TY - JOUR A1 - Menzel, Florian A1 - Blüthgen, Nico A1 - Tolasch, Till A1 - Conrad, Jürgen A1 - Beifuss, Uwe A1 - Beuerle, Till A1 - Schmitt, Thomas T1 - Crematoenones - a novel substance class exhibited by ants functions as appeasement signal JF - Frontiers in Zoology N2 - Background: Parasitic, commensalistic, and mutualistic guests in social insect colonies often circumvent their hosts' nestmate recognition system to be accepted. These tolerance strategies include chemical mimicry and chemical insignificance. While tolerance strategies have been studied intensively in social parasites, little is known about these mechanisms in non-parasitic interactions. Here, we describe a strategy used in a parabiotic association, i.e. two mutualistic ant species that regularly share a common nest although they have overlapping food niches. One of them, Crematogaster modiglianii, produces an array of cuticular compounds which represent a substance class undescribed in nature so far. They occur in high abundances, which suggests an important function in the ant's association with its partner Camponotus rufifemur. Results: We elucidated the structure of one of the main compounds from cuticular extracts using gas chromatography, mass spectrometry, chemical derivatizations and nuclear magnetic resonance spectroscopy (NMR). The compound consists of two fused six-membered rings with two alkyl groups, one of which carries a keto functionality. To our knowledge, this is the first report on the identification of this substance class in nature. We suggest naming the compound crematoenone. In behavioural assays, crematoenones reduced interspecific aggression. Camponotus showed less aggression to allospecific cuticular hydrocarbons when combined with crematoenones. Thus, they function as appeasement substances. However, although the crematoenone composition was highly colony-specific, interspecific recognition was mediated by cuticular hydrocarbons, and not by crematoenones. Conclusions: Crematenones enable Crematogaster to evade Camponotus aggression, and thus reduce potential costs from competition with Camponotus. Hence, they seem to be a key factor in the parabiosis, and help Crematogaster to gain a net benefit from the association and thus maintain a mutualistic association over evolutionary time. To our knowledge, putative appeasement substances have been reported only once so far, and never between non-parasitic species. Since most organisms associated with social insects need to overcome their nestmate recognition system, we hypothesize that appeasement substances might play an important role in the evolution and maintenance of other mutualistic associations as well, by allowing organisms to reduce costs from antagonistic behaviour of other species. KW - cuticular hydrocarbons KW - appeasement substance KW - bees KW - ecology KW - parasitism KW - alkyloctahydronaphthalene KW - usurpation KW - venom KW - pheromone KW - crematogaster KW - parabiotic ants KW - Dufours gland KW - polyergus rufescens KW - formicidae KW - interspecific aggression KW - nestmate recognition cues KW - parabiotic association Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-122595 SN - 1742-9994 VL - 10 IS - 32 ER - TY - JOUR A1 - Polidori, Carlo A1 - Ballesteros, Yolanda A1 - Wurdack, Mareike A1 - Asís, Josep Daniel A1 - Tormos, José A1 - Baños-Picón, Laura A1 - Schmitt, Thomas T1 - Low host specialization in the cuckoo wasp, Parnopes grandior, weakens chemical mimicry but does not lead to local adaption JF - Insects N2 - Insect brood parasites have evolved a variety of strategies to avoid being detected by their hosts. Few previous studies on cuckoo wasps (Hymenoptera: Chrysididae), which are natural enemies of solitary wasps and bees, have shown that chemical mimicry, i.e., the biosynthesis of cuticular hydrocarbons (CHC) that match the host profile, evolved in several species. However, mimicry was not detected in all investigated host-parasite pairs. The effect of host range as a second factor that may play a role in evolution of mimicry has been neglected, since all previous studies were carried out on host specialists and at nesting sites where only one host species occurred. Here we studied the cuckoo wasp Parnopes grandior, which attacks many digger wasp species of the genus Bembix (Hymenoptera: Crabronidae). Given its weak host specialization, P. grandior may either locally adapt by increasing mimicry precision to only one of the sympatric hosts or it may evolve chemical insignificance by reducing the CHC profile complexity and/or CHCs amounts. At a study site harbouring three host species, we found evidence for a weak but appreciable chemical deception strategy in P. grandior. Indeed, the CHC profile of P. grandior was more similar to all sympatric Bembix species than to a non-host wasp species belonging to the same tribe as Bembix. Furthermore, P. grandior CHC profile was equally distant to all the hosts' CHC profiles, thus not pointing towards local adaptation of the CHC profile to one of the hosts' profile. We conducted behavioural assays suggesting that such weak mimicry is sufficient to reduce host aggression, even in absence of an insignificance strategy, which was not detected. Hence, we finally concluded that host range may indeed play a role in shaping the level of chemical mimicry in cuckoo wasps. KW - Chrysididae KW - Bembix KW - chemical mimicry KW - cuticular hydrocarbons Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-200651 SN - 2075-4450 VL - 11 IS - 2 ER - TY - JOUR A1 - Moris, Victoria C. A1 - Christmann, Katharina A1 - Wirtgen, Aline A1 - Belokobylskij, Sergey A. A1 - Berg, Alexander A1 - Liebig, Wolf-Harald A1 - Soon, Villu A1 - Baur, Hannes A1 - Schmitt, Thomas A1 - Niehuis, Oliver T1 - Cuticular hydrocarbons on old museum specimens of the spiny mason wasp, Odynerus spinipes (Hymenoptera: Vespidae: Eumeninae), shed light on the distribution and on regional frequencies of distinct chemotypes JF - Chemoecology N2 - The mason wasp Odynerus spinipes shows an exceptional case of intrasexual cuticular hydrocarbon (CHC) profile dimorphism. Females of this species display one of two CHC profiles (chemotypes) that differ qualitatively and quantitatively from each other. The ratio of the two chemotypes was previously shown to be close to 1:1 at three sites in Southern Germany, which might not be representative given the Palearctic distribution of the species. To infer the frequency of the two chemotypes across the entire distributional range of the species, we analyzed with GC–MS the CHC profile of 1042 dry-mounted specimens stored in private and museum collections. We complemented our sampling by including 324 samples collected and preserved specifically for studying their CHCs. We were capable of reliably identifying the chemotypes in 91% of dry-mounted samples, some of which collected almost 200 years ago. We found both chemotypes to occur in the Far East, the presumed glacial refuge of the species, and their frequency to differ considerably between sites and geographic regions. The geographic structure in the chemotype frequencies could be the result of differential selection regimes and/or different dispersal routes during the colonization of the Western Palearctic. The presented data pave the route for disentangling these factors by providing information where to geographically sample O. spinipes for population genetic analyses. They also form the much-needed basis for future studies aiming to understand the evolutionary and geographic origin as well as the genetics of the astounding CHC profile dimorphism that O. spinipes females exhibit. KW - cuticular hydrocarbons KW - chemotypes KW - dry-mounted samples KW - collections KW - distribution Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-306999 SN - 0937-7409 SN - 1423-0445 VL - 31 IS - 5 ER - TY - JOUR A1 - Maihoff, Fabienne A1 - Bohlke, Kyte A1 - Brockmann, Axel A1 - Schmitt, Thomas T1 - Increased complexity of worker CHC profiles in Apis dorsata correlates with nesting ecology JF - PLoS ONE N2 - Cuticular hydrocarbons (CHC) are known to serve as discrimination cues and will trigger defence behaviour in a plethora of eusocial insects. However, little is known how about nestmate recognition ability selects for CHC diversification. In this study we investigate differences in CHC composition of four major honey bee species with respect to the differences in their nesting behavior. In contrast to A. mellifera, A. cerana and A. florea, the giant honey bee A. dorsata prefers to build their nests in aggregations with very small spatial distances between nests, which increases the probability of intrusions. Thus, A. dorsata exhibits a particularly challenging nesting behavior which we hypothesize should be accompanied with an improved nestmate recognition system. Comparative analyses of the worker CHC profiles indicate that A. dorsata workers exhibit a unique and more complex CHC profile than the other three honey bee species. This increased complexity is likely based on a developmental process that retains the capability to synthesize methyl-branched hydrocarbons as adults. Furthermore, two sets of behavioral experiments provide evidence that A. dorsata shows an improved nestmate discrimination ability compared to the phylogenetically ancestral A. florea, which is also open-nesting but does not form nest aggregations. The results of our study suggest that ecological traits like nesting in aggregation might be able to drive CHC profile diversification even in closely related insect species. KW - Apis dorsata KW - cuticular hydrocarbons KW - nesting Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-301353 VL - 17 IS - 7 ER - TY - JOUR A1 - Castillo, Ruth A1 - Wurdack, Mareike A1 - Pauli, Thomas A1 - Keller, Alexander A1 - Feldhaar, Heike A1 - Polidori, Carlo A1 - Niehuis, Oliver A1 - Schmitt, Thomas T1 - Evidence for a chemical arms race between cuckoo wasps of the genus Hedychrum and their distantly related host apoid wasps JF - BMC Ecology and Evolution N2 - Background Brood parasites can exert strong selection pressure on their hosts. Many brood parasites escape their detection by mimicking sensory cues of their hosts. However, there is little evidence whether or not the hosts are able to escape the parasites’ mimicry by changing these cues. We addressed this question by analyzing cuticular hydrocarbon (CHC) profiles of Cerceris and Philanthus wasps and their brood parasites, cuckoo wasps mimicking the CHC profiles of their hosts. Some of these hosts use hydrocarbons to preserve their prey against fungal infestation and thus, they cannot significantly change their CHC composition in response to chemical mimicry by Hedychrum brood parasites. Results We found that the CHC overlap between brood parasites and their hosts was lower in case of host wasps not preserving their prey than in case of prey-preserving host wasps, whose CHC evolution is constrained. Furthermore, the CHC profiles in non-preserving host wasps is more strongly diversified in females than in males, thus in the sex that is chemically mimicked by brood parasites. Conclusion Our results provide evidence for a chemical arms race between those hosts that are liberated from stabilizing selection on their chemical template and their parasites. KW - chemical mimicry KW - philanthidae KW - hymenoptera KW - evolutionary arms race KW - cuticular hydrocarbons KW - chrysididae Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-301289 VL - 22 IS - 1 ER -