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  • Daphnia  (1)
  • Key words: Lake La Cruz, trophic changes, meromixis, diatoms, cladocera, ostracoda and pollen stratigraphy.  (1)
Document type
Keywords
Publisher
Years
  • 1
    Electronic Resource
    Electronic Resource
    Meromixis origin and recent trophic evolution in the Spanish mountain lake La Cruz (1998)
    Springer
    Aquatic sciences 60 (1998), S. 279-299 
    Details
    ISSN: 1420-9055
    Keywords: Key words: Lake La Cruz, trophic changes, meromixis, diatoms, cladocera, ostracoda and pollen stratigraphy.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract: A sediment core from a Mediterranean karstic lake was studied through its pollen, diatom, chydorid, ostracod, charcoal and authigenic mineral composition. Information about environmental history recorded in the sediment sequence since the Middle Ages is presented. The main fluctuations of water volume and trophic status of the lake occurred during periods of great change in land management and during climatic cold phases. The synergetic effect of these two factors led to a high water level phase and triggered a rising of the trophic level which produced meromixis. The onset of meromictic conditions at about 1700 AD coincides with the Maunder minimum in the Little Ice Age as well as with a period of increasing human population, woodland clearance and agricultural expansion to the detriment of the nomadic livestock breeding or transhumance ("Mesta").
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000270050042
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Large Hardy-Weinberg equilibrium deviations in the Daphnia longispina of Lake El Tobar (1995)
    Springer
    Hydrobiologia 307 (1995), S. 15-23 
    Details
    ISSN: 1573-5117
    Keywords: Daphnia ; allozymes ; Hardy-Weinberg equilibrium ; parthenogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The population structure of Daphnia longispina in Lake El Tobar, Spain was studied by measuring variation at the aldehyde oxidase (AO), phosphoglucose isomerase (PGI) and phosphoglucose mutase (PGM) loci in each of 1337 individuals from four collections. In 9 of the 12 comparisons between observed allele frequencies and those expected by Hardy-Weinberg equilibrium there was an excess of heterozygotes. We found 27 of the potential number of 54 composite electromorphs (‘clones’) based on the three allozymes. Clone diversities were rather high in all collections. Three clones reached frequencies of over 25% and different clones were dominant in each of the four collections. Strong temporal variation was found in the genetic structure of this Daphnia population. This variation was driven by changes in the relative frequencies of the component clones in the lake rather than by a recruitment of novel clones into the population. We conclude with a consideration of the role of models relating allele and genotype frequencies in populations of cyclical parthenogens. Because the breeding system of these populations infrequently involves recombination between clones, models such as the Hardy-Weinberg have limited value in providing meaningful measures of population structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00031993
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    Paper (German National Licenses)
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