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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 413 (2001), S. 512-514 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Understanding the early evolution of aposematic (warning) coloration has been a challenge for scientists, as a new conspicuous morph in a population of cryptic insects would have a high predation risk and would probably die out before local predators learnt to avoid it. Fisher presented the ...
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 382 (1996), S. 708-710 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] On the basis of the fact that hand-reared predators with no experience of aposematic prey are not naive in the evolutionary sense, we created a world in which there were two types of symbols (crosses and filled squares) that were switched to form the background or the warning signal. As the symbols ...
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 385 (1997), S. 402-403 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In his influential book The Structure of Scientific Revolutions, Kuhn1 described scientific endeavour in terms of occasional revolutionary shifts from one favoured paradigm to another. Although research is not totally uncritical between revolutions, currently popular explanations can be accepted ...
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 352 (1991), S. 155-156 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Black grouse males were caught at a feeding site in central Finland (Petajavesi, 62°10' N, 20°05' E) during the winters of 1987-90, and marked individually with colour rings. Copulations were recorded on the four leks within 3 km of the site of capture, in late April and early May11'12 each ...
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  • 5
    ISSN: 1573-8477
    Keywords: body mass ; maturation ; phenotypic plasticity ; reaction norms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In invertebrates, the size at maturation is considered to be important for adult fitness. In the wolf spider Hygrolycosa rubrofasciata, however, it is only females that clearly benefit of larger size through augmented egg production, while male mating success is determined by display activity not related to size. Thus, we can expect conflicting growth patterns for the sexes. Additionally, populations differ greatly in adult size: individuals from dry habitats are smaller than those from wet habitats. To study the sexual differences in reaction norms of growth, we reared spiderlings from seven populations at two food levels under controlled laboratory conditions and compared size at sexual maturity. The shapes of reaction norms for adult size differed between the sexes. In females, the reaction norms were parallel, but individuals from dry habitats tended to grow larger at the given food levels. In males, there was a significant interaction between food level and population without any consistent differences between populations. Maturation time was a plastic character in both sexes with no genetic differences among populations. However, females on low food level matured later and significantly smaller in size than those on high food level. Males also matured later on low food level, but they were nearly of the same size as males that received more food. Female growth patterns reflected the strong selection for large size at maturity. However, the patterns for males were highly variable, which could be explained by the weak overall selection on male size, which means that any environmental factors can affect male growing patterns.
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 323 (1986), S. 152-153 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The pied flycatcher (Ficedula hypoleuca, Muscicapinae), a hole-nesting, migratory, territorial bird species, can easily be attracted to nest boxes. It is sexually dimorphic in plumage, and males have a very complex song repertoire. Some males achieve polygyny by being polyterritorial13'14. Males ...
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 397 (1999), S. 249-251 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Aposematic species, which signal conspicuously of their unprofitability to predators, have puzzled evolutionary biologists for over a century,. Although conspicuousness of unpalatable prey improves avoidance learning by predators, it also involves an evolutionary paradox: with increasing ...
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 45 (1980), S. 190-196 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The five most abundant species were included in a year-round study with respect to six foraging niche dimensions. Approximately full multidimensional utilization functions were used for niche metrics. During summer foraging overlaps were invariably high, but in other seasons periodically lower. Foraging site breadth was lower in winter, when fewer sites are profitable for foraging than in summer. Feeding posture versatility, by contrast, was highest in winter. Seasonal foraging shifts were very prominent, as great in fact as between-species differences. Often seasonal trends were parallel in different species. Niche axes of macrohabitat-type (e.g. tree) were more open for foraging variation and axes of microhabitat-type (tree part) more rigid. Among the resident species seasonal variation in foraging was greatest in Regulus regulus and Parus cristatus, whereas the foraging behaviour was more stable for P. montanus (an abundant species with broad niche), perhaps owing to greater intraspecific competition. In these northern forests foliage-gleaners must be versatile generalists to cope with the unpredictable resources, and thus they overlap broadly in their general resource niches which are determined by their genetically fixed cost and benefit relations to each resource type. Anyhow, presumably during periodical food shortage, the actual resource uses adjusted by resource availability and competition may overlap narrowly.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 114 (1998), S. 127-132 
    ISSN: 1432-1939
    Keywords: Key wordsGalerucella nymphaeae ; Leaf beetle ; Male size ; Offspring viability ; Sexual selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of active female choice in sexual selection is frequently difficult to ascertain, and this is particularly the case for many insect species. Also, it is uncertain whether choosing between males would affect offspring viability. We designed an experiment to investigate the presence of female choice in a Coleoptera species (Galerucella nymphaeae). We also estimated whether mate choice would have any effect on offspring performance. Females were first placed with two males in a test arena to see which of the males copulated with the virgin female, and how quickly. Subsequently the loser male was offered a new virgin female to test for any change in latency time until mating. The two-male tests indicated that males with wider upper prothoraxes were more likely to mate with the female, and the latency time until mating was shorter when the winner male had relatively long wings. When the loser males were placed singly with females the latency time was not correlated with male size, and was the same as when two males were used. These results suggest that male-male competition is the most likely cause of sexual selection on size, and if females have any preferences they are not very strong. The seemingly passive female strategy may be sufficient to ensure that females mate with the most vigorous males, since in the field several males usually compete for access to each female. Finally, the benefits of female choosiness were estimated to be low and non-significant. The eggs of the winner males were no more likely to hatch, offspring survival into adulthood was no greater among descendants of winner males, and the offspring did not differ in adult size.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 96 (1993), S. 410-414 
    ISSN: 1432-1939
    Keywords: Ficedula hypoleuca ; Male fitness ; Blood parasites ; Trypanosoma ; Haemoproteus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vertebrates the effect of parasites on host ecology has almost been ignored. Recently the view that well-adapted parasites do not harm their hosts has been challenged and there is growing evidence that parasites do have a present-day effect on a great variety of host fitness components. The pied flycatcher is a small migratory passcrine bird. Any decrease in condition caused by disease should affect its ability to cope with physical demands of migration. Here we examine whether blood parasites have any effect on male arrival time. Males infected with Trypanosoma arrived on average 2 days later than males with no Trypanosoma infection. Infected males also had shorted tails and tended to have shorter wings. By contrast, there was no difference in male arrival time between males infected with Haemoproteus and healthy males. It seems that Trypanosoma infection lowered male condition and consequently the ability to moult and migrate. The difference in length of feathers may have generated the difference in arrival times. Early arrival is highly important for males, since only the first males become polygynous and breeding prospects deteriorate rapidly with any delay in egg laying. Estimated reduction in breeding success for infected males was about 20%.
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