高寒草甸植物群落中物种多样性与群落变异性的关系及其机制初探

通过对高寒草甸植物群落中采集的群落数据进行分析,探讨了物种构成的相似性、统计平均、种群变异性和净协方差等机制对形成高寒草甸植物群落中多样性与群落地上生物量变异性之间关系的影响。结果表明,地上生物量的年际变异性随着多样性的增加而减小。物种构成相似性是多样性一变异性负关系产生的原因之一,而相似性与多样性之间并无显著相关关系;统计平均效应是另一个多样性一变异性负关系的主要决定者;净协方差效应、种群变异性对多样性一变异性关系产生的影响不显著或非常有限。     

高寒草甸植物群落中相似性、物种多样性与地上生物量的年际变异性

相似性似说通过物种构成的相似性来解释物种丧失是如何影响生物量的变异性的,但还没有得到检验。本研究通过设置在青藏高原东部地区的高寒草甸植物群落中的74个永久样方．采集3年(1999～2001)植物生长高峰期的群落数据,试图检验物种构成的相似性是如何解释物种多样性对地上生物量年际变异性的影响。结果表明：随着物种丰富度增加,生物量变异性降低;而随着均匀度的增加,生物量的变异性尽管在均匀度中等程度时似乎保持在同一水平,但总体上呈下降趋势;物种构成上的相似性解释了地上生物量变异性的大部分,而且随着物种构成上的相似性的增加,生物量的变异性降低;物种丰富度和均匀度均与物种构成上的相似性没有显著相关关系。这些结果表明：尽管生物多样性的丧失可能不必导致物种丰富群落中物种构成上的相似性,但相似性与地上生物量的变异性的因果联系可能是稳健的．由于本研究是在自然群落中进行的,对物种构成的相似性没有进行直接控制,因此,要深入理解相似性是如何影响生物多样性对生态系统功能变异性的效应的机制,可能还需要直接对物种构成的相似性进行控制的实验研究。     

锡林河流域羊草草原植物种群和功能群的长期变异性及其对群落稳定性的影响

 分析了内蒙古锡林河流域羊草(Leymus chinensis)草原群落植物种群、功能群和群落生物量的长期变异性,以及植物功能群间的补偿作用对群落稳定性的影响,结果表明：从种群水平到功能群和群落水平,地上生物量的年度间变异性逐渐降低,而稳定性则逐渐增加。植物功能群组成对群落稳定性具有更强烈的影响,在植物生活型功能群组成中多年生根茎禾草与多年生丛生禾草和多年生杂类草功能群,在生物量的年度变化上具有补偿作用,在生态类群组成中,旱生植物与中旱生植物也具有补偿作用。植物种群多度的长期变异性可能依赖于物种对环境波动的敏感性和种间相互作用对环境波动的放大效应,生物多样性使物种对环境波动响应的多样性增加,并通过不同响应类型(功能群)间的补偿作用使群落稳定性增加。     

植物边缘种群遗传多样性研究进展

边缘种群指地理分布边缘可检测到的一定数量的同种个体集合,准确评价其遗传多样性对于理解第四纪冰期后气候变化对物种边缘扩展或收缩、遗传资源保护与利用以及物种形成等有重要意义。该文探讨了维持植物边缘种群遗传多样性的进化机制,分析交配系统对物种边缘及其遗传多样性的影响,比较了边缘与中心种群遗传多样性的差异及其形成的生态与进化过程,并探讨了边缘种群遗传多样性与其所在的群落物种多样性的关系及理论基础。该文提出今后研究的重点是应用全基因组序列或转录组基因序列研究前缘-后缘种群之间或边缘-中心种群之间的适应性差异,边缘种群与所在群落其他物种之间相互作用的分子机制,深入解析边缘种群对环境的适应及边缘种群遗传多样性与群落物种多样性关系的生态与进化过程。     

植物边缘种群遗传多样性研究进展

边缘种群指地理分布边缘可检测到的一定数量的同种个体集合, 准确评价其遗传多样性对于理解第四纪冰期后气候变化对物种边缘扩展或收缩、遗传资源保护与利用以及物种形成等有重要意义。该文探讨了维持植物边缘种群遗传多样性的进化机制, 分析交配系统对物种边缘及其遗传多样性的影响, 比较了边缘与中心种群遗传多样性的差异及其形成的生态与进化过程, 并探讨了边缘种群遗传多样性与其所在的群落物种多样性的关系及理论基础。该文提出今后研究的重点是应用全基因组序列或转录组基因序列研究前缘-后缘种群之间或边缘-中心种群之间的适应性差异, 边缘种群与所在群落其他物种之间相互作用的分子机制, 深入解析边缘种群对环境的适应及边缘种群遗传多样性与群落物种多样性关系的生态与进化过程。     

集合群落及其在土壤动物群落构建中的应用

集合群落(metacommunity)指的是一系列由多个潜在的相互作用的物种通过扩散联系起来的局域群落。集合群落研究的基本问题是同一系统中多物种共存的机理、多样性的成因与维持机制。为了解决这些经典问题,Leibold提出了集合群落理论的4个经典范式,即斑块动态理论、物种分配理论、中性理论和集群效应理论。集合群落理论可以应用于土壤动物群落构建研究领域,解决多空间尺度土壤动物空间分布模式与驱动机制等问题。本文采用文献计量学方法梳理了集合群落自1992年提出到目前为止,集合群落理论、结构、驱动力以及基于功能性状的集合群落机制研究等四大核心方向与研究热点。同时,本文结合目前国内外土壤动物集合群落理论研究现状,提出进一步深入开展多尺度土壤动物多样性时空格局动态研究,旨在为土壤生物多样性管理提供对策措施。     

生产力、可靠度与物种多样性:微宇宙实验研究

近年来,生物多样性与生态系统功能的关系成为生态领域内一个重大科学问题。有一些实验研究表明,物种多样性的降低会使生态系统的生产力、稳定性等功能受损,然而对这些实验结果的解释却产生了激烈的争论,因为有两种机制-“生态位互补”和“抽样效应”都可能会产生这种结果。本项研究通过微宇宙实验探讨了物种多样性与生态系统生产力及其可靠度的关系。在10种单细胞藻类中随机抽取物种,构建具有不同物种丰富度的水生群落,并使同一物种丰富度水平的群落之间没有物种交叉,然后检测物种丰富度对群落生产力及其可靠度的作用,群落生产力以藻类干重表示,自实验开始后第4周起,每周测定1次,共测5次。结果显示：物种丰富度对群落生产力有正效应,并且这种正效应随时间推移而增强;许多混合群落的生产力超过了该群落内所有物种的单产,即发生了超产现象,在实验初期某些特定物种对一些混合群落生产力有主要贡献,而在实验后期却没有任何多物种群落的生产力受个别物种存在与否的影响,群落生产力的可靠度与物种丰富度之间不存在显著相关。从以上结果可以得知：物种多样性对群落生产力有着逐渐增强的正效应;物种多样性对生产力的正效应是生态位互补和抽样效应共同作用的结果,但随时间推移,抽取效应逐渐减弱,本顶研究支持了关于生态位互补与抽样效应在多样性正效应中共同起作用的认识,并说明了这两种机制的相对重要性随时间推移而发生改变。     

应用中性理论分析局域群落中的物种多样性及稳定性

如何解释群落中物种的丰富与稀少,并对物种多样性和群落稳定性进行合理的量化评价是群落生态学研究中的一个热点问题。20世纪中期,MacArthur将影响自然群落稳定性的因素归结为物种数量多少以及物种间相互作用的大小,20世纪末Doak等学者提出群落的容纳能力和物种间的维持机制是决定群落稳定性的关键因素。同时对群落结构及物种间维持机制的研究也有了新的突破,Hubbell提出"生物多样性与生物地理学统一的中性理论(Unified Neutral Theory of Biodiversity and Biogeography)"为群落生态学研究提供了新的思路和方法。从群落中性理论的基本假设出发,对Hubbell中性理论中局域群落的物种多度动态模型进行分析,归纳得出群落中性理论中物种多样性与群落稳定性之间的量化关系。封闭的局域群落中,出现物种灭绝或单物种独占的时间与群落大小及物种相对多度成正比,物种多样性程度的增加可延长物种灭绝或独占的时间;开放的局域群落中,物种多度期望值与局域群落大小、物种在集合群落中的物种相对多度成正比,周围群落中物种的灭绝会引起局域群落中相应物种的灭绝,最终导致整个生态群落物种多样性的降低;群落中物种多度的方差与局域群落大小、迁移率、物种在集合群落中的物种相对多度相关,局域群落物种多度的波动幅度随着群落间生态隔离的减弱或物种多样性程度的增加而减小。由此,集合群落物种多样性是影响局域群落物种多样性的重要因素,生态隔离程度的减弱及物种多样性的增加都将增强群落的稳定性。     

中国湿地物种多样性与生境面积关系及其生态学机理的模拟研究

生物群落中的物种多样性是群落生态学研究的一个基本问题。大量的实验研究表明物种多样性和生境面积的常数次幂成比例,这说明它们的对数数量级呈线性正相关。我们研究了中国境内15块湿地的高等植物和32块湿地鸟类多样性,发现它们分别和湿地面积在对数尺度上呈线性正相关．进一步支持了种数与面积的幂指数关系。我们还借助计算机模拟系统地讨论了产生这种简单规律的生态学机理,包括中性理论、集合种群动态和物种分布的自相似性。中性理论假设了群落中物种的个体之间只有竞争关系,忽略了其它的种间关系。集合种群动态理论考虑的是由多个亚群落构成的集合群落,在研究种数和面积关系时也忽略了种间关系,所以也是中性的。尽管物种分布的自相似性可导致这种面积幂指数关系,但在自然界中自相似性也可能不成立。     

刈割、施肥对高寒草甸物种多样性与生态系统功能关系的影响及群落稳定性机制

植物群落中不同“功能身份”物种的多样性与特定生态系统功能之间具有何种关系及其作用机制尚不明确。通过在高寒矮嵩草(Kobresia humilis)草甸为期5年的刈割(不刈割、留茬3 cm、留茬1 cm)、施肥(施肥、不施肥)和浇水(浇水、不浇水)控制实验, 研究了刈割与土壤资源获得性梯度上不同“功能身份”物种(群落中所有物种、响应物种、作用物种和共有物种)的多样性变化与群落地上净初级生产力和稳定性的关系以及稳定性机制。研究结果显示: 群落中响应物种、作用物种和共有物种数分别占全部物种数的36.6%、18.3%和64.8%, 物种多样性对生态系统功能具有不同的效应, 净初级生产力主要受响应物种和作用物种的多样性变化影响, 而稳定性则主要由共有物种的多样性变化决定; 群落稳定性的维持主要依赖于共有物种的多样性增加, 其作用机制是投资组合效应, 而超产效应和异步性效应对稳定性并无作用; 刈割和施肥对物种多样性、稳定性和净初级生产力具有相反的影响, 前者能增加物种多样性和稳定性, 并降低净初级生产力, 而后者的作用正相反。这与群落中全部物种的多样性变化受刈割影响较大, 而作用物种的多样性变化受资源获得性影响较大有关。上述结果表明高寒草甸生态系统地上净初级生产力主要由少数影响生产力的作用物种的多样性决定, 而稳定性则由大量共有物种的多样性所掌控。投资组合效应是物种多样性导致稳定性的机制。由于群落中不同物种的多样性效应具有分异性, 对于特定的生态系统功能而言, 物种的“功能身份”可能比物种多样性本身更重要, 不加区别地笼统定义物种多样性与生态系统功能的关系可能欠妥。     

Biodiversity may regulate the temporal variability of ecological systems

The effect of biodiversity on natural communities has recently emerged as a topic of considerable ecological interest. We review studies that explicitly test whether the number of species in a community (species richness) regulates the temporal variability of aggregate community (total biomass, productivity, nutrient cycling) and population (density, biomass) properties. Theoretical studies predict that community variability should decline with increasing species richness, while population variability should increase. Many, but not all, empirical studies support these expectations. However, a closer look reveals that several empirical studies have either imperfect experimental designs or biased methods of calculating variability. Furthermore, most theoretical studies rely on highly unrealistic assumptions. We conclude that evidence to support the claim that biodiversity regulates temporal variability is accumulating, but not unequivocal. More research, in a broader array of ecosystem types and with careful attention to methodological considerations, is needed before we can make definitive statements regarding richness‐variability relationships.     

Population stability is higher in more diverse annual plant communities

Abstract Theoretical work suggests a paradoxical effect of diversity on the temporal stability of ecological systems: increasing diversity should result in decreased stability of populations while community stability is enhanced. While empirical work indicates that community stability tends to increase with diversity, investigations of the effect of diversity on populations have resulted in few clear patterns. Here, we examine relationships between community diversity and population stability in unmanipulated annual plant communities. We show that, counter to theory, the temporal stability of annual plant populations increases with diversity. In addition, and again counter to theoretical assumptions, mean population size tends to increase with diversity, a pattern most likely due to variation in local productivity. The fact that community diversity, population size and the temporal stability of populations covaried positively suggests that abiotic factors such as productivity may govern population stability to such an extent as to override potential effects of diversity.     

Contrasting effects of diversity on the temporal stability of plant populations

Recent theoretical and empirical work suggests that diversity enhances the temporal stability of a community. However, the effect of diversity on the stability of the individual populations within the community remains unclear. Some models predict a decrease of population stability with diversity, whereas others suggest that diversity has a stabilizing effect on populations. Empirical evidence for either relationship between population stability and diversity is weak. The few studies that directly assessed the stability of populations reported contradicting results. We used a six-year data-set from a plant diversity experiment to examine the relationships between diversity and temporal stability of plant biomass. Our results show that stability increased with diversity at the community-level, while the stability of populations, averaged over all species, decreased with diversity. However, when examining species separately we found positive, negative and neutral relationships between population stability and diversity. Our findings suggest that diversity may contribute to the stability of ecosystem services at the community level, but the effect of diversity on the stability of the individual populations within the community are generally negative. However, different species within the community may show strikingly different relationships between diversity and stability.     

Species richness, environmental fluctuations, and temporal change in total community biomass

Theory and empirical results suggest that high biodiversity should often cause lower temporal variability in aggregate community properties such as total community biomass. We assembled microbial communities containing 2 to 8 species of competitors in aquatic microcosms and found that the temporal change in total community biomass was positively but insignificantly associated with diversity in a constant temperature environment. There was no evidence of any trend in variable temperature environments. Three non-exclusive mechanisms might explain the lack of a net stabilising effect of species richness on temporal change. (1) A direct destabilising effect of diversity on population level variances caused some populations to vary more when embedded in more diverse communities. (2) Similar responses of the different species to environmental variability might have limited any insurance effect of increased species richness. (3) Large differences in the population level variability of different species (i.e., unevenness) could weaken the relation between species richness and community level stability. These three mechanisms may outweigh the stabilising effects of increases in total community biomass with diversity, statistical averaging, and slightly more negative covariance in more diverse communities. Our experiment and analyses advocate for further experimental investigations of diversity-variability relations.     

再论生物多样性与生态系统的稳定性

本文在简述生物多样性与生态系统稳定性研究动态的基础上,从生物多样性和稳定性的概念出发,指出忽视多样性和稳定性的生物组织层次可能是造成观点纷争的根源之一。特定生物组织层次的稳定性可能更多地与该层次的多样性特征相关,探讨多样性和稳定性的关系应从不同的生物组织层次上进行,抗动是生态系统多样性与稳定性关系悖论中的重要因子,如果根据扰动的性质,把生态系统（或其他组织层次）区分为受非正常外力干扰和受环境因子时间异质性波动干扰2类系统,稳定性的4个内涵可以理解为：对于受非正常外力干扰的系统而言,抵抗力和恢复力是稳定性适宜的测度指标;对于受环境因子时间异质性波动干扰和系统而言。利用持久性和变异性衡量系统的稳定性则更具实际意义。结合对群落和种群层次多样性与稳定性相关机制的初步讨论,本文认为;在特定的前提下,多样性可以导致稳定性。     

The effects of long-term fertilization on the temporal stability of alpine meadow communities

Recent theoretical and experimental work suggests that species diversity enhances the temporal stability of communities. However, empirical support largely comes from experimental communities. The relationship between diversity and stability in natural communities, and the ones facing environmental changes in particular, has received less attention. We created a gradient of fertility in a natural alpine meadow community to test the effects of diversity and fertilization on the temporal variability of community cover and cover of component species and to determine the importance of asynchrony, portfolio effects, cover and dominance for diversity-stability relationships. Although fertilization strongly reduced species richness, the temporal stability in community cover increased with fertilization. Most species showed a decline of temporal stability in mean population cover with fertilization, but two grass species, which dominated fertilized communities after 10 years, showed an increase of stability. Detailed analysis revealed that the increased dominance of these two highly stable grass species was associated with increased community stability at high levels of fertilization. In contrast, we found little support for other mechanisms that have been proposed to contribute to community stability, such as changes in asynchrony and portfolio effects. We conclude that the presence of highly productive species that have stabilizing properties dominate fertilized assemblages and enhance ecosystem stability.     

Eco-evolutionary maintenance of diversity in fluctuating environments

Growing evidence suggests that temporally fluctuating environments are important in maintaining variation both within and between species. To date, however, studies of genetic variation within a population have been largely conducted by evolutionary biologists (particularly population geneticists), while population and community ecologists have concentrated more on diversity at the species level. Despite considerable conceptual overlap, the commonalities and differences of these two alternative paradigms have yet to come under close scrutiny. Here, we review theoretical and empirical studies in population genetics and community ecology focusing on the ‘temporal storage effect’ and synthesise theories of diversity maintenance across different levels of biological organisation. Drawing on Chesson's coexistence theory, we explain how temporally fluctuating environments promote the maintenance of genetic variation and species diversity. We propose a further synthesis of the two disciplines by comparing models employing traditional frequency-dependent dynamics and those adopting density-dependent dynamics. We then address how temporal fluctuations promote genetic and species diversity simultaneously via rapid evolution and eco-evolutionary dynamics. Comparing and synthesising ecological and evolutionary approaches will accelerate our understanding of diversity maintenance in nature.     

Trophic network structure emerges through antagonistic coevolution in temporally varying environments

Understanding the mechanisms underlying ecological specialization is central to our understanding of community ecology and evolution. Although theoretical work has investigated how variable environments may affect specialization in single species, little is known about how such variation impacts bipartite network structure in antagonistically coevolving systems. Here, we develop and analyse a general model of victim-enemy coevolution that explicitly includes resource and population dynamics. We investigate how temporal environmental heterogeneity affects the evolution of specialization and associated community structure. Environmental productivity influences victim investment in resistance, which will shape patterns of specialization through its regulating effect on enemy investment in infectivity. We also investigate the epidemiological consequences of environmental variability and show that enemy population density is maximized for intermediate lengths of productive seasons, which corresponds to situations where enemies can evolve higher infectivity than victims can evolve defence. We discuss our results in the light of empirical studies, and further highlight ways in which our model applies to a range of natural systems.     

Temporal population variability in local forest communities has mixed effects on tree species richness across a latitudinal gradient

Among the local processes that determine species diversity in ecological communities, fluctuation‐dependent mechanisms that are mediated by temporal variability in the abundances of species populations have received significant attention. Higher temporal variability in the abundances of species populations can increase the strength of temporal niche partitioning but can also increase the risk of species extinctions, such that the net effect on species coexistence is not clear. We quantified this temporal population variability for tree species in 21 large forest plots and found much greater variability for higher latitude plots with fewer tree species. A fitted mechanistic model showed that among the forest plots, the net effect of temporal population variability on tree species coexistence was usually negative, but sometimes positive or negligible. Therefore, our results suggest that temporal variability in the abundances of species populations has no clear negative or positive contribution to the latitudinal gradient in tree species richness.     

Species richness–variability relationships in multi-trophic aquatic microcosms

While species loss may affect the temporal variability of populations and communities differently in multi- versus single-trophic level communities, the nature of these differences are poorly understood. Here, we report on an experiment where we manipulated species richness of multi-trophic rock pool invertebrate communities to determine the effects of species richness, S, on the temporal variability of communities, populations, and individual species. As in single-trophic level studies, temporal variability in community abundance decreased with increasing species richness. However, in contrast to most studies in single-trophic level systems, temporal variability of populations also decreased as species richness increased. Furthermore, the variability of the constituent populations strongly correlated with variability of community abundance suggesting that, in rock pools, S affects community variability through its stabilizing effect on component populations. Our results suggest that species loss may affect population and community variability differently in multi-trophic versus single trophic level communities. If this is so, then the mechanisms proposed to underlie the effects of S on community variability in single-trophic communities may have to be supplemented by those that describe contributions to population stability in order to fully describe the patterns observed in multi-trophic communities.