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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Experimental Gerontology 8 (1973), S. 199-206 
    ISSN: 0531-5565
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Mutation Research/Environmental Mutagenesis and Related Subjects 64 (1979), S. 148 
    ISSN: 0165-1161
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 85 (1997), S. 247-256 
    ISSN: 1570-7458
    Keywords: bean weevil ; Acanthoscelides obtectus ; genetic variation ; host preference ; preference/performance correlation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We explored the extent to which two populations of Acanthoscelides obtectus (Coleoptera: Bruchidae), maintained in the laboratory for about 60 generations on common bean (Phaseolus vulgaris) and chickpea (Cicer arietinum) seeds, differ genetically in life history traits. Using a half-sib breeding design, we screened for genetic variation in oviposition preference for two hosts within both populations, and examined whether this variation is correlated with weevil pre-adult (egg-to-adult viability and egg-to-adult developmental time) and adult (female fecundity and longevity) fitness components on these two hosts. Significant differences between the Phaseolus and Cicer population were detected in viability, developmental time and oviposition preference, but not in female fecundity and longevity. The absence of a significant population × host interaction in all traits, except for developmental time in males, indicates that the Cicer population has not attained the status of ‘host race’. The estimated narrow-sense heritabilities within population within host plant were in the low-to-moderate level (range: 1%–79%), with an overall average of about 24%. Within the population maintained on the chickpeas we detected significant genetic correlations between female developmental time on chickpea seeds and preference for chickpeas. In the population maintained on the primary host of this weevil species (the ‘Phaseolus’ population) we found no significant preference/performance genetic correlations. Data are also presented on the genetic correlations of preference and performance across host seeds within both populations. These correlations are found to be positive for all traits in both populations, indicating the absence of trade-offs in either performance or behavioural response that might impose selection for host specialization within populations.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Genetica 56 (1981), S. 61-69 
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The origin and maintenance of genetic recombination are unsettled evolutionary issues. Genetic variation affecting recombination frequency appears to be pervasive in nature, suggesting that natural selection must increase recombination frequency under some circumstances. However, theoretical arguments and experimental evidence indicate that the frequency of recombination should be reduced by natural selection. A hypothesis not previously explored is that recombination modifiers may directly affect the fitness of their carriers; rather than only indirectly (through the production of recombinant progeny) as generally assumed. We have tested this hypothesis by examining three fitness components (viability, male fertility, and female fecundity) in Drosophila melanogaster homozygous for second chromosomes isolated from a natural population. Then, we have measured the frequency of recombination in flies heterozygous for each wild second chromosome and a chromosome carrying five recessive alleles. The results indicate that genes modulating the frequency of recombination have direct effects on fitness as proposed by the hypothesis. However, the correlation between frequency of recombination and fitness is negative. Thus, the riddle of recombination remains unexplained and, in fact, more puzzling that ever.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1615-6110
    Keywords: Angiosperms ; Iridaceae ; Iris pumila ; Phenotypic plasticity ; morphological variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Variation patterns in phenotypic plasticity and broad sense heritability of 26 characters were examined within and among closely adjacent habitats of the bearded iris,Iris pumila. It was found thatI. pumila has considerable differentiation for phenotypic plasticity and genetic variation over short distances. An analysis of relationships between character differentiation and phenotypic plasticity suggests that they could have evolved independently. Possible mechanisms for maintaining local differentiation of the observed plastic and genetic variation are also discussed.
    Type of Medium: Electronic Resource
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