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  • 1
    In: American Journal of Botany, Wiley, Vol. 105, No. 6 ( 2018-06), p. 1088-1095
    Abstract: Plant pathogens that form persistent systemic infections within plants have the potential to affect multiple plant life history traits, yet we tend to focus only on visible symptoms. Anther smut of Silene latifolia caused by the fungus Microbotryum lychnidis‐dioicae induces the anthers of its host to support fungal spore production instead of pollen, and the pathogen is primarily transmitted among flowering plants by pollinators. Nevertheless, most of its life cycle is spent in the asymptomatic vegetative phase, and spores falling on seedlings or nonflowering plants can also infect the host. The purpose of this study was to ask whether the fungus also had an effect on its host plant in the juvenile vegetative phase before flowering as this is important for the disease dynamics in species where infection of seedlings is commonplace. Methods Leaf length and leaf number of inoculated and uninoculated juvenile plants were compared in greenhouse experiments, and in one experiment, disease status of the plants at flowering was determined. Key Results Inoculated plants had shorter but more leaves, and reduced root mass at the early juvenile (preflowering) stage. Some of these effects were detectable in plants that were inoculated but showed no disease symptoms at flowering. Conclusions These results show that pathogenic fungi can have endophyte‐like effects even in the total absence of their typical and more charismatic symptoms, and conversely that the assessment of endophyte effects on the fitness of their hosts should include all stages of the host life cycle.
    Type of Medium: Online Resource
    ISSN: 0002-9122 , 1537-2197
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2053581-8
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Wiley ; 2023
    In:  Journal of Evolutionary Biology Vol. 36, No. 5 ( 2023-05), p. 753-763
    In: Journal of Evolutionary Biology, Wiley, Vol. 36, No. 5 ( 2023-05), p. 753-763
    Abstract: Host‐shifts, where pathogens jump from an ancestral host to a novel host, can be facilitated or impeded by standing variation in disease resistance, but only if resistance provides broad‐spectrum general resistance against multiple pathogen species. Host resistance comes in many forms and includes both general resistance, as well as specific resistance, which may only be effective against a single pathogen species or even genotype. However, most evolutionary models consider only one of these forms of resistance, and we have less understanding of how these two forms of resistance evolve in tandem. Here, we develop a model that allows for the joint evolution of specific and general resistance and asks if the evolution of specific resistance drives a decrease in the evolution of general resistance. We also explore how these evolutionary outcomes affect the risk of foreign pathogen invasion and persistence. We show that in the presence of a single endemic pathogen, the two forms of resistance are strongly exclusionary. Critically, we find that specific resistance polymorphisms can prevent the evolution of general resistance, facilitating the invasion of foreign pathogens. We also show that specific resistance polymorphisms are a necessary condition for the successful establishment of foreign pathogens following invasion, as they prevent the exclusion of the foreign pathogen by the more transmissible endemic pathogen. Our results demonstrate the importance of considering the joint evolution of multiple forms of resistance when evaluating a population's susceptibility to foreign pathogens.
    Type of Medium: Online Resource
    ISSN: 1010-061X , 1420-9101
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 92624-3
    detail.hit.zdb_id: 1465318-7
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  • 3
    In: Journal of Ecology, Wiley, Vol. 105, No. 5 ( 2017-09), p. 1413-1424
    Abstract: Theory has shown that sterilizing diseases with frequency‐dependent transmission (characteristics shared by many sexually transmitted diseases) can drive host populations to extinction. Anther‐smut disease (caused by Microbotryum sp.) has become a model plant pathogen system for studying the dynamics of vector‐ and sexually transmitted diseases: infected individuals are sterilized, producing spores instead of pollen, and the disease is spread between reproductive individuals by insect pollinators. We investigated anther‐smut disease in a heavily infected population of Dianthus pavonius (alpine carnation) over an 8‐year period to determine disease impacts on host population dynamics. Over the 8 years, disease prevalence remained consistently high ( 〉 40%), while the host population numbers declined by over 50%. The observed rate of vector transmission to reproductive, adult hosts was inadequate to explain the high disease prevalence. Additional density‐dependent aerial transmission to highly susceptible juveniles, indicated from experimental field and greenhouse studies, is likely to play a key role in maintaining the high disease prevalence. Epidemiological models that accounted for the mixed transmission mode predicted an eventual decline in disease. Synthesis . Our results demonstrate that high prevalence of a sterilizing disease does not necessarily drive host populations towards extinction and also highlights the importance of demographic studies for establishing the presence of alternative transmission modes.
    Type of Medium: Online Resource
    ISSN: 0022-0477 , 1365-2745
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 3023-5
    detail.hit.zdb_id: 2004136-6
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  • 4
    In: Evolution, Wiley, Vol. 73, No. 3 ( 2019-03), p. 497-510
    Type of Medium: Online Resource
    ISSN: 0014-3820 , 1558-5646
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2036375-8
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  • 5
    Online Resource
    Online Resource
    The Royal Society ; 2023
    In:  Proceedings of the Royal Society B: Biological Sciences Vol. 290, No. 1991 ( 2023-01-25)
    In: Proceedings of the Royal Society B: Biological Sciences, The Royal Society, Vol. 290, No. 1991 ( 2023-01-25)
    Abstract: Innate, infection-preventing resistance often varies between host life stages. Juveniles are more resistant than adults in some species, whereas the opposite pattern is true in others. This variation cannot always be explained by prior exposure or physiological constraints and so it has been hypothesized that trade-offs with other life-history traits may be involved. However, little is known about how trade-offs between various life-history traits and resistance at different life stages affect the evolution of age-specific resistance. Here, we use a mathematical model to explore how trade-offs with natural mortality, reproduction and maturation combine to affect the evolution of resistance at different life stages. Our results show that certain combinations of trade-offs have substantial effects on whether adults or juveniles are more resistant, with trade-offs between juvenile resistance and adult reproduction inherently more costly than trade-offs involving maturation or mortality (all else being equal), resulting in consistent evolution of lower resistance at the juvenile stage even when infection causes a lifelong fecundity reduction. Our model demonstrates how the differences between patterns of age-structured resistance seen in nature may be explained by variation in the trade-offs involved and our results suggest conditions under which trade-offs tend to select for lower resistance in juveniles than adults.
    Type of Medium: Online Resource
    ISSN: 0962-8452 , 1471-2954
    Language: English
    Publisher: The Royal Society
    Publication Date: 2023
    detail.hit.zdb_id: 1460975-7
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    SSG: 25
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  • 6
    In: Journal of Ecology, Wiley, Vol. 107, No. 1 ( 2019-01), p. 1-11
    Abstract: Sebbene la malattia sia ampiamente riconosciuta come capace di influenzare le dimensioni della popolazione ospite, raramente è stato considerato il suo ruolo nel determinare i limiti di distribuzione della specie ospite. Molte malattie potrebbero non essere in grado di persistere vicino al margine di distribuzione se la densità della popolazione ospite scende al di sotto del livello soglia critico per l'invasione del patogeno. Tuttavia, nelle malattie trasmesse da vettori e in quelle trasmesse sessualmente, la trasmissione del patogeno può essere largamente indipendente dalla densità dell'ospite e la teoria dimostra che le malattie con modalità di trasmissione frequenza‐dipendente possono persistere vicino al margine delle piccole popolazioni. Gli studi empirici condotti sulla malattia ai limiti di distribuzione della specie sono rimasti indietro rispetto alla teoria e, ad oggi, nessuno studio precedente risulta avere verificato l'ipotesi che il vettore o le malattie trasmesse sessualmente possano essere mantenute ai limiti di distribuzione dell'ospite. In questo lavoro abbiamo studiato la distribuzione della malattia detta “del carbone delle antere”, una patologia sterilizzante trasmessa dall'impollinatore su quattro specie di piante alpine, per determinare se la stessa fosse presente ai limiti dell'intervallo di distribuzione dell'ospite. Abbiamo scoperto che l'abbondanza dell'ospite diminuiva verso i limiti superiori altitudinali e che la malattia si estendeva fino ai limiti altitudinali più estremi in tre delle quattro specie ospiti. La stima della massima probabilità dell'ampiezza del limite dell'area senza la malattia mostrava che essa era minima o inesistente per tutte le specie ospiti. Inoltre, la prevalenza della malattia all'interno delle popolazioni era sovente più alta vicino al limite di distribuzione dell'ospite rispetto che al centro ed era indipendente dalla densità dell'ospite. Sintesi : i nostri risultati mostrano che le malattie in cui la trasmissione è di tipo frequenza‐dipendente potenzialmente influenzano le distribuzioni dell'ospite non solo in teoria, ma anche nelle popolazioni reali.
    Type of Medium: Online Resource
    ISSN: 0022-0477 , 1365-2745
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 3023-5
    detail.hit.zdb_id: 2004136-6
    SSG: 12
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  • 7
    In: Ecology, Wiley, Vol. 104, No. 3 ( 2023-03)
    Abstract: Theoretical models suggest that infectious diseases could play a substantial role in determining the spatial extent of host species, but few studies have collected the empirical data required to test this hypothesis. Pathogens that sterilize their hosts or spread through frequency‐dependent transmission could have especially strong effects on the limits of species' distributions because diseased hosts that are sterilized but not killed may continue to produce infectious stages and frequency‐dependent transmission mechanisms are effective even at very low population densities. We collected spatial pathogen prevalence data and population abundance data for alpine carnations infected by the sterilizing pathogen Microbotryum dianthorum , a parasite that is spread through both frequency‐dependent (vector‐borne) and density‐dependent (aerial spore transmission) mechanisms. Our 13‐year study reveals rapid declines in population abundance without a compensatory decrease in pathogen prevalence. We apply a stochastic, spatial model of parasite spread that accommodates spatial habitat heterogeneity to investigate how the population dynamics depend on multimodal (frequency‐dependent and density‐dependent) transmission. We found that the observed rate of population decline could plausibly be explained by multimodal transmission, but is unlikely to be explained by either frequency‐dependent or density‐dependent mechanisms alone. Multimodal pathogen transmission rates high enough to explain the observed decline predicted that eventual local extinction of the host species is highly likely. Our results add to a growing body of literature showing how multimodal transmission can constrain species distributions in nature.
    Type of Medium: Online Resource
    ISSN: 0012-9658 , 1939-9170
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 1797-8
    detail.hit.zdb_id: 2010140-5
    SSG: 12
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  • 8
    In: Animal Biotelemetry, Springer Science and Business Media LLC, Vol. 9, No. 1 ( 2021-10-16)
    Abstract: Understanding what animals do in time and space is important for a range of ecological questions, however accurate estimates of how animals use space is challenging. Within the use of animal-attached tags, radio telemetry (including the Global Positioning System, ‘GPS’) is typically used to verify an animal’s location periodically. Straight lines are typically drawn between these ‘Verified Positions’ (‘VPs’) so the interpolation of space-use is limited by the temporal and spatial resolution of the system’s measurement. As such, parameters such as route-taken and distance travelled can be poorly represented when using VP systems alone. Dead-reckoning has been suggested as a technique to improve the accuracy and resolution of reconstructed movement paths, whilst maximising battery life of VP systems. This typically involves deriving travel vectors from motion sensor systems and periodically correcting path dimensions for drift with simultaneously deployed VP systems. How often paths should be corrected for drift, however, has remained unclear. Methods and results Here, we review the utility of dead-reckoning across four contrasting model species using different forms of locomotion (the African lion Panthera leo , the red-tailed tropicbird Phaethon rubricauda , the Magellanic penguin Spheniscus magellanicus , and the imperial cormorant Leucocarbo atriceps ). Simulations were performed to examine the extent of dead-reckoning error, relative to VPs, as a function of Verified Position correction (VP correction) rate and the effect of this on estimates of distance moved. Dead-reckoning error was greatest for animals travelling within air and water. We demonstrate how sources of measurement error can arise within VP-corrected dead-reckoned tracks and propose advancements to this procedure to maximise dead-reckoning accuracy. Conclusions We review the utility of VP-corrected dead-reckoning according to movement type and consider a range of ecological questions that would benefit from dead-reckoning, primarily concerning animal–barrier interactions and foraging strategies.
    Type of Medium: Online Resource
    ISSN: 2050-3385
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 2711027-8
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  • 9
    In: Health Research Policy and Systems, Springer Science and Business Media LLC, Vol. 21, No. 1 ( 2023-10-02)
    Abstract: Adolescent girls and young women (AGYW) remain disproportionately affected by HIV in Zimbabwe. Several HIV prevention options are available, including oral tenofovir-based pre‐exposure prophylaxis (PrEP), however AGYW face unique barriers to PrEP uptake and continuation and novel approaches are therefore needed to empower AGYW to use PrEP. The objective of this study was to characterize early learnings from implementing a multi-level intervention consisting of fashionable branding (including a “V Starter Kit”), service integration, and peer education and support throughout a young woman's journey using oral PrEP across four phases of implementation, from creating demand, preparing for PrEP, initiation of PrEP, and adherence to PrEP. Methods A mixed methods implementation research study was undertaken, including site observations and interviews to explore the acceptability of “V” and its relevance to target users, as well as the feasibility of integrating “V” with existing service delivery models. Interviews ( n = 46) were conducted with healthcare workers, Brand Ambassadors, and young women purposively sampled from four implementation sites. Interview data was analyzed thematically using the framework method for qualitative data management and analysis. Project budgets and invoices were used to compile unit cost and procurement data for all “V” materials. Results “V” was acceptable to providers and young women due to attractive branding coupled with factual and thought-provoking messaging, establishing “a girl code” for discussing PrEP, and addressing a gap in communications materials. “V” was also feasible to integrate into routine service provision and outreach, alongside other services targeting AGYW. Cost for the “V” branded materials ranked most essential—FAQ insert, pill case, makeup bag, reminder sticker—were $7.61 per AGYW initiated on PrEP. Conclusion “V” is a novel approach that is an acceptable and feasible multi-level intervention to improve PrEP access, uptake, and continuation among AGYW, which works through empowering AGYW to take control of their HIV prevention needs. In considering “V” for scale up in Zimbabwe, higher volume procurement and a customized lighter package of “V” materials, while still retaining V’s core approach, should be explored.
    Type of Medium: Online Resource
    ISSN: 1478-4505
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
    detail.hit.zdb_id: 2101196-5
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  • 10
    Online Resource
    Online Resource
    Wiley ; 2021
    In:  Evolution Vol. 75, No. 10 ( 2021-10), p. 2494-2508
    In: Evolution, Wiley, Vol. 75, No. 10 ( 2021-10), p. 2494-2508
    Type of Medium: Online Resource
    ISSN: 0014-3820 , 1558-5646
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2036375-8
    SSG: 12
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