TY - JOUR A1 - Lehenberger, Maximilian A1 - Foh, Nina A1 - Göttlein, Axel A1 - Six, Diana A1 - Biedermann, Peter H. W. T1 - Nutrient-Poor Breeding Substrates of Ambrosia Beetles Are Enriched With Biologically Important Elements JF - Frontiers in Microbiology N2 - Fungus-farming within galleries in the xylem of trees has evolved independently in at least twelve lineages of weevils (Curculionidae: Scolytinae, Platypodinae) and one lineage of ship-timber beetles (Lymexylidae). Jointly these are termed ambrosia beetles because they actively cultivate nutritional “ambrosia fungi” as their main source of food. The beetles are obligately dependent on their ambrosia fungi as they provide them a broad range of essential nutrients ensuring their survival in an extremely nutrient-poor environment. While xylem is rich in carbon (C) and hydrogen (H), various elements essential for fungal and beetle growth, such as nitrogen (N), phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), and manganese (Mn) are extremely low in concentration. Currently it remains untested how both ambrosia beetles and their fungi meet their nutritional requirements in this habitat. Here, we aimed to determine for the first time if galleries of ambrosia beetles are generally enriched with elements that are rare in uncolonized xylem tissue and whether these nutrients are translocated to the galleries from the xylem by the fungal associates. To do so, we examined natural galleries of three ambrosia beetle species from three independently evolved farming lineages, Xyleborinus saxesenii (Scolytinae: Xyleborini), Trypodendron lineatum (Scolytinae: Xyloterini) and Elateroides dermestoides (Lymexylidae), that cultivate unrelated ambrosia fungi in the ascomycete orders Ophiostomatales, Microascales, and Saccharomycetales, respectively. Several elements, in particular Ca, N, P, K, Mg, Mn, and S, were present in high concentrations within the beetles’ galleries but available in only very low concentrations in the surrounding xylem. The concentration of elements was generally highest with X. saxesenii, followed by T. lineatum and E. dermestoides, which positively correlates with the degree of sociality and productivity of brood per gallery. We propose that the ambrosia fungal mutualists are translocating essential elements through their hyphae from the xylem to fruiting structures they form on gallery walls. Moreover, the extremely strong enrichment observed suggests recycling of these elements from the feces of the insects, where bacteria and yeasts might play a role. KW - ambrosia beetle KW - ecological stoichiometry KW - microbiome KW - nutrients KW - macro- and micro-elements KW - element translocation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-237602 SN - 1664-302X VL - 12 ER - TY - JOUR A1 - Lehenberger, Maximilian A1 - Benkert, Markus A1 - Biedermann, Peter H. W. T1 - Ethanol-Enriched Substrate Facilitates Ambrosia Beetle Fungi, but Inhibits Their Pathogens and Fungal Symbionts of Bark Beetles JF - Frontiers in Microbiology N2 - Bark beetles (sensu lato) colonize woody tissues like phloem or xylem and are associated with a broad range of micro-organisms. Specific fungi in the ascomycete orders Hypocreales, Microascales and Ophistomatales as well as the basidiomycete Russulales have been found to be of high importance for successful tree colonization and reproduction in many species. While fungal mutualisms are facultative for most phloem-colonizing bark beetles (sensu stricto), xylem-colonizing ambrosia beetles are long known to obligatorily depend on mutualistic fungi for nutrition of adults and larvae. Recently, a defensive role of fungal mutualists for their ambrosia beetle hosts was revealed: Few tested mutualists outcompeted other beetle-antagonistic fungi by their ability to produce, detoxify and metabolize ethanol, which is naturally occurring in stressed and/or dying trees that many ambrosia beetle species preferentially colonize. Here, we aim to test (i) how widespread beneficial effects of ethanol are among the independently evolved lineages of ambrosia beetle fungal mutualists and (ii) whether it is also present in common fungal symbionts of two bark beetle species (Ips typographus, Dendroctonus ponderosae) and some general fungal antagonists of bark and ambrosia beetle species. The majority of mutualistic ambrosia beetle fungi tested benefited (or at least were not harmed) by the presence of ethanol in terms of growth parameters (e.g., biomass), whereas fungal antagonists were inhibited. This confirms the competitive advantage of nutritional mutualists in the beetle’s preferred, ethanol-containing host material. Even though most bark beetle fungi are found in the same phylogenetic lineages and ancestral to the ambrosia beetle (sensu stricto) fungi, most of them were highly negatively affected by ethanol and only a nutritional mutualist of Dendroctonus ponderosae benefited, however. This suggests that ethanol tolerance is a derived trait in nutritional fungal mutualists, particularly in ambrosia beetles that show cooperative farming of their fungi. KW - ambrosia fungi KW - bark and ambrosia beetles KW - symbiont selection KW - ethanol KW - detoxification KW - Ips typographus Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-222222 SN - 1664-302X VL - 11 ER - TY - THES A1 - Lehenberger, Maximilian T1 - Ecology and Evolution of symbiotic microbial communities in fungus farming ambrosia beetles T1 - Ökologie und Evolution von symbiotischen mikrobiellen Gemeinschaften in Pilzzüchtenden Ambrosiakäfern N2 - Within my PhD project I gained several novel insights into the poorly investigated symbiotic world of fungus farming ambrosia beetles and their bark beetle ancestors, where I especially focused on physiological interactions and capabilities of associated fungal symbionts. Here, (i) I could confirm the association of mutualistic Phialophoropsis fungi with the ambrosia beetle genus Trypodendron and found hints for a possible new Phialophoropsis species in T. signatum and T. domesticum. Moreover, I could show that mutualistic fungi of Trypodendron ambrosia beetles are able to decompose major woody polysaccharides such as cellulose and xylan. Additionally, (ii) I provided the first images using micro-computed tomography (µCT) of the formerly unknown structure of the mycetangium of Trypodendron leave. (iii) I could confirm a general tolerance towards ethanol in mutualistic ambrosia beetle fungi, while antagonistic fungi as well as most examined fungal bark beetle associates (e.g. possibly tree-defense detoxifying species) were highly sensitive to even low concentrations of ethanol. Further, (iv) I found that natural galleries of ambrosia beetles are highly enriched with several biologically important elements (such as N, P, S, K, Mg) compared to the surrounding woody tissue and suggest that mutualistic fungi are translocating and concentrating elements from the immediate surrounding xylem to the beetles galleries. Furthermore, (v) I could show that various fungi associated with bark and ambrosia beetles (mutualists, possibly beneficial symbionts) are emitting several volatile organic compounds mostly within aliphatic and aromatic alcohols and esters, while non-mutualistic and free living species were generally emitting a lower number and amount of volatiles. Finally, especially bark and ambrosia beetle fungi were found to incorporate several amino acids, from which some are especially important for the production of certain volatile organic compounds. Amino acid content also indicated a higher nutritional value for certain species. Here, I propose that especially volatile organic compounds are widespread key players in maintaining various symbioses between fungi and beetles, as already proven by a recent study on the bark beetle Ips typographus (as well as for some other bark beetle-fungus symbioses, see summary in Kandasamy et al. 2016) and also suggested for ambrosia beetles. N2 - Im Rahmen meiner Promotion konnte ich einige neue Einblicke in die symbiotische Welt von Pilz-züchtenden Ambrosiakäfern sowie ihren direkten Vorfahren den Borkenkäfern, mit speziellen Fokus auf physiologische Interaktionen und Besonderheiten der assoziierten Pilzen, erlangen. Hier konnte ich (i) die Assoziation der europäischen Trypodendron Arten mit mutualistischen Pilzen in der Gattung Phialophoropsis generell bestätigen und fand des weiteren Hinweise auf eine vermutlich neue Phialophoropsis Art in den beiden Ambrosiakäfern T. domesticum und T. signatum. Außerdem konnte ich zeigen, dass mutualistische Pilze, welche mit Ambrosiakäfern der Gattung Trypodendron assoziiert sind, wesentliche Polysaccharide im Holz (Cellulose und Xylan) abbauen können. Zusätzlich war es mir möglich, (ii) erstmals die Pilzsporen übertragende Struktur „Mycetangium“ des Ambrosiakäfers Trypodendron laeve zu untersuchen und durch den Einsatz von Mikro-Computertomographie (µCT) somit die ersten detaillierten Aufnahmen bereit zu stellen. Außerdem bestätigten und ergänzten meine Studien, (iii) das Ethanol� Toleranz unter Ambrosiakäfer-Pilzen eine wohl sehr weit verbreitete Besonderheit ist, wohingegen für die Käfer bzw. für die Ambrosiapilze schädliche Pilze stark durch schon geringe Ethanol-Konzentrationen gehemmt werden. Interessanterweise wurden auch nahezu alle mit Borkenkäfern assoziierten Pilze stark durch Ethanol gehemmt. Des Weiteren konnte ich zeigen, (iv) das natürliche Brutsysteme von Ambrosiakäfern, im Gegensatz zu unbesiedeltem Splintholz, sehr stark mit verschiedenen essentiellen Elementen (wie etwa N, P, S, K und Mg) angereichert sind. Sehr wahrscheinlich ist es den Pilzsymbionten möglich, Elemente aus unmittelbar umliegendem Splintholz abzuziehen und diese in den Brutsystemen der Käfer entsprechend anzureichern. Außerdem konnte ich zeigen, (v) das nahezu alle untersuchten Borken- und Ambrosiakäfer-Pilze (Mutualisten sowie möglicherweise begünstigende Symbionten) eine Vielzahl an flüchtigen Inhaltsstoffen produzieren, welche sich hier vor allem in die Gruppe der aliphatischen und aromatischen Alkohole und Ester eingliedern. Nicht mutualistische Pilze sowie freilebende Arten produzierten im Vergleich eine geringere Anzahl an unterschiedlichen flüchtigen Inhaltsstoffen und emittierten zumeist geringere Mengen davon. Schließlich konnte ich zeigen, dass vor allem Pilze welche mit Borken- und Ambrosiakäfern assoziiert sind, größere Mengen an verschiedenen Aminosäuren in ihrer Biomasse einbauen, von welchen einige besonders wichtig sind um bestimmte flüchtige Inhaltsstoffe zu bilden. Dazu kann durch den Anteil der gefundenen Aminosäuren in der Pilzbiomasse auf den nährstoffreichen Charakter der Pilze geschlossen werden. Diese flüchtigen Inhaltsstoffe haben mit sehr hoher Wahrscheinlichkeit eine essenzielle Rolle innerhalb einer Vielzahl an Käfer-Pilz Symbiosen und sind vermutlich maßgeblich an dem Erfolg und Bestand solcher Symbiosen beteiligt. Dies wurde bereits in jüngster Vergangenheit bei dem Borkenkäfer Ips typographus mit seinen assoziierten Pilzen gezeigt (aber auch bei einigen weiteren Borkenkäfern, siehe Zusammenfassung von Kandasamy et al., 2016), während es bei Ambrosiakäfern bisher nur vermutet wurde. KW - Ambrosia beetles KW - Ambrosiakäfer KW - bark beetles KW - fungi KW - symbiosis KW - mutualism KW - Borkenkäfer KW - Pilze KW - Symbiose Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-241546 PB - Fungal Ecology, Frontiers in Microbiology, Deutsche Gesellschaft für allgemeine und angewandte Entomologie ER -