Fig. 2.

Connections between plant cardenolides, monarch sequestration, and monarch growth. (A) Sequestration was predicted by the concentration of the dominant plant cardenolide, voruscharin, although this compound was itself not sequestered (it was converted to calactin and calotropin). (B) In multiple regression, sequestered cardenolides were predictive of monarch growth (whereas plant cardenolides were not), indicating a cost of converting or storing cardenolides. The weak relationships of growth predicted by total leaf cardenolides and leaf voruscharin are shown in SI Appendix, Fig. S6. Monarch image credit: Frances Fawcett.