The haustorium as a driving force for speciation in thallus-forming Laboulbeniomycetes

Abstract

Laboulbeniomycetes is a class of fungi that have obligate associations with arthropod hosts, either for dispersal (order Pyxidiophorales) or as biotrophic parasites (orders Herpomycetales and Laboulbeniales). Here, we focus on Herpomycetales and Laboulbeniales, which include fungi that form thalli, 3-dimensional, multicellular units of 1000 s of cells. Based on recently published data regarding patterns of speciation, we present the One-Host-One-Parasite model (1H1P) for haustorial thallus-forming Laboulbeniomycetes. We hypothesize that taxa with haustoria, rhizoidal structures that make contact with the host’s body cavity, have very strict host specificity. For taxa without haustoria, the microhabitat—as selected by the host—governs host shifting, presence or absence of the fungus, abundance, effective host range, and geographic distribution. We make suggestions for future research including fluorescent labeling of waxy lipids and mass spectrometry. These techniques have the potential to generate the data necessary to evaluate the here proposed 1H1P hypothesis for Herpomycetales and Laboulbeniales.

Hesperomyces (Fungi, Ascomycota) associated with Hyperaspis ladybirds (Coleoptera, Coccinellidae): Rethinking host specificity

“…The one-host-one-parasite (1H1P) model states that species of Laboulbeniales with a haustorium, like those in the genus Hesperomyces , have higher host specificity compared to species without a haustorium because the fungi are in closer contact with their host ( Haelewaters et al., 2022a ). The species within He.…”

Editorial: Biodiversity and conservation of fungi and fungus-like organisms

“…Some taxonomic and functional groups of fungi have traditionally been neglected. Examples are the arthropodassociated Laboulbeniomycetes (Haelewaters et al, 2022), early-diverging fungi (Spatafora et al, 2016), and fungal hyperparasites. Van Caenegem et al study Laboulbeniales microfungi associated with ladybirds using morphology, single-locus and multilocus phylogeny, and host association.…”

“…Some taxonomic and functional groups of fungi have traditionally been neglected. Examples are the arthropod-associated Laboulbeniomycetes ( Haelewaters et al., 2022 ), early-diverging fungi ( Spatafora et al., 2016 ), and fungal hyperparasites. Van Caenegem et al.…”