The bacterial gut microbiota of many animals is known to be important for many physiological functions including detoxification. The selective pressures imposed on insects by exposure to toxins may also be selective pressures on their symbiotic bacteria, who thus may contribute to the mechanism of toxin tolerance for the insect. Amatoxins are a class of cyclopeptide mushroom toxins that primarily act by binding to RNA polymerase II and inhibiting transcription. Several species of mycophagous
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Understanding the often antagonistic plant–herbivore interactions and how host defenses can influence herbivore dietary breadth is an area of ongoing study in ecology and evolutionary biology. Typically, host plants/fungi that produce highly noxious chemical defenses are only fed on by specialists. We know very little about generalist species that can feed and develop on a noxious host. One such example of generalists feeding on toxic host occurs in the mushroom‐feeding
- Award ID(s):
- 1737869
- NSF-PAR ID:
- 10492169
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Ecology and Evolution
- Volume:
- 14
- Issue:
- 2
- ISSN:
- 2045-7758
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Drosophila are tolerant to amatoxins found in mushrooms of the genusAmanita , despite these toxins being lethal to most other known eukaryotes. These species can tolerate amatoxins in natural concentrations to utilize toxic mushrooms as larval hosts, but the mechanism by which these species are tolerant remains unknown. Previous data have shown that a local population ofD. tripunctata exhibits significant genetic variation in toxin tolerance. This study assesses the potential role of the microbiome in α‐amanitin tolerance in six wild‐derived strains ofDrosophila tripunctata . Normal and antibiotic‐treated samples of six strains were reared on diets with and without α‐amanitin, and then scored for survival from the larval stage to adulthood and for development time to pupation. Our results show that a substantial reduction in bacterial load does not influence toxin tolerance in this system, while confirming genotype and toxin‐specific effects on survival are independent of the microbiome composition. Thus, we conclude that this adaptation to exploit toxic mushrooms as a host is likely intrinsic to the fly's genome and not a property of their microbiome. -
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Dracula orchids mimic mushrooms in appearance and scent, and are pollinated by mushroom flies. This study examined the guilds of insect visitors toDracula species and to co‐occurring mushrooms in an Ecuadorean cloud forest. Significant visitor overlap was documented (mostly in the generaZygothrica andHirtodrosophila ; Drosophilidae). To test the brood‐site mimicry hypothesis, behavioural observations were also performed and rearing success was examined.2. Many fly species that visit
Dracula are also found on mushrooms. Furthermore, the presence of pollinia enabled us to document the fact that particular individuals visiting mushrooms also visitDracula . Roughly two‐thirds of the visitors to these unusual flowers are fungal‐associated, and the rest appear to beDracula specialists.3. A variety of behaviours common on both host groups were observed, including courtship semaphoring, feeding, sheltering, defending territory, and mating. Given this suite of shared reproductive behaviour, it was hypothesised that flies may also oviposit in both substrates. Flies were reared from mushrooms,
Dracula spp., and other flowers (controls) to determine which substrate led to the highest fitness for the flies. Very few flies emerged from theDracula flowers and there was no species overlap between the emergent insects and the known pollinators.4. Despite the fact that there is evidence for brood‐site mimicry, the
Dracula situation is complex. All the flies could derive many of the same fitness benefits from the flowers as they do from mushrooms (shelter, food, mating), but they are clearly not gaining the same fitness benefit, in terms of progeny, on flowers compared with mushrooms. -
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Abstract Adult and juvenile herbivores of the same species can use divergent feeding strategies, and thus may inhabit and consume different parts of the plant. Because the expression of chemical defences often differs between host plant tissues, this variation may result in disparate performance outcomes for adult and juvenile conspecifics that feed on distinct dietary substrates.
The goal of this study was to evaluate how host range may differ between adults and juveniles in a generalist herbivore. We addressed the impacts of among‐ and within‐plant defence variation using the wood‐feeding Asian longhorned beetle (
Anoplophora glabripennis ) and three host plants having a range of putative resistance.Impacts of host plants on adult and offspring performance were assessed using a series of controlled bioassays. We evaluated adult‐feeding and egg‐laying behaviours in choice and no‐choice experiments using the different hosts, and subsequent offspring establishment. We then evaluated host plant chemical composition related to nutrition and defence.
Different plants had strong impacts on adult performance, but these patterns did not extend to effects on offspring. Females were capable of developing eggs when provided
Acer rubrum , but notPopulus deltoides orPopulus tomentosa . Females that produced eggs by feeding onA. rubrum, however, deposited eggs into all three plant species. Larvae hatched and consumed tissues in all three hosts. The differences between adult and juvenile utilization ofPopulus spp. were reflected in markedly higher salicinoid phenolic concentrations in bark (>2% dw), while wood had trace quantities.Our results demonstrate that plant resistance mechanisms can differentially act upon adult and juvenile life stages of a polyphagous herbivore when there is differential expression of chemical defences among plant tissue types.
Anoplophora glabripennis has been a globally successful invader due in part to its broad host range, and our results suggest a mechanism that permits the beetle to exploit marginally resistant plants. This study has implications for how host range differs between insect feeding stages, which is particularly important for invasive, polyphagous species encountering novel food sources. -
Abstract Background The recognition and delineation of morphologically indistinguishable cryptic species can have broad implications for wildlife conservation, disease ecology and accurate estimates of biodiversity. Parasites are intriguing in the study of cryptic speciation because unique evolutionary pressures and diversifying factors are generated by ecological characteristics of host-parasite relationships, including host specificity. Bat flies (Diptera: Nycteribiidae and Streblidae) are obligate, hematophagous ectoparasites of bats that generally exhibit high host specificity. One rare exception is Penicillidia fulvida (Diptera: Nycteribiidae), an African bat fly found in association with many phylogenetically distant hosts. One explanation for P. fulvida ’s extreme polyxeny is that it may represent a complex of host-specific yet cryptic species, an increasingly common finding in molecular genetic studies of supposed generalist parasites. Methods A total of 65 P. fulvida specimens were collected at 14 localities across Kenya, from bat species representing six bat families. Mitochondrial cytochrome c oxidase subunit 1 ( COI ) and nuclear 28S ribosomal RNA (rRNA) sequences were obtained from 59 specimens and used to construct Bayesian and maximum likelihood phylogenies. Analysis of molecular variance was used to determine how genetic variation in P. fulvida was allocated among host taxa. Results The 28S rRNA sequences studied were invariant within P. fulvida . Some genetic structure was present in the COI sequence data, but this could be more parsimoniously explained by geography than host family. Conclusions Our results support the status of P. fulvida as a rare example of a single bat fly species with primary host associations spanning multiple bat families. Gene flow among P. fulvida utilizing different host species may be promoted by polyspecific roosting behavior in bats, and host preference may also be malleable based on bat assemblages occupying shared roosts. The proclivity of generalist parasites to switch hosts makes them more likely to vector or opportunistically transmit pathogens across host species boundaries. Consequently, the presence of polyxenous bat flies is an important consideration to disease ecology as bat flies become increasingly known to be associated with bat pathogens. Graphical Abstractmore » « less
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Summary Environmental variation can have profound and direct effects on fitness, fecundity, and host–symbiont interactions. Replication rates of microbes within arthropod hosts, for example, are correlated with incubation temperature but less is known about the influence of host–symbiont dynamics on environmental preference. Hence, we conducted thermal preference (
T p) assays and tested if infection status and genetic variation in endosymbiont bacteriumWolbachia affected temperature choice ofDrosophila melanogaster Wolbachia preferred lower temperatures compared with uninfectedDrosophila . Moreover,T pvaried with respect to three investigatedWolbachia variants (w Mel,w MelCS, andw MelPop). While uninfected individuals preferred 24.4°C, we found significant shifts of −1.2°C inw Mel‐ and −4°C in flies infected either withw MelCS orw MelPop. We, therefore, postulate thatWolbachia‐ associatedT pvariation within a host species might represent a behavioural accommodation to host–symbiont interactions and trigger behavioural self‐medication and bacterial titre regulation by the host.
