Pyrrolizidine Alkaloids Negatively Affect a Generalist Herbivore Feeding on the Chemically Protected Legume Crotalaria pallida

Abstract

Plant secondary metabolites can have opposing effects on adapted specialist and non-adapted, generalist herbivores. In this study, we used Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) as a generalist, non-adapted model herbivore to test the possible effects of Crotalaria pallida (Fabaceae: Papilionoideae) defenses on herbivore performance. Neonate H. virescens larvae were able to consume C. pallida leaves and fruits and grow for a few instars, but none of them survived to pupation. We added isolated pyrrolizidine alkaloids (PAs) to an artificial diet at different concentrations, and PA concentration significantly affected the number of larvae that achieved pupation. Larval survival was not reduced at a PA concentration similar to the concentration on green seeds of C. pallida, but it was significantly reduced at PA concentration 5 and 100 times higher. These results suggest that PAs in isolation are not the defense responsible for the mortality in fresh C. pallida plants, indicating the importance of other possible defenses. The negative effect of PAs on fitness of the non-adapted, generalist herbivore is in agreement with few previous studies, but it is in clear contrast to a previous study on the effects of PAs on the adapted specialist herbivore Utetheisa ornatrix (L.) that were able to sequester PAs with no fitness costs.

The geographical and seasonal mosaic in a plant-herbivore interaction: patterns of defences and herbivory by a specialist and a non-specialist

“…Third, we do not know if the levels of PAs present in the field affect E. zinckenella . Previous studies showed that the negative effect of PAs on generalist herbivores depends on the concentration 70,71 . Forth, since C. pallida is an introduced species, it has not coevolved with these two herbivores for a long evolutionary time, and therefore may not be well adapted to avoid them 40 .…”

“…We expected that the specialist U. ornatrix would act as selection agent that decreases the concentration of PAs in natural populations, while the non-specialist E. zinckenella would act as a selection agent that increases the concentration of PAs. This expectation is based on the fact that PAs are known to deter generalist herbivores 16,17,70,71 , but have no negative effect on the specialist U. ornatrix 36 . U. ornatrix can sequester PAs and use them as defences against predators as well as a male pheromone 15,19,35,48,70,72 .…”

The conservation of native, lowland Indonesian Begonia species (Begoniaceae) in Bogor Botanic Gardens

“…The content is in line with those reported by Govindappa et al (2011), by stating that the ethanol extract of C. pallida all parts of the plant contain alkaloids, flavonoids, tannins, steroids, terpenoids, saponins, and phenol. In addition it was reported also by Cogni and Trigo (2016) that has been isolated alkaloid from the leaf and fruit of C. pallida.…”

Evolution of Increased Photosynthetic Capacity and Its Underlying Traits in Invasive Jacobaea vulgaris

“…Jb chemotype plants from the native populations contained, on average, 7.7% Er-like PAs, while in the introduced range, only trace amounts of erucifoline were present in this chemotype ( Figure 2 ), suggesting that erucifoline has been selected against. Several studies have shown that generalist insect herbivores respond differently to the same PA and that the relative effects of individual PAs can differ between herbivore species (Macel et al, 2005; Cheng et al, 2013; Wei et al, 2015; Cogni and Trigo, 2016). Thus, generalist herbivores, in turn, might play an important role in the evolution and maintenance of the diversity of PAs (Macel et al, 2005).…”