Acquisition and allocation of nutrients across life stages: Can nectar-feeding compensate for nutritional deficiencies from the larval diet in Pieris rapae butterflies?

Insect pollinators typically feed on floral nectar throughout their adult lives. A growing number of studies indicate that nutrients in nectar may be as important as larval-derived reserves to support different adult functions, including flight and reproduction. For example, carbohydrates in nectar provide the energy necessary to fuel flight and also contribute to the synthesis of nonessential amino acids for egg production. Importantly, floral nectars also contain small amounts of essential and nonessential amino acids. Consequently, nutrient deficiencies in the larval stage, which often lead to resource allocation tradeoffs in the adult, might be compensated with the subsequent acquisition and allocation of nectar nutrients, especially if nectar-derived essential amino acids are used. In this study, we manipulated both the larval and adult diets, and used stable isotope techniques to determine whether nectar-feeding by adult Pieris rapae butterflies ameliorates resource nutritional deficiencies imposed by a low-nitrogen larval diet. Results revealed that effects of a low nitrogen diet, which include flight-fecundity tradeoffs, might be compensated with the subsequent acquisition and allocation of nectar nutrients. Our results provide new insights into the functional physiology of tradeoffs and the importance of examining acquisition and allocation of nutrients as dynamic processes that may change continually across an organism’s life.