排序方式: 共有26条查询结果,搜索用时 93 毫秒
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Thomas JA Knapp JJ Akino T Gerty S Wakamura S Simcox DJ Wardlaw JC Elmes GW 《Nature》2002,417(6888):505-506
Insect social parasites are extreme specialists that typically use mimicry or stealth to enter ant colonies to exploit the rich, but fiercely protected, resources within their nests. Here we show how a parasitic wasp (parasitoid) contrives to reach its host, itself an endangered species of social parasite that lives inside the brood chambers of ant nests, by releasing semiochemicals to induce in-fighting between worker ants, locking the colony in combat and leaving it underprotected. Four of these chemicals are new to biology and have the potential to control pest species by inducing different agonistic behaviours in ants. 相似文献
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KU Ludwig E Mangold S Herms S Nowak H Reutter A Paul J Becker R Herberz T Alchawa E Nasser AC Böhmer M Mattheisen MA Alblas S Barth N Kluck C Lauster B Braumann RH Reich A Hemprich S Pötzsch B Blaumeiser N Daratsianos T Kreusch JC Murray ML Marazita I Ruczinski AF Scott TH Beaty FJ Kramer TF Wienker RP Steegers-Theunissen M Rubini PA Mossey P Hoffmann C Lange S Cichon P Propping M Knapp MM Nöthen 《Nature genetics》2012,44(9):968-971
We have conducted the first meta-analyses for nonsyndromic cleft lip with or without cleft palate (NSCL/P) using data from the two largest genome-wide association studies published to date. We confirmed associations with all previously identified loci and identified six additional susceptibility regions (1p36, 2p21, 3p11.1, 8q21.3, 13q31.1 and 15q22). Analysis of phenotypic variability identified the first specific genetic risk factor for NSCLP (nonsyndromic cleft lip plus palate) (rs8001641; P(NSCLP) = 6.51 × 10(-11); homozygote relative risk = 2.41, 95% confidence interval (CI) 1.84-3.16). 相似文献
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R. Knapp 《Cellular and molecular life sciences : CMLS》1957,13(10):405-406
Summary The influence of a series of constant temperatures on some annual plant species was studied in otherwise constant conditions. There are big differences in the behaviour of the species. But also within a species the properties studied can have different optimal temperatures. These differences are especially characteristic in some cases for the properties of fertility and of the vegetative growth. One species, for instance, can under certain conditions be very high and can even have numerous big flowers, but the plants can be simultaneously entirely sterile. 相似文献
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Little is known about the basic characteristics of the western harvester ant ( Pogonomyrmex owyheei ) in the absence of anthropogenic disturbances. We examined the role of P. owyheei as an agent of disturbance in an area of semiarid vegetation in central Oregon known as the Horse Ridge Research Natural Area (HRRNA) that has been largely free of livestock grazing and other significant anthropogenic influences for over 23 yr. We determined density and size characteristics of nest sites and estimate total area cleared by P. owyheei activities on HRRNA. From random sampling of twenty-five 0.04-ha plots we found a mean nest density/standard error of 1.6(± 0.16) nests/0.04 ha. Mean area cleared per nest site was 4.8 m 2 , which results in an estimated barren area of 46,080 m 2 on the 240-ha HRRNA. Comparing our findings to others on P. owyheei and P. occidentalis , we found nest density and mean cleared area to be in the middle range of reported observations under a variety of land-use influences. The literature suggests that moderate disturbance may increase nest site density, but little relationship exists between disturbance history and mean size of nest sites. 相似文献
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Convergence across biomes to a common rain-use efficiency 总被引:7,自引:0,他引:7
Huxman TE Smith MD Fay PA Knapp AK Shaw MR Loik ME Smith SD Tissue DT Zak JC Weltzin JF Pockman WT Sala OE Haddad BM Harte J Koch GW Schwinning S Small EE Williams DG 《Nature》2004,429(6992):651-654
Water availability limits plant growth and production in almost all terrestrial ecosystems. However, biomes differ substantially in sensitivity of aboveground net primary production (ANPP) to between-year variation in precipitation. Average rain-use efficiency (RUE; ANPP/precipitation) also varies between biomes, supposedly because of differences in vegetation structure and/or biogeochemical constraints. Here we show that RUE decreases across biomes as mean annual precipitation increases. However, during the driest years at each site, there is convergence to a common maximum RUE (RUE(max)) that is typical of arid ecosystems. RUE(max) was also identified by experimentally altering the degree of limitation by water and other resources. Thus, in years when water is most limiting, deserts, grasslands and forests all exhibit the same rate of biomass production per unit rainfall, despite differences in physiognomy and site-level RUE. Global climate models predict increased between-year variability in precipitation, more frequent extreme drought events, and changes in temperature. Forecasts of future ecosystem behaviour should take into account this convergent feature of terrestrial biomes. 相似文献
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Zusammenfassung Beschreibung einer Präparationstechnik, durch die von einzelnen mit einem kurzen Glasoder Metallzylinder von der Umgebung abgegrenzten Plaques mit zwei Tropfen Suspensionsmedium genügend Bakteriophagen für eine Untersuchung im Negativkontrastverfahren gewonnen werden. 相似文献
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Oceanography: a marine nitrogen cycle fix? 总被引:2,自引:0,他引:2