Drought Influences Monarch Host Plant Selection

Butterflies (Lepidoptera) use many chemical cues to select their host plants. In plants within the Asclepias genus (milkweeds) the primary chemical signals for monarch butterflies (Danaus plexippus) are cardenolide and flavonol glycosides. Gravid females can detect oviposition stimulants within plants by tapping the leaf surface with olfactory organs on their feet and antennae. We do not currently understand how changes to plant chemistry as a result of water-availability will influence monarch host-plant selection. Understanding oviposition preferences are crucial to predicting monarch population responses to changing climatic conditions, particularly in the arid Western United States where water-availability is decreasing. As early stage monarch larvae are limited in mobility, maternal host-plant selection has a direct effect on offspring performance. In this experiment, oviposition preference will be determined by the number of eggs deposited per narrowleaf milkweed (A. fascicularis) from either control or water-limited treatments. The results from this study will shed light on the ecological impacts of climate change and inform future conservation measures for an insect species that is rapidly declining.