甘肃荒漠蜥蜴群落结构的研究

甘肃民勤地区荒漠晰蝎群落多样性与植物种数、植物多样性呈不显著负相关,与植物高度呈不显著正相关(P>0.1),与土壤含水量和pH值几乎无关。而与植物密度,植被覆盖度,食物种数、密度和多样性显著负相关(P<0.05)。植物密度、植被覆盖度和食物是荒漠晰蝎群落结构的主导因子。主导因子通过对群落中优势种种群密度的调节控制群落结构。     

温度适应的分子生物学机制

对温度的适应是机体对抗环境的一种主动行为,表现在细胞内转录和表达模式的改变,出现新基因的开放和新蛋白因子的合成。已在多种动植物中找到温度诱导产生的特异性蛋白。深入的研究表明,它们往往与糖代谢、渗透压调节及蛋白质代谢有关。这些分子大多具有相同的特征,它们同属于一种称作ｄｅｈｙｄｒｉｎ的蛋白家族,对热稳定,表现亲水特征等。它们以多种机制保护细胞,抵抗恶劣环境温度的损害。     

温度对蜥蜴红红蛋白及血浆总蛋白浓度的影响

研究在不同实验温度下驯化的荒漠沙蜥和密点麻蜥的血红蛋白浓度、血浆总蛋白浓度以及血浆清蛋白与球蛋白比例的变化,结果表明：在５℃下驯化的两种蜥蜴的血红蛋白浓度都很低;而在１５－３０℃之间驯化的蜥蜴血红蛋白浓度较高且比较稳定;３５℃时蜥蜴的血红蛋白浓度则下降。在同温度下密眯麻蜥的血红蛋白浓度高于荒漠沙蜥。同种蜥蜴中,雄性的血红蛋白浓度高于雌性。两种蜥蜴的血浆总蛋白浓度均随驯化温度的升高而增加;荒漠沙蜥在     

生态环境对甘肃河西荒漠蜥蜴多样性的调控

本文对甘肃河西地区荒漠蜥蜴及其环境因子的生态数据通过数学建模,利用SPSS／PC^ 软件在计算机上运行求解,将各种生态因子按其对蜥蜴多样性的重要性程度排序,并通过聚类分析对12个调查地区分类。确定了决定甘肃河西多数地区荒漠蜥蜴多样性的主导因子依次是植被类型的多样性、海拔、降水量、年平均气温、7月平均最高气温。通常植被类型复杂多样,海拔低,降水量少,年均温和月平均最高气温的地区蜥蜴种类多;植被类型少,海拔高、降不量少、年均和7月平均最高气温低的地区蜥蜴种类少。由于特殊原因,少数地区各主导因子的作用有一定变化。从而揭示了环境因子调控蜥蜴多样性的综合机制。     

荒漠沙蜥繁殖生态研究

荒漠沙蜥（Ｐｈｒｙｎｏｃｅｐｈａｌｕｓｐｒｚｅｗａｌｓｋｉｉ）１年繁殖１次,有明显的季节性周期。４月初出蛰时雄性精巢已相当发育,５月其重量和体积最大,６月变小,进入精子发生的晚期,７月降到最小,８月开始回升,１０月中旬入蛰时已接近春季出蛰时水平。１年内仅７月精巢中无精子。雌性出蛰后卵细胞开始发育,４月下旬进入成熟期,６月达高峰,７月下降,８月进入休止期。每雌年产卵１～３枚或１～４枚,平均１．８３（ｎ＝４８,１９８７）和２．１７（ｎ＝４８,１９９３）。特定体长组的生殖率是影响种群年平均生殖率的主要因素。生殖周期与光周期相符,光周期是影响荒漠沙蜥生殖周期的主要气候因子。     

三种荒漠蜥蜴空间和营养生态位研究

同一荒漠蜥蜴群落中,荒漠沙蜥（Ｐｈｒｙｎｏｃｅｐｈａｌｕｓｐｒｚｅｗａｌｓｋｉｉ）和虫纹麻蜥（Ｅｒｅｍｉａｓｖｅｒｍｉｃｕｌａｔａ）,密点麻蜥（Ｅｒｅｍｉａｓｍｕｌｔｉｏｃｅｌｌａｔａ）占不有同的空间生态位,其间几乎不存在竞争。两个近缘种虽然占有相同空间生态位,但个体大的密点麻蜥食物种类特化,个体小的虫纹麻蜥偏重于利用较小的食物资源。占有相同空间生态位的近缘种,营养生态位向不同方向特化,利用不同的食物资源,从而在竞争中共存,保持群落结构的稳定性。     

植物对荒漠生境的趋同适应

植物体的表型特征是其基因与生态因子二者共同作用的结果,生活在荒漠生境中的植物由于遭受相同的自然选择压力,在外部形态、内部结构、生活史特征、生理特性、次生代谢产物的合成以及大分子物质的诱导产生等诸多表型方面均表现出高度趋同的现象。随着研究手段的改善,对植物趋同适应的研究已逐渐深入到了分子水平。研究荒漠生境中植物的趋同适应对于人们深刻地认识和理解植物与环境间的相互关系及其分子基础,以及利用功能基因改良重要作物的抗逆性等将会产生深远的影响;对极端干旱环境下特殊次生代谢产物的定向发现及重要先导化合物的筛选等有着重大的指导意义;同时对我国的西部开发及干旱区的生态恢复亦有重要的参考价值。     

内蒙古荒漠草原牧户对气候变化的感知和适应

荒漠草原是气候变化影响的脆弱和敏感地区.荒漠草原的牧户主要依赖天然草原维持生计,正面临着严峻的气候变化挑战.本文采用问卷调查的实证分析方法,在获取内蒙古苏尼特右旗荒漠草原牧户对气候变化和极端气候事件感知和适应的第一手资料基础上,分析了荒漠草原牧户对气候变化趋势和极端气候事件感知和适应的现状与行为特征.结果表明:在降水稀少、气象灾害频繁发生的荒漠草原,干旱是影响范围最广、影响程度最深、发生频率最高的极端气候事件;牧户不仅对干旱的敏感度远高于其他极端气候事件,而且对大风、沙尘暴和大雪等极端气候事件的深刻感知伴随着对干旱的感知而产生;相对于长期气候变化的感知,牧户对短期气候变化趋势的感知更深刻、准确,并主要依据近10年气候变化的感知结果来判断较长期气候变化的总体趋势;牧户认为,气候变化在很大程度上影响了牲畜健康和草场产量,但牧户应对气候变化的行为相对单一,且多为自发性被动适应,缺乏行之有效的主动适应.     

环境因子对荒漠沙蜥种群密度影响的研究

本文研究人类改造荒漠的活动,植被,潜在的可利用的食物资源,竞争种的密度,土壤理化性质等坏境因子对荒漠沙蜥种群密度的影响。结果说明：人类的活动对沙蜥种群密度没有显著影响;决定沙蜥种群密度的主导因子是潜在的可利用的食物资源,植被,土壤含水量,竞争种的密度。这些因子的任何改变都能改变沙蜥的种群密度,均具有调节种群的作用。     

温度对荒漠沙蜥心脏活动影响的实验研究

本文通过描记不同温度下荒漠沙晰(Phrynocephalus przewalskii)的心电图(ECG),对其心脏活动进行了分析研究。结果表明:随实验温度的升高,其心电图中各间期的持续时间相应地缩短;温度和各间期值呈显著负相关(P<0.01)。在一个心动周期中,温度的变化,对房室传导时间和静息期的影响最大,而对心室去极化与复极化的时程影响较小。随实验温度的升高,心率随之加快,其因素在于心动周期中静息期和房室传导时间相对值的缩短。     

Phenotypical temperature adaptation of protein turnover in desert annuals

Protein synthesis and protein degradation rates were measured in three desert annual species at four different experimental temperatures. The taxa chosen for this study were the C₃ winter annuals, Bowlesia incana Ruiz & Pavon and Plantago insularis Eastw., and a C₄ summer annual, Atriplex elegans (Moq.) D. Dietr. Peak rates of protein synthesis correlated well with the preferred habitat temperatures of B. incana and A. elegans; optima occurred at 25 and 35°C, respectively. Plants of P. insularis showed an optimum protein synthesis rate at 35°C; however, this optimum rate was considerably lower than for the other two species. Higher activation energies for protein synthesis tended to parallel adaptation to higher temperature habitats. Responses of protein degradation to temperature in A. elegans and B. incana were consistent with their natural thermal regimes, when evaluated for the transition from 25 to 35°C. Again, protein degradation in P. insularis shows an intermediate response to temperature during the 25 to 35°C transition.     

不同沙地共有种沙生植物对环境的生理适应机理

选择3个温带沙地(松嫩沙地、呼伦贝尔沙地、科尔沁沙地)4个共有种沙生植物(黄柳(Salix gordejevii)、差巴嘎蒿(Artimisia halodendron)、扁蓿豆(Melissitus ruthenica),猪毛菜(Salsola collina),通过自然状况下其叶片抗氧化酶活力和渗透调节物及丙二醛(MDA)含量日变化分析,探讨抗氧化酶活力和渗透调节物在沙生植物适应沙漠环境强光辐射和温度日变化中的作用,以及不同科属沙生植物抗逆生理调控机理的差异。结果表明:(1)不同沙地的4个共有沙生植物种可通过自身快速生理代谢调解,积累渗透调节物、提高抗氧化酶活力应对沙漠环境强光辐射和温度日变化,但生理调控幅度较小。(2)3个沙地不同科属的4个共有种在渗透调节物含量和抗氧化酶活力及种类上存在差异。扁蓿豆叶片日均MDA含量、POD(peroxidase)活力、CAT(catalase)活力、脯氨酸含量均最高,分别较其它3个种平均高2、10、2和2.5倍。黄柳叶片日均MDA含量较高,SOD(superoxide dismutase)活力和可溶性糖含量最高,分别较其它3个种高1.2和3倍。差巴嘎蒿和猪毛菜叶内MDA含量较低,POD、CAT、SOD活力和脯氨酸、可溶性糖含量均最低。沙生植物细胞中膜脂过氧化程度和抗氧化酶活力及渗透调节物含量呈正相关。自然状况下3个沙地的扁蓿豆和黄柳通过生理代谢调节维持细胞水分和氧自由基代谢平衡适应沙漠环境,差巴嘎蒿和猪毛菜依靠特殊的叶片形态结构变异减少光辐射吸收、降低水分蒸腾、维持叶片水分平衡、降低细胞膜脂过氧化。因此不同科属沙生植物维持叶片水分和氧自由基代谢平衡可能是其适应沙漠环境生存的重要生理调控机理。由于不同科属沙生植物种对沙漠环境适应的生理调节机理的不同,在未来农作物、林木抗逆育种中,根据具体科属植物选择合适的沙生植物作为亲本对提高抗逆育种效率是十分重要的。     

Managed relocation as an adaptation strategy for mitigating climate change threats to the persistence of an endangered lizard

The distributional ranges of many species are contracting with habitat conversion and climate change. For vertebrates, informed strategies for translocations are an essential option for decisions about their conservation management. The pygmy bluetongue lizard, Tiliqua adelaidensis, is an endangered reptile with a highly restricted distribution, known from only a small number of natural grassland fragments in South Australia. Land‐use changes over the last century have converted perennial native grasslands into croplands, pastures and urban areas, causing substantial contraction of the species' range due to loss of essential habitat. Indeed, the species was thought to be extinct until its rediscovery in 1992. We develop coupled‐models that link habitat suitability with stochastic demographic processes to estimate extinction risk and to explore the efficacy of potential climate adaptation options. These coupled‐models offer improvements over simple bioclimatic envelope models for estimating the impacts of climate change on persistence probability. Applying this coupled‐model approach to T. adelaidensis, we show that: (i) climate‐driven changes will adversely impact the expected minimum abundance of populations and could cause extinction without management intervention, (ii) adding artificial burrows might enhance local population density, however, without targeted translocations this measure has a limited effect on extinction risk, (iii) managed relocations are critical for safeguarding lizard population persistence, as a sole or joint action and (iv) where to source and where to relocate animals in a program of translocations depends on the velocity, extent and nonlinearities in rates of climate‐induced habitat change. These results underscore the need to consider managed relocations as part of any multifaceted plan to compensate the effects of habitat loss or shifting environmental conditions on species with low dispersal capacity. More broadly, we provide the first step towards a more comprehensive framework for integrating extinction risk, managed relocations and climate change information into range‐wide conservation management.     

Influence of a broad temperature range on the oxygen consumption rates of three desert lizard species

Oxygen consumption rates of three desert lizard species: (Acanthodactylus boskianus, Lacertidae; Scincus mitranus, Scincidae; Diplometopon zarudnyi, Amphisbaenidae) were determined in relation to ambient temperatures ranging from 10 to 35 degrees C using a double-chamber, volumetric closed system. The interspecific differences in the oxygen consumption rates were found to have a close relationship between the characteristics of the M-T curves, the thermoregulatory behaviour and the ecology of the respective species. The M-T curves of the studied lizards were specifically modified and adjusted to their climatic region.     

Body temperature regulation in a desert lizard, Sauromalus obesus, under undisturbed field conditions

1. Mean selected body temperatures (MSBTs), measured by radiotelemetry, are presented for 15 chuckwallas on 26 animal days. 2. MSBT, during the period of activity, ranged from 37.3 to 39.8 degrees C (means = 38.8 +/- 0.2 SE degrees C) while MSBTs, from the time lizards attained their first high set point to the time that solar radiation ceased, ranged from 36.1 to 39.6 degrees C (means = 38.3 +/- 0.2 SE degrees C). 3. On cloudy, cool days, animals could not maintain high Tbs because of the absence of solar radiation. 4. On sunny March and April days, animals were active for 5-6 hr but Tb then fell rapidly to low levels. 5. From late April to mid May, animals were active for 7-8 hr and Tbs did not fall as drastically because of higher Tas after sunset. 6. August was the time of year (for this study) when chuckwallas had the highest effective 24 hr Tb but it was also the time when they had the shortest activity interval.     

An analysis of photosynthetic response and adaptation to temperature in higher plants: temperature acclimation in the desert evergreen Nerium oleander L*

Abstract. Factors underlying the process of photosynthetic acclimation to temperature were investigated for the shrub Nerium oleander L. Ramets of a single clone were grown under day/night temperature regimes of 20°C/15°C or 45°C/32°C. Plants grown at the lower temperature regime possessed rates of photosynthesis twice that of the high-temperature grown plants when CO₂ fixation was measured at 20°C. In contrast, the plants grown at the high-temperature regime had twice the rate of CO₂ fixation of the 20°C/l 5°C-grown plants at a measurement temperature of 45° C. It was determined that the ability to acclimate to changes in temperature regime was present in fully mature leaves. A reciprocal transfer of plants between the two growth regimes resulted in the appearance of the CO₂ fixation characteristics appropriate to the new growth temperature after 12–14d. The response of CO₂ fixation to light, temperature, and CO₂ partial pressure and the temperature responses of soluble and membrane-bound photosynthetic enzyme systems were analysed to determine which components might be responsible for the superior photosynthetic performance of the 20°C/I5°C-grown plants at 20°C, and the enhanced high-temperature stability of the 45°C/32°C plants. The measured photosynthetic capacity of the 20°C/15°C plants could not be attributed to gross morphological, stomatal, or other physical changes, or to a general increase in the concentration of components of the photosynthetic process. Only a single enzyme, Fru-P₂ phosphatase, was affected to an extent similar to that of photosynthesis. The enhanced thermal stability of the 45°C/32°C plants may be attributed primarily to an enhanced stability of the chloroplast membrane-bound enzymatic activities and the stability of the photosynthetic carbon metabolism enzymes which require lighl for activation.     

The role of phytosterols in plant adaptation to temperature

Membranes of composition approaching those found in “rafts” of plants, fungi and mammals were investigated by means of solidstate ²H-NMR, using deuterated dipalmitoyl-phosphatidylcholine (²H-DPPC) as a reporter. The dynamics of such membranes was determined through measuring of membrane ordering or disordering properties. The presence of the liquid-ordered, lo, phase, as an indicator of rigid sterol-sphingolipid domains, was detected in all cases. Of great interest, the dynamics of mixtures mimicking rafts in plants showed the lesser temperature sensitivity to thermal shocks. The presence of an additional ethyl group branched on the alkyl chain of major plant sterols (sitosterol and stigmasterol) is proposed as reinforcing the membrane cohesion. The fine tuning of the sterol structure thus appears to be the evolution response for plant adaptation to large temperature variations.Key words: sitosterol, stigmasterol and glucosylcerebrosides, regulation of membrane dynamics, membrane rafts, deuterium NMRIt is widely recognized that lipids play multiple roles that either individually or collectively influence cell processes. Glycerolipids and sphingolipids through charge and structure are involved in DNA replication, protein translocation, cell recognition, signalling pathways, energetic, signal transduction, and cell trafficking. Together with diacylglycerols their collective properties modulate lipid polymorphism, through phase transitions (lamellar, hexagonal, cubic, micelles), which are involved in enzyme conformational changes, cell division, cell fusion, and apoptosis.¹Sterols, the third lipid class, also regulate biological processes and sustain the domain structure of cell membranes where they are considered as membrane reinforcers.^2,3 While cholesterol (CHO) is the major sterol of vertebrates, ergosterol plays a key role in fungi. Plants usually possess more complex sterol compositions. Stigmasterol (STI) and sitosterol (SIT), two 24-ethyl sterols, are major constituents of the sterol profiles of plant species. They are involved in the embryonic growth of plants.^4,5 Sterols are critical for the formation of liquid-ordered (lo) lipid domains (lipid rafts) that are supposed to play an important role in fundamental biological processes like signal transduction, cellular sorting, cytoskeleton reorganization and infectious diseases.^6,7 In plants, specialized lipid domains are involved in the polarized growth of pollen tube and root hair⁸ and the asymmetric growth of plant cells is in general due to the asymmetric distribution of membrane components.We recently documented the effect of sitosterol and stigmasterol, two major plant sterols, on the structure and dynamics of membranes whose composition is representative of domains (rafts) in plants.⁹ Liposomes of phytosterols associated with glucosylcerebroside (GC) and with deuterium-labelled dipalmitoylphosphatidylcholine (²H-DPPC) were analysed with deuterium solid state nuclear magnetic resonance (²H-NMR). For comparison, membrane systems representative of raft composition in fungi and mammals were also investigated. ²H-NMR is known to be the best non-invasive technique to analyse membrane dynamics¹⁰ because it is non-destructive and because replacement of DPPC protons with their deuterium isotope brings very little membrane perturbation.^11,12 Acyl chain deuteration affords analysis of both structure and dynamics of the hydrophobic membrane interior. Spectra such as that shown in Figure 1 insert, allow detection of the lo phase, characteristic of a membrane state half-way between solid-ordered (so) and liquid-disordered (ld) states. The so state, also called “gel”, is found at low temperatures (below 35°C), when membranes are essentially composed of sphingomyelins (SM)¹³ or GC (Fig. 1). This membrane state allows little biological function because in forbids membrane trafficking due to its very rigid state (order parameter close to 1). In turn, the ld or “fluid” state is found at high temperatures, in the absence of SM, GC and sterols (low order parameter). At the opposite such a high membrane dynamics may lead to excessive membrane passages. Following with ²H-NMR the temperature behaviour of membrane systems containing GC and plant sterols, we found that the so-ld, order-disorder, transition was totally abolished: SIT and STI fluidized the so state and ordered the ld state to produce the lo state where membrane fluctuations vary smoothly with temperature (Fig. 1). This effect was already documented with CHO in mammals^14–16 but on a much narrower temperature range. The case of the fungus system was found in between that of plants and mammals.Open in a separate windowFigure 1Regulation of temperature-driven membrane dynamics by plant sterols. Central panel: first spectral moment (left y-axis) or order parameter (right y-axis) as a function of temperature; solid line: ²H-DPPC with glucosylcerebroside; open circles: plus stigmasterol; filled circles: plus sitosterol. Insert: ²H-NMR spectrum typical of a liquid-ordered, lo, state. Left panel: schematics of solid-ordered, so (gel), and liquid-disordered, ld (fluid), membrane states. Right panel: schematics of the lo (raft) membrane state together with the structures of cholesterol and sitosterol. Adapted from reference ⁹.Summarizing, it appears that plant membranes of “raft” composition are less sensitive to temperature variations than those of animals. This suggests that cell membrane components like sitosterol, stigmasterol and glucosylcere-brosides, which are typical of plants, are produced in order to extend the temperature range in which membrane-associated biological processes can take place. This observation is well in accordance with the fact that plants have to face higher temperature variations than animals, which usually can either regulate their body temperature or change their location in order to avoid extreme heat or coldness.Compared to cholesterol, the two phytosterols possess additional ethyl groups branched on C-24 (Fig. 1). We proposed that the presence of an additional ethyl group may reinforce the attractive van der Waals interactions leading to more membrane cohesion and therefore less temperature sensitivity. Our results also suggest that domains of smaller size would be promoted in the presence of phytosterols and especially with sitosterol. Such domains may be viewed as dynamic, with sterols laterally exchanging at the microsecond time scale.¹⁴ In plant cells, enzymes transfer alkyl groups to the C-24 of sterols. If we suppose that the relative activities of the different branches of the plant sterol biosynthesis are regulated, the concentrations of major sterols in plants, like sitosterol, stigmasterol, and cholesterol could be controlled.^4,17 This shows the importance of equilibrated sterol concentrations for plant growth and development. Sterols have been historically considered as membrane reinforcers because they bring order to membranes.^2,3Our works^{9,15,16,18,19} show that they could better be named as “membrane dynamics regulators”, by maintaining the membrane in a state of microfluidity suitable for cell function on large temperature scales. It thus appears that a fine tuning of the sterol structure, i.e., the presence of branched ethyl groups in plant sterols increasing membrane cohesion through formation of smaller membrane domains, may be the evolution response for plant adaptation to large temperature variations.     

Ecological organization of a Chihuahuan desert lizard community

Summary Niche relationships among 11 diurnal lizard species were studied for 3 years. The community appeared to be subdivided spatially into different subsets of only four to six species. Coexisting species of each subgroup were separated further by differential utilization of microhabitats. In late spring and early summer, when food shortage is likely, dietary overlaps between syntopic species were generally low but increased broadly after the rains, when food became plentiful. Because of the high similarity in prey-size utilization among large and medium species, effects of prey selection according to size were generally slight except for very different-sized species. Overlap in the three-dimensional resource space was high between Cnemidophorus scalaris and C. tigris, but close observation of the ecology of the two populations showed many small differences between them. We suggest that the very diversified ecological opportunism of C. scalaris allows it to coexist with C. tigris in a very heterogeneous ecosystem. Several hypotheses are discussed to explain the ecological determinism of resource partitioning within such a community.