The effects of variable larval and adult nutrition on the fecundity and longevity of Vanessa cardui L. (Lepidoptera: Nymphalidae)

Nectar has historically been thought to be an energy rich reward for foraging pollinators. Recent studies have shown that nectar-derived amino acids benefitted female fecundity when females were reared on low quality larval diet, based on leaf nitrogen content. The aim of this study was to determine the relative importance of larval and adult dietary nutrient intake on Vanessa cardui fitness through the use of artificial diets. This study specifically addressed the importance of larval protein and carbohydrate intake, and adult carbohydrate and amino acid intake on overall female fecundity and longevity. I determined that overall adult nutrition plays a greater role in realized fitness than larval nutrition for V. cardui, but that these effects may be mediated by larval dietary history. Increased fitness by females was mostly due to the fact that butterflies with access to sugars as adults, whether alone or in combination with amino acids, lived significantly longer than those without access to a carbohydrate source and were able to maintain egg production for a longer period of time. Butterflies reared on diet of equal protein and carbohydrate ratio (1P:1C) performed best when provided only sugars as adults. In contrast, butterflies reared on protein biased diet (5P:1C) fared better when they were given sugars and amino acids as adults. Nectar-derived amino acids do not appear to aid female V. cardui fitness, possibly even having a negative effect on total egg production when butterflies are reared on an optimal larval diet.