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  • Articles: DFG German National Licenses  (2)
  • 1990-1994  (2)
  • Sex ratio  (1)
  • cotton  (1)
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  • Articles: DFG German National Licenses  (2)
Material
Years
  • 1990-1994  (2)
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Demographic analyses of organophosphate-resistant and susceptible strains of greenhouse whitefly, Trialeurodes vaporariorum, on three cotton cultivars (1992)
    Springer
    Entomologia experimentalis et applicata 65 (1992), S. 21-30 
    Details
    ISSN: 1570-7458
    Keywords: Greenhouse whitefly ; Trialeurodes vaporariorum ; demography ; resistant ; susceptible ; cotton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Laboratory experiments were conducted using organophosphate-resistant and susceptible strains of greenhouse whitefly, Trialeurodes vaporariorum Westwood, to assess age-specific vital rates in individually-held adults, and development and survival in preadults on three cotton cultivars at 27±1 °C, 50±10% RH, and a photoperiod of 16:8 (L:D). Female whiteflies lived longer than males, with a maximum life expectancy of 29 days. Heaviest egg laying occurred at ages between 7 and 18 days when individual whiteflies laid 〉 10 eggs/day. Greenhouse whitefly populations doubled weekly, with stable age distribution of 63% eggs, 28% larvae, 5% pupae, and 4% adults. Analysis of various life history parameters that combine aspects of survival, developmental rates, and fecundity indicated no consistent differences in reproductive fitness between the two greenhouse whitefly strains. Of the three cotton cultivars tested, Pima S-6 was most susceptible, Acala SJ-2 was intermediate and Gumbo 500 was most resistant to greenhouse whitefly. Resistance of Gumbo 500 was expressed as slower developmental rates, reduced survival to adulthood, lower reproductive rates, and lower intrinsic rate of increase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189713
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Male demographic constraints to extreme sex ratio in the twospotted spider mite (1990)
    Springer
    Oecologia 82 (1990), S. 417-423 
    Details
    ISSN: 1432-1939
    Keywords: Sex ratio ; Twospotted spider mite ; Demography ; Male reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Twospotted spider mites, Tetranychus urticae Koch are arrhenotokous. As a result of this genetic structure, primary and secondary sex ratios diverge from the 1:1 female:male ratio commonly found in diploid systems. Ratios vary, but 3:1 is the most common. The influence of life history parameters on spider mite sex ratio is unclear, although maternal genetic effects, resource quality and maternal age are known to play a role. An area that has not been studied is the relationship between male reproductive capabilities and spider mite sex ratio. A prior study on male reproduction in spider mites suggests that males have far too high a reproductive capacity to explain sex ratio patterns, but that study was not conducted under realistic mating conditions. Thus, this study was conducted to determine if there is a link between male reproduction and spider mite sex ratio. This was done by exposing males to various exposure regimes of females and recording the number of copulations, inseminations and daughters fathered by each male. Results include the following: i) males are most virile when one day old; ii) virgin males become nearly completely devoid of sperm (or other copulatory products) after about 15 matings and then take about four days to recover; and iii) the optimal number of matings per day (defined as that which produces the greatest number of daughters in the least number of inseminations) is four females per day. The principle conclusion is that although males have a high potential reproductive output, insemination quality is only high for the first four or five matings each day. Therefore, to ensure full inseminations of all daughters by sons, females are constrained to producing primary sex ratios of about 5:1 or less.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317492
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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