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141.
Biesmeijer JC Giurfa M Koedam D Potts SG Joel DM Dafni A 《Die Naturwissenschaften》2005,92(9):444-450
Several recent hypotheses, including sensory drive and sensory exploitation, suggest that receiver biases may drive selection
of biological signals in the context of sexual selection. Here we suggest that a similar mechanism may have led to convergence
of patterns in flowers, stingless bee nest entrances, and pitchers of insectivorous plants. A survey of these non-related
visual stimuli shows that they share features such as stripes, dark centre, and peripheral dots. Next, we experimentally show
that in stingless bees the close-up approach to a flower is guided by dark centre preference. Moreover, in the approach towards
their nest entrance, they have a spontaneous preference for entrance patterns containing a dark centre and disrupted ornamentation.
Together with existing empirical evidence on the honeybee's and other insects’ orientation to flowers, this suggests that
the signal receivers of the natural patterns we examined, mainly Hymenoptera, have spontaneous preferences for radiating stripes,
dark centres, and peripheral dots. These receiver biases may have evolved in other behavioural contexts in the ancestors of
Hymenoptera, but our findings suggest that they have triggered the convergent evolution of visual stimuli in floral guides,
stingless bee nest entrances, and insectivorous pitchers. 相似文献
142.
Alan Lock Dirk Wallschläger Nelson Belzile Graeme Spiers Celine Gueguen 《环境科学学报(英文版)》2018,30(4):338-347
Sediments from an arsenic(As) contaminated groundwater vent site were used to investigate As( Ⅲ) binding, transformation and redistribution in native and iron oxide amended lake sediments using aging spiked batch reactions and a sequential extraction procedure that maintains As(V) and As( Ⅲ) speciation. In the native sediments, fractionation analysis revealed that 10% of the spiked As( Ⅲ) remained intact after a 32-day aging experiment and was predominantly adsorbed to the strongly sorbed(NH_4H_2PO_4 extractable) and amorphous Fe oxide bound(H_3PO_4 extractable) fractions. Kinetic modelling of the experimental results allowed identifying the dominant reaction path for depletion of dissolved As( Ⅲ) to As( Ⅲ)absorbed on to the solid phase, followed by oxidation in the solid phase. Arsenite was initially adsorbed primarily to the easily exchangeable fraction((NH_4)_2SO_4 extractable), then rapidly transformed into As(V) and redistributed to the strongly sorbed and amorphous Fe oxide bound fractions. Oxidation of As( Ⅲ) in recalcitrant fractions was less efficient. The iron oxide amendments illustrated the controls that iron oxides can have on As( Ⅲ) binding and transformation rates. In goethite amended samples As( Ⅲ) oxidation was faster and primarily occurred in the strongly sorbed and amorphous Fe oxide bound fractions. In these samples,19.3 μg Mn was redistributed(compared to the native sediment) from the easily exchangeable and crystalline Fe oxide bound fractions to the strongly sorbed and amorphous Fe oxide bound fractions, indicating that goethite may act as a catalyst for Mn(Ⅱ) oxidation, thereby producing sorbed Mn( Ⅲ/Ⅳ ), which then appears to be involved in rapidly oxidizing As( Ⅲ). 相似文献
143.
Plan und Muster im zellulären Stoffwechsel 总被引:1,自引:0,他引:1
Dirk Pette 《Die Naturwissenschaften》1965,52(22):597-616
144.
Intrageneric differences in the four stereoisomers of stenusine in the rove beetle genus, Stenus (Coleoptera, Staphylinidae) 总被引:1,自引:1,他引:0
Lusebrink I Burkhardt D Gedig T Dettner K Mosandl A Seifert K 《Die Naturwissenschaften》2007,94(2):143-147
Most species of the rove beetle genus Stenus employ the spreading alkaloid stenusine as an escape mechanism on water surfaces. In the case of danger, they emit stenusine
from their pygidial glands, and it propels them over the water very quickly. Stenusine is a chiral molecule with four stereoisomers:
(2′R,3R)-, (2′S,3R)-, (2′S,3S)-, and (2′R,3S)-stenusine. The percentile ratio of these four isomers is only known for the most common species of the genus: Stenus comma. With the intention of determining the stereoisomer ratios of five additional species from the two subgenera, Stenus and Hypostenus, we used GC/mass spectrometry measurements with a chiral phase. The results showed that the ratio differs among the genus. These findings can be a basis for chemotaxonomy. It is also possible
that the biological function of stenusine, e.g., as antibiotic or fungicide, varies with changing stereoisomer composition.
相似文献
Inka LusebrinkEmail: |
145.
146.
Integrating Stressor and Response Monitoring into a Resource-Based Water-Quality Assessment Framework 总被引:1,自引:0,他引:1
Dirk J. Roux Phillip L. Kempster Cornelius J. Kleynhans Henk R. Van Vliet Hein H. Du Preez 《Environmental management》1999,23(1):15-30
Following a global trend, the new policy goals emphasize the need to protect rather than to use the ability of ecosystems
to recover from disturbances. This necessitates the adoption of response measurements to quantify ecological condition and
monitor ecological change. Response monitoring focuses on properties that are essential to the sustainability of the ecosystem.
These monitoring tools can be used to establish natural ranges of ecological change within ecosystems, as well as to quantify
conceptually acceptable and unacceptable ranges of change. Through a framework of biological criteria and biological impairment
standards, the results of response monitoring can become an integral part of future water resource management strategies in
South Africa. 相似文献
147.
Uta Berger Marion Glaser Boris Koch Gesche Krause Rubén Lara Ulrich Saint-Paul Dirk Schories Matthias Wolff 《Journal of Coastal Conservation》1999,5(2):125-134
The main objective of the MADAM project (Mangrove Dynamics and Management) is to generate the scientific basis enabling the
sustainable stewardship of the resources of the Caeté mangrove estuary in Northeast Brazil in the sense of integrated coastal
(zone) management. To achieve this, it is necessary to acquire in-depth knowledge of natural processes as well as of the relevant
institutional, cultural, economic, social and political dynamics. Causal linkages within the ecosystem, as well as between
ecosystem, economy and society, are analysed and explained via dynamic and trophic modelling. Scenario construction is intended
to forecast the effects of acute or chronic interference on utilized resources, and to answer wider, management-related questions
(e.g. restoration of destroyed areas, utilization potential for aquaculture). This paper describes the project strategy as
developed and modified in the context of research results from the initial 2-yr project phase. It is argued that a continuous
discussion process is essential to assess the validity of the strategies formulated at the beginning of a medium-time project,
particularly if the project is of interdisciplinary nature. 相似文献
148.
Aristides Moustakas Konstantinos Sakkos Kerstin Wiegand David Ward Katrin M. Meyer Dirk Eisinger 《Ecological modelling》2009
Savannas are ecosystems characterized by the coexistence of woody species (trees and bushes) and grasses. Given that savanna characteristics are mainly formed from competition, herbivory, fire, woodcutting, and patchy soil and precipitation characteristics, we propose a spatially explicit model to examine the effects of the above-mentioned parameters on savanna vegetation dynamics in space and time. Furthermore, we investigate the effects of the above-mentioned parameters on tree–bush–grass ratios, as well as the degrees of aggregation of tree–bush–grass biomass. We parameterized our model for an arid savanna with shallow soil depth as well as a mesic one with generally deeper and more variable soil depths. Our model was able to reproduce savanna vegetation characteristics for periods of time over 2000 years with daily updated time steps. According to our results, tree biomass was higher than bush biomass in the arid savanna but bush biomass exceeded tree and grass biomass in the simulated mesic savanna. Woody biomass increased in our simulations when the soil's porosity values were increased (mesic savanna), in combination with higher precipitation. Savanna vegetation varied from open savanna to woodland and back to open savanna again. Vegetation cycles varied over ∼300-year cycles in the arid and ∼220-year cycles in the mesic-simulated savanna. Autocorrelation values indicated that there are both temporal and spatial vegetation cycles. Our model indicated cycling savanna vegetation at the landscape scale, cycles in cells, and patchiness, i.e. patch dynamics. 相似文献
149.
150.
Community-based approaches to fisheries management has emerged as a mainstream strategy to govern dispersed, diverse and dynamic small scale fisheries. However, amplifying local community led sustainability outcomes remains an enduring challenge. We seek to fill a theoretical gap in the conceptualization of ‘scaling up community-based fisheries management’. We draw on literature of agriculture innovations to provide a framework that takes into account process-driven and structural change occurring across multiple levels of governance, as well as different phases of scaling. We hypothesize that successful scaling requires engagement with all aspects of a governing regime, coalescing a range of actors, and therefore, is an enterprise that is larger than its parts. To demonstrate where the framework offers value, we illustrate the development of community-based fisheries management in Vanuatu according to the framework’s main scaling dimensions. 相似文献