净多样化速率和进化时间对虎耳草目科间物种多样性差异的影响

不同生物类群包含的物种数目常存在巨大差异,这是生态学和生物学研究中普遍观察到的现象。然而,这一现象产生的原因仍然是未解之谜。从宏观进化的角度,进化时间假说和多样化速率假说是两个比较流行的假说。进化时间假说认为类群的演化时间越长,积累的物种丰富度越高;而多样化速率假说认为类群的净多样化速率越快,则其物种丰富度越高。为验证这两个假说,该文以一棵包含1 539个物种化石定年的虎耳草目系统发育树为基础,通过宏观进化分析获取了虎耳草目内15个科的物种形成和灭绝速率,并计算了每个科的平均多样化速率。结果表明：(1)虎耳草目的物种多样化速率有着增加的趋势,并且多样化速率的增加主要出现在温带和高山类群,如茶藨子科、景天科和芍药科等。(2)采用系统发育广义最小二乘模型(PGLS)和线性回归模型(LM)结果表明,虎耳草目15个科的物种丰富度与科的分化时间和科内物种的最近共同祖先年龄都没有显著相关关系,而与净多样化速率显著正相关(R² =0.380,P<0.05)。该研究支持了多样化速率假说,认为不同科的净多样化速率的差异是导致虎耳草目科间物种数目差异的主要原因之一。全球气候变冷...     

气候生态位进化与物种多样化的关系——以泛热带植物番荔枝科为例

热带地区较高的物种多样性与其气候条件有关,但气候如何影响热带地区物种的多样化却未有定论。为了解气候对热带植物多样性的影响,本研究以泛热带植物番荔枝科为研究对象,利用系统发育比较分析方法,计算了该科植物气候生态位的进化速率,并与该科的净多样化速率进行了相关性分析。结果显示：（1）番荔枝科气候生态位的进化速率较低,但新近分化类群的进化速率相对较高;（2）气候生态位下界（低温与低降水）的进化速率较上界（高温与高降水）快;（3）净多样化速率与气候生态位的进化速率,尤其是温度生态位的进化速率紧密相关。本研究揭示了番荔枝科植物气候生态位的进化对其物种多样性形成的重要作用,对该科在当前气候变化下的保护具有参考意义。     

河北小五台山北坡植物物种多样性的垂直梯度变化

通过野外群落调查,分析了小五台山北坡植物物种多样性的垂直梯度变化。结果表明：(1)小五台山北坡的物种丰富度随海拔的升高逐渐减小,物种组成趋于简单,乔木树种渐少。d多样性指数变化较小,但呈现出随海拔升高先增大、后减小的趋势。(2)β多样性指数很好地反映了群落之问的变化。相异系数峰值出现在海拔1．400-1500m处灌丛向森林的过渡带和海拔2600—2700m处森林向亚高山草甸的过渡带。海拔1400-1500m处出现的Cody指数极大值反映了灌丛群落向森林群落的变化,而Cody指数在海拔2100—2200m的极大值反映了阔叶林和针叶林之间的过渡。(3)作为小五台山两种最为重要的阔叶树种,白桦(Betula platyphylla)和红桦(Betula albosinensis)沿海拔梯度出现明显的替代现象,随着海拔的升高,白桦逐渐为红桦所取代。     

高黎贡山种子植物物种丰富度沿海拔梯度的变化

物种丰富度沿海拔梯度的分布格局成为生物多样性研究的热点。为探讨中尺度区域物种丰富度沿海拔梯度的分布,本文以高黎贡山为研究对象,利用该地区的地方植物志资料,结合通过GIS生成的区域数字高程模型(DEM)数据,分析了该区域全部种子植物和乔木、灌木、草本三种生活型种子植物物种丰富度的垂直分布格局以及物种密度沿海拔梯度的变化特征。结果表明：(1)全部种子植物和不同生活型植物物种丰富度随着海拔的升高呈现先增加后减小的趋势,最大值出现在海拔1500—2000m的范围;(2)物种密度与海拔也呈现单峰曲线关系;(3)物种丰富度和物种密度分布格局的形成主要受海拔所反映的水、热状况组合以及物种分布的边界影响。     

逆境诱导植物开花的研究进展

植物在长期的进化过程中形成了对环境改变的适应机制。在逆境条件下,例如干旱、高盐、低温、强光、弱光、紫外线等,植物会提前开花结实以尽早完成其生命周期,这种生物学现象被称为\"逆境诱导的开花\"。植物的这种避逆应激反应不但在进化上具有非常重要的生物学意义,而且对农业生产也具有重要的指导意义。逆境诱导植物开花与光周期、春化、环境温度、自主途径、赤霉素和年龄等开花途径的分子调控机制不同,有其自身的特点。文中对逆境诱导植物开花的研究历史、代谢调控以及分子机制等进行了阐述,并展望了未来的研究方向。     

贵州省植物物种多样性空间分布特征及影响因素

为探索植物物种多样性空间分布特征及宏观形成机制,分别运用地理空间自相关和地理探测器方法分析贵州省植物物种多样性空间分布特征及影响因素.研究结果表明,贵州省植物物种数量最丰富的地区是兴义市、安龙、荔波县、榕江县、剑河县、台江县、雷山县、江口县、印江县、黎平县和道真县,密度最高的地区是雷山县、台江县和道真县;贵州省植物物种...     

多倍体植物中基因表达模式的变化

植物杂交和多倍化能导致基因组结构发生变化,并显著影响了基因表达,因此认为杂交和多倍化是促进植物进化的一个重要力量。近些年大量的研究表明植物多倍化后基因表达模式发生了复杂的改变,包括基因沉默、基因表达的基因组偏向性及组织特异性、基因激活等现象,本文对这些现象及其特点和机制进行了综述。     

基于WebGIS的植物园植物物种管理信息系统

鉴于植物园现代化管理和国内外植物资源信息交流的迫切需要,利用WebGIS系统集成技术在Internet上建立了中国科学院武汉植物园植物物种管理信息系统。系统实现了基于网络的图形属性数据的双向查询,并具有新增、编辑、缩放、漫游、定位等功能,为植物迁地保育的动态管理提供了管理工具,为科研、科普等应用部门和科技人员提供了获取植物物种信息的工作平台。文中详细介绍了该系统的设计要求、数据来源、开发运行环境、数据库构成、系统功能等。     

垫状植物囊种草对群落物种多样性的影响

在甘肃盐池湾国家级自然保护区内海拔4137 m处,选择典型的囊种草垫状植被设置研究样地,研究了垫状植物囊种草对群落物种组成和群落物种多样性的影响,并且定量的研究了囊种草对群落物种丰富度的影响能力和维持潜力。研究结果表明:囊种草为群落中增加了新的植物种类,并且提高了部分生境一般种的多度;囊种草的出现提高了群落物种密度和物种丰富度,进而提高了群落物种多样性;囊种草斑块的增加将会引起景观水平物种丰富度的增加,表明囊种草具有为群落中引入新的植物种类进而提高群落物种丰富度的能力;在景观水平,囊种草所创造的生境多样性则成为一种保障,可以维持景观中物种丰富度从而降低物种损失的风险,表明囊种草具有较高的群落物种丰富度维持潜力。     

代谢速率调控物种丰富度格局的研究进展

提出生物多样性分布格局的普适性理论和探索其内在形成机制一直是生态学家们研究的焦点之一.到目前为止,已有很多假说被用来解释生物多样性分布规律,但是这些假说的普适性均受到学者们的质疑.最新理论--代谢速率假说以能量相当法则和代谢分形分配网络模型为基础,定量预测了个体及种群生态进化动态过程与群落生物多样性分布格局之间的关系,以及物种丰富度和环境因子之间的关系.代谢速率假说解释了生物多样性的起源问题,也回答了生物多样性如何维持的问题.该文重点综述了代谢生物多样性理论的发展及其相关研究进展.通过和其他假说比较、分析,我们认为随着代谢理论假说的不断发展和完善,代谢生物多样性理论将更具有普适性.同时我们也提出了进一步完善该假说需要解决的一些科学问题.     

植物叶片气孔性状变异的影响因素及研究方法

气孔是陆生植物与外界环境进行水分和气体交换的主要通道,在全球水和碳循环中发挥着重要作用.植物的气孔性状包括气孔密度、气孔形状和大小、气孔指数等,是植物在进化过程中对外界环境因子长期适应的结果,并对环境因子变化表现出高度的敏感性.本文评述了国内外近30年来植物气孔性状与大气CO₂浓度、温度、水分、光照等环境因素的关系研究的主要方法和成果,展望了今后植物气孔性状对气候变化响应的主要研究方向.     

Effect of tall-grass invasion on the flowering-related functional pattern of submediterranean hay-meadows

Several studies demonstrated that abandonment changes the functional composition of grasslands; nevertheless, little is known about the effects of grassland abandonment on the flowering-related functional pattern. We hypothesized that invasion by tall grasses affects this pattern. We counted the number of flowering shoots per species at five times during the growing season, in 80 plots placed in mown and in abandoned grasslands (central Apennines), and assessed the differences in the trait composition of flowering species between the two treatments. The selected traits were linked to resource acquisition and stress tolerance strategies. Our results indicated that abiotic environmental control is prevalent in determining the phenological pattern in both conditions and in accordance with the phenological “mid-domain hypothesis”. We demonstrated that when the dominant species is a tall grass with competitive behaviour, the magnitude of this phenomenon is amplified due to the abiotic changes yielded by the tall grass invasion. Indeed, in the central and late phases of the growing season (when invasive tall grasses are growing and blooming), abandoned grasslands were marked by a set of traits devoted to stress tolerance or underlying a long reproductive cycle or linked to competition for light.     

Heterozygosity in 2n gametes of potato evaluated by RFLP markers

The heterozygosity transmitted through 2n gametes in potato was evaluated by following the segregation of RFLP markers in tetraploid progeny from bilateral sexual polyploidization in a cross between two diploid (2x) interspecific hybrids which produce 2n SDR eggs or 2n FDR pollen. Out of 84 probe/enzyme combinations tested, 23 revealed polymorphism between the parents and were heterozygous in at least one of the parents. These probes characterized 13 loci distributed on five different chromosomes of the potato RFLP map. The heterozygosity transmitted through SDR and FDR gametes was estimated to be 31.8% and 71.4%, respectively. Two different indices (LH and RHI) were used to select plants showing a high level of heterozygosity in the tetraploid progeny. The recombination events and the centromere positions were estimated for chromosomes I, VI and VII, following the segregation ratios of SDR or FDR gametes produced by the parents. A different recombination rate was observed between the two interspecific hybrids.Contribution no. 119 from Research Centre for Vegetable Breeding, C.N.R., Portici, Italy. Research supported by National Research Council of Italy, special Project RAISA, Sub-project No. 2, Paper No. 2090     

Sex ratio and sexual dimorphism in the dioecious Borderea pyrenaica (Dioscoreaceae)

Sex ratio and sexual dimorphism of Borderea pyrenaica, a long-lived dioecious geophyte endemic to the Pyrenees (north-east Iberian Peninsula), were examined in three alpine populations. In this species, age can be estimated and the sex of nonreproductive adult plants identified. Male plants attain sexual maturity earlier, flower more frequently and grow faster than female plants, whereas females allocate a higher biomass to reproduction than males. These results support the hypothesis that female plants incur a higher cost of sexual reproduction and that this higher cost is measurable as reduced vegetative growth and lower flowering frequency. Variation of sex ratio among young, intermediate and old adults within populations suggests, however, that this higher female reproductive investment does not result in sexual differences in mortality. The overall male-biased sex ratio in B. pyrenaica is mainly a consequence of the tendency of males to reproduce at an earlier age and more frequently than females.     

植物性状研究的机遇与挑战:从器官到群落

植物性状(Plant trait)或植物功能性状(Plant functional trait)通常是指植物对外界环境长期适应与进化后所表现出的可量度、且与生产力优化或环境适应等密切相关的属性。近几十年来,植物性状研究在性状-生产力、性状-养分、性状间相互关系、性状-群落结构维持等方面取得了卓越成就。然而,由于大多数性状调查都是以植物群落内优势种或亚优势种为对象,使其在探讨群落尺度的性状-功能关系、性状数据如何用于改进或优化模型、性状数据如何与遥感连接等问题时,存在空间尺度和量纲不匹配的极大挑战。为了破解上述难题,亟需发展新的、基于单位土地面积的群落性状(Community trait)概念体系、数据源和计算方法等,推动植物性状数据与快速发展的宏观生态学新技术(遥感、模型和通量观测等)相结合,既拓展了植物性状研究范畴,又可推动其更好地服务于区域生态环境问题的解决。所定义的群落性状(如叶片氮含量、磷含量、比叶面积、气孔密度、叶绿素含量等),是在充分考虑群落内所有物种的性状实测数据,再结合比叶面积、生物量异速生长方程和群落结构数据等,推导而成的基于单位土地面积的群落性状。受测试方法的影响,传统的直接算术平均法或相对生物量加权平均法所获得的群落水平的植物性状(如叶片氮含量g/kg或%),虽然可以有效地探讨群落结构维持机制,由于无法实现对群落性状在量纲上向单位土地面积转换,使它很难与模型和遥感数据相匹配。基于单位土地面积的群落性状,可在空间尺度匹配(或量纲匹配)的前提下实现个体水平测定的植物性状数据与生态模型和遥感观测相联系,更好地探讨区域尺度下自然生态系统结构和功能的关系及其对全球变化的响应与适应。同时,它也可更好地建立群落水平的性状-功能的定量关系(非物种水平),为更好地探讨自然群落结构维持机制和生产力优化机制提供了新思路。     

Phylogeographic studies of plants in China: Advances in the past and directions in the future

<正>Phylogeography has been one major focus of evolutionary biology in recent years,with many important advances in Chinese species.In this issue,we collected 11 phylogeographic studies of plants by Chinese laboratories. We further synthesized the main findings and patterns emerging from these and previous phylogeographic studies in China and asked where phylogeographic research should be directed in the coming years.Numerous examples have shown that phylogeographic patterns in China did not show an expected expansion-contraction pattern at large scale, mirroring the geological records showing that no unified ice sheet had developed in China during the Quaternary Period.Instead,regional expansions and intraspecific divergences are very common in most studied species during the Quaternary oscillations.Different intraspecific lineages or alleles(haplotypes) were detected in multiple localized refugia,from where regional or local expansions are likely to have started.Hybridizations and introgressions are frequent between intraspecific lineages or between different species.We also reviewed computational methods for phylogeographic analyses.Despite the great progress made in recent years,there remains much to discover about the spatial-temporal dimensions and underlying speciation mechanisms of Chinese plants.Phylogeographic studies represent a key knot that connects the genus phylogeny(macroevolution) and speciation and adaptation (microevolution).Therefore,we advocate that:(i) phylogeographic studies of plants in China should be directed to the closely related species or a monophyletic group(for example,a genus or a section) in the coming years;and (ii) population genetic data based on direct sequencing multiple loci,especially those from nuclear genome and statistical tests should be widely adopted and enforced.The recovered intraspecific divergences and phylogeographic patterns of multiple-species may allow us to better understand the high plant diversity in China and set up concrete hypotheses for studying plant speciation and diversification mechanisms in this region.