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  • 1
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    Mass Spawning by Green Algae on Coral Reefs (1997)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1997-02-21
    Description: Predawn episodes of mass spawning by green algae (up to nine species in five genera on a single morning) intermittently cloud Caribbean waters. Species- and sex-specific bouts of anisogamous gamete release occurred synchronously and predictably on a given morning, with closely related species spawning at different times. Algal sexual reproduction was seasonal, but, unlike the mass-spawning behavior of other sessile marine organisms, showed no lunar or tidal cycling. The discovery of mass-spawning behavior by these algae has important implications for future studies of the reproductive ecology and speciation of a vital, yet poorly understood, component of the coral reef community.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Clifton -- New York, N.Y. -- Science. 1997 Feb 21;275(5303):1116-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Smithsonian Tropical Research Institute, Apartado 2072, Balboa, Panama.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9027310" target="_blank"〉PubMed〈/a〉
    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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  • 2
    Electronic Resource
    Electronic Resource
    The fine-scale mapping of grassland protein densities (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 49 (1994), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A simple and accurate remote sensing technique for the fine-scale mapping of grassland protein densities was developed during a study of sward quality and antelope dispersion in Kenya, East Africa. Using measures of spectral reflectance and a vehicular navigation system, estimates of protein densities were recorded at rates exceeding 1000 samples per hour. Nitrogen analyses confirmed that reflectance measures were accurate predictors of protein density for a variety of grass swards but not for two species of sedge. Because the regression coefficients linking reflectance to protein density differed significantly between sward types, good estimates using this method will require a separate calibration for each type of grassland. By monitoring and correcting for variations in ambient light levels, the method can be used under a wide range of lighting conditions and for long periods. This facilitates sampling sufficiently systematically and intensively that contour plots of protein density can be constructed and then correlated with distributions of underlying abiotic factors, foraging activity of sympatric herbivores, or prior maps to characterize successional and historical change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1994.tb01970.x
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    Paper (German National Licenses)
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  • 3
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    The ideal free antelope: foraging dispersions (2015)
    Oxford University Press
    Details
    Publication Date: 2015-09-15
    Description: The theory of ideal free distributions seeks to predict the dispersions of organisms given heterogeneous resource landscapes and density dependent fitness. Behavioral ecologists usually test this theory by examining outcomes, particularly whether the equilibrium fraction of animals in each alternative site equals the fraction of resource there (proportional settlement). Population ecologists instead focus on the relevant process: how does dispersion relate to resource distributions and is it density dependent? Isodar analysis is a process-focused method that assesses the relative roles of quantitative and qualitative factors in shaping density dependent settlement. Here, we apply isodar analysis to the dispersions of wild Thomson’s gazelles foraging on natural swards in Kenya. Frequent and detailed mapping of resource levels allowed us to delineate rich and poor regions, and to record the densities of foraging females in each region throughout an annual cycle. Whereas quantitative differences attracted more foragers into the rich region at low-ambient densities, the poor region became increasingly favored at higher densities, implying the competing influence of a qualitative factor. Additional regressions suggested that this factor involved predation risk through the following scenario. Intakes were found to increase with proximity to ruminating conspecifics. The latter favored poor regions perhaps for improved predator detection. High wet season food abundance both increased gazelle densities and decreased the costs of foraging in the poor region next to vigilant ruminators. Low dry season food levels resulted in lower gazelle densities, and higher costs of foraging in the poor region despite shared vigilance burdens.
    Print ISSN: 1045-2249
    Electronic ISSN: 1465-7279
    Topics: Biology
    Published by Oxford University Press
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