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211.
Wolfgang Wiltschko Lars Dehe Katrin Stapput Peter Thalau Roswitha Wiltschko 《Die Naturwissenschaften》2010,97(1):37-42
Under 502 nm turquoise light combined with 590 nm yellow light and in total darkness, European robins, Erithacus rubecula, no longer prefer their migratory direction, but exhibit so-called fixed direction responses that do not show the seasonal
change between spring and autumn. We tested robins under these light conditions in the local geomagnetic field of 46 μT, a
field of twice this intensity, 92 μT, and a field of three times this intensity, 138 μT. Under all three magnetic conditions,
the birds preferred the same easterly direction under turquoise-and-yellow light and the same northwesterly direction under
dark, while they were oriented in their seasonally appropriate direction under control conditions. “Fixed direction” responses
are thus not limited to a narrow intensity window as has been found for normal compass orientation. This can be attributed
to their origin in the magnetite-based receptor in the upper beak, which operates according to fundamentally different principles
than the radical pair mechanism in the retina mediating compass orientation. “Fixed direction” responses are possibly a relict
of a receptor mechanism that changed its function, now mainly providing information on magnetic intensity. 相似文献
212.
Andrea Meyn Sebastian Schmidtlein Stephen W. Taylor Martin P. Girardin Kirsten Thonicke Wolfgang Cramer 《Regional Environmental Change》2013,13(1):165-177
Trends of summer precipitation and summer temperature and their influence on trends in summer drought and area burned in British Columbia (BC) were investigated for the period 1920–2000. The complexity imposed by topography was taken into account by incorporating high spatial resolution climate and fire data. Considerable regional variation in trends and in climate–fire relationships was observed. A weak but significant increase in summer temperature was detected in northeastern and coastal BC, whereas summer precipitation increased significantly in all regions—by up to 45.9 %. A significant decrease in province-wide area burned and at the level of sub-units was strongly related to increasing precipitation, more so than to changing temperature or drought severity. A stronger dependence of area burned on precipitation, a variable difficult to predict, implies that projected changes in future area burned in this region may yield higher uncertainties than in regions where temperature is predominantly the limiting factor for fire activity. We argue that analyses of fire–climate relationships must be undertaken at a sufficiently high resolution such that spatial variability in limiting factors on area burned like precipitation, temperature, and drought is captured within units. 相似文献
213.
The photolysis of musk ketone in cyclohexane and methanol afforded several cyclization products while the product spectrum in cyclohexene and squalene was characterized by an amino derivative and a ring expansion product, respectively. On cellulose stearate layers the photochemical reactions of musk ketone proceeded readily both under sun simulator and in natural sunlight and several photoproducts identified in solvent experiments were detected. Photoproducts were isolated by preparative HPLC and TLC and analyzed by means of HPLC, GC/MS, MS, LC/MS, 1H‐ and 13C‐NMR. 相似文献
214.
Elaine Tweneboah Lawson Wolfgang Schluchter Chris Gordon 《Journal of Coastal Conservation》2010,14(3):231-238
Like many developing countries, Ghana is grappling with environmental issues, such as the degradation of coastal natural resources.
In an attempt to ameliorate the current state of affairs, broad institutional arrangements and policy interventions have been
put in place. However coastal natural resources are still being overexploited and the effects of this are felt more strongly
by certain groups (such as women and the rural poor) than others. This has led to the argument pointing to an urgent need
to include local resource users as active participants in environmental decision making and to incorporate their environmental
values in the management of coastal natural resources. Using empirical data from women in two Ghanaian coastal communities,
this paper highlights the importance of exploring how the environmental attitudes and values of women might be considered
in the management of local coastal natural resources. It assesses effectiveness of the paired comparison methodology in this
respects and how this method can be also used to prioritise their environmental concerns. The results show that in both areas
respondents place the greatest importance on the coastal natural resources as sources of wealth creation and of food, values
which are often described as being “anthropocentric”. The paper thus argues that having discovered that the ecological value
placed on natural resources is low, initiatives that could win the support of people would be those that link the livelihood
and wellbeing to coastal NRM. It emphasizes the fact that conservation cannot exist outside of people and social systems;
nor will it succeed unless they are linked to the welfare of resource users. 相似文献
215.
Travis C. Glenn †‡ Wolfgang Stephan and Michael J. Braun† 《Conservation biology》1999,13(5):1097-1107
Abstract: The Whooping Crane ( Grus americana ) is an endangered bird that suffered a severe population bottleneck; only 14 adults survived in 1938. We assessed the genetic effect of this human-caused bottleneck by sequencing 314 base pairs ( bp) of the mitochondrial DNA control region from cranes that lived before, during, and after this bottleneck. The maximum length of DNA amplifiable from museum specimens was negatively correlated with age, and only 10 of 153 specimens yielded the entire 314 bp sequence. Six haplotypes were present among the prebottleneck individuals sequenced, and only one of these persists in the modern population. The most common modern haplotype was in low frequency in the prebottleneck population, which demonstrates the powerful effect of genetic drift in changing allele frequencies in very small populations. By combining all available data, we show that no more than one-third of the prebottleneck haplotypes survived the human-caused population bottleneck. High levels of variation of substitution rates among nucleotide sites prevented us from estimating the prebottleneck population size. Our data will be incorporated into the captive breeding program to allow better management decisions regarding the preservation of current genetic diversity. These data offer the first glimpse into the genetic toll this species has paid for human activities. 相似文献
216.
217.
Altitude profiles of total chlorinated paraffins in humus and spruce needles from the Alps (MONARPOP) 总被引:1,自引:0,他引:1
Saverio Iozza Peter Schmid Rodolfo Bassan Gert Jakobi Karl-Werner Schramm Wolfgang Moche Peter Weiss Wilhelm Knoth 《Environmental pollution (Barking, Essex : 1987)》2009,157(12):3225-3231
Chlorinated paraffins (CPs) are toxic, bioaccumulative, persistent, and ubiquitously present in the environment. CPs were analyzed in humus and needle samples, which were taken within the Monitoring Network in the Alpine Region for Persistent and other Organic Pollutants (MONARPOP) at sampling sites of 7 different altitude profiles in the Alps. Gas chromatography combined with electron ionization tandem mass spectrometry (EI-MS/MS) was used for the determination of total CPs (sum of short, medium and long chain CPs). CPs were found in all samples; the concentrations varied between 7 and 199 ng g−1 dry weight (dw) and within 26 and 460 ng g−1 dw in humus and needle samples, respectively. A clear vertical tendency within the individual altitude profiles could not be ascertained. Within all altitude profiles, elevated concentrations were observed in humus samples taken between 700 and 900 m and between 1300 and 1500 m. In the needle samples no similar correlation could be observed due to higher variation of the data. 相似文献
218.
Birth sex ratios in toque macaques and other mammals: integrating the effects of maternal condition and competition 总被引:2,自引:0,他引:2
Wolfgang P. J. Dittus 《Behavioral ecology and sociobiology》1998,44(3):149-160
Mammalian life histories suggest that maternal body condition and social dominance (a measure of resource-holding potential)
influence the physical and social development of offspring, and thereby their reproductive success. Predictably, a mother
should produce that sex of offspring which contributes most to her fitness (as measured by the number of her grandchildren)
and that she is best able to raise within the constraints imposed by her condition, social rank, and environment. Such combined
effects were investigated by monitoring variations in body condition (weight) and behavior of female toque macaques, Macaca sinica of Sri Lanka, in a changing forest environment over 18 years. Maternal rank, by itself, had no influence on offspring sex,
but did affect maternal body condition. The combined effects of rank and condition indicated the following: mothers in robust
condition bore more sons, whereas those in moderate condition bore more daughters, but both effects were expressed most strongly
among mothers of high rank. Where the consequences of low rank were felt most acutely, as shown by poor condition, mothers
underproduced daughters. Environmental quality directly influenced rank and condition interactions, and thus sex ratios. These
relationships, and data from other mammals suggest an empirically and theoretically consistent pattern of sex allocation in
mammals. New predictions integrate effects, proposed by Trivers and Willard, that are rooted in male mate competition, which
is universal among polygynous mammals, with those of local resource competition (and/or female reproductive competition),
which are not universal and differ in intensity between the socioecologies and local environments of different species.
Received: 30 May 1998 / Accepted after revision: 29 August 1998 相似文献
219.
220.