity in tropical coral islands

Background and aims Biological invasions have tremendous effects on soil biodiversity. Although the effects of invasive plants on soil biota have been widely investigated, how soil fauna invasion affects native soil biodiversity in island ecosystems remains unclear. Methods Field survey in non-invaded and invaded sites was conducted to investigate the effects of the giant African snail invasion on native soil biodiversity on tropical coral islands. Results The effects of snail invasion on native soil biodiversity were strongly dependent on sampling seasons. Fungal biomass, microbial diversity, and nematode abundance (except omnivores/predators) increased by snail invasion in the dry season but decreased in the wet season. Mite abundance and diversity increased, whereas the activities of β-1,4-glucosidase, β-D-cellobiosidase, β-N-acetyl-glucosaminidase, and alkaline phosphatase decreased by snail invasion in both dry and wet seasons. Snail invasion homogenized the seasonal community composition of nematodes, the fungi: bacteria ratio (F: B ratio), and the Gram-positive: Gram-negative bacteria ratio (GP: GN ratio). These results together indicate that snail invasion does not have greater effects on soil biota at lower trophic levels but also has great effects on those at higher trophic levels. Soil moisture, soil organic carbon, available phosphorus, and potassium were important factors explaining the variation of soil biodiversity under snail invasion. Conclusion These results together indicate that alien snail invasion weakens the seasonal variation of native soil biodiversity by altering soil resource availability. Such information is valuable for improving our understanding of the ecological consequences of alien organism invasion on soil biodiversity in tropical coral islands.