ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

Travelling waves in vole population dynamics (1997)

Ranta, Esa ; Kaitala, Veijo

[s.l.] : Macmillan Magazines Ltd.

Nature 390 (1997), S. 456-456

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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

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Red/blue chaotic power spectra (1996)

Kaitala, Veijo ; Ranta, Esa

[s.l.] : Nature Publishing Group

Nature 381 (1996), S. 198-199

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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

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Population dynamics and harvesting of semelparous species with phenotypic and genotypic variability in reproductive age (1995)

Kaitala, Veijo ; Getz, Wayne M.

Springer

Journal of mathematical biology 33 (1995), S. 521-556

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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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4

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Host-parasite dynamics and the evolution of host immunity and parasite fecundity strategies (1997)

Kaitala, Veijo ; Heino, Mikko ; Getz, Wayne M.

Springer

Bulletin of mathematical biology 59 (1997), S. 427-450

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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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5

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Delayed female reproduction in equilibrium and chaotic populations (1997)

Kaitala, VEIJO ; Mappes, TAPIO ; Ylonen, HANNU

Springer

Evolutionary ecology 11 (1997), S. 105-126

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ISSN: 1573-8477

Keywords: delayed reproduction ; evolutionarily stable strategy ; life history polymorphism ; population dynamics ; chaos

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Behavioural and life history polymorphisms are often observed in animal populations. We analyse the timing of maturation and reproduction in risky and resource-limited environments. Field and laboratory evidence suggests that female voles and mice, for example, can adjust their breeding according to the level of risk to their own survival and to survival probabilities and recruitment of young produced under different environmental conditions. Under risky or harsh conditions breeding can be postponed until later in the current breeding season or even to the next breeding season. We develop a population dynamics and life history model for polymorphism in reproduction (co-existence of breeding and non-breeding behaviours) of females in an age-structured population, with two temporally distinct mating events within the breeding season. We assume that, after overwintering, the females can breed in spring and again in summer or they can delay breeding in spring and breed in summer only. Young females born in spring can either mature and breed in summer or stay immature and postpone breeding over the winter to the next breeding season. We show that an evolutionarily stable breeding strategy is either an age-structured combination of pure breeding behaviours (old females breed and young delay maturity) or a mixed breeding behaviour within age-classes (a fraction of females breed and the rest of the age class postpones breeding). Co-occurrence of mixed reproductive behaviour in spring and summer within a single breeding season is observed in fluctuating populations only. The reproductive patterns depend on intraspecific, possibly interspecific, and ecological factors. The density dependence (e.g. social suppression) and predation risk are shown to be possible evolutionary mechanisms in adjusting the relative proportions of the different but co-existing reproductive behaviours.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1018491630846

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6

Electronic Resource

Resource leasing and optimal periodic capital investments (1995)

Novak, Andreas ; Kaitala, Veijo ; Feichtinger, Gustav

Springer

Mathematical methods of operations research 42 (1995), S. 47-67

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ISSN: 1432-5217

Source: Springer Online Journal Archives 1860-2000

Topics: Mathematics , Economics

Notes: Abstract In this paper we analyse a fishery resource exploitation model in which a single firm or a cartel has leased the rights to manage the resources independently. Two variables, resource level and the capital level, determine the dynamics of the resource system. The leasing contract includes an incentive for the agent to maintain the resource level high. The main result is that sole-agent resource management and efficiency of the resource use do not necessarily imply that the fishery is stabilized at a unique steady state level. Instead, the optimal resource exploitation may lead to periodic capital investments in fishing vessels and gear which in turn causes cycles in the resource economy. We show analytically that nonzero discount rate and low capital depreciation rate both favor the conditions under which periodic optimal solutions may occur. Simulation results related to a Baltic herring fishery are used to illustrate the results.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01415673

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