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  • 1
    Electronic Resource
    Electronic Resource
    The influence of colonization in nested species subsets (1995)
    Springer
    Oecologia 102 (1995), S. 413-424 
    Details
    ISSN: 1432-1939
    Keywords: Species composition ; Islands ; Nested subsets ; Conservation ; Colonization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Biotic communities inhabiting collections of insular habitat patches often exhibit compositional patterns described as “nested subsets”. In nested biotas, the assemblages of species in relatively depauperate sites comprise successive subsets of species in relatively richer sites. In theory, nestedness may result from selective extinction, selective colonization, or other mechanisms, such as nested habitats. Allopatric speciation is expected to reduce nestedness. Previous studies, based largely on comparisons between land-bridge and oceanic archipelagos, have emphasized the role of selective extinction. However, colonization could also be important in generating strong patterns of nestedness. We apply a recently published index of nestedness to more than 50 island biogeographic data sets, and examine the roles of colonization, extinction, endemism, and, to a limited extent, habitat variability on the degree on nestedness. Most data sets exhibit a significant degree of nestedness, although there is no general tendency for land-bridge biotas to appear more nested than oceanic ones. Endemic species are shown to generally reduce nestedness. Comparisons between groups of non-endemic species differing in overwater or inter-patch dispersal ability indicate that superior dispersers generally exhibit a greater degree of nestedness than poorer dispersers, a result opposite that expected if colonization were a less predictable process than extinction. These results suggest that frequent colonization is likely to enhance nestedness, thereby increasing the compositional overlap among insular biotas. The prevalence of selective extinction in natural communities remains in question. The importance of colonization in generating and maintaining nested subsets suggests that (1) minimum critical areas will be difficult to determine from patterns of species distributions on islands; (2) multiple conservation sites are likely to be required to preserve communities in subdivided landscapes; and (3) management of dispersal processes may be as important to preserving species and communities as is minimizing extinctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341353
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The relationship between nested subsets, habitat subdivision, and species diversity (1995)
    Springer
    Oecologia 101 (1995), S. 204-210 
    Details
    ISSN: 1432-1939
    Keywords: Nested subsets ; Habitat subdivision ; Species assemblages ; Biogeography ; Conservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Biotic assemblages are said to be nested when the species making up relatively species-poor biotas comprise subsets of the species present at richer sites. Because species number and site area are often correlated, previous studies have suggested that nestedness may be relevant to questions of how habitat subdivision affects species diversity, particularly with respect to the question of whether a single large, contiguous patch of habitat will generally contain more species than collections of smaller patches having the same total combined area. However, inferences from analyses of nestedness are complicated by (1) variability in degrees of nestedness measured in natural communities, (2) variability in species-area relationships, and (3) the fact that nestedness statistics do not account for the size of habitat patches, only in the degree of overlap among sites with different numbers of species. By comparing various indices of nestedness with a “saturation index” that more directly measures the effect of habitat subdivision, it is shown that the first two of these factors are not as important as the third. Whether a single large site or several smaller ones having the same total combined area maximizes species diversity is dependent on (1) overlap in species composition among sites and (2) the number of species per unit area in the different sites. Because nestedness indices do not account for species number at a site, they cannot accurately predict how habitat subdivision affects species diversity patterns. Still, nestedness analyses are important in that they indicate the degree to which rare species tend to be found in the largest, or the most species-rich, sites, patterns not revealed by the saturation index. Both types of analysis are important in order to obtain a more complete picture of how species richness and compositional patterns are influenced by habitat subdivision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317285
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  • 3
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    Duplicating a tangled genome (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-09-28
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cook, P -- New York, N.Y. -- Science. 1998 Sep 4;281(5382):1466-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cell Biology, Sir William Dunn School of Pathology, Oxford OX2 3RE, UK. peter.cook@path.ox.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9750117" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Nucleus/*metabolism ; *DNA Replication ; *Genome ; Genome, Human ; Humans ; Models, Biological ; *Transcription, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    The organization of replication and transcription (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-06-12
    Description: Models for replication and transcription often display polymerases that track like locomotives along their DNA templates. However, recent evidence supports an alternative model in which DNA and RNA polymerases are immobilized by attachment to larger structures, where they reel in their templates and extrude newly made nucleic acids. These polymerases do not act independently; they are concentrated in discrete "factories," where they work together on many different templates. Evidence for models involving tracking and immobile polymerases is reviewed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cook, P R -- Wellcome Trust/United Kingdom -- New York, N.Y. -- Science. 1999 Jun 11;284(5421):1790-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK. Peter.Cook@Path.OX.AC.UK〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10364545" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *DNA Replication ; DNA-Directed DNA Polymerase/*metabolism ; DNA-Directed RNA Polymerases/*metabolism ; Humans ; Models, Genetic ; Replication Origin ; Templates, Genetic ; *Transcription, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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