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排序方式: 共有149条查询结果,搜索用时 15 毫秒
61.
OLIVERA VUCIC‐PESTIC ROSWITHA B. EHNES BJÖRN C. RALL ULRICH BROSE 《Global Change Biology》2011,17(3):1301-1310
Predictions on the consequences of the rapidly increasing atmospheric CO2 levels and associated climate warming for population dynamics, ecological community structure and ecosystem functioning depend on mechanistic energetic models of temperature effects on populations and their interactions. However, such mechanistic approaches combining warming effects on metabolic (energy loss of organisms) and feeding rates (energy gain by organisms) remain a key, yet elusive, goal. Aiming to fill this void, we studied the metabolic rates and functional responses of three differently sized, predatory ground beetles on one mobile and one more resident prey species across a temperature gradient (5, 10, 15, 20, 25 and 30 °C). Synthesizing metabolic and functional‐response theory, we develop novel mechanistic predictions how predator–prey interaction strengths (i.e., functional responses) should respond to warming. Corroborating prior theory, warming caused strong increases in metabolism and decreases in handling time. Consistent with our novel model, we found increases in predator attack rates on a mobile prey, whereas attack rates on a mostly resident prey remained constant across the temperature gradient. Together, these results provide critically important information that environmental warming generally increases the direct short‐term per capita interaction strengths between predators and their prey as described by functional‐response models. Nevertheless, the several fold stronger increase in metabolism with warming caused decreases in energetic efficiencies (ratio of per capita feeding rate to metabolic rate) for all predator–prey interactions. This implies that warming of natural ecosystems may dampen predator–prey oscillations thus stabilizing their dynamics. The severe long‐term implications; however, include predator starvation due to energetic inefficiency despite abundant resources. 相似文献
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D.W. Keats D.H. Steele G.R. South 《Journal of experimental marine biology and ecology》1984,80(1):77-91
Reproductive output of green sea urchins (Strongylocentrotus droebachiensis O.F. Müller) in the field was highest at depths where preferred macro-algae were abundant, and lowest at depths where preferred macro-algae were overgrazed or replaced by non-preferred species (Agarum and Ptilota). Feeding rate and gonad indices of sea urchins in the laboratory were highest on a diet of preferred algae (Fucusdistichus L. subsp. edentatus (Pyl.) Powell, Laminaria longicruris Pyl., Desmarestia spp. and Saccorhizadermatodea (Pyl.) J. Ag.), and lowest on the less preferred Agarum cribrosum (Mert.) Bory, Ptilota serrata Kütz., and crustose corallines. Gamete production/unit area in overgrazed habitats was as great or greater than in kelp beds because of the higher biomass of urchins in overgrazed areas. Gonad weight and reproductive output of urchins from habitats poor in food can be increased by providing preferred foods. 相似文献
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Bronya Keats 《Human genetics》1981,58(3):271-275
Summary Genetic maps of chromosomes 2 and 4 constructed from pair-wise lod score data from family studies and regional assignments for markers are presented. Two loci are mapped on chromosome 2 and multiple crossing-over is suggested as an explanation for the poor fit to the data in females. The best map of chromosome 4 gives the genetic locations of five markers with the Stoltzfus (SF) blood group distal to MNS on the long arm and GC close to the centromere on the short arm. This position for GC is outside its provisional regional assignment and possible reasons for this discrepancy are discussed. The GM-PI linkage group has a score of less than-1.0 with chromosome 4 suggesting that it may be excluded from that chromosome.The regional assignment for markers on chromosome 2–5 are also shown. 相似文献
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Transmission electron microscopic study of Lithophyllum neoatalayense Masaki demonstrated that this alga used two mechanisms by which it sloughed cells from its surface. Epithallial filaments, produced by a layer of underlying initial cells, were two to four cells long. Terminal epithallial cells, those closest to the thallus surface, underwent senescence and shedding as previously described for other coralline algae. In addition, deep-layer sloughing occurred. During this process, which is known for only one other coralline alga, cell death occurred uniformly within a surface layer 40-50 μm thick. No pathogens or evidence of mechanical damage was detected. The zone of dead cells included the epithallial layer, the layer of initial cells, and some cortex cells beneath the initials. Pit plugs connecting living and dead cells at the edge of the necrotic zone were sealed by wall material deposited by the surviving cells, but cells within the necrotic zone showed no evidence of sealed pit plugs. The outermost surviving cells became new initial cells, which then divided to form new epithallial cells. Regeneration of the epithallial layer occurred before the thick layer of dead cells peeled away. The extensive deep shedding of both epithallial and initial cells in L. neoatalayense and the effectiveness of regeneration from cortex cells challenge the assumption that protection of initial cells is an important function of epithallial cells. 相似文献
66.
Friedreich ataxia in Louisiana Acadians: demonstration of a founder effect by analysis of microsatellite-generated extended haplotypes. 总被引:9,自引:7,他引:2 下载免费PDF全文
G Sirugo B Keats R Fujita F Duclos K Purohit M Koenig J L Mandel 《American journal of human genetics》1992,50(3):559-566
Eleven Acadian families with Friedreich ataxia (FA) who were from southwest Louisiana were studied with a series of polymorphic markers spanning 310 kb in the D9S5-D9S15 region previously shown to be tightly linked to the disease locus. In particular, three very informative microsatellites were tested. Evidence for a strong founder effect was found, since a specific extended haplotype spanning 230 kb from 26P (D9S5) to MCT112 (D9S15) was present on 70% of independent FA chromosomes and only once (6%) on the normal ones. There was no evident correlation between haplotypes and clinical expression. The typing of an additional microsatellite (GS4) located 80 kb from MCT112 created a divergence of the main FA-linked haplotype, generating four minor and one major haplotype. A similar split was observed with GS4 in a patient homozygous for a rare 26P-to-MCT112 haplotype. These results suggest that GS4 is flanking marker for the disease locus, although other interpretations are possible. 相似文献
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