Environmentally Based Maternal Effects are the Primary Factor in Determining the Developmental Response of Gypsy Moth (Lepidoptera: Lymantriidae) to Dietary Iron Deficiency

Abstract

We investigated the inheritance of the developmental response of 2 laboratory substrains of Lymantria dispar L. to dietary iron bioavailability. The total phenotypic variance in instar at 10 d was higher for progeny of parents reared on diet containing crystalline FePO4 than for progeny of parents reared on diet containing amorphous FePO4, regardless of the form of FePO4 used in the progeny diet or rearing site. The variability in developmental response of larvae to dietary iron bioavailability was caused primarily by a nutritionally-based maternal effect. Twenty-seven to 28% of the total phenotypic variance can be attributed to maternal effects when both parent and progeny are reared on iron-deficient diet. The female parent's physiological response to diet quality, specifically the amount of FePO4 in the amorphous form, determines the quantity or quality (or both) of the non-nuclear contribution she makes to her offspring. This contribution influences the potential for expression of genetic variation in iron requirements and phenotypic plasticity. The estimated heritability of larval developmental rate during the 1st 10 d was highest for those reared on diets deficient in iron. When both parents and progeny were reared on diet containing crystalline FePO4, 20-40% of the total variance was estimated to be caused by additive genetic effects, compared with 6-15% when both generations were reared on diet containing amorphous FePO4. When dietary iron is deficient for successive generations, it has many direct and indirect effects on critical components of population growth that could influence the population dynamics of gypsy moth. The bioavailability of iron in foliage and factors that could affect it may play a role in the population dynamics of gypsy moths.