Combined effects of elevated CO₂ concentration and Wolbachia on Hylyphantes graminicola (Araneae: Linyphiidae)

The increasing concentration of carbon dioxide in atmosphere is not only a major cause of global warming, but it also adversely affects the ecological diversity of invertebrates. This study was conducted to evaluate the effect of elevated CO₂ concentration (ambient, 400 ppm and high, 800 ppm) and Wolbachia (Wolbachia-infected, W⁺ and Wolbachia-uninfected, W^-) on Hylyphantes graminicola. The total survival rate, developmental duration, carapace width and length, body weight, sex ratio, net reproductive rate, nutrition content, and enzyme activity in H. graminicola were examined under four treatments: W^- 400 ppm, W^- 800 ppm, W⁺ 400 ppm, and W⁺ 800 ppm. Results showed that Wolbachia-infected spiders had significantly decreased the total developmental duration. Different instars showed variations up to some extent, but no obvious effect was found under elevated CO₂ concentration. Total survival rate, sex ratio, and net reproductive rate were not affected by elevated CO₂ concentration or Wolbachia infection. The carapace width of Wolbachia-uninfected spiders decreased significantly under elevated CO₂ concentration, while the width, length and weight were not significantly affected in Wolbachia-infected spiders reared at ambient CO₂ concentration. The levels of protein, specific activities of peroxidase, and amylase were significantly increased under elevated CO₂ concentration or Wolbachia-infected spiders, while the total amino content was only increased in Wolbachia-infected spiders. Thus, our current finding suggested that elevated CO₂ concentration and Wolbachia enhance nutrient contents and enzyme activity of H. graminicola and decrease development duration hence explore the interactive effects of factors which were responsible for reproduction regulation, but it also gives a theoretical direction for spider's protection in such a dynamic environment. Increased activities of enzymes and nutrients caused by Wolbachia infection aids for better survival of H. graminicola under stress.