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  • Population dynamics modeling  (1)
  • photorespiration  (1)
  • 1995-1999  (2)
  • 1
    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
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  • 2
    ISSN: 1573-5028
    Keywords: cucumber ; light-regulated gene expression ; NADH-dependent hydroxypyruvate reductase ; organ-specific gene expression ; peroxisome ; photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 5′- and 3′-flanking regions of HPRA, a cucumber gene that encodes hydroxypyruvate reductase, were evaluated for regulatory activity with respect to light responsiveness and organ specificity. To define the functional regions of the 5′-flanking region of HPRA, a series of deletions was generated and the remaining portions fused to the β-glucuronidase (GUS) reporter gene (uidA) containing a minimal 35S promoter truncated at −90. The region from −66 to +39 was found to be necessary for light-regulated expression of the uidA reporter gene, while the region from −382 to −67 was found to be necessary for its leaf-specific expression. Further deletion of the HPRA 5′ flanking region to −590 resulted in high levels of root expression, suggesting the presence of a negative regulatory element responsible for silencing root expression of the HPRA gene between −590 and −383. The 3′-flanking region of the HPRA gene downstream of the polyadenylation site contains several sequence motifs resembling regulatory elements present in the promoters of several light-responsive genes. An 823 bp portion of the HPRA 3′-flanking region containing these putative regulatory elements enhanced GUS expression in leaves when placed downstream of the uidA reporter gene in the forward orientation, but not in the reverse orientation. When placed 5′ of the −90 35S promoter, the 823 bp fragment enhanced slightly, independently of orientation, the root tip-specific expression pattern intrinsic to the −90 35S promoter, indicating that in some cases this region can act as a transcriptional enhancer.
    Type of Medium: Electronic Resource
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