Journal article

Publication year: 2022

Pages: E211-E228

Journal: The American Naturalist

Volume number: 199

Issue number: 6

ISSN: 0003-0147

eISSN: 1537-5323

Open access status: Hybrid

DOI Link: https://doi.org/10.1086/719196

Publisher: The University of Chicago Press

Abstract: 
Host plant specialization across herbivorous insects varies dramatically, but while the molecular mechanisms of host plant adaptations are increasingly known, we often lack a comprehensive understanding of the selective forces that favor specialization. The milkweed bugs (Heteroptera: Lygaeinae) are ancestrally associated with plants of the Apocynaceae from which they commonly sequester cardiac glycosides for defense, facilitated by resistant Na+/K+-ATPases and adaptations for transport, storage, and discharge of toxins. Here, we show that three Lygaeinae species independently colonized four novel nonapocynaceous hosts that convergently produce cardiac glycosides. A fourth species shifted to a new source of toxins by tolerating and sequestering alkaloids from meadow saffron (Colchicum autumnale, Colchicaceae). Across three milkweed bug species tested, feeding on seeds containing toxins did not improve growth or speed of development and even impaired growth and development in two species, but sequestration mediated protection of milkweed bugs against two natural predators: lacewing larvae and passerine birds. We conclude that physiological preadaptations and convergent phytochemistry facilitated novel specialized host associations. Since toxic seeds did not improve growth but either impaired growth or, at most, had neutral effects, selection by predators on sequestration of defenses, rather than the exploitation of additional profitable dietary resources, can lead to obligatory specialized host associations in otherwise generalist insects.

Harvard Citation style: Petschenka, G., Halitschke, R., Zust, T., Roth, A., Stiehler, S., Tenbusch, L., et al. (2022) Sequestration of Defenses against Predators Drives Specialized Host Plant Associations in Preadapted Milkweed Bugs (Heteroptera: Lygaeinae), The American Naturalist, 199(6), pp. E211-E228. https://doi.org/10.1086/719196

APA Citation style: Petschenka, G., Halitschke, R., Zust, T., Roth, A., Stiehler, S., Tenbusch, L., Hartwig, C., Gamez, J., Trusch, R., Deckert, J., Chalusova, K., Vilcinskas, A., & Exnerova, A. (2022). Sequestration of Defenses against Predators Drives Specialized Host Plant Associations in Preadapted Milkweed Bugs (Heteroptera: Lygaeinae). The American Naturalist. 199(6), E211-E228. https://doi.org/10.1086/719196