Adaptation of acaricide stress facilitates <i>Tetranychus urticae</i> expanding against <i>Tetranychus cinnabarinus</i> in China

Abstract

The two-spotted spider mite, <i>Tetranychus urticae</i>, and the carmine spider mite, <i>Tetranychus cinnabarinus</i>, are invasive and native species in China, respectively. Compared with <i>T. cinnabarinus</i>, <i>T. urticae</i> has expanded into most parts of China and has become the dominant species of spider mite since 1983, when it was first reported in China. However, the mechanism of the demographic conversion has not been illuminated. In this study, one <i>T. urticae</i> field population and one <i>T. cinnabarinus</i> field population were isolated from the same plant in the same field, and the toxicological characteristics were compared between these two species. Laboratory bioassays demonstrated that <i>T. urticae</i> was more tolerant to commonly used acaricides than <i>T. cinnabarinus</i>. The activities of detoxification enzymes were significantly greater in <i>T. urticae</i>, and the fold changes of enzymes activities in <i>T. urticae</i> were also greater following exposure to acaricides. Furthermore, more metabolism-related genes were upregulated at a basal level, and more genes were induced in <i>T. urticae</i> following exposure to acaricides. The comparison of proteins and genes between both species led credence to the hypothesis that <i>T. urticae</i> was more resistant to acaricides, which was the reason explaining the expansion of invasive <i>T. urticae</i> against native <i>T. cinnabarinus</i>. Laboratory simulation experiments demonstrated that following the application of acaricides, the composition of a mixed <i>T. urticae</i>/<i>T. cinnabarinus</i> population would change from a <i>T. cinnabarinus</i>-dominant to a <i>T. urticae</i>-dominant population. This study not only reveals that <i>T. urticae</i> possesses stronger detoxification capacity than its sibling species <i>T. cinnabarinus</i>, which facilitated its persistent expansion in China, but also points to the need to accurately identify <i>Tetranychus</i> species and to develop species-specific management strategies for these pests.