Evidence for multiple ecological roles of Leptographium abietinum, a symbiotic fungus associated with the North American spruce beetle

Davis, Thomas S.; Stewart, Jane E.; Mann, Andrew J.; Bradley, C.; Hofstetter, Richard W.

doi:10.1016/j.funeco.2018.04.008

Cited by 34 publications

(15 citation statements)

References 66 publications

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“…Such evolutionary naïve tree species are often favorable hosts as they have little resistance against invasive insects and their symbionts (Cudmore et al, 2010;Raffa et al, 2013;Sun et al, 2013 Beer et al (2014), that are moderately virulent to their host trees (Solheim and Safranyik, 1997). Leptographium abietinum appears to benefit its bark beetle vector by providing vital nutrients, metabolizing toxic host terpenes, and protecting beetles from an entomopathogenic fungus (Davis et al, 2019). Ips typographus has previously been shown to breed successfully in several North American spruce species (Økland et al, 2011;Flø et al, 2018) and if introduced in North America it will probably be exposed to the fungal symbionts of D. rufipennis.…”

Section: Introductionmentioning

confidence: 99%

Fungal Interactions and Host Tree Preferences in the Spruce Bark Beetle Ips typographus

2021

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The spruce bark beetle Ips typographus is the most damaging pest in European spruce forests and has caused great ecological and economic disturbances in recent years. Although native to Eurasia, I. typographus has been intercepted more than 200 times in North America and could establish there as an exotic pest if it can find suitable host trees. Using in vitro bioassays, we compared the preference of I. typographus for its coevolved historical host Norway spruce (Picea abies) and two non-coevolved (naïve) North American hosts: black spruce (Picea mariana) and white spruce (Picea glauca). Additionally, we tested how I. typographus responded to its own fungal associates (conspecific fungi) and to fungi vectored by the North American spruce beetle Dendroctonus rufipennis (allospecific fungi). All tested fungi were grown on both historical and naïve host bark media. In a four-choice Petri dish bioassay, I. typographus readily tunneled into bark medium from each of the three spruce species and showed no preference for the historical host over the naïve hosts. Additionally, the beetles showed a clear preference for bark media colonized by fungi and made longer tunnels in fungus-colonized media compared to fungus-free media. The preference for fungus-colonized media did not depend on whether the medium was colonized by conspecific or allospecific fungi. Furthermore, olfactometer bioassays demonstrated that beetles were strongly attracted toward volatiles emitted by both con- and allospecific fungi. Collectively, these results suggest that I. typographus could thrive in evolutionary naïve spruce hosts if it becomes established in North America. Also, I. typographus could probably form and maintain new associations with local allospecific fungi that might increase beetle fitness in naïve host trees.

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Section: Introductionmentioning

confidence: 99%

Fungal Interactions and Host Tree Preferences in the Spruce Bark Beetle Ips typographus

2021

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“…One hypothesis that might explain spruce beetle colonisation success in the field is association with fungal symbionts, which may have the metabolic pathways necessary for detoxifying monoterpenes. Earlier studies indicate that the primary fungal symbiont of spruce beetle (Leptographium abietinum) is capable of metabolising at least some monoterpenes (Davis et al 2019). In addition, in the toxicity assay reported here, beetles were prevented from avoiding exposure to monoterpene vapours, but active behavioural avoidance and repeated emergence during gallery construction and oviposition may also help beetles to limit toxic effects of exposure to monoterpenes.…”

Section: Introductionmentioning

confidence: 67%

Toxicity of two Engelmann spruce (Pinaceae) monoterpene chemotypes from the southern Rocky Mountains to North American spruce beetle (Coleoptera: Scolytidae)

Davis

2020

Can Entomol

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Engelmann spruce, Picea engelmannii Parry ex Engelm. (Pinaceae), in the southern Rocky Mountains is composed of two distinct phloem monoterpene chemotypes that differ in relative abundances of multiple monoterpenes, particularly α-pinene and Δ3-carene (hereafter, the “α-pinene chemotype” and the “Δ3-carene chemotype”). Here, relative toxicity of these chemotypes is tested on spruce beetle (Dendroctonus rufipennis Kirby) (Coleoptera: Scolytinae), a phloeophagous herbivore that colonises trees of both types. Synthetic monoterpene blends representing each chemotype were tested across a range of concentrations (0, 10, 50, 100, 200, and 500 µg/L) in the lab, and probability of survival of adult beetles exposed to each blend was modelled using a logit function. Logit curves were solved to determine LC25, LC50, and LC75 of each monoterpene blend. On average, probability of beetle survival was lower when exposed to the Δ3-carene chemotype than when exposed to the α-pinene chemotype. However, both chemotypes were completely lethal to beetles at concentrations exceeding 100 µg/L. Adult body mass did not affect survival probability. It is concluded that spruce phloem chemotypes may differ in their toxicity to spruce beetles, with potential consequences for patterns of host-tree colonisation by spruce beetle.

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“…A common method for examining competition between entomopathogenic fungi and bark beetle‐associated microorganisms is through dual culture Petri dish assays that allow researchers to compare primary aspects of resource capture, or growth rates, and secondary aspects of competition, such as the ability to overtake or inhibit a competing fungus. On malt extract agar, Leptographium abietinum , a symbiont of the bark beetle Dendroctonus rufipennis , is a slightly faster grower than commercial and sympatric B. bassiana isolates and can more rapidly exploit uncolonized resource space; though both fungi can exclude one another from colonized areas 19 . The same deadlock is found in the fungi Ambrosiella roeperi and A .…”

Section: Entomopathogenic Fungi and Bark Beetle Environmentsmentioning

confidence: 95%

“…Bark beetles are associated with a consistent community of symbiotic microorganisms that aid in beetle development and the ability to colonize host trees 19 . Knowledge of the interactions among bark beetles, entomopathogenic fungi, and bark beetle‐symbionts is important for successful fungal application.…”

Section: Entomopathogenic Fungi and Bark Beetle Environmentsmentioning

confidence: 99%

Entomopathogenic fungi to control bark beetles: a review of ecological recommendations

Mann

Davis

2021

Pest Management Science

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There is considerable interest in applying entomopathogenic fungi as a biological control to limit insect populations due to their low environmental and human applicator impacts. However, despite many promising laboratory tests, there are few examples where these fungi were successfully applied to manage bark beetles. Here, we explore how environmental conditions unique to bark beetle habitats may have limited previous entomopathogenic fungus applications, including variable temperatures, ultraviolet light, bark beetle symbiotic microorganisms, tree phytochemicals, and cryptic bark beetle behaviors. Based on the existing literature, we provide a framework for interpreting the pathogenicity of entomopathogenic fungi to bark beetles, with emphasis on both standardizing and improving laboratory approaches to enhance field applications. Our synthesis indicates that most previous laboratory evaluations are conducted under conditions that are not representative of actual bark beetle systems; this may render fungal isolates functionally non‐pathogenic in field settings. We recommend that future studies place particular effort into understanding entomopathogen response to the presence of bark beetle symbiotic microorganisms, plant phytochemicals, and potential as a tree endophyte. Additionally, field application methods should aid entomopathogens in overcoming stressful conditions and allow the fungus to infect multiple bark beetle life stages. © 2021 Society of Chemical Industry.

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Evidence for multiple ecological roles of Leptographium abietinum, a symbiotic fungus associated with the North American spruce beetle

Cited by 34 publications

References 66 publications

Fungal Interactions and Host Tree Preferences in the Spruce Bark Beetle Ips typographus

Fungal Interactions and Host Tree Preferences in the Spruce Bark Beetle Ips typographus

Toxicity of two Engelmann spruce (Pinaceae) monoterpene chemotypes from the southern Rocky Mountains to North American spruce beetle (Coleoptera: Scolytidae)

Entomopathogenic fungi to control bark beetles: a review of ecological recommendations

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