Host plant quality mediates dispersal, oviposition, and sex allocation in a Tetranychus spider mite

Dispersal is a key adaptative strategy to escape deteriorating environments, and habitat selection by dispersers is critical to their own and offspring fitness. Using the haplodiploid spider mite Tetranychus ludeni Zacher as a model species, this study investigated how host plant quality influenced dispersal probability, habitat selection, and subsequent reproductive performances of mated females. We designed two dispersal scenarios, i.e., females were allowed to disperse from low-quality (LQ) or high-quality (HQ) habitat and select between LQ and HQ habitats. Results show that significantly more females dispersed from LQ habitats than from HQ habitats, and dispersers significantly preferring and settling in HQ habitats regardless of the dispersal scenarios. However, aggregating in HQ habitats resulted in higher number of eggs cumulated but also increased immature mortality. Individual females restrained reproductive output under the deteriorating environments. Egg size had no significant effect on egg hatching or immature survival. Females dispersed from LQ habitats produced significantly smaller eggs but maintained similar proportion of daughters compared to those remaining in LQ habitats. Females dispersed from HQ habitats produced eggs of similar size but significantly higher proportion of daughters. These results suggest that dispersing females might manipulate offspring sex ratio by lowing the fertilization threshold to fertilise relatively smaller eggs. Population density has less impact on egg size and offspring sex ratio. This study delivers insights into the dispersal and reproductive strategies of a haplodiploid spider mite, highlighting how host quality shapes adaptive responses in challenging environments.