Comparison of the community composition of aquatic insects between wetlands with and without the presence of Procambarus clarkii: a case study from Japanese wetlands.
The red swamp crayfish Procambarus clarkii (Cambaridae) has been introduced globally and has caused enormous biodiversity losses in freshwater ecosystems. Recently, this invasive species has been acknowledged as factor causing the decline of aquatic insect populations (Odonata, Hemiptera, and Coleoptera) in Japan. Although the negative impacts of P. clarkii on aquatic insect communities have been validated by observational studies and laboratory experiments, field studies have not yet been performed. In this study, we investigated whether the presence of P. clarkii was a significant factor influencing the community composition of aquatic insects and identified vulnerable taxa by comparing the aquatic insect communities in wetlands invaded by P. clarkii and uninvaded wetlands. We recorded a total of 52 species and 2721 individuals: 50 species and 2405 individuals in non-invaded wetlands, and 23 species and 316 individuals in invaded wetlands. This indicates that the aquatic insect diversity of non-invaded wetlands was higher than that of invaded wetlands. The composition of aquatic insect communities differed between the invaded and non-invaded wetlands. The effect of P. clarkii on aquatic insects differed according to their habit-related traits: species that utilize on the water surface and float near the water surface was less vulnerable than those that utilize aquatic plants as food, oviposition substrates, and perches and hide in the bottom substrate. The eradication of P. clarkii at the early stages of invasion, as well as the prevention of its spread in invaded ecosystems is essential to prevent negative impacts on aquatic insects.