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991.
Simon A. Lei 《西北部美国博物学家》2011,63(3)
Discovery of distinct mid-elevational bands of blackbrush ( Coleogyne ramosissima Torr.) shrublands on desert mountain slopes in the Mojave Desert caused an investigation of the relationships between environmental factors and Coleogyne distribution. Environmental factors were quantitatively examined to determine which were significant predictors of Coleogyne density at upper-elevational limits (ecotones) in the Spring Mountains of southern Nevada. Path analysis revealed significant, direct causal effects of air temperature, soil moisture, soil depth, and percent litter cover on the distribution of Coleogyne . Specifically, air temperature was a significant positive predictor, while soil moisture, soil depth, and percent litter cover were significant negative predictors of Coleogyne density, with the effects of other environmental variables parceled out. Path analysis also indicated that indirect effects of soil pH, bulk density, compaction, percent pore space, organic matter, soil temperature, salinity, cryptogam, and percent bare soil and rock cover on Coleogyne density were substantially more potent than their direct casual effects. Environmental attributes associated with elevational changes correlate with and may determine the density of Coleogyne shrubs at upper ecotones in southern Nevada. 相似文献
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D. E. Dussourd C. A. Harvis J. Meinwald T. Eisner 《Cellular and molecular life sciences : CMLS》1989,45(9):896-898
Summary Pyrrolizidine alkaloid sequestered by adult maleDanaus gilippus from plants is transferred in large measure to the female at mating, and by the female to the eggs. The eggs, presumably, are protected as a result. The male's courtship pheromone, danaidone, derived from the sequestered alkaloid, may function to advertise the male's alkaloid-donating capacity.Acknowledgments. Paper Nr. 89 of the series Defense Mechanisms of Arthropods. Study supported by NIH (Grants AI-02908 and AI-12020; Predoctoral Traineeship to DED), Hatch funds (191-7416), the Bache Fund (National Academy of Sciences, to DED), and the Theodore Roosevelt Memorial Fund (American Museum of Natural History, to DED). We thank M. Weingarner and J. Miller forD. gilippus collection, J. Boggan for technical assistance, and the staff of the Archbold Biological Station, Lake Placid, Florida, for assistance and hospitality. One of us (DED) is indebted to M. D. Achey, who by demonstrating nuptial cardenolide transfer in the monarch butterfly [Honors Thesis, Amherst College, Amherst, Massachusetts (1979)] raised the possibility that other plant metabolites might be similarly transferred in danaines.Deceased July, 1985. This paper is affectionately dedicated to his memory. 相似文献
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Heterosexual chemoattraction studies on juvenile worms showed that 20- and 21-day-old worms do not attract each other, whereas 23- and 28-day-old worms are attracted to each other and pair with worms of the opposite sex. This onset of chemoattraction in vitro corresponds to the time when worms begin pairing in vivo. The ability of single worms to locate each other and mate is presumably mediated by chemoreceptors. 相似文献
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R. G. Knodell P. P. Toskes H. A. Reber F. P. Brooks 《Cellular and molecular life sciences : CMLS》1970,26(5):515-517
Zusammenfassung Nachweis, dass die Zufuhr von dibutyryl-zyklischem AMP (DcAMP) in vitro die Enzymproduktion erhöht und zwar mit nur geringer Gewichtsveränderung des Kaninchenpankreas. Die Enzymproduktion wird ebenso durch Theophyllin vermehrt und es wird vermutet, das DcAMP der Vermittler der pankreozymen Wirkung im Kaninchen ist. 相似文献