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Ambrosia gall midges (Diptera: Cecidomyiidae) and their microbial symbionts as a neglected model of fungus-farming evolution

Summary

Ambrosia gall midges are tiny insects that grow plants into special structures called galls where they farm fungi as food. These midges and their fungal partners have evolved a remarkable relationship where the fungi provide nutrition and protection while the midges help the fungi spread to new plants. This system offers scientists an excellent opportunity to study how insects and fungi can evolve together and influence each other’s evolution, with potential implications for understanding how new insect species form.

Background

Ambrosia gall midges (AGMs) represent a unique group within Cecidomyiidae that form galls on plants while cultivating fungal symbionts through phytomycetophagy. This mutualistic relationship plays critical roles in larval nutrition, gall morphogenesis, and protection against natural enemies. Despite advances in studying other fungus-farming taxa, AGMs have remained largely neglected as a model system.

Objective

This review synthesizes current knowledge on AGM diversity, biology, and ecological interactions with fungal symbionts, examining their roles in adaptive radiation, speciation, and coevolution. The authors identify pressing issues in understanding AGM-fungi interactions and recommend future research directions for elucidating this unique evolutionary association.

Results

AGMs harbor complex fungal communities dominated by Botryosphaeria dothidea in some tribes, with varying degrees of specificity. Fungi provide nutrition and gall morphogenesis induction, while AGMs facilitate fungal dispersal and proliferation. Multiple transmission routes exist (vertical and horizontal), and fungal associates influence host plant specialization and facilitate host shifts, contributing to speciation and adaptive radiation.

Conclusion

AGMs represent a compelling but understudied model for insect-fungus coevolution and mutualism with significant implications for understanding insect speciation. Future research should employ advanced molecular techniques, comprehensive microbiome analyses, controlled experiments, and phylogenetic reconstructions to elucidate fungal acquisition mechanisms, symbiont specificity, and the evolutionary pathways leading to phytomycetophagy.
  • Published in:FEMS Microbiology Reviews,
  • Study Type:Review,
  • Source: PMID: 40175297, DOI: 10.1093/femsre/fuaf010
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