Lifetime Nutrient Dynamics Reveal Simultaneous Capital and Income Breeding in a Parasitoid

Abstract

Models of host handling decisions and physiologically structured host–parasitoid population dynamics make diverging assumptions, untested as of this writing, about the allocation rules of nutrients to survival and reproduction. Our aim is to develop a data‐rich multidimensional dynamical budget of nutrient acquisition and allocation in survival and reproduction in the host‐feeding, synovigenic bruchid ectoparasitoid Eupelmus vuilletti (Hymenoptera: Eupelmidae) over the entire lifetime of the animal in order to address the above questions. We quantified sugar, glycogen, protein, and lipid reserves of single females at birth and death and their daily maintenance needs. We recorded each host‐feeding and oviposition event over entire lifetimes and quantified the amounts acquired and invested in eggs using microcolorimetric techniques. We then built two nutrient budgets, with and without hosts, encompassing 20 measured biochemical parameters and tested their predictions using time of death. Carbohydrate reserves are burned at a high rate for maintenance and can be used to predict lifetime in absence of hosts. The model without hosts is adequate, but the one with hosts is not, as it predicts a continuous increase of proteins from the massive host‐feeding intake, contrasting with the observed decline. A good prediction of time of death could be achieved in that model by assuming that the large amounts of ingested proteins and carbohydrates from host‐feeding are used for maintenance, thereby enabling females to spare lipids for reproduction. We tested this assumption in a treatment with hosts and supplemental sugars, in which the maximal number of produced eggs is expected to be almost exclusively a function of lipids when other nutrients can be obtained to cover maintenance costs. Our results enable us to discriminate between competing hypotheses about nutrient allocation in models of parasitoid behavior and host–parasitoid population dynamics. They show that E. vuilletti is both a capital breeder for lipids and an income breeder for sugars, implying that this dichotomy is best superseded by a multidimensional and dynamical approach to nutrient acquisition and allocation.

How to get the most bang for your buck: the evolution and physiology of nutrition-dependent resource allocation strategies

“…In only a very few cases have resource acquisition and allocation been successfully estimated in terms of energy units (e.g. [13][14][15][16]). In the majority of studies, these patterns must instead be inferred indirectly from phenotypic patterns.…”

Life-history plasticity in female threespine stickleback

“…Stickleback emerge from a 5-6-month winter in early May in Alaska, and have 0.5-1.0 months to regenerate lipid stores and liver glycogen for reproduction. Thus, depending on their energy state emerging from the winter, and earlyseason food quantity, females may enter the reproductive period with varying levels of reproductive capital that then may cue plastic adjustments in traits that depend critically on energy flow for reproduction (Madsen and Shine, 1999;Casas et al, 2005).…”

Sustenance and Performance: Nutritional Reserves, Longevity, and Contest Outcomes of Fed and Starved Adult Parasitoid Wasps

“…In common with other parasitoids (Ellers, 1996;Eijs et al, 1998;Casas et al, 2005;Jervis et al, 2008;Visser and Ellers, 2008), G. legneri adults lack de novo lipogenesis (Visser et al, 2010) and adults are thus limited to utilizing fat reserves accumulated throughout larval development. In many species of parasitoids, adults acquire nutrients from feeding on plant nectar, honey dew and host haemolymph (Jervis et al, 1993;Eijs et al, 1998;Giron et al, 2002;Visser and Ellers, 2008) and decline in lipid reserves can be slower when carbohydrate and lipid-rich diets are available (Ellers, 1996;Heimpel et al, 1997;Lee et al, 2004;Wäckers et al, 2006;Winkler et al, 2006;Desouhant et al, 2010;Ellers et al, 2011;Gómez et al, 2012;Harvey et al, 2012).…”