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311.
Experimental evolution in fluctuating environments: tolerance measurements at constant temperatures incorrectly predict the ability to tolerate fluctuating temperatures
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The ability to predict the consequences of fluctuating environments on species distribution and extinction often relies on determining the tolerances of species or genotypes in different constant environments (i.e. determining tolerance curves). However, very little is known about the suitability of measurements made in constant environments to predict the level of adaptation to rapidly fluctuating environments. To explore this question, we used bacterial clones adapted to constant or fluctuating temperatures and found that measurements across a range of constant temperatures did not indicate any adaptation to fluctuating temperatures. However, adaptation to fluctuating temperatures was only apparent if growth was measured during thermal fluctuation. Thus, tolerance curves based on measurements in constant environments can be misleading in predicting the ability to tolerate fast environmental fluctuations. Such complications could lead to false estimates of the genetic merits of genotypes and extinction risks of species due to climate change‐induced thermal fluctuations. 相似文献
312.
Although multiple condition dependence in dispersal is common, the proximate mechanisms that integrate information from multiple sources remain largely unknown. In the common lizard (Lacerta vivipara), earlier studies have shown that maternal plasma corticosterone level interacts with maternal phenotype to affect offspring phenotype and dispersal strategy, and may reflect the mother's external and/or internal environment. However, the mechanism by which these two types of environmental information are integrated has not been identified. We explored the possibility that the timing and duration of the corticosterone signal are the key factors by which the message is modulated. We found that the timing of corticosterone exposure affects the juvenile phenotype: an exposure to corticosterone early in development has negative effects on juvenile size, weight, and body condition, that can nevertheless be restored in the case of a prolonged exposure. The duration of corticosterone exposure affects the dispersal strategy, although the precise effect depends on the sex ratio of the clutch. That is, in female-biased clutches, a prolonged exposure during gestation promotes philopatry of juveniles, while a short exposure enhances their dispersal, a result that is consistent with kin competition theory. Therefore, our results demonstrate that while corticosterone titer may signal a mother's external and/or internal environment to her developing young, differences in the timing and duration of this endocrine signal produce offspring with specialized phenotypes that exhibit different dispersal strategies. 相似文献
313.
Recently a new habitat for microbial life has been discovered at the base of polythermal glaciers. In ice from these subglacial
environments so far only non-photosynthetic bacterial communities were discovered, but no eukaryotic microorganisms. We found
high numbers of yeast cells, amounting to a maximum of 4,000 CFU ml−1 of melt ice, in four different high Arctic glaciers. Twenty-two distinct species were isolated, including two new yeast species.
Basidiomycetes predominated, among which Cryptococcus liquefaciens was the dominant species (ca. 90% of total). Other frequently occurring species were Cryptococcus albidus, Cryptococcus magnus, Cryptococcus saitoi and Rhodotorula mucilaginosa. The dominant yeast species were psychrotolerant, halotolerant, freeze-thaw resistant, unable to form mycelium, relatively
small-sized and able to utilize a wide range of carbon and nitrogen sources. This is the first report on the presence of yeast
populations in subglacial ice. 相似文献
314.
Pafilis P Foufopoulos J Poulakakis N Lymberakis P Valakos E 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(1):49-60
Temperature sensitivity of digestive processes has important ramifications for digestive performance in ectothermic vertebrates.
We conducted a comparative analysis of temperature effects on digestive processes [gut passage times (GPTs) and apparent digestive
efficiencies (ADEs)] in five lacertid lizards occurring in insular (Podarcis erhardii, P. gaigeae), and mainland (P. muralis, P. peloponnesiaca, Lacerta graeca) Mediterranean environments. GPTs were negatively correlated to temperature with mainland taxa having 10–20% longer GPTs
than island taxa. In contrast to previous studies that estimate ADEs using bomb calorimetry, we compare ADEs by analyzing
discrete efficiencies for lipids, sugars and proteins at three temperature regimes (20, 25, and 30°C); each of these categories
produces different results. ADEs for lipids and sugars showed a monotonic increase with temperature whereas ADEs for proteins
decreased with temperature. Island taxa had consistently higher ADEs than their mainland counterparts for lipids and for proteins
but not for sugars. They are characterized by superior energy acquisition abilities despite significantly shorter GPTs. Their
increased digestive performance relative to the mainland species appears to allow them to maximize energy acquisition in unproductive
island environments where food availability is spatially and seasonally clustered. 相似文献
315.
Many soil invertebrates have physiological characteristics in common with freshwater animals and represent an evolutionary transition from aquatic to terrestrial life forms. Their high cuticular permeability and ability to tolerate large modifications of internal osmolality are of particular importance for their cold tolerance. A number of cold region species that spend some or most of their life-time in soil are in more or less intimate contact with soil ice during overwintering. Unless such species have effective barriers against cuticular water-transport, they have only two options for survival: tolerate internal freezing or dehydrate. The risk of internal ice formation may be substantial due to inoculative freezing and many species rely on freeze-tolerance for overwintering. If freezing does not occur, the desiccating power of external ice will cause the animal to dehydrate until vapor pressure equilibrium between body fluids and external ice has been reached. This cold tolerance mechanism is termed cryoprotective dehydration (CPD) and requires that the animal must be able to tolerate substantial dehydration. Even though CPD is essentially a freeze-avoidance strategy the associated physiological traits are more or less the same as those found in freeze tolerant species. The most well-known are accumulation of compatible osmolytes and molecular chaperones reducing or protecting against the stress caused by cellular dehydration. Environmental moisture levels of the habitat are important for which type of cold tolerance is employed, not only in an evolutionary context, but also within a single population. Some species use CPD under relatively dry conditions, but freeze tolerance when soil moisture is high. 相似文献
316.
The Role of Soil Nutrients in Boundaries between Mangrove and Herbaceous Assemblages in a Tropical Estuary 总被引:1,自引:0,他引:1
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Jose Pedro N. Ribeiro Fernanda C. S. Tiberio Alexandre A. de Oliveira 《Biotropica》2015,47(5):517-520
We aimed to determine the role of soil nutrients in the herbaceous‐tree boundary in a tropical mangrove forest. We assembled plots in this boundary such that each was initially covered by ~50% of each life form. We added NPK to three of the plots monthly and monitored them, along with the control plots, for 18 mo. In plots with added NPK, mangrove branches grew over and shaded the herbaceous plants, resulting in the presence of mostly bare soil. The mangrove trees eventually covered ~80% of the experimental plots, but the proportion of cover in the control plots remained unaltered. We conclude that soil nutrient level modulates the mangrove‐herbaceous plant interaction in steps, and from a given level there is a shift in the dominant life form. This mechanism leads to a sharp transition over a smooth nutritional gradient. 相似文献
317.
318.
Bartesaghi S Ferrer-Sueta G Peluffo G Valez V Zhang H Kalyanaraman B Radi R 《Amino acids》2007,32(4):501-515
Summary. In this review we address current concepts on the biological occurrence, levels and consequences of protein tyrosine nitration
in biological systems. We focused on mechanistic aspects, emphasizing on the free radical mechanisms of protein 3-nitrotyrosine
formation and critically analyzed the restrictions for obtaining large tyrosine nitration yields in vivo, mainly due to the
presence of strong reducing systems (e.g. glutathione) that can potently inhibit at different levels the nitration process.
Evidence is provided to show that the existence of metal-catalyzed processes, the assistance of nitric oxide-dependent nitration
steps and the facilitation by hydrophobic environments, provide individually and/or in combination, feasible scenarios for
nitration in complex biological milieux. Recent studies using hydrophobic tyrosine analogs and tyrosine-containing peptides
have revealed that factors controlling nitration in hydrophobic environments such as biomembranes and lipoproteins can differ
to those in aqueous compartments. In particular, exclusion of key soluble reductants from the lipid phase will more easily
allow nitration and lipid-derived radicals are suggested as important mediators of the one-electron oxidation of tyrosine
to tyrosyl radical in proteins associated to hydrophobic environments. Development and testing of hydrophilic and hydrophobic
probes that can compete with endogenous constituents for the nitrating intermediates provide tools to unravel nitration mechanisms
in vitro and in vivo; additionally, they could also serve to play cellular and tissue protective functions against the toxic
effects of protein tyrosine nitration. 相似文献
319.
Sylvie E. Blondelle Behrouz Forood Richard A. Houghten Enrique Prez-Pay 《Biopolymers》1997,42(4):489-498
The conformational propensity of the 20 naturally occurring amino acids was determined in aqueous 3-[N-morpholino]propane-sulfonic acid (MOPS) buffer, protein interior-like [nonmicellar sodium dodecylsulfate (SDS)] and membrane-like environments (micellar SDS and lysophosphatidylglycerol/lysophosphatidylcholine micelles) using a single “guest” position in a polyalanine-based model host peptide (Ac-KYA13K-NH2). This model system allows the intrinsic α-helical or β-sheet propensity of the amino acids to be determined without intra- and interchain side chain interactions. The overall environment dependence observed for the conformational propensity for the amino acids studied confirms the importance of determining propensity in lipidic environments to better elucidate the biological functions of proteins. The hydrophobic interactions between peptide side chains and lipids appeared to be the primary forces driving the conformational induction in lipidic environments of the model peptides studied. Finally, when comparing the results of these studies with those reported in the literature, the local environment was found to highly influence 65% of the 20 naturally occurring amino acids. © 1997 John Wiley & Sons, Inc. Biopoly 42: 489–498, 1997 相似文献
320.
植物性状反映了植物对生长环境的响应和适应,将环境、植物个体和生态系统结构、过程与功能联系起来(所谓的“植物功能性状”)。该文介绍了植物功能性状的分类体系,综述了国内外植物功能性状与气候(包括气温、降水、光照)、地理空间变异(包括地形地貌、生态梯度、海拔)、营养、干扰(包括火灾、放牧、生物入侵、土地利用)等环境因素,以及与生态系统功能之间关系的研究进展,探讨了全球变化(气候变化和CO2浓度升高)对个体和群落植物功能性状的影响。植物功能性状的研究已经取得很多成果,并应用于全球变化、古植被恢复和古气候定量重建、环境监测与评价、生态保护和恢复等研究中,但大尺度、多生境因子下的植物功能性状研究仍有待于加强,同时需要改进性状的测量手段;我国的植物功能性状研究还需要更加明朗化和系统化。 相似文献