孑遗植物四合木(Tetraena mongolica)的濒危肇因与机制

对我国特有单属种孑遗植物四合木 (Tetraena mongolica Maxim) 的地理分布、生境条件、种群数量动态、空间分布格局、种间关系、种群的生命表、生殖力表、有性生殖、无性繁殖和遗传变异等种群生态学特征及其濒危肇因进行了系统分析。研究结果表明：四合木种群为高群集分布,种群曲线属Leak凸型。年龄结构不合理,其存活曲线接近于Deevey ê型,且将演化为小种群,群落内的生境异质性显著,种群处于不稳定阶段。四合木从开花期到结果期,生殖分配 (RA) 呈下降的趋势,生殖过程中胚胎发生败育、种子向幼苗难以转化使其有性生殖受阻,生活史趋于断裂,是最终导致其濒危的重要内因。分布区城市化、工业化以及过度放牧等原因造成其种群孤立和生境破碎化是物种导致濒危的外因,四合木生态适应性和生境适宜性下降造成遗传多样性逐步丧失。同时提出对我国特有植物四合木进行异地保护的可能性与必然性。     

四合木种群生殖对策的研究

 通过研究四合木(Tetraena mongolica Maxim)种群的生殖对策,发现四合木既可进行有性生殖,又可进行营养繁殖,以有性生殖为其主要的生殖方式。有性生殖过程中具以下特征：1)具有自交和异交相结合的交配系统,异交比例(50％)高于自交比例(15％);2)具有花多果少的生殖格局,其开花率与生境、降水、植株年龄关系密切,不同种群的开花率有一定差异,种群的年龄结构对开花率有较大影响。在3～5月降水丰富的情况下,不仅开花比例高(40％～80％),且每一植株的花量很大。不同年份种群结实率普遍偏低,3～5月降雨较少的1996年平均结实率为19.8％;3～5月降雨较多的1998年为12.2％。只是由于开花基数大,对四合木种群种子的总产量不会造成较大威胁;3)胚胎发育过程中败育比率极高,只有约10％～20％的胚能发育成熟。     

鄂尔多斯高原特有种四合木生长和繁殖的种群间变异与濒危机制

四合木为中国特有种,其分布区局限于鄂尔多斯高原的西部。为了认识四合木濒危的机制并为其保护提供理论依据。对四合木生活史的关键阶段－－繁殖进行了野外研究,由于分布区内存在较大的生境异质性,并受到了不同强度的人类干扰,所以不同生境条件下的6个群进行了取样,通过对四合木的营养生长和繁殖的比较分析。得出如下结论：（1）四合木植要朱的基径和冠幅和高度与年龄显著相关,但是与其茎和冠幅相关性更大,冠幅可作为个体大小的测度估计种群的大小结构;（2）冠幅大小呈负偏斜分布,通过不同种群冠幅与年龄的相关分析,得出冠幅的增长速率随种群的衰老耐减缓;（3）四合木的冠幅与其果实量和种子量相关关系显著,随着冠幅的增大,四合木植株的果实产量和种子产量也相应增加,但是这种关系存在种群间差异;（4）四合木的大部分群都处于衰老期,种群内个体的大小变异性很小,对于种群的生存有不利影响;（5）由于空间上四合木的大小结构以及反映四合木繁殖状况的植株果实产量,种子产量等参数在不同种群之间存在显著差异（P＜0．001）,因此应对不同的种群采取相应的管理措施以促进种群的更新和续存。     

濒危物种四合木与其近缘种霸王遗传多样性的比较研究

 采用垂直板聚丙烯酰胺凝胶电泳技术,对西鄂尔多斯高原的濒危植物四合木(Tetraena mongolica)种群和生长于同一生境的普通种霸王(Zygophyllon xanthoxylon)种群的遗传多样性和遗传分化进行了比较研究。等位酶分析表明,与其他灌木相比,两种植物均维持较高的遗传多样性。但濒危植物四合木种群遗传多样性水平低于霸王种群,多态位点百分率P分别为60％和83.3％,等位基因平均数A为1.6和2.2,平均期望杂合度He为0.245和0.392。种群间遗传分化不明显,基因分化系数Gst为0.051和0.020。这一结果说明不同类型的濒危植物具有不同的遗传含义,采取的保护措施也不尽相同。     

珍稀植物蓑衣油杉濒危机制的初步研究

对云南特有珍稀植物蓑衣油杉（Keteleeria evelyniana var. pendula）的地理分布、自然生境概况及种群大小和年龄结构等种群特性进行研究,并掌握其形态特征、生长发育规律及种子散布和萌发等生物学特性。结果表明：蓑衣油杉在云南省华宁县主要分布于平地和吗哒等山区村寨周边地区;现有蓑衣油杉自然居群均为小种群,高群集分布,年龄结构不合理,种群处于相对不稳定阶段;虽然种子的种翅特征利于远距离传播,但可育种子产率极低,种子向幼苗难以转化使其有性生殖受阻,生活史趋于断裂,是最终导致其濒危的重要内因之一;自然生境的严重破坏、成年植株的过度采挖对蓑衣油杉种群的生存构成严重威胁,也是造成部分野生种群个体数量急剧减少的主要外因。本文还针对蓑衣油杉的濒危机制提出进行保护和利用的有效措施。     

木兰科濒危植物华盖木的生境脆弱性

华盖木(Manglietiastrum sinicum Law)为原始类群木兰科单种属植物,仅残存7株于中国三大特有中心之一的滇东南古特有中心的文山国家级自然保护区。对其生境条件,更新能力等的研究表明华盖木外围生境恶化,周边喀斯特型土壤利用过度,形成“孤岛”,使靠鸟类传播的华盖木失去了向四周扩散的机会,种子难于萌发生长,生存条件受到严重威胁。同时通过对华盖木的濒危机制及生境脆弱性探讨,提出了保护建议和措施。     

四合木（Tetraena mongolica）茎化学成分的GC-MS分析

近年来,特有植物天然成分分析与开发利用已经成为药物化学研究的热点问题之一[1]。四合木( Tetraena mongolica Maxim.)为蒺藜科( Zygophyllaceae)单属植物,仅分布于内蒙古高原和亚洲中部,为中国特有珍稀植物,也为国家二级濒危植物。四合木在防风固沙和维持荒漠生态系统功能方面具有突出的意义;此外,四合木也极易燃烧,在当地被称为“油柴”,因此,四合木有可能成为新的能源植物。目前,对四合木的相关研究主要集中在种群生态学和保护生物学方面[2-4],对四合木化学成分[5-7]及提取物生物活性[8-9]也进行了相关研究。     

不同生境条件四合木(Tetraena mongolica)内源激素季节变化及种群差异

四合木(Tetraena mongolica Maxim)是西鄂尔多斯地区特有的单种属古地中海残遗植物.选择了分布区内有代表性的低山、台地、丘陵、高平原、倾斜平原5个典型生境的四合木种群为研究对象.对不同生境四合木种群密度、盖度、年龄结构和根际土壤理化性质进行研究,运用酶联免疫吸附法对四合木叶片内源激素(ABA、IAA、GA3、ZT)季节变化和生境间差异性进行探讨.结果表明:(1)不同生境四合木种群密度、盖度、年龄结构存在显著差异,且低山、台地、丘陵种群所处生境有利于幼苗更新,其密度和盖度均显著大于高平原和倾斜平原种群;(2)四合木根际土壤有机质含量、土壤含水量、营养元素(N、P、K)、微量元素(Fe、Mn、Cu、Zn、Mo、B)含量均较低,pH偏高,体现出贫瘠碱性化的荒漠土壤特点.运用数理统计将5个样地土壤理化性质进行聚类分析,分为两类:低山、台地、丘陵种群为一类(A类),高平原、倾斜平原为一类(B类).方差分析表明:A类样地土壤营养元素(N、P、K)和微量元素(全Fe、Mn、Zn、B、Mo与有效量)、土壤有机质含量及土壤含水量都显著高于B类,而pH值显著低于B类.(3)5个四合木种群ABA和GA3含量均表现为:8月份＞6月份＞5月份;IAA的含量和ZT的含量均表现为:6月份＞8月份＞5月份.方差分析表明:5月份IAA含量表现为在A类样地＞B类样地,8月份ABA含量和GA3含量表现为在A类样地＞B类样地.(4)四合木分布区存在较大的生境异质性,在其长期适应过程中,生境条件差异导致了种群在生理生态方面的分化.四合木种群密度、盖度、年龄结构以及土壤养分、水分和内源激素在生境间存在着差异.     

不同生境条件下四合木（Tetraena mongolicaMaxim.）种群结构特征

对天然分布区及不同生境内四合木种群的径级结构、年龄结构、冠幅结构、高度结构及空间结构特征进行了比较分析,运用静态生命表描述了四合木种群年龄结构动态变化规律,应用Clark-Evans的 R值法计算出四合木个体空间分布格局指标.结果表明:四合木种群径级、龄级与高度级结构均基本呈正态分布,冠幅级结构呈现出近乎指数型的衰减趋势;但不同生境的四合木种群因所处微环境各异,在径级、龄级、高度级、冠幅级结构上表现出一定差异.四合木种群的存活率随龄级的增大而降低,死亡率和消失率随龄级的增大而升高,其存活曲线接近于DeeveyⅠ型,表明该种群为下降种群.不同生境的四合木种群个体分布均不均匀,其空间分布为随机型.     

中国特有珍稀濒危植物猪血木的研究进展

对我国特有珍稀濒危植物猪血木的分类地位、资源现状及分布、生物学和生态学特性、发育生物学、保护遗传学、繁殖生物学、和濒危机制进行了综述,为该物种的种群恢复研究提供了参考.     

Correlation between numerical dynamics and reproductive behavior in Cypripedium lentiginosum

Isolation, molecular identification and phylogenetic analysis were carried out to investigate the biodiversity of manganese bacteria in sediments which were collected from the Arctic Ocean during the 2^nd Chinese Arctic Scientific Expedition. 21 and 19 species of cultivable strains were isolated from sediments at Stations P11 and S11, respectively, according to their distinct morphological character on the screening plate of manganese medium. Molecular identification and phylogenetic analysis showed that the cultivable manganese bacteria from Station P11 were basically composed of γ-Proteobacteria (γ subgroup of the Proteobacteria branch of the domain Bacteria) and Actinobacteria, which accounted for 86% and 14%, respectively. The isolates of γ-Proteobacteria mainly included Psychrobacter, Shewanella, Acinetobacter and Marinobacter, of which Psychrobacter was the major genus, which accounted for 67% of the γ-Proteobacteria. The cultivable manganese bacteria from Station S11 included α-Proteobacteria, γ-Proteobacteria and Flavobacteria of Bacteroides. The γ-Proteobacteria mainly included Shewanella, Marinomonas and Alteromonas. The majority of α-Proteobacteria was Sphingomonas. The phylogenetic analysis indicated that bacteria from sediments at Stations P11 and S11 had different cultivable manganese microbial communities. All tested strains had higher resistance to Mn²⁺, of which Marinomonas sp. S11-S-4 had the highest resistant ability.     

Population characteristics of endangered species Taxus chinensis var. mairei and its conservation strategy in Shanxi, China

The conservation of the endemic, endangered, and first-class protected tree species, Taxus chinensis var. mairei (Lem. & H. Lev.) W. C. Cheng & L. K. Fu, is urgent in China. To assist the protection of this important medicinal plant species, the biological and ecological characteristics of its populations were investigated and analyzed in Shanxi. The study area, southeastern Shanxi, is a special region suitable for this species growth and development. The floristic composition, life form spectrum, and species diversity of T. chinensis var. mairei forests reflected the features of both warm-temperate and subtropical regions. Size classes in DBH and static life table analysis showed that the population structure of T. chinensis var. mairei was of the increase-type. Plant density, survivorship, and mortality decreased with increase in age. Distribution patterns of individuals were basically clumped and saplings tended to be distributed randomly. Disturbance from collection of leaves, branches, and stems for medicine was an important factor affecting population structure, dynamics, and distribution. The sex ratio of female/male and the efficiency of sexual reproduction were very low. The main way of reproduction for this species is vegetative propagation. Based on these characteristics, some suggestions, such as establishing nature reserves, improving population structure by cultivation and transplantation, developing seed gardens, and plantations, etc., for the conservation management of T. chinensis var. mairei and its forests in Shanxi are discussed.     

Sexual reproduction and diversity: Connection between sexual selection and biological communities via population dynamics

Sexual reproduction is a mysterious phenomenon. Most animals and plants invest in sexual reproduction, even though it is more costly than asexual reproduction. Theoretical studies suggest that occasional or conditional use of sexual reproduction, involving facultative switching between sexual and asexual reproduction, is the optimal reproductive strategy. However, obligate sexual reproduction is common in nature. Recent studies suggest that the evolution of facultative sexual reproduction is prevented by males that coerce females into sexual fertilization; thus, sexual reproduction has the potential to enforce costs on a given species. Here, the effect of sex on biodiversity is explored by evaluating the reproductive costs arising from sex. Sex provides atypical selection pressure that favors traits that increase fertilization success, even at the expense of population growth rates, that is, sexual selection. The strength of sexual selection depends on the density of a given species. Sexual selection often causes strong negative effects on the population growth rates of species that occur at high density. Conversely, a species that reduces its density is released from this negative effect, and so increases its growth rate. Thus, this negative density-dependent effect on population growth that arises from sexual selection could be used to rescue endangered species from extinction, prevent the overgrowth of common species and promote the coexistence of competitive species. Recent publications on sexual reproduction provide several predictions related to the evolution of reproductive strategies, which is an important step toward integrating evolutionary dynamics, demographic dynamics and community dynamics.     

濒危物种杏黄兜兰的保育生态学

杏黄兜兰(Paphiopedilum armeniacum)是中国特有的兰科濒危物种。自2000年4月1日至2005年10月10日,在云南省怒山的落砂坡山选取66个调查点进行杏黄兜兰保育生态学研究:对443基株共1302分株进行了繁殖式样、物候和生命周期等主要生物学特性,以及对该物种的生境要求、群落结构特征等生态学习性进行了观察研究,并在广东省深圳进行迁地保护和迁地繁殖后重返原产地的试验,研究了原产地的气候、植被和其他环境因素与杏黄兜兰之间的关系以及杏黄兜兰迁地栽培和繁殖的无性后代重返原生长地的生物学特性。研究结果表明:落砂坡山的杏黄兜兰在石灰岩上的次生灌木丛或草丛内生长良好;它兼具有性和无性繁殖,无性繁殖的目的就是实现有性繁殖和延长基株的寿命;无性繁殖有二种形式:产生分蘖或根茎;灌木丛或草丛的落叶为杏黄兜兰生长提供腐殖质,杏黄兜兰根茎繁殖是它对落叶等覆盖的一种适应;分株的开花率为7.39%±1.02%,开花分株的结果率为32.23%±12.08%;杏黄兜兰具有入侵适度破坏和正处于恢复初期的森林环境的能力,而在茂密连片的大树森林内不能生长。杏黄兜兰在深圳人工疏林下生长良好并繁殖许多无性的克隆分株,将繁殖的克隆分株重返原产地能正常开花和结实。试验结果显示,杏黄兜兰可以进行迁地保护以保存种质资源和迁地繁殖的植株回归原产地。基于杏黄兜兰濒危机制的分析,认为,杏黄兜兰生存所面临的威胁是生长空间被完全剥夺和人为灭绝性采集而不是其自身存在的生物学缺陷,为此,提出了相应的保育对策。     

Conservation ecology of endangered species Paphiopedilum armeniacum (Orchidaceae)

Paphiopedilum armeniacum is an endangered orchid species, endemic to China. During the period of April 2000 to October 2005, 66 observation sites were selected in Luoshapo of Nushan Mountains in Yunnan, China, to carry out the conservation ecological research on P. armeniacum. A total of 443 genets (1302 ramets in total) of P. armeniacum were sampled, their biological characteristics such as reproductive pattern, phenology, and life cycle were observed, and the ecological habits of the species such as the habitat and the structure of communities were studied. Experiments on ex-situ conservation were conducted, and the cloned ramets were replanted to their original habitat after ex-situ reproduction in Shenzhen, Guangdong, China. The relationships between P. armeniacum and climate, vegetation, other environmental factors in the original habitat, and the biological characteristics of asexual offsprings of P. armeniacum, which were replanted to the original habitat after ex-situ cultivation and reproduction, were investigated. The studies show that P. armeniacum in Luoshapo grows very well in secondary shrub boskets or in tussocks on limestone hills. It has both sexual and asexual reproduction. Asexual reproduction serves to complete the sexual reproduction and to extend the lifetime of genets, while it does not reduce sexual reproduction. There are two modes of asexual reproduction-by tillering or by producing rhizomes. The litter of shrub boskets or tussocks provides P. armeniacum with humus, and the rhizome reproduction of P. armeniacum is an adaptation to the litter-covered condition, i.e. to escape from the unfavorable environment. Blooming rate of ramets is 7.39% 1.02%, and fruit set rate from the blooming ramets is 32.23% 12.08%. P. armeniacum is able to invade the moderately destroyed forests and those in early restoring but is unable to grow in large dense forests. P. armeniacum also grows very well in artificial spare woods in Shenzhen and can reproduce many cloned ramets, which can normally bloom and yield fruits after being replanted to the original habitat. The results of this study show that P. armeniacum can be conserved by ex-situ conservation and by replanting the ex-situ reproduced ramets to original habitat. On the basis of the analysis of endangered mechanisms of P. armeniacum, it can be concluded that P. armeniacum has strong capability of both asexual and sexual reproductions, and an emergency mechanism consisted of massive production of rhizomes to cope with damage. Because highly effective pollinating insects that facilitate pollination in P. armeniacum are present in the habitat, flowering ramets produce fruits with large quantity of seeds, many of which in turn grow into new genets that can reproduce many cloned ramets. P. armeniacum makes very effective use of its environment and has distinct characteristics of enduring harsh environmental conditions; therefore, rather than its own inherent biological defects, the main threats facing this species are the destruction of its survival space and the wipe-out collecting of the plants as a result of trading. Based on the analysis mentioned above, certain appropriate strategies have been proposed for the conservation of P. armeniacum.     

浙江天目山苦槠种群结构和动态研究

选取了6个代表性样地对浙江天目山的苦槠种群结构和动态进行了研究,研究结果表明：苦槠种群的结构为衰败型：种群结构存在着幼龄种苗数量较少,部分样地有缺失现象。种群结构总体分布格局为随机型,不同阶段幼苗—幼树—中树—大树动态格局趋势表现为聚集—聚集—随机过渡—随机型。造成这种现象的原因一方面是由于大量的结实种子易被啮齿类捕食所致;另一方面也与苦槠的生物学特性和生境密切相关。苦槠种群维持和更新繁殖方式的适应性特点表现为无性萌生繁殖贡献率远远大于有性繁殖,种群主要通过萌生的方式来维持种群的更新和存活,并在一定程度上影响了演替的方向。衰败型苦槠种群的生态恢复可通过控制鼠害和移栽幼苗的策略。     

永瓣藤的分布现状及其保护

本文从自然环境、分布特征、种群数量和种群繁殖等方面研究了我国珍稀特有植物永瓣藤（Monimopetalum chinense）的分布和保护现状, 并从引种栽培、种子繁殖和无性繁殖等方面总结了近年来对永瓣藤进行迁地保存的初步研究结果, 最后提出了相应的保护建议。     

濒危种四合木与其近缘种霸王水分关系参数和光合特性的比较

运用压力室-容积技术(P-V技术)对西鄂尔多斯地区特有的濒危植物四合木(Tetraena mongolica Maxim.)和生长于同一生境的近缘种霸王(Zygophyllum xanthoxylon (Bunge) Maxim.)的7个水分关系参数饱和含水量时最大渗透势(Ψ_s^sat) 、初始质壁分离时的渗透势(Ψ_s^tlp) 、初始质壁分离时渗透水相对含量(ROWC^tlp) 、初始质壁分离时的相对含水量(RWC^tlp) 、质外体水的相对含量(AWC) 、束缚水与自由水的比值(V_a / V₀),以及细胞最大弹性模量(ε^max)进行了测定,同时利用Li-6400光合作用测定系统测定了二者叶片气体交换参数的日变化,从生理生态学角度探讨了二者生存力、适应力的差异。结果表明:1)四合木的ε^max、ROWC^tlp值和RWC^tlp值均显著低于霸王,而Ψ_s^sat值Ψ_s^tlp值、AWC和V_a / V₀高于霸王。二者保持膨压的能力和方式不同,四合木表现为较小的细胞体积和较强的持水能力,主要以高的组织弹性来保持膨压,而霸王主要以增加细胞质浓度的渗透调节来维持膨压,弹性调节较弱。且四合木保持最大膨压的能力和维持最低膨压的极限渗透势低于霸王,耐旱性弱于霸王。2)自然条件下,四合木和霸王叶片的光合速率(Pn)、蒸腾速率(Tr)日进程均呈"双峰"曲线,主峰出现在11:00时,次峰出现在15:00时左右,光合作用的午间降低是由气孔导度(Gs)降低造成的。二者相比,四合木光合速率和水分利用效率(WUE)低于霸王,光合能力和对干旱环境适应能力弱于霸王。研究表明四合木在生理生态学方面的生存力、适应力弱于霸王。     

An individual-based population model for the prediction of rotifer population dynamics and resting egg production

Most species of rotifers have a combination of sexual and asexual reproduction, with sexual reproduction resulting in resting eggs, which can lay dormant for long periods. The occurrence of sexual reproduction affects population dynamics through the temporary presence of male rotifers, and a reduction in the growth of the number of female rotifers. A previously published, individual-based model used dynamic energy budget theory to describe rotifer food intake, growth, egg production, and mortality, but assumed asexual reproduction only. In the current study, we have expanded the model to describe the entire reproductive cycle of the rotifers, making it usable for investigating relationships, such as those between the signal triggering mictic egg production, and the timing and number of resting eggs produced. The model is intended for use in predicting the specific future development of cultures, for instance, as a process model in rotifer or resting egg production for aquaculture. Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont & R. Rico-Martínez Advances in Rotifer Research