不同生态位计测方法在绿洲荒漠过渡带上的应用比较

生态位分化被认为是物种共存的基础 ,亦是物种进化的动力[10 ] ,所以生态位理论已在种间关系、群落结构、物种多样性、种群进化、群落演替等方面广泛应用 ,在现代生态学中占有愈来愈重要的地位[2 ,8] 。对于生态位宽度和生态位重叠已有多种计测公式 ,这些公式的生态学合理性和应用上的可操作性 ,一直是生态学家关注的问题[1,7,9] 。由于各公式有不同的生态学意义 ,侧重点不同 ,加之各种类型植被的结构和功能不同 ,种群的生态学特性各异 ,因而不同的公式对不同的植被类型的使用范围应有所区别。目前 ,常用的生态位测度公式往往被通用于各种植…     

甘肃祁连山脉雪豹及其同域分布大型食肉动物时间生态位关系

<正>群落内多物种如何共存是群落生态学和生物多样性研究的核心内容之一。经典物种共存理论强调物种之间的生态位分化,侧重于物种对环境的需求,Hutchinson (1957)提出超体积生态位概念,认为物种适合度是由多个因素共同决定,即物种只有在满足其生态位需求的多维空间,     

群落构建的中性理论和生态位理论

物种共存和生物多样性维持一直是生态学研究的中心论题。基于物种生态位分化的群落构建理论已经发展了近一个世纪, 但我们对群落构建和生物多样性维持的机理仍然不清楚。近年来, 群落中性理论以其简约性和预测能力成为群落生态学研究的焦点, 但由于其“物种在生态功能上等价”的假设与大量研究结果相悖, 同时对自然群落结构的准确预测也只限于少数的生态系统, 因而饱受质疑。如今, 越来越多的生态学家认为群落构建的生态位理论与中性理论之争的最终归宿应该是二者的整合。 在本文中, 我们在简要回顾生态位理论和群落中性理论发展的基础上, 分析二者之间的主要分歧和互补性, 试图梳理二者整合的途径。我们认为, 尽管中性理论的发展极大地丰富了群落构建理论, 但二者的整合尚处于初级阶段; 群落构建零模型假说、中性—生态位连续体假说、随机生态位假说等都不失为有价值的尝试, 今后需要在其他类型的生态系统中进行实验验证, 以更好地理解确定性过程和随机过程在决定群落构建和生物多样性维持中的作用。     

群落构建研究的新进展:进化和生态相结合的群落谱系结构研究

群落如何构建足群落生态学中的重要问题.群落谱系结构研究将物种间的亲缘进化关系运用到群落生态学研究中,利用物种的系统发育状况推测历史因素对现有群落的影响,为推断影响群落组成的生态学机制提供了有效方法.群落谱系结构的研究方法是首先建立可代表群落物种库的超级系统进化树,然后计算群落内物种间的谱系距离,最后通过统计方法检测其与随机模型下的谱系距离是否有显著差异来获得谱系结构(如谱系聚集、谱系发散),从而揭示群落构建中的关键生态过程(如生境过滤、竞争作用).群落谱系结构与空间尺度、分类群尺度、时间尺度等不同研究尺度有关.在小的空间尺度下,随着分类群尺度降低、树木年龄级增大,群落谱系结构从聚集逐渐转为发散;而随群落空间尺度的增大,谱系趋向于聚集.谱系结构受到环境因素影响,因此分析集合群落下的谱系可以揭示区域生态过程的影响.另外,群落谱系结构研究还有助于探讨中性理论、密度制约假说等生态学理论,并预测干扰作用下的群落演化趋势.在利用谱系结构深入探讨群落构建成因时,需要基于生态特征和环境变量共同分析,同时考虑小尺度局域过程(群落的微环境或群落内种间相互作用等)和大尺度区域过程(地史过程和物种形成等),并可结合生态控制实验,以确认群落构建的关键因素.在研究方法和手段上,今后需要注重通过选择合适的基因片段建立系统树,然后通过生态特征来加以校正,以更准确地反映物种间的亲缘距离.另外,获得谱系树后还需要寻找更加合理的统计模型和指数,增加统计分析和解决问题的能力.     

群落内物种多样性发生与维持的一个假说

本文根据作者对竞争排除法则的研究而提出了一个新的群落多样性假说。按照作者的观点,占用相同生态位的物种可以稳定共存;这样,群落内物种多样性将受到４个基本因子所控制。它们分别是：（Ⅰ）生态位的数量;（Ⅱ）区域物种库的大小;（Ⅲ）物种迁入速率,以及（Ⅳ）物种灭绝速率。该假说强调区域生物地理过程与局域生态过程共同决定了群落内种多样性的大小及分布模式。     

植物DNA条形码促进系统发育群落生态学发展

系统发育群落生态学是近年兴起的一个重要牛态学研究分支,它以群落生态学为基础并引入了系统发育的分析方法,全面动态地反映了群落中物种内和物种间的相互作用关系,揭示了群落格局形成的生态学过程,研究了生物多样性的形成及维持机制.巴拿马BCI(Barro Colorado Island)样地的成功例子说明,在固定样地进行长期的群落生态与系统发育研究切实可行且极具意义;DNA条形码的快速兴起对这一研究发挥着重要作用.本文先列举了群落生态与系统发育综合分析能解决的群落系统发育结构、群落生态位结构、生物地理学和性状进化等生态学问题;接着介绍了标准植物DNA条形码以及利用片段组合(rbcL+matK+trnH-psbA)进行快速物种识别和近缘种区分、精确群落系统发育关系的构建以及群落生态学研究;随后提出DNA条形码研究在类群水平上需注意两片段的条形码组合(matK+rbcL)在同属种鉴别能力上的不足,而在较大尺度群落水平上需对实验设计进行优化.DNA条形码将为探讨物种多样性及其维持机理、系统发育beta多样性以及群落水平上功能性状进化研究提供新的思路.     

草地群落物种多样性维持机制的研究Ⅱ物种实现的生态位

尽管为解释种类丰富的植物群落物种共存和多样性维持机制,生态学家位做了大量的努力并提出了许多假说和模型。但这一问题仍处在争议之中,需要更多的证据支持他们的观点或提出新的看法,使这一生物多样性难题不断地向前推进。以松赖平原物种丰富度较高的羊草－杂类草群落为对象,在土壤C、N、P、K和H2O等5个资源轴上,探讨了物种多样性与实现生态位的关系。结果表明：尽管物种生态位存在一定程度的分化,但多数物种的生态位是高度重叠的,物种生态位的分化在草地群落物种共存和多样性维持中,不是唯一的途径,认为应更加重视的物种在长期协同进化中所形成的生物学特性。     

草地群落物种多样性维持机制的研究（Ⅱ）：物种实现生态位

尽管为解释种类丰富的植物群落物种共存和多样性维持机制,生态学家们做了大量的努力并提出了许多假说和模型,但这一问题仍处在争议之中,需要更多的证据支持他们的观点或提出新的看法,使这一生物多样性难题不断地向前推进。以松嫩平原物种丰富度较高的羊草—杂类草群落为对象,在土壤C、N、P、K和H2O等5个资源轴上,探讨了物种多样性与实现生态位的关系。结果表明：尽管物种生态位存在一定程度的分化,但多数物种的生态位是高度重叠的,物种生态位的分化在草地群落物种共存和多样性维持中,不是唯一的途径,认为应更加重视物种在长期协同进化中所形成的生物学特性。     

西藏色季拉山川滇高山栎群落生态位特征

探索群落构建背后的包括生态位分化与重叠在内的过程机制对于预测环境变化背景下的群落动态和开展区域物种多样性保护至关重要。藏东南地区由于地理和交通条件限制, 森林群落受人为干扰相对较少, 是开展群落生态学理论研究的天然实验室。在样地调查的基础上, 以物种重要值作为资源状态指标, 应用Levins、Shannon-Wiener 生态位宽度指数和Horn 生态位重叠指数, 分析了色季拉山川滇高山栎群落49 个主要种生态位特征。结果表明: (1) 色季拉山川滇高山栎群落中, 川滇高山栎(Quercus aquifolioides)、小叶忍冬(Lonicera microphylla)、秦岭槲蕨(Drynariasinica)的生态位宽度分别在乔、灌、草本层中占有优势地位; (2) 群落各林层内部生态位重叠, 表现为草本层>灌木层>乔木层; (3) 群落各林层之间生态位重叠, 表现为灌草>乔灌>乔草。(4) 川滇高山栎作为先锋树种, 其群落在藏东南地区的水土保持与荒漠化防治作用突出, 群落内林层内和层间的不同植物对阳光、空间等资源的生态位重叠促进了物种的共存, 证明了高山地区强烈的环境过滤作用导致的生态位分化和对生境需求相似的物种间的生态位重叠是促进藏东南川滇高山栎群落生物多样性共存的重要机理。     

群落生态学的中性理论

生物多样性的分布格局和维持机制一直是群落生态学研究的核心问题,其中的关键是物种的共存机制。长期以来,生态位分化的思想在这一研究领域占据着主导地位。然而这一理论在解释热带雨林很高的物种多样性时遇到了困难。而以Hubbell为代表提出的群落中性漂变理论则假定在同一营养级物种构成的群落中不同物种的不同个体在生态学上可看成是完全等同的;物种的多度随机游走,群落中的物种数取决于物种灭绝和物种迁入/新物种形成之间的动态平衡。在这一假定之下,该理论预言了两种统计分布。一种是集合群落在点突变形成新物种的模式下其各个物种相对多度服从对数级数分布,而受扩散限制的局域群落以及按照随机分裂为新物种模式形成的集合群落则服从零和多项式分布。与生态位理论相反,中性理论不以种间生态位差异作为研究群落结构的出发点,而是以物种间在个体水平上的对等性作为前提。该理论第一次从基本生态学过程(出生、死亡、迁移、物种分化)出发,给出了群落物种多度分布的机理性解释,同时其预测的物种多度分布格局在实际群落中也得到了广泛的印证。因此,中性理论自诞生以来便在生态学界引发了极大的反响,也包括一些反对的声音。该文重点综述了关于中性理论的假设、预测和物种形成模式等方面的最新研究进展,包括中性理论本身的发展、关于中性理论的假设和预测的合理性检验以及在集合群落尺度上物种分化模式的讨论;并指出未来发展方向可能是在生态位理论和中性理论之间架起一座桥梁,同时发展包含随机性的群落生态位模型,以及允许种间差异的近中性模型。     

The roles of harsh and fluctuating conditions in the dynamics of ecological communities

Harsh conditions (e.g., mortality and stress) reduce population growth rates directly; secondarily, they may reduce the intensity of interactions between organisms. Near-exclusive focus on the secondary effect of these forms of harshness has led ecologists to believe that they reduce the importance of ecological interactions, such as competition, and favor coexistence of even ecologically very similar species. By examining both the costs and the benefits, we show that harshness alone does not lessen the importance of species interactions or limit their role in community structure. Species coexistence requires niche differences, and harshness does not in itself make coexistence more likely. Fluctuations in environmental conditions (e.g., disturbance, seasonal change, and weather variation) also have been regarded as decreasing species interactions and favoring coexistence, but we argue that coexistence can only be favored when fluctuations create spatial or temporal niche opportunities. We argue that important diversity-promoting roles for harsh and fluctuating conditions depend on deviations from the assumptions of additive effects and linear dependencies most commonly found in ecological models. Such considerations imply strong roles for species interactions in the diversity of a community.     

Trade-offs in community ecology: linking spatial scales and species coexistence

Trade‐offs in species performances of different ecological functions is one of the most common explanations for coexistence in communities. Despite the potential for species coexistence occurring at local or regional spatial scales, trade‐offs are typically approached at a single scale. In recent years, ecologists have increasingly provided evidence for the importance of community processes at both local and regional spatial scales. This review summarizes the theoretical predictions for the traits associated with trade‐offs under different conditions and at different spatial scales. We provide a spatial framework for understanding trade‐offs, coexistence and the supportive empirical evidence. Predictions are presented that link the patterns of diversity observed to the patterns of trade‐offs that lead to coexistence at different spatial scales. Recent evidence for the evolution of trade‐offs under different conditions is provided which explores both laboratory microcosm studies and phylogenetic tests. Examining trade‐offs within a spatial framework can provide a strong approach to understanding community structure and dynamics, while explaining patterns of species diversity.     

Emergent neutrality drives phytoplankton species coexistence

The mechanisms that drive species coexistence and community dynamics have long puzzled ecologists. Here, we explain species coexistence, size structure and diversity patterns in a phytoplankton community using a combination of four fundamental factors: organism traits, size-based constraints, hydrology and species competition. Using a 'microscopic' Lotka-Volterra competition (MLVC) model (i.e. with explicit recipes to compute its parameters), we provide a mechanistic explanation of species coexistence along a niche axis (i.e. organismic volume). We based our model on empirically measured quantities, minimal ecological assumptions and stochastic processes. In nature, we found aggregated patterns of species biovolume (i.e. clumps) along the volume axis and a peak in species richness. Both patterns were reproduced by the MLVC model. Observed clumps corresponded to niche zones (volumes) where species fitness was highest, or where fitness was equal among competing species. The latter implies the action of equalizing processes, which would suggest emergent neutrality as a plausible mechanism to explain community patterns.     

Trait plasticity in species interactions: a driving force of community dynamics

Evolutionary community ecology is an emerging field of study that includes evolutionary principles such as individual trait variation and plasticity of traits to provide a more mechanistic insight as to how species diversity is maintained and community processes are shaped across time and space. In this review we explore phenotypic plasticity in functional traits and its consequences at the community level. We argue that resource requirement and resource uptake are plastic traits that can alter fundamental and realised niches of species in the community if environmental conditions change. We conceptually add to niche models by including phenotypic plasticity in traits involved in resource allocation under stress. Two qualitative predictions that we derive are: (1) plasticity in resource requirement induced by availability of resources enlarges the fundamental niche of species and causes a reduction of vacant niches for other species and (2) plasticity in the proportional resource uptake results in expansion of the realized niche, causing a reduction in the possibility for coexistence with other species. We illustrate these predictions with data on the competitive impact of invasive species. Furthermore, we review the quickly increasing number of empirical studies on evolutionary community ecology and demonstrate the impact of phenotypic plasticity on community composition. Among others, we give examples that show that differences in the level of phenotypic plasticity can disrupt species interactions when environmental conditions change, due to effects on realized niches. Finally, we indicate several promising directions for future phenotypic plasticity research in a community context. We need an integrative, trait-based approach that has its roots in community and evolutionary ecology in order to face fast changing environmental conditions such as global warming and urbanization that pose ecological as well as evolutionary challenges.     

The tri‐trophic niche concept and adaptive radiation of phytophagous insects

A conceptual divide exists between ecological and evolutionary approaches to understanding adaptive radiation, although the phenomenon is inherently both ecological and evolutionary. This divide is evident in studies of phytophagous insects, a highly diverse group that has been frequently investigated with the implicit or explicit goal of understanding its diversity. Whereas ecological studies of phytophagous insects increasingly recognize the importance of tri‐trophic interactions as determinants of niche dimensions such as host‐plant associations, evolutionary studies typically neglect the third trophic level. Here we attempt to reconcile ecological and evolutionary approaches through the concept of the ecological niche. We specifically present a tri‐trophic niche concept as a foil to the traditional bi‐trophic niche concept for phytophagous insects. We argue that these niche concepts have different implications for understanding herbivore community structure, population divergence, and evolutionary diversification. To this end, we offer contrasting empirical predictions of bi‐ and tri‐trophic niche concepts for patterns of community structure, the process of population divergence, and patterns of evolutionary diversification of phytophagous insects.     

Phylogenetic niche conservatism, phylogenetic signal and the relationship between phylogenetic relatedness and ecological similarity among species

Ecologists are increasingly adopting an evolutionary perspective, and in recent years, the idea that closely related species are ecologically similar has become widespread. In this regard, phylogenetic signal must be distinguished from phylogenetic niche conservatism. Phylogenetic niche conservatism results when closely related species are more ecologically similar that would be expected based on their phylogenetic relationships; its occurrence suggests that some process is constraining divergence among closely related species. In contrast, phylogenetic signal refers to the situation in which ecological similarity between species is related to phylogenetic relatedness; this is the expected outcome of Brownian motion divergence and thus is necessary, but not sufficient, evidence for the existence of phylogenetic niche conservatism. Although many workers consider phylogenetic niche conservatism to be common, a review of case studies indicates that ecological and phylogenetic similarities often are not related. Consequently, ecologists should not assume that phylogenetic niche conservatism exists, but rather should empirically examine the extent to which it occurs.     

植物群落构建机制研究进展

群落构建研究对于解释物种共存和物种多样性的维持是至关重要的,因此一直是生态学研究的中心论题。尽管近年来关于生态位和中性理论的验证研究已经取得了显著的成果,但对于局域群落构建机制的认识仍存在很大争议。随着统计和理论上的进步使得用功能性状和群落谱系结构解释群落构建机制变为可能,主要是通过验证共存物种的性状和谱系距离分布模式来实现。然而,谱系和功能性状不能相互替代,多种生物和非生物因子同时控制着群落构建,基于中性理论的扩散限制、基于生态位的环境过滤和竞争排斥等多个过程可能同时影响着群落的构建。所以,综合考虑多种方法和影响因素探讨植物群落的构建机制,对于预测和解释植被对干扰的响应,理解生物多样性维持机制有重要意义。试图在简要回顾群落构建理论及研究方法发展的基础上,梳理其最新研究进展,并探讨整合功能性状及群落谱系结构的研究方法,解释群落构建和物种多样性维持机制的可能途径。在结合功能性状和谱系结构研究群落构建时,除了考虑空间尺度、环境因子、植被类型外,还应该关注时间尺度、选择性状的种类和数量、性状的种内变异、以及人为干扰等因素对群落构建的影响。     

Relationships between ecological interaction modifications and diffuse coevolution: similarities, differences, and causal links

A major empirical approach in community ecology is to describe the dynamics of a community by examining small subsets of species. Unfortunately, interaction modifications, which cause pair-wise interaction coefficients to depend on the presence or absence of additional species, can make it difficult to predict the overall dynamics of species within a community from experiments with pairs of species. In a similar fashion, one of the major approaches in evolutionary ecology has been to describe the likely evolutionary dynamics of a single species by focusing on the selection imposed by a limited number of other species within the community. However, recent work on diffuse coevolution indicates that selection pressures due to one species can change in the presence of other species. The magnitude of the difficulty that interaction modifications and diffuse coevolution present for predicting ecological and evolutionary dynamics is an unresolved question. Here we outline the similarities and differences between the two topics, discuss experimental and statistical approaches to studying them, and make predictions about when ecological interaction modifications are likely to cause diffuse coevolution. Since the currencies for interaction modifications are usually fitness components such as growth, fecundity, or survival, is it likely that these will translate into corresponding differences in the relative fitness of individuals or genotypes, and thus in general these two phenomena will occur together. We argue that community ecologists and evolutionary ecologists will both benefit from experiments that test for the effects of interaction modifications, and that studies of the mechanisms driving interaction modifications and diffuse coevolution (e.g., changes in behavior, nonlinear effects on shared resources, genetic covariances) will aid our progress in understanding the ecological and evolutionary dynamics of communities.     

Phylogenetic and morphological relationships between nonvolant small mammals reveal assembly processes at different spatial scales

The relative roles of historical processes, environmental filtering, and ecological interactions in the organization of species assemblages vary depending on the spatial scale. We evaluated the phylogenetic and morphological relationships between species and individuals (i.e., inter‐ and intraspecific variability) of Neotropical nonvolant small mammals coexisting in grassland‐forest ecotones, in landscapes and in regions, that is, three different scales. We used a phylogenetic tree to infer evolutionary relationships, and morphological traits as indicators of performance and niche similarities between species and individuals. Subsequently, we applied phylogenetic and morphologic indexes of diversity and distance between species to evaluate small mammal assemblage structures on the three scales. The results indicated a repulsion pattern near forest edges, showing that phylogenetically similar species coexisted less often than expected by chance. The strategies for niche differentiation might explain the phylogenetic repulsion observed at the edge. Phylogenetic and morphological clustering in the grassland and at the forest interior indicated the coexistence of closely related and ecologically similar species and individuals. Coexistence patterns were similar whether species‐trait values or individual values were used. At the landscape and regional scales, assemblages showed a predominant pattern of phylogenetic and morphological clustering. Environmental filters influenced the coexistence patterns at three scales, showing the importance of phylogenetically conserved ecological tolerances in enabling taxa co‐occurrence. Evidence of phylogenetic repulsion in one region indicated that other processes beyond environmental filtering are important for community assembly at broad scales. Finally, ecological interactions and environmental filtering seemed important at the local scale, while environmental filtering and historical colonization seemed important for community assembly at broader scales.     

Potential mechanisms of coexistence in closely related forbs

The stable coexistence of very similar species has perplexed ecologists for decades and has been central to the development of coexistence theory. According to modern coexistence theory, species can coexist stably (i.e. persist indefinitely with no long‐term density trends) as long as species' niche differences exceed competitive ability differences, even if these differences are very small. Recent studies have directly quantified niche and competitive ability differences in experimental communities at small spatial scales, but provide limited information about stable coexistence across spatial scales in heterogeneous natural communities. In this study, we use experimental and observational approaches to explore evidence for niche and competitive ability differences between two closely related, ecologically similar and widely coexisting annual forbs: Trachymene cyanopetala and T. ornata. We experimentally tested for stabilizing niche differences and competitive ability differences between these species by manipulating species' frequencies, under both well‐watered and water‐stressed conditions. We considered these experimental results in light of extensive field observations to explore evidence of niche segregation at a range of spatial scales. We found little evidence of intra‐specific stabilization or competitive ability differences in laboratory experiments while observational studies suggested niche segregation across pollinator assemblages and small‐scale microclimate heterogeneity. Though we did not quantify long‐term stabilization of coexisting populations of these species, results are consistent with expectations for stable coexistence of similar species via a spatial storage effect allowing niche differences to overcome even small (to absent) competitive ability differences.