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821.
The Science of Nature - 相似文献
822.
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G. Ruhenstroth-Bauer G. F. Fuhrmann E. Granzer W. Kübler F. Rueff 《Die Naturwissenschaften》1962,49(16):363-368
829.
The ant genus Cardiocondyla is characterized by a bizarre male polymorphism with wingless fighter males and winged disperser males. Winged males have
been lost convergently in several clades, and in at least one of them, wingless males have evolved mutual tolerance. To better
understand the evolutionary pathways of reproductive tactics, we investigated Cardiocondyla venustula, a species, which in a phylogenetic analysis clusters with species with fighting and species with mutually tolerant, wingless
males. Wingless males of C. venustula use their strong mandibles to kill freshly eclosed rival males and also engage in short fights with other adult males, but
in addition show a novel behavior hitherto not reported from social insect males: they spread out in the natal nest and defend
“territories” against other males. Ant males therefore show a much larger variety of reproductive tactics than previously
assumed. 相似文献
830.
An important aspect of present global energy scenarios is the assumption that the amount of biomass that can be grown on the
available area is so limited that a scenario based on biomass as the major source of energy should be unrealistic. We have
been investigating the question whether a Biomass Scenario may be realistic. We found that the global energy demand projected
by the International Energy Agency in the Reference Scenario for the year 2030 could be provided sustainably and economically
primarily from lignocellulosic biomass grown on areas which have been degraded by human activities in historical times. Moreover,
other renewable energies will contribute to the energy mix. There would be no competition with increasing food demand for
existing arable land. Afforestation of degraded areas and investment for energy and fuel usage of the biomass are not more
expensive than investment in energy infrastructure necessary up to 2030 assumed in the fossil energy based Reference Scenario,
probably much cheaper considering the additional advantages such as stopping the increase of and even slowly reducing the
CO2 content of the atmosphere, soil, and water conservation and desertification control. Most importantly, investment for a Biomass
Scenario would be actually sustainable, in contrast to investment in energy-supply infrastructure of the Reference Scenario.
Methods of afforestation of degraded areas, cultivation, and energetic usage of lignocellulosic biomass are available but
have to be further improved. Afforestation can be started immediately, has an impact in some few years, and may be realized
in some decades.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Jürgen O. MetzgerEmail: |