Abstract
Thelytokous Wolbachia-infected Trichogramma spp. are widely used egg parasitoids against lepidopteran pests in biological control programs. Wolbachia may manipulate host wasps for superparasitism and is sensitive to temperature. To explore effects of temperature and superparasitism, we compared fitness parameters and Wolbachia-mediated phenotype of thelytokous Wolbachia-infected Trichogramma dendrolimi between those emerging from superparasitised or single-parasitised hosts at 17, 21, 25, or 29 °C. Infected mothers of T. dendrolimi showed reduced superparasitism and parasitism increased with temperature. Wolbachia titre decreased with temperature when females emerged from singly-parasitised hosts, but there was no correlation in superparasitised hosts. Females showed higher Wolbachia titres at 21, 25, or 29 °C when developing from superparasitised hosts. The daily male ratio of offspring increased with temperature, and the day-age threshold for 5%, 50%, or 95% daily male ratio decreased with temperature in both parasitism forms. Females that emerged from superparasitised hosts had a shorter life span and reduced fecundity. These results indicate that Wolbachia may affect host behaviour by increasing superparasitism to enhance its spread, but this has negative effects on thelytokous Wolbachia-infected T. dendrolimi.
Highlights
Due to the interaction of Wolbachia and their host wasps, the biological characteristics of thelytokous Wolbachia-infected Trichogramma may be strongly influenced by both abiotic and biotic factors
Host eggs were reared until wasp emergence, and the penetrance of Wolbachia-mediated parthenogenesis and fitness parameters of T. dendrolimi offspring were evaluated at each temperature and parasitism form
Wolbachia-infected mothers of T. dendrolimi showed a higher parasitism rate and lower proportion of superparasitism at higher temperatures, and Wolbachia titres decreased with temperature in normal conditions
Summary
Due to the interaction of Wolbachia and their host wasps, the biological characteristics of thelytokous Wolbachia-infected Trichogramma may be strongly influenced by both abiotic and biotic factors. Reduction of Wolbachia titre and/or reduced penetrance of hosts can occur under high[13,14] or low temperatures[13,15]. Thelytokous Trichogramma may encounter fluctuating temperature in a day or across seasons, and Wolbachia and its host manipulation may be affected. Since determination of superparasitism in C. cephalonica is straightforward, we used its eggs in this study In this stdy, the female wasps were supplied with C. cephalonica eggs at 17 °C, 21 °C, 25 °C, and 29 °C, respectively. We determined single-parasitism and superparasitism rates in host eggs based on the number of offspring per egg. Following this, host eggs were reared until wasp emergence, and the penetrance of Wolbachia-mediated parthenogenesis and fitness parameters of T. dendrolimi offspring were evaluated at each temperature and parasitism form
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