Novel taxa and species diversity of Cordyceps sensu lato (Hypocreales, Ascomycota) developing on wireworms (Elateroidea and Tenebrionoidea, Coleoptera)

Species of Cordyceps sensu lato (Hypocreales, Sordariomycetes) have always attracted much scientific attention for their abundant species diversity, important medicinal values and biological control applications. The insect superfamilies Elateroidea and Tenebrionoidea are two large groups of Coleoptera and their larvae are generally called wireworms. Most wireworms inhabit humid soil or fallen wood and are often infected with Cordyceps s.l. However, the species diversity of Cordyceps s.l. on Elateroidea and Tenebrionoidea is poorly known. In the present work, we summarise taxonomic information of 63 Cordyceps s.l. species that have been reported as pathogens of wireworms. We review their hosts and geographic distributions and provide taxonomic notes for species. Of those, 60 fungal species are accepted as natural pathogens of wireworms and three species (Cordycepsmilitaris, Ophiocordycepsferruginosa and O.variabilis) are excluded. Two new species, O.borealis from Russia (Primorsky Krai) and O.spicatus from China (Guizhou), are described and compared with their closest allies. Polycephalomycesformosus is also described because it is reported as a pathogen of wireworms for the first time. Phylogeny was reconstructed from a combined dataset, comprising SSU, LSU and TEF1-α gene sequences. The results, presented in this study, support the establishment of the new species and confirm the identification of P.formosus.

Fungi Recorded on Folivorous Lepidoptera: High Diversity Despite Moderate Prevalence

The knowledge about the diversity and ecological role of entomopathogenic fungi is primarily based on agroecosystems whereas information derived from natural insect populations is much more limited. To contribute to filling this gap, we recorded the prevalence of fungal infections in laboratory rearing experiments with five species of Lepidoptera, and in a field rearing experiment including one of these moths. The diversity of detected fungi was found to be high; we isolated 25 species of fungi from insects that had died in the course of these experiments. Six species belonged to the family Cordycipitaceae known to include unambiguous insect pathogens. The trophic niche of the representatives of other taxa is less clear and requires further studies. Regarding the most abundant species, Cordyceps farinosa, in which this question could be addressed, there was no indication of specialization on particular insect hosts, whereas several of the less common species may have been recorded from lepidopteran hosts for the first time. Across the subsets of the data, the prevalence of fungal infections generally remained below 5%. Our results are thus consistent with the idea that entomopathogenic fungi are always present in insect populations but rarely reach epizootic levels. The detected species richness shows that much is to be gained from mapping the diversity of fungal species associated with folivorous insects in natural populations.

Interplay between Fungal Infection and Bacterial Associates in the Wax Moth Galleria mellonella under Different Temperature Conditions

Various insect bacterial associates are involved in pathogeneses caused by entomopathogenic fungi. The outcome of infection (fungal growth or decomposition) may depend on environmental factors such as temperature. The aim of this study was to analyze the bacterial communities and immune response of Galleria mellonella larvae injected with Cordyceps militaris and incubated at 15 °C and 25 °C. We examined changes in the bacterial CFUs, bacterial communities (Illumina MiSeq 16S rRNA gene sequencing) and expression of immune, apoptosis, ROS and stress-related genes (qPCR) in larval tissues in response to fungal infection at the mentioned temperatures. Increased survival of larvae after C. militaris injection was observed at 25 °C, although more frequent episodes of spontaneous bacteriosis were observed at this temperature compared to 15 °C. We revealed an increase in the abundance of enterococci and enterobacteria in the midgut and hemolymph in response to infection at 25 °C, which was not observed at 15 °C. Antifungal peptide genes showed the highest expression at 25 °C, while antibacterial peptides and inhibitor of apoptosis genes were strongly expressed at 15 °C. Cultivable bacteria significantly suppressed the growth of C. militaris. We suggest that fungi such as C. militaris may need low temperatures to avoid competition with host bacterial associates.

Coleopteran and Lepidopteran Hosts of the Entomopathogenic Genus Cordyceps sensu lato

Entomophthoralean and ascomycetous fungi are the two major groups known to parasitize arthropods in almost every terrestrial habitat of the earth. Within Ascomycota, Cordyceps sensu lato is a large genus with more than 400 spp. described on numerous orders of Arthropoda. Among the hosts of Cordyceps, Coleoptera and Lepidoptera are the two major orders. Out of the estimated 200 Cordyceps spp. recorded on coleopteran and lepidopteran hosts, we have documented 92 spp. based on the available information of their host species. Among coleopteran hosts, Scarabaeidae and Elateridae are the two major families. Similarly, among lepidopterans, Hepialidae is the largest host family. Cordyceps militaris shows the widest host range, extending to 2 orders, 13 families, and 32 spp. We hope such accumulative work will be useful as a quick reference for interested biologists, forest ecologists, biocontrol researchers, and fungal and insect taxonomists to apprehend host range and host specificities of Cordyceps fungi.