Abiotic factors influencing the presence and prevalence of parasitic microfungi on an invasive ladybird
Background
The introduction of and dramatic spread of non-native species is one of the main environmental threats to global ecosystems. One of the worst invasive species in Europe is the Asian ladybird, Harmonia axyridis (Coccinellidae). Harmonia axyridis is native to eastern Asia. Initially used as biocontrol in North America and later as augmentative biocontrol in Europe, Ha. axyridis has now spread at a very fast rate to every continent except Antarctica. However, the qualities that make Ha. axyridis a good biocontrol agent also result in it being a very effective competitor of locally native ladybird populations. Harmonia axyridis has a negative effect not only on native insects, but also on food production and human health. In assessing how invasive species like Ha. axyridis can be controlled, it is important to determine its natural enemies, how they spread, and which role they can have in regulating invasive populations.
Problems
One of these natural enemies is Hesperomyces virescens (Ascomycota, Laboulbeniomycetes, Laboulbeniales). It is part of a peculiar group of fungi, the Laboulbeniales, which are ectoparasites on arthropods. Laboulbeniales, with about 2,325 described species in 145 genera, are among the least studied groups of the Kingdom Fungi. They are obligate ectoparasites of arthropod hosts and form microscopic, three-dimensional fruiting bodies—thalli—instead of mycelia. Hesperomyces virescens is a globally occurring species and it causes mortality of ladybird hosts under laboratory conditions. The spread of He. virescens on Ha. axyridis is an invasion in action; the fungus was for the first time recorded in Europe during the winter of 2006–2007 but is currently already known from eleven European countries. We do not know which factors have contributed to this dramatic spread.
Goals
Knowing how biotic and abiotic factors influence the infection of Laboulbeniales on invasive ladybirds will help understand their global spread, as they cross many different ecosystems and environmental conditions. Resolving this question will also inform potential biocontrol strategies because it will inform us under which conditions fungal infection may (not) thrive. The aim of this project is to assess how temperature and humidity may affect presence and prevalence of He. virescens on Ha. axyridis ladybirds. Ladybirds (sampled by collaborators) will be screened for He. virescens, climatic data will be extracted from the WorldClim database for each sampling locality, and landscape variables will be extracted from Copernicus Corine Land Cover (European Environment Agency). Second, direct effects of temperature and humidity on the development of He. virescens will be assessed directly during controlled laboratory conditions. This will be done in the lab of collaborator Dr. Oldřich Nedvěd at the University of South Bohemia. The student will learn about statistical modeling and other methods in community ecology.
References
Haelewaters D, Hiller T, Kemp EA, van Wielink PS, Shapiro-Ilan DI, Aime MC, Nedvěd O, Pfister DH, Cottrell TE. 2020. Mortality of native and invasive ladybirds co-infected by ectoparasitic and entomopathogenic fungi. PeerJ 8: e10110. https://doi.org/10.7717/peerj.10110 [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]
