Rare species hanging out in my front yard
You’d think that in Belgium, a country with a very high population density, not much more biodiversity can be found in addition to what we already know today. This is far from the truth. In 2020, my colleague André De Kesel from Meise Botanic Garden and I described a new species of ectoparasitic microfungus for science, thus far only known from Belgium. We named it Laboulbenia quarantenae, with reference to the COVID-19 pandemic, which is still raging on (I also talk about this species in another post). In that same paper, we summarized all species of Herpomycetales and Laboulbeniales that were known in Belgium until then. Herpomycetales and Laboulbeniales are microfungi (class Laboulbeniomycetes) that are always associated with arthropod hosts as ectoparasites. (Well, we say that they are “ectoparasites” but we do not know for sure. It might be safer to refer to these fungi as ectobionts = fixed to the outside of a host’s body). Taxa in these two groups are unique among related fungi in that they form thalli, which are multicellular three-dimensional units of 100s to 1000s of cells recognized by determinate growth.
Studying insect-associated microfungi changes you forever; I always walk around with an aspirator and I collect insects when I see them. At work, at home, during vacation, I am collecting stuff. And so in June 2021, I collected a little beetle while I was working in my front yard. I screened it for Laboulbeniales (yes, I have a microscope set-up at home) and it was infected. Turned out that the beetle is a Chaetocnema hortensis, a common species in Europe, and the fungus is Laboulbenia temperei. The record of this fungus from my front yard only represents the second find in the world! I think this is pretty mindblowing. Laboulbenia temperei was described from France and was since its description in 1973 not found any more, until now.
Dimorphomyces phloeoporae, from Phloeopora sp. (Coleoptera, Staphylinidae) 
Laboulbenia scelophila, from Agonum viridicupreum (Coleoptera, Carabidae) 
Laboulbenia temperei, from Chaetocnema hortensis (Coleoptera, Chrysomelidae)
In addition to this record, André, his colleague Cyrille Gerstmans, and I reported nine other species for the first time in Belgium. Some of these are very rare in Europe.
- Dimeromyces oculatus
- Dimorphomyces phloeoporae
- Laboulbenia asperata
- Laboulbenia carelica
- Laboulbenia luxurians
- Laboulbenia scelophila
- Laboulbenia tenera
- Peyritschiella geminata
- Peyritschiella subinaequilatera
In 2020, we reported 115 species of thallus-forming Laboulbeniomycetes in Belgium. Two years later, this number has increased to 125. Also in the Netherlands, the number of Herpomycetales and Laboulbeniales is increasing quickly. Only 33 species were known until 2012, when I started my PhD research. In 2020, the same year we published the Catalogue of Laboulbeniomycetes of Belgium, we also published a checklist of thallus-forming Laboulbeniomycetes in the Netherlands—reporting 85 species, adding more than 50 species to the Dutch funga in just a few years time. And together with my student Warre Van Caenegem and collaborators in the Netherlands, we have now found an additional 16 species for which we are preparing another publication. (To be honest, I am holding off with this paper until we find a new species😊.)
References
De Kesel A, Gerstmans C, Haelewaters D. 2022. Rare Laboulbeniales from Belgium. Sterbeeckia 37: 27-38. [pdf]
De Kesel A, Gerstmans C, Haelewaters D. 2020. Catalogue of Laboulbeniomycetes of Belgium. Sterbeeckia 36: 3-143. [pdf]
Haelewaters D, De Kesel A. 2020. Checklist of thallus-forming Laboulbeniomycetes from Belgium and the Netherlands, including Hesperomyces halyziae and Laboulbenia quarantenae spp. nov. MycoKeys 71: 23-86. https://doi.org/10.3897/mycokeys.71.53421 [pdf]
