Natural Plant (natural + plant)

Distribution by Scientific Domains

Terms modified by Natural Plant

  • natural plant community
  • natural plant population

  • Selected Abstracts


    EVOLUTION, Issue 2 2007
    Joel M. Kniskern
    Although disease-resistance polymorphisms are common in natural plant populations, the mechanisms responsible for this variation are not well understood. Theoretical models predict that balancing selection can maintain polymorphism within a population if the fitness effects of a resistance allele vary from a net cost to a net benefit, depending upon the extent of pathogen damage. However, there have been a few attempts to determine how commonly this mechanism operates in natural plant,pathogen interactions. Ipomoea purpurea populations are often polymorphic for resistance and susceptibility alleles at a locus that influences resistance to the fungal pathogen, Coleosporium ipomoeae. We measured the fitness effects of resistance over three consecutive years at natural and manipulated levels of damage to characterize the type of selection acting on this locus. Costs of resistance varied in magnitude from undetectable to 15.5%, whereas benefits of resistance sometimes equaled, but never exceeded, these costs. In the absence of net benefits of resistance at natural or elevated levels of disease, we conclude that selection within individual populations of I. purpurea probably does not account completely for maintenance of this polymorphism. Rather, the persistence of this polymorphism is probably best explained by a combination of variable selection and meta-population processes. [source]

    Short-term transformation of matrix into hospitable habitat facilitates gene flow and mitigates fragmentation

    Summary 1Habitat fragmentation has major implications for demography and genetic structure of natural plant and animal populations as small and isolated populations are more prone to extinction. Therefore, many recent studies focus on spatial fragmentation. 2However, the temporal configuration of suitable habitat may also influence dispersal and gene flow in fragmented landscapes. We hypothesize that short-term switching of inhospitable matrix areas into suitable habitat can mitigate effects of spatial fragmentation in natural and seminatural ecosystems. 3To test our hypothesis, we investigated the hairy-footed gerbil (Gerbillurus paeba, Smith 1836), a ground-dwelling rodent, in fragmented Kalahari savannah areas. Here, rare events of high above mean annual rainfall suggest short-term matrix suitability. 4During the field survey in ,matrix' areas in the Kalahari (shrub encroachment by heavy grazing) we never observed the hairy-footed gerbil in years of average rainfall, but observed mass occurrences of this species during rare events of exceptionally high rainfall. 5In a second step, we developed an agent-based model simulating subpopulations in two neighbouring habitats and the separating matrix. Our mechanistic model reproduces the mass occurrences as observed in the field and thus suggests the possibly underlying processes. In particular, the temporary improvement in matrix quality allows reproduction in the matrix, thereby causing a substantial increase in population size. 6The model demonstrates further how the environmental trigger (rainfall) impacts genetic connectivity of two separated subpopulations. We identified seasonality as a driver of fragmentation but stochasticity leading to higher connectivity. 7We found that our concept of temporal fragmentation can be applied to numerous other fragmented populations in various ecological systems and provide examples from recent literature. We conclude that temporal aspects of fragmentation must be considered in both ecological research and conservation management. [source]

    Detecting local adaptation in a natural plant,pathogen metapopulation: a laboratory vs. field transplant approach

    Abstract Antagonistic coevolution between hosts and parasites in spatially structured populations can result in local adaptation of parasites. Traditionally parasite local adaptation has been investigated in field transplant experiments or in the laboratory under a constant environment. Despite the conceptual importance of local adaptation in studies of (co)evolution, to date no study has provided a comparative analysis of these two methods. Here, using information on pathogen population dynamics, I tested local adaptation of the specialist phytopathogen, Podosphaera plantaginis, to its host, Plantago lanceolata at three different spatial scales: sympatric host population, sympatric host metapopulation and allopatric host metapopulations. The experiment was carried out as a field transplant experiment with greenhouse-reared host plants from these three different origins introduced into four pathogen populations. In contrast to results of an earlier study performed with these same host and parasite populations under laboratory conditions, I did not find any evidence for parasite local adaptation. For interactions governed by strain-specific resistance, field studies may not be sensitive enough to detect mean parasite population virulence. Given that parasite transmission potential may be mediated by the abiotic environment and genotype-by-environment interactions, I suggest that relevant environmental variation should be incorporated into laboratory studies of parasite local adaptation. [source]

    Influences of habitat complexity on the diversity and abundance of epiphytic invertebrates on plants

    FRESHWATER BIOLOGY, Issue 4 2003
    Hiromi Taniguchi
    SUMMARY 1. The compound influence of habitat complexity and patch size on stream invertebrate assemblages associated with submerged macrophytes was investigated through field sampling of two natural macrophyte species with contrasting leaf morphologies (complex, Ranunculus yezoensis; simple, Sparganium emersum) and an experiment with two artificial plants with different levels of morphological complexity. 2. The artificial plant experiment was designed to separate the effects of habitat area (patch size) and habitat complexity, thus enabling a more rigorous assessment of complexity per se than in previous studies where only a single patch size was used. Simple and complex artificial plants were established with five different patch sizes corresponding to the range found in natural plants. 3. Invertebrates occurred on both complex and simple forms of natural and artificial plants at similar abundances with dipterans and ephemeropterans being predominant. Taxon richness was higher on structurally complex Ranunculus than on simple Sparganium and was similarly higher on the complex artificial plant than on the simple one, over the entire range of habitat patch sizes. Thus, architectural complexity affected the taxon richness of epiphytic invertebrates, independently of habitat scale. 4. On the natural plants there was no difference in the abundance (both number of individuals and biomass) of invertebrates between simple and complex forms, while on artificial plants more invertebrates occurred on complex than on simple forms. The amount of particulate organic matter, >225 ,m (POM) and chlorophyll a showed mixed patterns on natural and artificial plants, suggesting that the availability of these resources is not an overriding proximate factor controlling invertebrate abundance on plants. The difficulty of extrapolating from experimental results involving use of artificial plants is discussed, especially when considering the relationship between habitat structure and the occurrence of epiphytic invertebrates on natural plants. [source]

    Quercetin inhibited murine leukemia WEHI-3 cells in vivo and promoted immune response

    Chun-Shu Yu
    Abstract Enhanced flavonoid consumption is closely related with a reduced cancer incidence as shown in epidemiological studies. Quercetin (3,5,7,3,,4,-pentahydroxylflavone) is one of the active components of flavonoids which exist in natural plants, particularly in onions and fruits. It was reported that quercetin induced apoptosis in human cancer cell lines, including human leukemia HL-60 cells, but there is no available information as to its effects on leukemia cells in vivo. The purpose of the present studies was to focus on the in vivo effects of quercetin on leukemia WEHI-3 cells. The effects of quercetin on WEHI-3 cells injected into BALB/c mice were examined. Quercetin decreased the percentage of Mac-3 and CD11b markers, suggesting that the differentiation of the precursors of macrophages and T cells was inhibited. There was no effect on CD3 levels but increased CD19 levels. Quercetin decreased the weight of the spleen and liver compared with the olive oil treated animals. Quercetin stimulated macrophage phagocytosis of cells isolated from peritoneum. Quercetin also promoted natural killer cell activity. Based on pathological examination, an effect of quercetin was observed in the spleen of mice previously injected with WEHI-3 cells. Apparently, quercetin affects WEHI-3 cells in vivo. Copyright 2009 John Wiley & Sons, Ltd. [source]