Core Mycobiome and Their Ecological Relevance in the Gut of Five Ips Bark Beetles (Coleoptera: Curculionidae: Scolytinae)

Abstract

Bark beetles are destructive forest pests considering their remarkable contribution to forest depletion. Their association with fungi is useful against the challenges of survival on the noxious and nutritionally limited substrate, i.e., conifer tissues. Fungal symbionts help the beetles in nutrient acquisition and detoxification of toxic tree secondary metabolites. Although gut is the prime location for food digestion and detoxification, limited information is available on gut-mycobiome of bark beetles. The present study screened the gut-mycobiont from six bark beetles (five Ips and one non-Ips) from Scolytinae subfamily using high-throughput sequencing and explored their putative role in symbiosis with the host insect. Results revealed the predominance of four fungal classes-Sordariomycetes, Saccharomycetes, Eurothiomycetes, and Dothidomycetes in all bark beetles. Apart from these, Agaricomycetes, Leothiomycetes, Incertae sedis Basidiomycota, Tremellomycetes, Lecanoromycetes, and Microbotryomycetes were also documented in different beetles. Five Ips bark beetles share a consortium of core fungal communities in their gut tissues consisting of 47 operational taxonomic units (OTUs) belonging to 19 fungal genera. The majority of these core fungal genera belong to the phylum Ascomycota. LEfSe analysis revealed a set of species-specific fungal biomarkers in bark beetles. The present study identified the gut mycobiont assemblage in bark beetles and their putative ecological relevance. An enriched understanding of bark beetle-fungal symbiosis is not only filling the existing knowledge gap in the field but may also unleash an unforeseen potential for future bark beetle management.

Filamentous Fungi and Yeasts Associated with Mites Phoretic on Ips typographus in Eastern Finland

“…The other Saccharomycetaceae isolates included members of Ogataea, Kuraishia and Nakazawaea, which is consistent with the study of [53]. The common occurrence of these yeast genera as part of I. typographus mycobiome is also supported by the recent highthroughput sequencing study [24]. One of the species, K. capsulata, has been amongst the most commonly reported yeast species in surveys of I. typographus and other Ips species [23,50,53,54].…”

“…In contrast, little is known regarding the other fungi involved in these interactions. In addition to ophiostomatoid fungi, yeasts have also been recognized as constant components in bark and ambrosia beetle galleries [22,23] and in the guts of the beetles [24]. Yeasts have most likely been overlooked in majority of the previous collections.…”

Diversity and Functions of Yeast Communities Associated with Insects

“…However, for some species belonging to several insect groups, such as mosquitoes [ 53 ], bark or sap beetles [ 6 , 69 ], and planthoppers [ 64 ], all life stages were analyzed and the presence of yeast species was detected at all developmental stages ( Table S1 ). These insect-yeast communities are mainly acquired from the environment [ 68 , 70 , 71 , 72 , 73 ]. For example, mosquito larvae acquire yeast communities mainly from the water of breeding sites, while adults obtain it from water at emergence as well as from sugar (plants or flower nectars) and/or blood meals for females during their entire life span [ 74 ].…”

A Highly Contiguous Genome Assembly of a Major Forest Pest, the Eurasian Spruce Bark Beetle Ips Typographus

“…Abundant carbon-rich bio-polymers present in bark and adjoining sapwood, such as lignin, hemicellulose and cellulose may not be available to bark beetles as nutrients until prior degradation by fungi and other microbes 19 . Bark beetles, including I. typographus, are associated with a holobiont of diverse microbiota, including gut endo-symbionts 20,21 , yeasts 22 , and ecto-symbionts such as ophiostomatoid fungi that the beetles inoculate into attacked trees 23 . Once established in the tree, these fungi may serve as food for developing beetles, metabolise conifer chemical defences, and accelerate tree death 24,25,26 .…”