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Host plant specificity of the monarch butterfly Danaus plexippus: A systematic review and meta-analysis

Citation

Greenstein, Lewis; Steele, Christen; Taylor, Caz M. (2022), Host plant specificity of the monarch butterfly Danaus plexippus: A systematic review and meta-analysis, Dryad, Dataset, https://doi.org/10.5061/dryad.7wm37pvvp

Abstract

The preference-performance hypothesis explains host specificity in phytophagous insects, positing that host plants chosen by adults confer the greatest larval fitness. However, adults sometimes oviposit on plants supporting low larval success because the components of host specificity (adult preference, plant palatability, and larval survival) are non-binary and not necessarily correlated. Palatability (willingness to eat) is governed by chemical cues and physical barriers such as trichomes, while survival (ability to complete development) depends upon nutrition and toxicity. Absence of a correlation between the components of host specificity results in low-performance hosts supporting limited larval development. Most studies of specificity focus on oviposition behavior leaving the importance and basis of palatability and survival under-explored. We conducted a comprehensive review of 127 plant species that have been claimed or tested to be hosts for the monarch butterfly Danaus plexippus to classify them as non-hosts, low performance, or high performance. We performed a meta-analysis to test if performance status could be explained by the properties of neurotoxic cardenolides or trichome density. We also conducted a no-choice larval feeding experiment to identify the causes of low performance. We identified 34 high performance, 42 low performance, 33 non-hosts, and 18 species with unsubstantiated claims. Mean cardenolide concentration was greater in high- than low-performance hosts and a significant predictor of host status, suggesting possible evolutionary trade-offs in monarch specialization. Other cardenolide properties and trichome density were not significant predictors of host status. In the experiment, we found, of the 62% of larvae that attempted to eat low-performance hosts, only 3.5% survived to adult compared to 85% of those on the high-performance host, demonstrating that multiple factors affect larval host plant specificity. Our study is the first to classify all known host plants for monarchs and has conservation implications for this threatened species.

Usage Notes

Details are included in README.txt.

The milkweed phylogeny used for phylogenetic analyses was initially published in Fishbein et al. 2018 (https://doi.org/10.1002/ajb2.1062) and provided to us by Dr. Mark Fishbein. These data may be requested from Dr. Mark Fishbein (mark.fishbein@okstate.edu).

Funding

National Science Foundation, Award: DEB-1754434