Feeding on Host Plants with Different Concentrations and Structures of Pyrrolizidine Alkaloids Impacts the Chemical-Defense Effectiveness of a Specialist Herbivore

Author(s)

Martins, Carlos H. Z. ^{[1, 2]} ; Cunha, Beatriz P. ^[3] ; Solferini, Vera N. ^[3] ; Trigo, Jose R. ^[1]

Affiliation

^[1] Univ Estadual Campinas, Inst Biol, Dept Biol Anim, Lab Ecol Quim, BR-13083970 Campinas, SP - Brazil

^[2] Univ Estadual Campinas, Inst Biol, Programa Posgrad Biol Func & Mol, BR-13084970 Campinas, SP - Brazil

^[3] Univ Estadual Campinas, Inst Biol, Dept Genet & Evolucao, BR-13083970 Campinas, SP - Brazil

• Document type: Journal article
• Source: PLoS One; v. 10, n. 10 OCT 30 2015.
• Web of Science Citations: 12

Abstract

Sequestration of chemical defenses from host plants is a strategy widely used by herbivorous insects to avoid predation. Larvae of the arctiine moth Utetheisa omatrix feeding on unripe seeds and leaves of many species of Crotalaria (Leguminosae) sequester N-oxides of pyrrolizidine alkaloids (PAs) from these host plants, and transfer them to adults through the pupal stage. PAs confer protection against predation on all life stages of U. omatrix. As U. ornatrix also uses other Crotalaria species as host plants, we evaluated whether the PA chemical defense against predation is independent of host plant use. We fed larvae from hatching to pupation with either leaves or seeds of one of eight Crotalaria species (C. incana, C. juncea, C. micans, C. ochroleuca, C. pallida, C. paulina, C. spectabilis, and C. vitellina), and tested if adults were preyed upon or released by the orb-weaving spider Nephila clavipes. We found that the protection against the spider was more effective in adults whose larvae fed on seeds, which had a higher PA concentration than leaves. The exceptions were adults from larvae fed on C. paulina, C. spectabilis and C. vitellina leaves, which showed high PA concentrations. With respect to the PA profile, we describe for the first time insect-PAs in U. ornatrix. These PAs, biosynthesized from the necine base retronecine of plant origin, or monocrotaline-and senecionine-type PAs sequestered from host plants, were equally active in moth chemical defense, in a dose-dependent manner. These results are also partially explained by host plant phylogeny, since PAs of the host plants do have a phylogenetic signal (clades with high and low PA concentrations in leaves) which is reflected in the adult defense. (AU)

• FAPESP's process: 11/17708-0 - Chemical defense in plants and insects in neotropical environments
• Grantee: Jose Roberto Trigo
• Support type: Regular Research Grants
• FAPESP's process: 12/02526-7 - Phylogeography and populational genetic structure of spiders species (Arachnida, Araneae)
• Grantee: Vera Nisaka Solferini
• Support type: Regular Research Grants