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  • 1
    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
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Reproductive limits and heterogeneity of male twospotted spider mites (1989)
    Springer
    Entomologia experimentalis et applicata 50 (1989), S. 209-214 
    Details
    ISSN: 1570-7458
    Keywords: Demography ; male population biology ; sex ratio ; Tetranychus urticae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé La reproduction est un processus qui nécessite généralement un mâle et une femelle. Cependant la biologie des populations ne s'est traditionnellement intéressée qu'à la contribution des femelles dans ce processus. Un effet de cet accent sur les femelles est que l'activité reproductrice des mâles a été très ignorée. Cet article examine, dans un contexte démographique, l'activité reproductrice des mâles de T. urticae, acarien arrhénotoque et phytophage. Trois séquences de l'activité reproductrice des mâles ont été examinées: 1) la copulation, 2) l'insémination, 3) la reproduction. En moyenne un mâle de 1 jour a copulé 15 fois, inséminé 15 femelles et a eu 336 filles. Pendant les 8 premiers jours, le mâle moyen a inséminé 70 femelles et a eu 1145 filles. Ces résultats suggèrent que le nombre de spermatozoïdes transférés à chaque insémination, plus que le nombre d'inséminations, est le facteur limitant d'une forte contribution du mâle à la reproduction.
    Notes: Abstract This paper determines reproductive limits and variation in performance of male twospotted spider mites Tetranychus urticae Koch when virgin females are provided ad libitum over the first eight days of adult life. Theree phases of male reproduction were studied: copulations, insemination and reproduction. An average one day old male copulated 15 times, inseminated 15 females, and contributed to 336 daughters. All parameters declined with age. The average male inseminated 70 females and contributed to 1145 daughters in the first days. Variability between males was small for all parameters considered. These data suggest that the number of sperm transferred at each insemination, rather than the number of inseminations, is the limiting step to higher male reproductive output.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341169
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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