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Fungal alkaloids mediate defense against bruchid beetles in field populations of an arborescent ipomoea

Summary

Morning glory trees (Ipomoea murucoides) form beneficial relationships with fungal partners that live inside their tissues and produce toxic compounds called alkaloids. These alkaloids accumulate in the tree’s seeds and protect them from beetle damage. Trees hosting the common fungal partner Ceramothyrium produce more of the protective alkaloid swainsonine and suffer less seed damage than those with a different fungal partner, demonstrating how this natural partnership helps the plant defend its offspring.

Background

Convolvulaceae species harbor heritable fungal endophytes that produce alkaloids translocated to plant tissues. Evidence for the distribution and ecological role of these fungal alkaloids remains incomplete for many host species and growth forms, particularly in arborescent Ipomoea species.

Objective

To identify fungal endophytes colonizing Ipomoea murucoides, quantify alkaloid concentrations in leaves and seeds, and evaluate the defensive role of fungal alkaloids against bruchid beetle herbivory in field populations.

Results

Two main fungal taxa colonized the trees: Ceramothyrium (Chaetothyriales) in 70% of trees and Truncatella (Xylariales) in 27% of trees. Seeds had significantly higher swainsonine concentrations than leaves. Seeds from Ceramothyrium-colonized trees contained higher swainsonine levels and exhibited less bruchid damage compared to Truncatella-colonized trees.

Conclusion

Fungal-derived swainsonine provides significant defense against seed-feeding bruchid beetles in Ipomoea murucoides, demonstrating the ecological value of fungal symbiosis. The system suggests both vertical and horizontal transmission of fungal symbionts and provides an excellent model for studying plant-fungal defensive mutualisms.
  • Published in:Journal of Chemical Ecology,
  • Study Type:Field Study,
  • Source: PMID: 39994115, DOI: 10.1007/s10886-025-01578-2
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