Life-History Consequences of Chronic Nutritional Stress in an Outbreaking Insect Defoliator

Abstract

Food shortage is a common situation in nature but little is known about the strategies animals use to overcome it. This lack of knowledge is especially true for outbreaking insects, which commonly experience nutritional stress for several successive generations when they reach high population densities. The aim of this study is to evaluate the life history consequences of chronic nutritional stress in the outbreaking moth Choristoneura fumiferana. Larvae were reared on two different artificial diets that emulate nutritional conditions larvae face during their natural population density cycle (low and medium quality artificial diets). After four generations, a subset of larvae was fed on the same diet as their parents, and another on the opposite diet. We explored larval life-history strategies to cope with nutritional stress, its associated costs and the influence of nutritional conditions experienced in the parental generation. We found no evidence of nutritional stress in the parental generation increasing offspring ability to feed on low quality diet, but the contrary: compared to offspring from parents that were fed a medium quality diet, larvae from parents fed a low quality diet had increased mortality, reduced growth rate and reduced female reproductive output. Our results support a simple stress hypothesis because the negative effects of malnutrition accumulated over successive generations. Density-dependent deterioration in plant quality is thought to be an important factor governing the population dynamics of outbreaking insects and we hypothesize that chronic nutritional stress can be a driver of outbreak declines of C. fumiferana, and of forest insects in general.

Maternal and paternal nutrition in a mosquito influences offspring life histories but not infection with an arbovirus

“…In holometabolous insects, both larval and adult nutrients, acquired through feeding or transferred during mating, can influence reproduction (Boggs 1997, Rivero et al 2001). Nutrition has also been linked to parental effects on a variety of different offspring traits in insects including fecundity (Futuyma et al 1993, Grech et al 2007, Frago and Bauce 2014, feeding strategy (Grech et al 2007), growth rate (Rotem et al 2003, Franzke and Reinhold 2012, Valtonen et al 2012, Frago and Bauce 2014, size (Franzke andReinhold 2012, Cahenzli andErhardt 2013), and immunity (Boots and Roberts 2012).…”

Transgenerational effects of nutrition are different for sons and daughters

“…However, studies in the context of food availability have returned mixed results in both invertebrates and vertebrates (see e.g. Franzke & Reinhold, 2013;Uller et al, 2013;Frago & Bauce, 2014;Giordano et al, 2014). Thus, the debate whether a mismatch between parental and offspring environments generates adverse effects in the offspring is still open.…”

Adaptation of an outbreaking insect defoliator to chronic nutritional stress

“…The second diet had a lower sugar (1.5%) and a higher nitrogen content (7%). This diet induces detrimental impact on insect survival and development representative of conditions found at the end of an outbreak (Bidon, ; Frago & Bauce, ) and will hereafter be referred to as low‐quality diet. Lower nitrogen contents have been shown to induce very high mortality (close to 100%; Bidon, ) and were therefore not suitable for this study.…”

“…Larval developmental time was counted in days from larval emergence after hibernation until the pupal stage. Pupal mass was taken as fresh weight 24 h after pupation with a precision of 0.1 mg. Growth rate was calculated as described in detail by Frago & Bauce () to measure the efficiency of individuals to use developmental time to reach adult mass. Realized fecundity was measured by counting the total number of eggs produced by a female, and fecundity by counting all viable eggs.…”