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  • 1
    Electronic Resource
    Electronic Resource
    Travelling waves in vole population dynamics (1997)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 390 (1997), S. 456-456 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Spatial self-organization patterns in population dynamics have been anticipated, but demonstrating their existence requires sampling over long periods of time at a range of sites. Voles cause severe economic damage and are therefore extensively monitored, providing a source of the required ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/37261
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  • 2
    Electronic Resource
    Electronic Resource
    Red/blue chaotic power spectra (1996)
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 198-199 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - We wish to add to the debate about colour in the power spectra of the complex dynamics of natural populations1'2'7'8. Power spectra of population trajectories are observed to be white (no dominating frequency) or red (dominance of low-frequency fluctuations2'9). Thus, low frequencies might be ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/381198b0
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  • 3
    Electronic Resource
    Electronic Resource
    Biodiversity Coexistence and resource competition (2000)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 407 (2000), S. 694-694 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] How large numbers of species coexist on a seemingly limited number of different resources is a classic problem in ecology, and attempts have been made to solve it experimentally. But we are not convinced that Huisman and Weissing's proposal to add non-stationary dynamics in species ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35037672
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  • 4
    Electronic Resource
    Electronic Resource
    Geographical patterns of species turnover in aquatic plant communities (2001)
    Oxford UK : Blackwell Science Ltd
    Freshwater biology 46 (2001), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. A classic theory in biogeography predicts that high latitude communities are unstable. This may be because of decreased species richness or decreased environmental predictability and productivity towards the poles.2. We studied latitudinal patterns in long-term community persistence of aquatic vascular plants in 112 Finnish lakes, situated within a 1000-km range from the northernmost to the southernmost lake.3. Contrary to theoretical predictions, we found that the turnover rate of plant species in 45 years was inversely related to latitude. That is, plant communities in northern lakes were more persistent than communities in southern lakes. When we used multiple regression to find the best predictors of species turnover rate (TR), latitude was the only variable that was highly significantly related to species turnover rate. Area, species number, water transparency, pH and change in transparency did not notably explain the gradient observed.4. The latitudinal trend was mainly because of lower species immigration rates at higher latitudes, whereas extinction rate did not so strongly decrease with increasing latitude. Immigrations and extinctions in the lakes were not in balance: the species numbers between the 1930s and 1980s increased more strongly in the southern than northern lakes.5. We suggest that the inverse relationship between latitude and plant species TR in Finland is most probably caused by human influence on lakes, especially eutrophication and immigration of new species in southern latitudes. In addition, although species richness per lake did not decrease towards the north, the total species pool probably does, which means that in the north there are fewer species that can actually immigrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2001.00767.x
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  • 5
    Electronic Resource
    Electronic Resource
    Sex ratio genetics and the competitiveness of parasitic wasps (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 295-311 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In the first part of the paper we analyse dynamics of the genetic mechanisms responsible for maintaining biased sex ratios in host-parasitoid interactions. We begin by reviewing recent results relating to the maintenance of sibmating in haplo-diploid populations. We then investigate the evolutionary stable sex ratio in populations in which all or some of the females mate with their brothers. In particular, we derive a diallelic one-locus model for studying evolutionary stable sex ratios in partially sibmating haplo-diploid populations. In the second part of the paper we review the impact of sex ratio on host-parasitoid populations. We then analyse how the sex ratio strategy of one parasitoid species may affect its interaction with another parasitoid species competing for the same host. In particular we show that, although a female biased sex ratio may enhance the inherent competitiveness of one species, it may also destabilize the ecological interaction of the three species so that all become extinct.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02464835
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  • 6
    Electronic Resource
    Electronic Resource
    Population dynamics and harvesting of semelparous species with phenotypic and genotypic variability in reproductive age (1995)
    Springer
    Journal of mathematical biology 33 (1995), S. 521-556 
    Details
    ISSN: 1432-1416
    Keywords: Population dynamics modeling ; Evolutionarily stable strategies ; Polymorphic life histories ; Age-at-maturity ; Harvesting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We study the evolution of polymorphic life histories in anadromous semelparous salmon and the effects of harvesting. We derive dynamic phenotypic and genetic ESS models for describing the evolutionary dynamics. We show in our deterministic analysis that polymorphisms are not possible in a panmictic random mating population. Instead, genetic or behavioral polymorphisms may be observed in populations with assortative mating systems. Positive assortative mating may be supported and generated by behavioral and phenotypic traits like male mate choice, spawning ground selection by phenotype, or within-river homing-migration-distance by size. In the case of an evolutionarily stable dimorphism, the ESS is characterized by a reproductive ideal free distribution such that at an equilibrium the individuals are indifferent from the fitness point of view between the two life histories of early and late reproduction. Different strategy models - that is, phenotypic and genetic ESS models - yield identical behavioral predictions and, consequently, genetics does not seem to play an important role in the present model. An evolutionary response to increased fishing mortality is obvious and may have resource management implications. High sea fishing mortalities drive the populations toward early spawning. Thus it is possible that unselective harvesting at sea may eliminate, depending on the biological system, behavioral polymorphisms or genetic heterozygozity and drive the population to a monomorphic one. If within-river homing migration distances depend on the size of fish, unselective harvesting at sea, or selective harvesting of spawning runs in rivers, may reduce local population sizes on spawning grounds high up rivers. Finally, harvesting in a population may cause a switch in a dominant life-history strategy in a population so that anticipated sustainable yields cannot be realized in practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00163041
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  • 7
    Electronic Resource
    Electronic Resource
    Host-parasite dynamics and the evolution of host immunity and parasite fecundity strategies (1997)
    Springer
    Bulletin of mathematical biology 59 (1997), S. 427-450 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We explore evolutionarily stable co-evolution of host-macroparasite interactions in a discrete-time two-species population dynamics model, in which the dynamics may be stable, cyclic or chaotic. The macroparasites are assumed to harm host individuals through decreased reproductive output. Hosts may develop costly immune responses to defend themselves against parasites. Parasites compete with conspecifics by adjusting their fecundities. Overall, the presence of both parasites and the immune response in hosts produces more stable dynamics and lower host population sizes than that observed in the absence of the parasites. In our evolutionary analyses, we show that maximum parasite fecundity is always an evolutionarily stable strategy (ESS), irrespective of the type of population interaction, and that maximum parasite fecundity generally induces a minimum parasite population size through over-exploitation of the host. Phenotypic polymorphisms with respect to immunity in the host species are common and expected in ESS host strategies: the benefits of immunication depend on the frequency of the immune hosts in the population. In particular, the steady-state proportions of immune hosts depend, in addition to all the parameters of the parasite dynamics only on the cost of immunity and on the virulence of parasites in susceptible hosts. The implicit ecological dynamics of the host-parasite interaction affect the proportion of immune host individuals in the population. Furthermore, when changes in certain population parameters cause the dynamics of the host-parasite interaction to move from stability to cyclicity and then to chaos, the proportion of immune hosts tends to decrease; however, we also detected counter-examples to this result. As a whole, incorporating immunological and genetic aspects, as well as life-history trade-offs, into host-macroparasite dynamics produces a rich extension to the patterns observed in the models of ecological interactions and epidemics, and deserves more attention than is currently the case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02459459
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  • 8
    Electronic Resource
    Electronic Resource
    Transboundary air pollution and soil acidification: A dynamic analysis of an acid rain game between Finland and the USSR (1992)
    Springer
    Environmental and resource economics 2 (1992), S. 161-181 
    Details
    ISSN: 1573-1502
    Keywords: Pollution contron ; acidification ; acid rain game ; transboundary air pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract Transboundary air pollution is analysed as a dynamic game between Finland and the nearby areas of the Soviet Union. Sulphur emissions are used as the environmental control variables and the acidities of the soils as the state variables. Acidification is consequently considered to be a stock pollutant having long-lasting harmful effects on the environment. The state dynamics consist of two relationships: first, of a sulphur transportation model between the regions and, second, of a model describing how the quality of the soil is affected by sulphur deposition. The countries are assumed to be interested in maximizing the net benefits from pollution control as measured by the impacts on the values of forest growth net of the abatement costs. Cooperative and noncooperative solutions of the game are compared to assess the benefits of bilateral cooperation. Using empirical estimates of abatement costs, acidification dynamics and impacts on forest growth it is shown that cooperation is beneficial to Finland but not to the Soviet Union. Consequently, Finland has to offer monetary compensation to induce her neighbor to invest in environmental protection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338241
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  • 9
    Electronic Resource
    Electronic Resource
    The management of high seas fisheries (2000)
    Springer
    Annals of operations research 94 (2000), S. 183-196 
    Details
    ISSN: 1572-9338
    Keywords: fisheries management ; game theory ; Norwegian spring‐spawning herring ; straddling and highly migratory stocks ; United Nations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The intergovernmental United Nations Conference on Highly Migratory and Straddling Stocks, initiated in 1993 and finished in 1995, addressed the conservation and management of fishery resources located both within the coastal state 200 mile Exclusive Economic Zone (EEZ) and the adjacent high seas. These types of marine resources continue to be a source for international conflicts and debates. The original United Nations Law of the Sea of 1982 failed to address transboundary fisheries in a proper way. In particular, the agreement did not recognize the emergence of the complicated “straddling stock” issue. In the new United Nations Law of the Sea agreement of 1995, a consensus was reached that the management of the straddling and highly migratory fish stocks should be carried out through regional fisheries management organizations. We present a review of the straddling stock issues in the international agreement emerging from the negotiations within the United Nations. The review is contrasted with and clarified by game theoretic analyses. We also discuss one international fishery exemplifying the case, the Norwegian spring‐spawning herring. The main conclusion is that the local problems, faced during the stage of setting up regional fisheries organizations for the management of straddling and highly migratory fish stocks, are expected to be much more complicated and difficult to solve as compared to the cases of “shared fish stocks”. In the current paper, we present two reasons for this increased complexity. The first is the larger number of players as compared to the case of “shared fish stocks” and the second is the possibility of new members entering the regional fisheries organizations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018925302021
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  • 10
    Electronic Resource
    Electronic Resource
    Evolutionarily stable dispersal of a waterstrider in a temporally and spatially heterogeneous environment (1989)
    Springer
    Evolutionary ecology 3 (1989), S. 283-298 
    Details
    ISSN: 1573-8477
    Keywords: Evolutionarily stable strategy ; risk-spreading ; dispersal behavior ; flight muscle histolysis ; waterstrider
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Evolutionary stable dispersal and wing muscle histolysis strategies are studied in the waterstriderGerris thoracicus. These strategies relate to spreading reproductive risk. Overwintering individuals have the choice of dispersing to either a brackish sea bay or a rock pool habitat. The former is reproductively more favorable than the latter during warm dry years and less favorable during cool wet years. After spring migration, individuals may histolyse their flight muscles and lay all their eggs in one pool or they may retain their flight ability and lay fewer eggs in total but spread them in several pools. We use a simple two-habitat model to examine the question of habitat dispersal. Our results indicate that, although the value of the evolutionary stable dispersal depends on the degree of variability in the environment and on the probability of local extinctions in either habitat, the population always disperses to both habitats as a consequence of density dependent growth. We use a more detailed multiple-rockpool habitat model to examine the question of wing muscle histolysis as a response to density dependence. Our results indicate that a wing muscle histolysis response to population density is an evolutionarily stable strategy when compared with the two alternatives of females always histolysing or never histolysing their flight muscles. The application of evolutionarily stable theory to stochastic problems presents a number of difficulties. We discuss these difficulties in the context of computing evolutionarily stable strategies for the problems at hand.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02285260
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