Thirty years ago, researchers discovered that nectars of flowers pollinated by butterflies contain substantial amounts of amino acids. Recent experiments have shown that butterflies actually prefer nectars with a high amino acid content. These findings led to speculations about the significance of nectar amino acids for butterfly fitness and insinuated that butterflies have acted as agents of natural selection on nectar composition.
In order to determine whether butterflies actually need nectar amino acids, researchers from the University of Basel raised map butterfly caterpillars on both nitrogen poor and nitrogen rich stinging nettle. After the butterflies emerged, they were fed nectar with or without amino acids.
Butterflies raised under natural, nitrogen poor larval food conditions laid more eggs when fed nectar containing amino acids. These results provide the long missing evolutionary link between costly nectar amino acid production by plants, nectar preferences of and fitness benefits to butterflies.
This article by Jovanne Mevi-Schütz and Andreas Erhardt will appear in the April 2005 issue of The American Naturalist.