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  • 1. Abeli, Thomas
    et al.
    Orsenigo, Simone
    Guzzon, Filippo
    Fae, Matteo
    Balestrazzi, Alma
    Carlsson-Graner, Ulla
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Mueller, Jonas V.
    Mondoni, Andrea
    Geographical pattern in the response of the arctic-alpine Silene suecica (Cariophyllaceae) to the interaction between water availability and photoperiod2015In: Ecological research, ISSN 0912-3814, E-ISSN 1440-1703, Vol. 30, no 2, p. 327-335Article in journal (Refereed)
    Abstract [en]

    We hypothesized a geographical pattern of the plant performance (seedling development, biomass production, relative water content and chlorophyll content) as a result of response to the interaction between photoperiod and water availability in populations of the arctic-alpine Silene suecica from different latitudes, thus experiencing different photoperiods during the growing season. Particularly, we expected a lower drought sensitivity in northern compared to southern populations as a consequence of harsher conditions experienced by the northern populations in terms of water availability. The experiment was carried out under common garden conditions, manipulating the water availability (wet and dry) and the photoperiod (21 and 16 h). We found an interaction between photoperiod and water availability on plant height, leaves, growth, biomass and total chlorophyll. However, the photoperiod neither counteracted nor intensified the effect of drought. Plants exposed to drought compensated for decreasing water availability by reducing their shoot growth. Changes in the chlorophyll content and chlorophyll a/b ratio were observed. Northern populations showed a higher basal growth performance and a greater response to the changed water regime (from wet to dry) than the southern populations. Southern populations showed a reduced ability to respond to drought, but their low basal performance may be advantageous under low water availability, avoiding water loss. In contrast, northern populations showed a stronger plastic response that limited the negative effects of reduced water availability. This study highlights the possibility that the plant response to environmental constraints (specifically water availability) may follow a geographical pattern.

  • 2.
    Carlsson-Graner, Ulla
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Giles, Barbara
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Thrall, P. H.
    Centre for Plant Biodiversity Research, CSIRO - Plant Industry, GPO Box 1600, Canberra, ACT, 2601, Australia.
    Patterns of disease and host resistance in spatially structured systems2014In: European journal of plant pathology, ISSN 0929-1873, E-ISSN 1573-8469, Vol. 138, no 3, p. 499-511Article in journal (Refereed)
    Abstract [en]

    We use data from species of the anther-smut fungi and the host plants Lychnis alpina and Silene dioica to show that spatial structuring at different scales can influence patterns of disease and host resistance. Patterns of disease and host resistance were surveyed in an archipelago subject to land-uplift where populations of S. dioica constitute an age-structured metapopulation, and in three contrasting areas within the mainland range of L. alpina, where population distributions range from continuous, through patchy but spatially connected to highly isolated demes. In S. dioica, disease levels depend on the age, size and density of local patches and populations. Disease is most predictably found in larger dense host patches and populations of intermediate age, and more frequently goes extinct in small old populations. The rate of local disease spread is affected by the level of host resistance; S. dioica populations showing an increase in disease over time are more susceptible than populations where the disease has remained at low levels. Among-population variation in resistance is driven by founding events and populations remain differentiated due to limited gene flow between islands. As observed in the L. alpina system, when populations are more connected, a greater fraction of populations have disease present. Results from a simulation model argue that, while increased dispersal in connected systems can increase disease spread, it may also favour selection of host resistance which ultimately reduces disease levels within populations. This could explain the observed lower disease prevalence in L. alpina in regions where populations are more continuous.

  • 3.
    Carlsson-Graner, Ulla
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Thrall, Peter H.
    Host resistance and pathogen infectivity in host populations with varying connectivity2015In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 69, no 4, p. 926-938Article in journal (Refereed)
    Abstract [en]

    Theory predicts that hosts and pathogens will evolve higher resistance and aggressiveness in systems where populations are spatially connected than in situations in which populations are isolated and dispersal is more local. In a large cross-inoculation experiment we surveyed patterns of host resistance and pathogen infectivity in anther-smut diseased Viscaria alpina populations from three contrasting areas where populations range from continuous, through patchy but spatially connected to highly isolated demes. In agreement with theory, isolated populations of V. alpina were more susceptible on average than either patchily distributed or continuous populations. While increased dispersal in connected systems increases disease spread, it may also increase host gene flow and the potential for greater host resistance to evolve. In the Viscaria-Microbotryum system, pathogen infectivity mirrored patterns of host resistance with strains from the isolated populations being the least infective and strains from the more resistant continuous populations being the most infective on average, suggesting that high resistance selects for high infectivity. To our knowledge this study is the first to characterize the impacts of varying spatial connectivity on patterns of host resistance and pathogen infectivity in a natural system.

  • 4.
    Carlsson-Granér, Ulla
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Disease dynamics, host specificity and pathogen persistence in isolated host populations2006In: Oikos, Vol. 112, p. 178-184Article in journal (Refereed)
  • 5.
    Carlsson-Granér, Ulla
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ericson, Lars
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Giles, Barbara E.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Plant disease and islands2009In: Encyclopedia of Islands / [ed] Rosemary G. Gillespie and David A. Clague, University of California Press , 2009, p. 748-752Chapter in book (Refereed)
  • 6.
    Carlsson-Granér, Ulla
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Thrall, P H
    The impact of host longevity on disease transmission: Host-pathogen dynamics and evolution of resistance2006In: Evol Ecol Res, Vol. 8, p. 659-675Article in journal (Refereed)
  • 7.
    Carlsson-Granér, Ulla
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Thrall, Peter H
    The spatial distribution of plant populations, disease dynamics and evolution of resistance2002In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 97, no 1, p. 97-110Article in journal (Refereed)
    Abstract [en]

    Empirical studies of the interaction between the anther smut fungus Microbotryum violaceum and its host plant Lychnis alpina were combined with modelling approaches to investigate how variation in the spatial distribution of host populations influences disease dynamics and variation in resistance. Patterns of disease incidence and prevalence were surveyed in three contrasting systems of natural L. alpina populations where there is substantial variation in spatial structure, ranging from large continuous populations through to small isolated patches. Disease incidence (fraction of populations where disease was present) was highest in the continuous situation, and lowest in the most isolated populations. The reverse was true for prevalence (fraction of individuals diseased). To better understand the long-term ecological and evolutionary consequences of differences in among population spatial structure, we developed a two-dimensional spatially explicit simulation model in which host-population spacing was modelled by varying the percentage of sites suitable for the host. The general patterns of disease incidence and prevalence generated in the simulations corresponded well with the patterns observed in natural populations of L. alpina and M. violaceum; i.e. the fraction of sites with disease increased while the average disease prevalence in diseased populations decreased when host populations became more connected. One likely explanation for the differences in disease incidence and prevalence seen in natural populations is that the evolution of host resistance varies as a function of the degree of fragmentation. This is supported by simulation results that were qualitatively similar to the survey data when resistance was allowed to vary, but not when hosts were assumed to be uniformly susceptible. In the former, the frequency of resistance increased markedly as host populations became more connected.

  • 8.
    Giles, Barbara E.
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Granberg, Åsa
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Carlsson-Granér, Ulla
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Race-specific and spatially variable resistance to Microbotryum violaceum, a systemic anther smut disease in Silene dioica metapopulationsManuscript (Other (popular science, discussion, etc.))
  • 9.
    Granberg, Åsa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Carlsson-Granér, Ulla
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Arnqvist, Per
    Giles, Barbara E
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Variation in breeding system traits within and among populations of Microbotryum violaceum on Silene dioica2008In: International journal of plant sciences, ISSN 1058-5893, E-ISSN 1537-5315, Vol. 169, no 2, p. 293-303Article in journal (Refereed)
    Abstract [en]

    Breeding systems exert profound effects on the amount and distribution of genetic diversity within and among populations. Knowledge of breeding systems is also important for understanding dynamics between coevolving organisms, e.g., pathogen‐host interactions. Here we study the breeding system of the obligate anther smut Microbotryum violaceum on Silene dioica. Microbotryum violaceum is capable of both inbreeding and outcrossing, but several recent studies on other host races have indicated that automixis via intrapromycelial mating is the predominant breeding system. Compared with conjugations between cells from different meioses, automixis results in slower loss of heterozygosity and faster production of infectious hypha. However, high rates of intrapromycelial matings have been suggested to invoke a fitness cost due to production of fewer infectious dikaryons. Working with single strains under standardized laboratory conditions, we studied traits that could influence the distribution of genetic variability and pathogen fitness. We found that intrapromycelial mating is the dominant conjugation form for M. violaceum var. dioica but that the breeding system varies, partly because of genetic differences, both within and among populations. Further, we did not find the predicted fitness reduction for intrapromycelial matings, suggesting that intrapromycelial mating is a highly favorable breeding system for M. violaceum.

  • 10.
    Granberg, Åsa
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Carlsson-Granér, Ulla
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Giles, Barbara E.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Genetic architecture of biochemical resistance to the anther smut Microbotryum violaceum in Silene dioicaManuscript (Other (popular science, discussion, etc.))
  • 11.
    Granberg, Åsa
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Carlsson-Granér, Ulla
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Giles, Barbara E.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Neutral gene diversity in the range margins of an obligate fungal pathogen: Microbotryum violaceum on Silene dioicaManuscript (Other (popular science, discussion, etc.))
  • 12. Mondoni, Andrea
    et al.
    Orsenigo, Simone
    Müller, Jonas V.
    Carlsson-Graner, Ulla
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jiménez-Alfaro, Borja
    Abeli, Thomas
    Seed dormancy and longevity in subarctic and alpine populations of Silene suecica2018In: Alpine Botany, ISSN 1664-2201, E-ISSN 1664-221X, Vol. 128, no 1, p. 71-81Article in journal (Refereed)
    Abstract [en]

    Despite the strong environmental control of seed dormancy and longevity, their changes along latitudes are poorly understood. The aim of this study was to assess seed dormancy and longevity in different populations across the distribution of the arctic-alpine plant Silene suecica. Seeds of seven populations collected from alpine (Spain, Italy, Scotland) and subarctic (Sweden, Norway) populations were incubated at four temperature regimes and five cold stratification intervals for germination and dormancy testing. Seed longevity was studied by exposing seeds to controlled ageing (45 A degrees C, 60% RH) and regularly sampled for germination. Fresh seeds of S. suecica germinated at warm temperature (20/15 A degrees C) and more in subarctic (80-100%) compared to alpine (20-50%) populations showed a negative correlation with autumn temperature (i.e., post-dispersal period). Seed germination increased after cold stratification in all populations, with different percentages (30-100%). Similarly, there was a large variation of seed longevity (p(50) = 12-32 days), with seeds from the wettest locations showing faster deterioration rate. Subarctic populations of S. suecica were less dormant, showing a warmer suitable temperature range for germination, and a higher germinability than alpine populations. Germination and dormancy were driven by an interplay of geographical and climatic factors, with alpine and warm versus subarctic and cool autumn conditions, eliciting a decrease and an increase of emergence, respectively. Germination and dormancy patterns typically found in alpine habitats may not be found in the arctic.

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