Phylogeny, biogeography, and host range of gall midges (Diptera: Cecidomyiidae) feeding on spores of rust fungi (Basidiomycota: Pucciniales)

Authors: GOMEZ-ZAPATA, PAULA - Purdue University; Johnson, Melissa; BONACCI, TERESA - University Of Calabria; AIME, CATHERINE - Purdue University

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2024
Publication Date: 8/28/2024
Citation: Gomez-Zapata, P.A., Johnson, M.A., Bonacci, T., Aime, C.M. 2024. Phylogeny, biogeography, and host range of gall midges (Diptera: Cecidomyiidae) feeding on spores of rust fungi (Basidiomycota: Pucciniales). Journal of Insect Science. 24(4):18. https://doi.org/10.1093/jisesa/ieae077.
DOI: https://doi.org/10.1093/jisesa/ieae077

Interpretive Summary: Characterization studies of natural enemies of rust fungi are essential to develop biological controls of rust diseases. Although the gall midge Mycodiplosis is commonly found feeding on rust spores and has great potential as a biological control agent, studies on this insect are scarce. In this study, we screened 5,665 rust specimens in 99 rust genera and 104 countries for the presence of Mycodiplosis. From this screening, we found 363 individual larvae on 315 rust specimens from 17 countries. We resolved 14 clades that roughly correspond to species. We identified four species: M. coniophaga, M. melampsorae, M. puccinivora, and M. sphaerothecae. Of these, three were associated with rust fungi (M. coniophaga, M. melampsorae, and M. puccinivora) and one exclusively with powdery mildews (M. sphaerothecae). Data were also used to infer aspects of the natural history of the genus, including host-specificity of the species, geographic range of species, and suitability as biocontrol agents.

Technical Abstract: Rust diseases are plant pathogens that can cause devastating yield losses to economically important crops worldwide and threaten native plants to extinction. These diseases are usually controlled with fungicides when rust-resistant plant varieties are unavailable. However, natural enemies of rusts may offer an alternative to chemicals by acting as biological controls. Fly larvae in the genus Mycodiplosis feed on the spores of rusts or powdery mildew fungi. However, little is known about the biogeography, host-specificity, and species diversity of Mycodiplosis due to the scarcity of characterization studies. In this study, we screened 5,665 rust specimens from fungarium collections and fresh specimens collected in more than 100 countries for the presence of Mycodiplosis. We collected 363 individual larvae on 315 rust specimens from 17 countries. We amplified five loci from 131 larval specimens confirmed to be Mycodiplosis. Our phylogenetic tree recovered 14 clades of Mycodiplosis. Our data suggest that Mycodiplosis taxa generally show no feeding preference for specific rust species. Examination of biogeographic patterns also revealed clades of taxa with a broad distribution across multiple continents and climatic regions, as well as clades comprising taxa restricted to a single region. Due to challenges in identification (Mycodiplosis species can only be identified by adult males morphology), only three taxa were confidently identified at the species level, highlighting the need for additional taxonomic and phylogenetic work on this group. The potential for Mycodiplosis to be used as a biocontrol against fungal plant diseases as part of an integrated pest management strategy is discussed.