Studies of Laboulbeniales onMyrmicaants (IV): host-related diversity and thallus distribution patterns ofRickia wasmannii

Abstract

Fungal species identities are often based on morphological features, but current molecular phylogenetic and other approaches almost always lead to the discovery of multiple species in single morpho-species. According to the morphological species concept, the ant-parasitic fungus Rickia wasmannii (Ascomycota, Laboulbeniales) is a single species with pan-European distribution and a wide host range. Since its description, it has been reported from ten species of Myrmica (Hymenoptera, Formicidae), of which two belong to the rubra-group and the other eight to the phylogenetically distinct scabrinodis-group. We found evidence for R. wasmannii being a single phylogenetic species using sequence data from two loci. Apparently, the original morphological description (dating back to 1899) represents a single phylogenetic species. Furthermore, the biology and host-parasite interactions of R. wasmannii are not likely to be affected by genetic divergence among different populations of the fungus, implying comparability among studies conducted on members of different ant populations. We found no differences in total thallus number on workers between Myrmica species, but we did observe differences in the pattern of thallus distribution over the body. The locus of infection is the frontal side of the head in Myrmica rubra and M. sabuleti whereas in M. scabrinodis the locus of infection differs between worker ants from Hungary (gaster tergites) and the Netherlands (frontal head). Possible explanations for these observations are differences among host species and among populations of the same species in (i) how ant workers come into contact with the fungus, (ii) grooming efficacy, and (iii) cuticle surface characteristics.

Effects of fungal infection on the survival of parasitic bat flies

“…Position specificity (infection occurrence on certain body parts) in Laboulbeniales have been observed in multiple studies among wide variety of host taxa. Position specificity might change depending on host species [61], host sex [59] and mating behaviour [58,62,63], but also seasonally [58] or based on the intensity of infection [27]. Fungi thalli dominantly occur on the head, abdomen and thorax (but can be present on any body parts) of infected Myrmica scabrinodis (Hymenoptera: Formicidae), however it can vary based on the intensity of infection [27].…”

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

“…However, without molecular data and data from transmission studies (including host specificity and host shifting), it is impossible to draw limits among (1) morphologically similar thalli that have different host species, (2) morphologically different thalli on different sexes of the same host species, or (3) morphologically different thalli that occupy different positions on the same host specimen (Scheloske 1969 , 1976 ). This is why we have advocated an integrative approach to the taxonomy of thallus-forming Laboulbeniomycetes (Haelewaters et al 2018 , 2019a , c )—an effort that has long been adopted in many other groups of fungi (Wijayawardene 2019 ), including Aspergillus (Pringle et al 2005 ), Cortinarius (Stefani et al 2014 ), Geastrum (Accioly et al 2019 ), Helvella (Skrede et al 2017 ), Leptographium (Yin et al 2019 ), Octospora (Sochorová et al 2019 ), Ophiocordyceps (Araújo et al 2018 ), Phialocephala (Grünig et al 2008 ), Protoparmelia (Singh et al 2015 ), and Tranzscheliella (Li et al 2017 ). This push towards an integrative fungal taxonomy has been met with some resistance among laboulbeniologists faced with the impracticability of performing molecular work, who perhaps perceive it as a threat to the long-standing traditional morphology-based species descriptions.…”

“…For example, Hesperomyces virescens forms a haustorium and is in fact a complex of many near-cryptic species, each with their own host (Haelewaters et al 2018 ). In contrast, Rickia wasmannii does not form a haustorium and is a single phylogenetic species with different Myrmica hosts that are placed in phylogenetically unrelated species groups (Haelewaters et al 2019a ). Both examples provide support for the haustorium theory (Fig.…”

Penetrative and non-penetrative interaction between Laboulbeniales fungi and their arthropod hosts

“…A parasite itself can be infected with another parasite, which defines the latter as a hyperparasite 2 . Understanding parasitism, especially hyperparasitism, requires a complex multidisciplinary approach involving ecology, evolution and behaviour of the three participants in the interaction 2 – 5 .…”