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  • 1
    Electronic Resource
    Electronic Resource
    Ecology Bagging the lag (2001)
    [s.l.] : Nature Publishing Group
    Nature 409 (2001), S. 992-993 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Predicting changes in the size of natural populations has long been a goal of ecologists. But it is often far from simple to unravel the dynamics of populations. We rarely know all of the factors that affect them, let alone the many ways in which individual populations interact. Hence the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35059194
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  • 2
    Electronic Resource
    Electronic Resource
    When three is a crowd (1996)
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 276-277 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] MUCH of the edifice of community ecology is built upon the study of interactions involving pairs or small webs of species. This is perfectly sensible, for communities are in many ways akin to clocks: to understand what makes a clock tick, a good starting point is to fiddle with small ensembles of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/381276a0
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of habitat reduction on the persistence of Ichneumon eumerus (Hymenoptera: Ichneumonidae), the specialist parasitoid of Maculinea rebeli (Lepidoptera: Lycaenidae) (1998)
    Springer
    Journal of insect conservation 2 (1998), S. 59-66 
    Details
    ISSN: 1572-9753
    Keywords: environmental gradient ; extinction ; conservation ; persistence ; parasite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Nature of Science, Research, Systems of Higher Education, Museum Science
    Notes: Abstract The lycaenid butterfly, Maculinea rebeli, and its specialist parasitoid, Ichneumon eumerus, live in small, closed populations. Given the threatened status of the butterfly, it is reasonable to assume that its specialist parasitoid is even more vulnerable to local extinction than the butterfly host. Based on a mechanistic model recently developed for the tightly-woven community surrounding M. rebeli at a site in the Spanish Pyrenees, we investigate how the removal of habitat, and more particularly, specific habitat promoting the persistence of the butterfly, affects the population persistence of the parasitoid. Because of the relatively small impact of the parasitoid on the butterfly population in the Spanish Pyrenees, guidelines for conserving the parasitoid are only slightly more restrictive than those for its host. It is argued that at sites of more marginal quality for the butterfly than the reference site, achieving the dual aims of conserving both species will be more problematic. © Rapid Science Ltd. 1998
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009644807126
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  • 4
    Electronic Resource
    Electronic Resource
    Control engineering (1991)
    [s.l.] : Nature Publishing Group
    Nature 352 (1991), S. 16-17 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] REPORTS on pages 82l and 852 of this issue take the development of effective 'biopesticides' a long step further. Tomalski and Miller1 and Stewart and colleagues2 show that the rate at which an insect virus kills a pest can be increased by incorporating toxin-producing genes from other arthropods ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/352016a0
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  • 5
    Electronic Resource
    Electronic Resource
    The potential role of pathogens in biological control (1989)
    [s.l.] : Nature Publishing Group
    Nature 337 (1989), S. 262-265 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Models of invertebrate host-pathogen interactions often assume that the transmissibility and lifespan of the pathogen does not differ between pathogen individuals, or stages1'2. In nature, however, pathogen populations are far from uniform, because heterogeneities can exist in their spatial and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/337262a0
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  • 6
    Electronic Resource
    Electronic Resource
    The evolution of dispersal in a two-patch system:Some consequences of differences between migrants and residents (1997)
    Springer
    Evolutionary ecology 11 (1997), S. 613-629 
    Details
    ISSN: 1573-8477
    Keywords: dispersal ; evolution ; evolutionarily stable strategy ; migrant ; resident ; survival
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigate how age-structure and differences in certain demographic traits between residents and immigrants of a single species act to determine the evolutionarily stable dispersal strategy in a two-patch environment that is heterogeneous in space but constant in time. These two factors have been neglected in previous models of the evolution of dispersal, which generally consider organisms with very simple life-cycles and assume that, whatever their origin, individuals in a given habitat have the same bio-demographic characteristics. However, there is increasing empirical evidence that dispersing individuals have different demographic properties from phylopatric ones. We develop a matrix model in which recruitment depends on local population densities. We assume that dispersal entails a proportional cost to immigrant fecundity, which can be compensated by differences in survival rates between immigrants and residents. The evolutionarily stable strategies (ESS) for dispersal are identified using a combination of analytical expressions and numerical simulations. Our results show that philopatry is selected (1) when dispersal rates do not vary in space, (2) when the metapopulation is a source-sink system and (3) when dispersal rates vary in space (asymmetric dispersal) and immigrants do not compensate for their reduced fecundity. We observe that non-zero asymmetric dispersal rates may be evolutionarily stable when (1) immigrants and residents are demographically alike and (2) immigrants compensate totally for their reduced fecundity through an increase in adult survival. Under these conditions, we find that the ESS occurs when the fitnesses at equilibrium in the two habitats, measured in our model by the realized reproductive rates, are each equal to unity. A comparison with previous studies suggests a unifying rule for the evolution of dispersal: the dispersal rates which permit the spatial homogenization of fitnesses are ESSs. This condition provides new insight into the evolutionary stability of source-sink systems. It also supports the hypothesis that immigrants have adapted demographic strategies, rather than the hypothesis that dispersal is costly and immigrants are at a disavantage compared with residents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10682-997-1516-z
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  • 7
    Electronic Resource
    Electronic Resource
    Will plant vigor and tolerance be genetically correlated? Effects of intrinsic growth rate and self-limitation on regrowth (2000)
    Springer
    Evolutionary ecology 14 (2000), S. 331-352 
    Details
    ISSN: 1573-8477
    Keywords: growth rate ; herbivory ; plant defense ; tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plants are known to maintain fitness despite herbivore attack by a variety of damage-induced mechanisms. These mechanisms are said to confer tolerance, which can be measured as the slope of fitness over the proportion of plant biomass removed by herbivore damage. It was recently supposed by Stowe et al. (2000) that another plant property, general vigor, has little effect on tolerance. We developed simple models of annual monocarpic plants to determine if a genetic change in components of growth vigor will also change the fitness reaction to damage. We examined the impact of intrinsic growth rate on the tolerance reaction norm slope assuming plants grow geometrically, i.e., without self-limitation. In this case an increase in intrinsic growth rate decreases tolerance (the reaction norm slope becomes more negative). A logistic growth model was used to examine the impact of self-limiting growth on the relationship between intrinsic growth rate and the tolerance reaction norm slope. With self-limitation, the relationship is sensitive to the timing of attack. When attack is early and there is time for regrowth, increasing growth rate increases tolerance (slope becomes less negative). The time limitations imposed by late attack prevent appreciable regrowth and induce a negative relationship between growth rate and tolerance. In neither of these simple cases will the correlation between vigor and tolerance constrain selection on either trait. However, a positive correlation between growth rate and self-limitation will favor fast growth/strong self-limitation in a high-damage environment, but slow growth/weak self-limitation in a low-damage environment. Thus, fundamental growth rules that determine vigor have constitutive effects on tolerance. The net costs and benefits of damage-induced tolerance mechanisms will thus be influenced by the background imposed by fundamental growth rules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010950932468
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  • 8
    Electronic Resource
    Electronic Resource
    Maintenance of two genetic entities by habitat selection (1995)
    Springer
    Evolutionary ecology 9 (1995), S. 131-138 
    Details
    ISSN: 1573-8477
    Keywords: Selected polymorphism ; habitat selection ; genetic isolation ; habitat specialization ; soft selection ; competition ; parasitic copepods ; specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the laboratory, the two species of copepodsLepeophtheirus thompsoni andLepeophtheirus europaensis, ectoparasites of flatfishes, can meet and mate on at least one host species. In the wild however, these two species are found isolated on their sympatric hosts. Habitat selection theoretically represents a powerful enough mechanism to explain the maintenance of genetic heterogeneity in the wide sense. In this paper, the host colonization process is studied for both parasite species. It is shown that each parasite can develop and reach adult age on each host species. However,L. thompsoni is highly selective; it almost totally refuses to colonize hosts other than its natural one.Lepeophtheirus europaensis, on the contrary, readily infests turbot and brill in single-host experiments, but strongly prefers the brill when it has a choice. It appears that these two genetic entities are sympatrically maintained due to strong habitat selection. Such a pattern could theoretically only occur in a soft-selection context (density dependence). This point is discussed with respect to the different patterns in host use found in the geographical distribution of these parasites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01237752
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  • 9
    Electronic Resource
    Electronic Resource
    Refuge evolution and the population dynamics of coupled host—parasitoid associations (1995)
    Springer
    Evolutionary ecology 9 (1995), S. 633-661 
    Details
    ISSN: 1573-8477
    Keywords: co-evolution ; parasitoid ; population dynamics ; refuge ; biological control ; population stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have investigated the theoretical consequences of character evolution for the population dynamics of a host—parasitoid interaction, assuming a monophagous parasitoid. In the purely ecological model it is assumed that hosts can escape parasitism by being in absolute refuges. A striking property of this model is a threshold effect in control of the host by the parasitoid, when host density dependence is weak. The approximate criteria for the parasitoid to regulate the host to low densities are (1) that the parasitoid's maximum population growth rate should exceed the host's and (2) that the maximum growth rate of the host in the refuge should be less than unity. We then use this ecological framework as a basis for a model which considers evolutionary changes in quantitative characters influencing the size of the absolute refuge. For each species, an increase in its refuge-determining character comes at a cost to maximum population growth rate. We show that refuge evolution can substantially alter the population dynamics of the purely ecological model, resulting in a number of emergent and sometimes counter-intuitive properties. In general, when the host has a high carrying capacity, systems are polarized either with low or minor refuge and ‘top-down’ control of the host by the parasitoid or with a refuge and ‘bottom-up’ control of the host by a combination of its own density dependence and the parasitoid. A particularly tantalizing result is that co-evolutionary dynamics can modify ecologically unstable systems into ones which are either stable or quasi-stable (with bouts of unstable dynamics, punctuating long-term periods of quasi-stable behaviour). We present five quantitative criteria which must all be met for the parasitoid to be the agent responsible for control of the host at a co-evolutionary equilibrium. The apparent stringency of this full set of requirements supports the empirically-based suggestion that monophagous parasitoid-driven systems should be less common in nature than those driven by multiple forms of density dependence. Further, we apply our theory to the question of whether exploiters may ‘harvest’ their victims at maximum sustainable yields and to the evolutionary stability of biological control. Finally, we present a series of testable predictions of our theory and methods useful for testing them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01237660
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  • 10
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    Antibiotic stress selects against cooperation in the pathogenic bacterium Pseudomonas aeruginosa (2017)
    National Academy of Sciences
    Details
    Publication Date: 2017-01-03
    Description: Cheats are a pervasive threat to public goods production in natural and human communities, as they benefit from the commons without contributing to it. Although ecological antagonisms such as predation, parasitism, competition, and abiotic environmental stress play key roles in shaping population biology, it is unknown how such stresses generally affect the ability of cheats to undermine cooperation. We used theory and experiments to address this question in the pathogenic bacterium, Pseudomonas aeruginosa. Although public goods producers were selected against in all populations, our competition experiments showed that antibiotics significantly increased the advantage of nonproducers. Moreover, the dominance of nonproducers in mixed cultures was associated with higher resistance to antibiotics than in either monoculture. Mathematical modeling indicates that accentuated costs to producer phenotypes underlie the observed patterns. Mathematical analysis further shows how these patterns should generalize to other taxa with public goods behaviors. Our findings suggest that explaining the maintenance of cooperative public goods behaviors in certain natural systems will be more challenging than previously thought. Our results also have specific implications for the control of pathogenic bacteria using antibiotics and for understanding natural bacterial ecosystems, where subinhibitory concentrations of antimicrobials frequently occur.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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