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  • Holocene  (2)
  • Gene isolation
  • Drosophila melanogaster
  • Springer  (3)
  • 1995-1999  (3)
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  • Springer  (3)
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  • 1
    ISSN: 1573-6857
    Keywords: Drosophila melanogaster ; isofemale lines ; isogroups ; natural populations ; pigmentation ; body size
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies of short or medium range geographic variations play an increasing role in ecological genetics, and sensitive techniques are required to detect them. In this respect, two sampling techniques were compared inD. melanogaster. The biological data were provided by the analysis of four natural populations from the same geographic area, Spain (one) and Southern France (three), for four morphometrical traits: abdomen and thoracic pigmentation, and wing and thorax lengths. Traits were measured on wild living females and on their progeny reared in the laboratory at 25°C. For progeny analyses, two techniques were compared: the usual isofemale line technique, sib families issued from a single female, and a new isogroup technique, the progeny produced by a group of 20 wild-collected parents. Large phenotypic variations were observed in wild living flies, corresponding to the unstability of natural environmental conditions during their development. Among laboratory grown flies, variations were much smaller. Between isogroups, differences were small, due to sampling error and some common environment effects. Variations between lines were much greater, thus demonstrating a strong genetic component. When different populations have to be compared, the isogroup technique should be preferred since, for the same amount of work, the lesser variability between groups provides a more precise characterization of the population means.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-6278
    Keywords: Pollen analysis ; Late-glacial ; Holocene ; Iberian peninsula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Archaeology , Biology
    Notes: Abstract This paper presents the results of pollen analyses from organic sediments of seven cores (299 spectra) in a mountainous area of the north-west Iberian peninsula. The pollen diagrams, supported by seven14C dates, are used to construct a regional pollen sequence covering the main stages of vegetation dynamics, from the last phases of the Late-glacial until the present. During the Late-glacial Interstadial an important development of cryophilous forests (Betula andPinus) was recorded, although various mesophilous and thermophilous tree elements were also present. The Younger Dryas, palynologically clearly defined, is characterized by an important reduction in tree pollen percentages and the expansion of steppe formations (Poaceae andArtemisia). At the beginning of the Holocene, there was an expansion ofQuercus and a spread of other trees, which combined to give a vegetation cover of varied composition but dominated by mixed deciduous forests. Such forest formations prevailed in these mountains until 3000 years ago, when successive deforestation phases are recorded at various times as a result of increased farming activity. The results are compared with data from other mountainous areas in the northern Iberian peninsula and southern France.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5052
    Keywords: Holocene ; Lateglacial ; North Iberian Peninsula ; Pollen analysis ; Vegetation development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dynamics of vegetation in the North Iberian Peninsula have been historically established from peaty and lacustrine records obtained in strongly continental mountainous areas. Pollen records located in areas with a more oceanic climate, have allowed a more precise evaluation of the changes and differences in the vegetation development of the various biogeographical areas in the North Iberian Peninsula, during the Late-glacial and Holocene. It was found that: (1) The vegetation of the Cantabrian–Atlantic province in northern Iberian Peninsula responded to climatic changes during the last 16000 years. (2) Tree vegetation declined during the Oldest Dryas, with steppe vegetation in the interior and cryophilous vegetation along the coast. (3) During the time of the Lateglacial Interestadial, lowlands, arboreal vegetation was dominant in the landscape (Pinus, Betula, Quercus, Corylus). (4) During the Younger Dryas the differences between coast and interior are less obvious. (5) During the Holocene oceanic decidious forests of Quercus robur, Corylus avellana, Tilia sp. and Fagus sylvatica were present along the coast. At low altitudes, in the interior, forests of Quercus robur / pyrenaica, enclaves of pine woods and Mediterranean types of forest (Quercus ilex, Olea europea) were present. At higher altitudes Pinus (P. sylvestris and P. uncinata) or mixed forests of Pinus and Betula were dominant.
    Type of Medium: Electronic Resource
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