Abstract
ABSTRACTLife history theory predicts that females should produce few large eggs under food stress and many small eggs when food is abundant. We tested this prediction in three female-biased size-dimorphic predatory mites feeding on herbivorous spider mite prey: Phytoseiulus persimilis, a specialized spider mite predator; Neoseiulus californicus, a generalist preferring spider mites; Amblyseius andersoni, a broad diet generalist. Irrespective of predator species and offspring sex, most females laid only one small egg under severe food stress. Irrespective of predator species, the number of female but not male eggs decreased with increasing maternal food stress. This sex-specific effect was probably due to the higher production costs of large female than small male eggs. The complexity of the response to the varying availability of spider mite prey correlated with the predators' degree of adaptation to this prey. Most A. andersoni females did not oviposit under severe food stress, whereas N. californicus and P. persimilis did oviposit. Under moderate food stress, only P. persimilis increased its investment per offspring, at the expense of egg number, and produced few large female eggs. When prey was abundant, P. persimilis decreased the female egg sizes at the expense of increased egg numbers, resulting in a sex-specific egg size/number trade-off. Maternal effects manifested only in N. californicus and P. persimilis. Small egg size correlated with the body size of daughters but not sons. Overall, our study provides a key example of sex-specific maternal effects, i.e. food stress during egg production more strongly affects the sex of the large than the small offspring.
Highlights
How should a female cope with food limitation during the reproductive phase? Life history theories predict that females should flexibly respond to food limitation and adjust their reproduction to the prevailing environmental conditions to optimize their own and offspring fitness (Roff, 1992; Stearns, 1992)
When provided with 9 spider mites, significantly fewer A. andersoni females produced eggs compared with P. persimilis and N. californicus females (Fig. 1A)
The level of adaptation to maternal food stress and the complexity of maternal response corresponded with the degree of specialization on spider mite prey in the three predator species
Summary
How should a female cope with food limitation during the reproductive phase? Life history theories predict that females should flexibly respond to food limitation and adjust their reproduction to the prevailing environmental conditions to optimize their own and offspring fitness (Roff, 1992; Stearns, 1992). Food-stressed females commonly shift energy from current reproduction to their own survival and future reproduction by reducing offspring number Food-stressed females could only reduce the egg size of the larger sex, resulting in sex-specific phenotypic changes of offspring body size at maturity
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