Fungicide treatment and clipping of Oxytropis sericea does not disrupt swainsonine concentrations

Cook, Daniel; Gardner, Dale R.; Roper, Jessie M.; Ransom, Corey V.; Pfister, James A.; Panter, Kip E.

doi:10.1016/j.toxicon.2016.09.012

Cited by 2 publications

(1 citation statement)

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“…Thus, the interaction between Astragalus and swainsonine producing fungal symbionts is unlikely to have evolved as a defense against herbivory by mammals. Furthermore, clipping of locoweeds to simulate herbivory does not lead to an increase in swainsonine production, indicating swainsonine is unlikely to be an induced defense response , Cook et al 2016. Plant toxins are often associated with coevolutionary defenses against insect herbivores, especially pre-dispersal seed predators of legumes (Janzen 1971).…”

Section: Introductionmentioning

confidence: 99%

Extensive local geographic variation in locoweed toxin produced by a fungal endophyte

Davis,

Scott,

Cook

et al. 2024

Preprint

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Legumes are notorious for coevolutionary arms races where chemical defenses are employed to ward off herbivores—particularly insect seed predators. Locoweeds are a group of plants containing the toxic alkaloid swainsonine which can poison livestock and causes millions in economic damage every year. Swainsonine is known to be produced by the fungal endophyte Alternaria section Undifilum, and the chemical composition of the toxin has been well characterized. Despite this knowledge, the ecological roles and evolutionary drivers of swainsonine toxins in locoweeds remain uncertain. Here, we quantitate swainsonine concentrations and herbivory levels in the hyper-diverse locoweed Astragalus lentiginosus to evaluate its role as an evolved chemical defense. We found that A. lentiginosus shows considerable variation in swainsonine concentrations according to variety, in particular showing presence/absence variation at both population and local geographic scales. Surprisingly, herbivory levels from presumed generalist insects emerging from fruits showed no correlation with swainsonine concentrations. Conversely, seed and fruit herbivory levels linked to specialist Acanthoscelides seed beetles actually increased with concentrations of swainsonine—suggesting a possible coevolutionary arms race. Our results highlight that variation in endophyte-produced toxin systems may not follow classical expectations for geographic variation and ecological roles of plant chemicals. We discuss the implications of these results on plant-endophytic toxin systems and coevolutionary dynamics more broadly, highlighting a considerable need for more research in these systems.

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Section: Introductionmentioning

confidence: 99%