Laboulbeniales (Ascomycota) are obligate associates of arthropod hosts. Species in this order are microscopic in size and produce 3-dimensional structures—named thalli—instead of hyphae and mycelia. These fungi are dependent on a living host for the entire duration of their life cycle. With about 2325 described species in 145 genera, Laboulbeniales form the most diverse fungal assemblage associated with representatives of the phylum Arthropoda, predominantly insects. Laboulbeniales are a poorly studied group, with most research having focused on alpha taxonomy, which refers to species descriptions solely based on morphology. Our research group at Ghent University studies the Laboulbeniales using an integrative taxonomy approach (meaning that we also use evidence from ecology and molecular phylogeny). In addition, we focus on trophic interactions and community ecology.
To date, community ecology research of Laboulbeniales is in its infancy, with only three published studies. Szentiványi et al. (2019) investigated whether climatic variables (temperature, humidity) influenced the distribution of ant- and bat fly-associated Laboulbeniales. They found that both the presence and prevalence of Laboulbeniales on their hosts were positively associated with low annual mean temperature and humidity. Gippet et al. (2021), based on the study of more than 9,374 workers of the invasive ant Lasius neglectus in 66 colonies, found that the presence of Laboulbenia formicarum on the ants was positively linked to warmer and dryer conditions at lower elevations. Haelewaters et al. (2022) studied the prevalence of Hesperomyces harmoniae on Harmonia axyridis ladybirds in Europe considering biotic and abiotic factors. These authors found that elytral color had a significant effect on the parasite prevalence, whereas host sex, climate, and landscape composition did not.
These first community ecology studies do not give us a full picture of general patterns that are in play. On the contrary, the results from Szentiványi et al. (2019) and Gippet et al. (2021) are seemingly contrasting, while the data from Haelewaters et al. (2022) point at no influence by climate factors. Are our current datasets too small? Are ant-associated fungal patterns governed by ant nest-specific factors rather than outside climate factors? Do different study systems simply show different patterns? We do not know the answer to these questions at this time.
Laboulbeniales occur in many different ecosystems but we have currently no idea about their environmental preferences. Knowing how abiotic factors influence infection of Laboulbeniales on their host will help to improve our understanding of their global distribution. This master thesis will use multi-year specimen data from Zuid-Kennemerland National Park in The Netherlands to test the effect of selected climate and landscape variables. Insect specimens were collected using standardized pitfall traps between 2017 and 2022 and then screened for the presence of Laboulbeniales. Infected specimens were sent to the laboratory. The student that takes on this project will identify the Laboulbeniales based on available keys in combination with molecular methods (to confirm ID, if necessary). Parasite prevalence will be analyzed in light of selected characters: temperature, humidity, season, landscape composition. This will be done for the overall dataset as a whole but perhaps also at the species-level for the most frequently collected species—depending on sampling. The student will learn about statistical modeling and methods in community ecology. Finally, there will also be the opportunity for fieldwork in Zuid-Kennemerland National Park.
Cazabonne J, Bartrop L, Dierickx G, Gafforov Y, Hofmann TA, Martin TE, Piepenbring M, Rivas-Ferreira M, Haelewaters D. 2022. Molecular-based diversity studies and field surveys are not mutually exclusive: On the importance of integrated methodologies in mycological research. Frontiers in Fungal Biology 3: 860777. https://doi.org/10.3389/ffunb.2022.860777 [pdf]
De Kesel A, Gerstmans C, Haelewaters D. 2020. Catalogue of the Laboulbeniomycetes of Belgium. Sterbeeckia 36: 3-143. [pdf]
Gippet JM, Colin T, Grangier J, Winkler F, Haond M, Dumet A, Tragust S, Mondy N, Kaufmann B. 2021. Land-cover and climate factors contribute to the prevalence of the ectoparasitic fungus Laboulbenia formicarum in its invasive ant host Lasius neglectus. Fungal Ecology 51: 101045. https://doi.org/10.1016/j.funeco.2021.101045 [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]
Haelewaters D, Gorczak M, Kaishian P, De Kesel A, Blackwell M. 2021. Laboulbeniomycetes, Enigmatic Fungi With a Turbulent Taxonomic History. pp. 263-283. In: Zaragoza Ó, Casadevall A (eds.) Encyclopedia of Mycology, Volume 1. Elsevier, Oxford. https://doi.org/10.1016/B978-0-12-819990-9.00049-4 [pdf]
Haelewaters D, Hiller T, Ceryngier P, Eschen R, Gorczak M, Houston ML, Kisło K, Knapp M, Landeka N, Pfliegler WP, Zach P, Aime MC, Nedvěd O. 2022. Do biotic and abiotic factors influence the prevalence of a common parasite of the invasive alien ladybird Harmonia axyridis? Frontiers in Ecology and Evolution 10: 773423. https://doi.org/10.3389/fevo.2022.773423 [pdf]
Szentiványi T, Haelewaters D, Rádai Z, Mizsei E, Pfliegler WP, Báthori F, Tartally A, Glaizot O, Christe P. 2019. Climatic effects on the distribution of ant- and bat fly-associated fungal ectoparasites (Ascomycota, Laboulbeniales). Fungal Biology 39: 371-379. https://doi.org/10.1016/j.funeco.2019.03.003 [pdf]