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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 103 (1995), S. 133-139 
    ISSN: 1432-1939
    Keywords: Rainfall ; Climate ; Predation ; Spiders ; Lizards
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The objective of this study was to ascertain whether the impact of lizards on spiders varies temporally, and if so, whether this variability is related to rainfall. We compared annual censuses of orb-spider populations on 24 islands with diurnal lizards present, and on 20 islands with diurnal lizards absent, to rainfall over a 10-year period. A strong positive correlation (Pearson r=0.877) was found between mean spider density on nolizard islands and the number of days of rain that occurred 2 months prior to spider censuses; correlation coefficients declined with longer and shorter time periods prior to censuses. Correlation coefficients between mean spider density on lizard islands and rainfall showed a similar pattern but were generally lower than those for no-lizard islands. The strength of the impact of lizards on spiders, measured as the ratio of mean spider density on no-lizard islands to mean spider density on lizard islands, varied considerably and was positively correlated with rainfall; the correlation was highest with number of rain days 6 months prior to spider censuses (r=0.741). Repeated-measures analysis of variance on the time series of spider densities showed that the lizard factor (present versus absent) varied significantly among years. Split-plot ANOVA with rainfall as a covariate indicated that spider density and the impact of lizards on spider density were both significantly correlated with rainfall. We discuss several hypotheses on the causal mechanisms that integrate abiotic and biotic factors.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 90 (1992), S. 457-466 
    ISSN: 1432-1939
    Keywords: Spiders ; Philoponella ; Coloniality ; Prey consumption ; Competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary I studied the relationship between prey consumption and colony size in the orb spiderPhiloponella semiplumosa. Observations of unmanipulated colonies showed that prey biomass per juvenile spider was positively correlated with colony size, indicating that prey consumption was highest in the largest colonies observed. In contrast, the relationship between prey biomass per adult female and colony size was curvilinear; prey consumption tended to be highest in intermediatesized colonies. Adult female cephalothorax width was positively correlated with colony size. Number of egg sacs per adult female tended to be highest in intermediate-sized colonies. Prey biomass per juvenile was lower in experimentally reduced colonies than in large control colonies. Aerial-arthropod abundance was not correlated with colony size, and experimental prey supplementation did not affect colony size. Thus, the relationship between prey consumption and colony size was influenced by coloniality directly, rather than by a correlation between prey abundance at a site and colony size.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 83 (1990), S. 150-161 
    ISSN: 1432-1939
    Keywords: Competition ; Field experiment ; Lizards ; Predation ; Spiders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To determine the effect of lizards on webspider populations, we conducted a long-term field experiment in the Bahamas. Numbers of spider individuals were about 3 times higher in lizard-removal enclosures than in control enclosures with natural densities of lizards. Dietary analyses showed that lizards ate spiders and that lizard and spider diets overlapped substantially. Lizards reduced biomass of prey consumed by spiders; details indicated that they reduced biomass of large (〉 4 mm) prey consumed by spiders more than biomass of small (≤4 mm) prey. Similarly, lizards reduced biomass of large aerial arthropods caught in sticky traps but not biomass of small aerial arthropods. We found no evidence that the lizard effect on prey consumption by spiders was caused by a spatial shift from areas with high aerial arthropod abundance to areas with low aerial arthropod abundance. Lizards reduced adult female cephalothorax width and fecundity of spiders. In a separate experiment, food-supplemented spiders were more fecund than control spiders. This study indicates that the interaction between lizards and spiders includes both predation and competition for food.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2006-11-18
    Description: As the environment changes, will species be able to adapt? By conducting experiments in natural environments, biologists can study how evolutionary processes such as natural selection operate through time. We predicted that the introduction of a terrestrial predator would first select for longer-legged lizards, which are faster, but as the lizards shifted onto high twigs to avoid the predator, selection would reverse toward favoring the shorter-legged individuals better able to locomote there. Our experimental studies on 12 islets confirmed these predictions within a single generation, thus demonstrating the rapidity with which evolutionary forces can change during times of environmental flux.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Losos, Jonathan B -- Schoener, Thomas W -- Langerhans, R Brian -- Spiller, David A -- New York, N.Y. -- Science. 2006 Nov 17;314(5802):1111.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Box 1137, Washington University, St. Louis, MO 63130 USA. jlosos@oeb.harvard.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17110568" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bahamas ; *Biological Evolution ; Brazil ; Ecosystem ; Environment ; Lizards/*anatomy & histology/physiology ; *Predatory Behavior ; *Selection, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2012-02-04
    Description: The extent to which random processes such as founder events contribute to evolutionary divergence is a long-standing controversy in evolutionary biology. To determine the respective contributions of founder effects and natural selection, we conducted an experiment in which brown anole (Anolis sagrei) lizard populations were established on seven small islands in the Bahamas, from male-female pairs randomly drawn from the same large-island source. These founding events generated significant among-island genetic and morphological differences that persisted throughout the course of the experiment despite all populations adapting in the predicted direction-shorter hindlimbs-in response to the narrower vegetation on the small islands. Thus, using a replicated experiment in nature, we showed that both founder effects and natural selection jointly determine trait values in these populations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kolbe, Jason J -- Leal, Manuel -- Schoener, Thomas W -- Spiller, David A -- Losos, Jonathan B -- New York, N.Y. -- Science. 2012 Mar 2;335(6072):1086-9. doi: 10.1126/science.1209566. Epub 2012 Feb 2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA. jjkolbe@gmail.com〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22300849" target="_blank"〉PubMed〈/a〉
    Keywords: Adaptation, Biological ; Animals ; Bahamas ; *Biological Evolution ; *Ecosystem ; Female ; *Founder Effect ; Genetic Variation ; Genotype ; Hindlimb/anatomy & histology ; Introduced Species ; Lizards/*anatomy & histology/*genetics ; Male ; Microsatellite Repeats ; Phenotype ; Population Density ; *Selection, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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