物种多样性变化格局与时空尺度

物种多样性时空格局作为生物多样性研究的重要内容, 是针对物种的数量变化和物种的生物学多样性程度,在不同尺度范围内探讨物种多样性的时空格局及其变化规律。本文首先讨论物种多样性的空间格局,特别是不同尺度上的“物种－面积”模式,分析了纬度梯度、栖息地因素对物种多样性格局形成的作用。在时间尺度上,本文分析了物种多样性在不同时间尺度的变化格局：从生物长期进化的地史时间看,物种多样性稳定增长受到周期性大绝灭事件中断。最新研究表明,物种多样性时间格局决定于最近一次大绝灭后的初始状态。在较短的时间范围内,如生态群落演替、季节周期等,物种多样性变化呈现特殊的模式。此外,也发现寄主上寄生物种的多样性有随着时间而增加的趋势。     

生物多样性事业需要科学、可操作的物种概念

物种概念(species concept)是生物学家们持续关注的中心问题。物种概念决定物种划分, 而物种划分的合理性关系到生物多样性的研究、保护和可持续利用。本文把现有较流行的物种概念分为6类, 并对它们予以述评后指出: 虽然生物学物种概念、遗传学物种概念、进化物种概念、系统发生物种概念等从不同方面认识了物种的客观真实性和物种的本质, 但在实践中都难以操作。绝大多数物种是由分类学家划分的, 但目前所有的分类学物种概念都包含有不同程度的主观因素, 从而造成物种划分的人为性, 对生物多样性研究造成负面影响。因此, 生物多样性事业需要科学、可操作的物种概念。本文在吸收了生物学物种概念、遗传学物种概念、进化物种概念以及系统发生物种概念等的长处, 也分析了它们的不足和问题的基础上提出一个新的物种概念, 即形态-生物学物种概念。最后, 以芍药属(Paeonia)几个物种的处理为例, 说明这一新的物种概念是可操作的, 划分的物种在形态上区别分明, 易于鉴别。更重要的是, 其结果得到基于25或26个单拷贝或寡拷贝核基因DNA序列所作的系统发生分析的强有力支持。各个物种在系统发生树上形成单系和独立的谱系, 表明其间各自形成独立的基因库, 没有基因交换, 它们独立进化, 有各自的生态位和独立的分布区。因此, 利用这一新的物种概念能够达到预期目标。     

菌物分类学研究中常见的物种概念

物种是生物多样性与分类学研究的基本单元, 物种识别是生物学研究的基本问题之一。物种的划分一直以来都没有一个明确统一的标准, 这使得分类学多少带有主观的色彩, 并经常被看作艺术而不完全是科学的研究。本文简要概述了菌物分类学研究中常见的3个物种概念, 即形态学种、生物学种和系统发育学种的背景和应用现状, 并通过实例讨论了这3个物种概念的特点及应用中存在的问题, 特别是各个物种概念之间的交错, 以期为菌物分类学研究和物种概念探讨提供参考。     

物种濒危的机制与保护对策

本文以生物多样性和保护生物学的若干基础理论为依据,分析了物种濒危的现状,论述了濒危物种的概念和特征、易于濒危和灭绝的类型,阐明了物种濒危的机制,并由此提出了濒危物种种质资源的保护对策。     

物种多样性研究的进展

物种多样性是生物多样性研究的一个重要层次。为适应资源与环境可发展的要求,物种多样性的研究受到了广泛的重视。文章阐述了物种多样性的概念、研究方法等,分析了当今物种多样性研究的几个热点问题。     

物种的全球性丧失能得到制止吗？

物种的全球性丧失能得到制止吗？１物种绝灭危机问题是否该引起人们的重视？地球上的物种正以惊人的速度绝灭！１９８６年由美国国家科学院和史密森研究院共同发起的“生物多样性全国论坛”,论证了人类对自然生境破坏致使物种绝灭的危机正日益严重,甚至比得上约在６千５...     

植物群落物种多样性研究综述

物种多样性是生物多样性在物种水平上的表现形式 ,包括两方面的含义 ,一是指一定区域内物种的总和 ,主要从分类学、系统学和生物地理学角度对一个区域内物种的状况进行研究 ,也称区域物种多样性 ;二是指生态学方面物种分布的均匀程度 ,常常是从群落组织水平上进行研究 ,也称为生态多样性或群落多样性[1] 。本文所涉及物种多样性即为群落组织水平上的物种多样性。植物群落物种多样性的研究是其它多样性 (遗传多样性、生态系统多样性等 )的基础 ,有大量的研究成果相继报道 ,也有一些综述对植物群落物种多样性某一领域的研究进行总结。Ｍａｇｕ…     

基于层次分析法的旗舰物种遴选方法

旗舰物种是保护生物学中一个广泛应用的概念, 用于获得公众对保护行为的支持, 在生物多样性保护领域发挥着重要作用。但目前尚未见量化分析遴选和确定旗舰物种的公开报道, 致使学术界对旗舰物种的定义和使用相对主观, 缺乏科学依据。本文对旗舰物种的定义进行了梳理, 探讨了旗舰物种的内涵, 确定了旗舰物种的属性, 制定了遴选标准和量化遴选方法, 以便读者更好地理解和运用这一概念。目前旗舰物种的定义仍然局限在其社会学属性, 作者建议今后应加强其生物生态学属性。作者认为除了公众的关注度和认可度之外, 旗舰物种还应具备以下3个生态生物学和社会文化特征: (1)物种在当地的濒危程度及生存现状; (2)物种在当地生态系统中的重要性; (3)物种在当地民众中的影响力和认可度。基于此, 本文确定了表征旗舰物种社会文化属性和生态生物学属性的8个要素, 基于层次分析法提出了一种量化的旗舰物种遴选方法。该方法综合上述8个要素进行评判和计算分值, 以塔吉克斯坦境内分布的14种大型濒危哺乳动物的生态生物学属性和社会文化影响力为基础, 描述基于层次分析法遴选塔吉克斯坦哺乳类旗舰物种的方法和过程, 最终依据每个备选物种所得分值高低排序, 得到塔吉克斯坦旗舰物种的优先备选物种。本文首次提出了一种量化遴选旗舰物种的方法, 期望今后可基于该方法开发更加合理的旗舰物种遴选模型和算法。     

物种多样性与植物群落的维持机制

物种多样性的形成与维持是生物多样性研究中的核心问题之一,形成了许多假说。剖析了群落物种多样性维持具有增加、减少和稳定共存三方面内容,着重阐明物种稳定共存的内因是物种的生物学与生态学特性差异,外因是生境具有小尺度的差异;群落生境异质性是其物种多样性维持的基础,并影响着群落的组织过程;群落的斑块镶嵌结构源于林隙形成的生境异质性,导致了物种多样性;群落斑块镶嵌结构是群落的基本属性,使群落的结构和功能得以长期维持等论点。最后,还以鼎湖山季风常绿阔叶林为例,对群落斑块镶嵌结构的形成及其对物种多样性维持和群落生产力构成与维持等方面的意义予以说明。     

塔里木河下游植物群落的物种数量变化与生态系统动态研究

物种多样性是指物种及其集合体的生物学多样性。物种多样性研究的核心是物种的数量变化和物种的生物学多样性程度。本文根据野外采集的数据 ,运用Simpson指数、McIn tosh指数以及Margalef指数 ,对塔里木河下游英苏、阿布达勒、喀尔达依、阿拉干、依干不及麻等地区的物种多样性指数分别进行了计算 ,并根据计算得到的生物多样性指数探讨了干旱区退化生态系统的物种多样性以及在干旱区物种多样性与生态系统稳定性之间的关系。结果表明 ,塔里木河下游从英苏至依干不及麻 ,Simpson多样性指数的变化范围为 0 82～ 0 2 6 ,McIn tosh均匀度指数的变化范围为 0 6 0～ 0 1 8,Margalef丰富度指数的变化范围为 1 4 7～ 0 38,物种数的变化范围是 9～ 2。分析表明塔里木河下游生态系统退化十分严重 ,并据此讨论了塔里木河下游生态系统退化的特征、演替动态及稳定性     

Heterogeneity, speciation/extinction history and climate: explaining regional plant diversity patterns in the Cape Floristic Region

This paper investigates the role of heterogeneity and speciation/extinction history in explaining variation in regional scale (c. 0.1–3000 km²) plant diversity in the Cape Floristic Region of south‐western Africa, a species‐ and endemic‐rich biogeographical region. We used species‐area analysis and analysis of covariance to investigate geographical (east vs. west) and topographic (lowland vs. montane) patterns of diversity. We used community diversity as a surrogate for biological heterogeneity, and the diversity of naturally rare species in quarter degree squares as an indicator of differences in speciation/extinction histories across the study region. We then used standard statistical methods to analyse geographical and topographic patterns of these two measures. There was a clear geographical diversity pattern (richer in the west), while a topographic pattern (richer in mountains) was evident only in the west. The geographical boundary coincided with a transition from the reliable winter‐rainfall zone (west) to the less reliable non‐seasonal rainfall zone (east). Community diversity, or biological heterogeneity, showed no significant variation in relation to geography and topography. Diversity patterns of rare species mirrored the diversity pattern for all species. We hypothesize that regional diversity patterns are the product of different speciation and extinction histories, leading to different steady‐state diversities. Greater Pleistocene climatic stability in the west would have resulted in higher rates of speciation and lower rates of extinction than in the east, where for the most, Pleistocene climates would not have favoured Cape lineages. A more parsimonious hypothesis is that the more predictable seasonal rainfall of the west would have favoured non‐sprouting plants and that this, in turn, resulted in higher speciation and lower extinction rates. Both hypotheses are consistent with the higher incidence of rare species in the west, and higher levels of beta and gamma diversity there, associated with the turnover of species along environmental and geographical gradients, respectively. These rare species do not contribute to community patterns; hence, biological heterogeneity is uniform across the region. The weak topography pattern of diversity in the west arises from higher speciation rates and lower extinction rates in the topographically complex mountains, rather than from the influence of environmental heterogeneity on diversity.     

Large-scale phylogenetic analyses reveal the causes of high tropical amphibian diversity

Many groups show higher species richness in tropical regions but the underlying causes remain unclear. Despite many competing hypotheses to explain latitudinal diversity gradients, only three processes can directly change species richness across regions: speciation, extinction and dispersal. These processes can be addressed most powerfully using large-scale phylogenetic approaches, but most previous studies have focused on small groups and recent time scales, or did not separate speciation and extinction rates. We investigate the origins of high tropical diversity in amphibians, applying new phylogenetic comparative methods to a tree of 2871 species. Our results show that high tropical diversity is explained by higher speciation in the tropics, higher extinction in temperate regions and limited dispersal out of the tropics compared with colonization of the tropics from temperate regions. These patterns are strongly associated with climate-related variables such as temperature, precipitation and ecosystem energy. Results from models of diversity dependence in speciation rate suggest that temperate clades may have lower carrying capacities and may be more saturated (closer to carrying capacity) than tropical clades. Furthermore, we estimate strikingly low tropical extinction rates over geological time scales, in stark contrast to the dramatic losses of diversity occurring in tropical regions presently.     

Is population subdivision different from speciation? From phylogeography to species delimitation

Species‐level diversity and the underlying mechanisms that lead to the formation of new species, that is, speciation, have often been confounded with intraspecific diversity and population subdivision. The delineation between intraspecific and interspecific divergence processes has received much less attention than species delimitation. The ramifications of confounding speciation and population subdivision are that the term speciation has been used to describe many different biological divergence processes, rendering the results, or inferences, between studies incomparable. Phylogeographic studies have advanced our understanding of how spatial variation in the pattern of biodiversity can begin, become structured, and persist through time. Studies of species delimitation have further provided statistical and model‐based approaches to determine the phylogeographic entities that merit species status. However, without a proper understanding and delineation between the processes that generate and maintain intraspecific and interspecific diversity in a study system, the delimitation of species may still not be biologically and evolutionarily relevant. I argue that variation in the continuity of the divergence process among biological systems could be a key factor leading to the enduring contention in delineating divergence patterns, or species delimitation, meriting future comparative studies to help us better understand the nature of biological species.     

How humans drive speciation as well as extinction

A central topic for conservation science is evaluating how human activities influence global species diversity. Humanity exacerbates extinction rates. But by what mechanisms does humanity drive the emergence of new species? We review human-mediated speciation, compare speciation and known extinctions, and discuss the challenges of using net species diversity as a conservation objective. Humans drive rapid evolution through relocation, domestication, hunting and novel ecosystem creation—and emerging technologies could eventually provide additional mechanisms. The number of species relocated, domesticated and hunted during the Holocene is of comparable magnitude to the number of observed extinctions. While instances of human-mediated speciation are known, the overall effect these mechanisms have upon speciation rates has not yet been quantified. We also explore the importance of anthropogenic influence upon divergence in microorganisms. Even if human activities resulted in no net loss of species diversity by balancing speciation and extinction rates, this would probably be deemed unacceptable. We discuss why, based upon ‘no net loss’ conservation literature—considering phylogenetic diversity and other metrics, risk aversion, taboo trade-offs and spatial heterogeneity. We conclude that evaluating speciation alongside extinction could result in more nuanced understanding of biosphere trends, clarifying what it is we actually value about biodiversity.     

Santa Rosalia revisited: Why are there so many species of bacteria?

The diversity of bacteria in the world is very poorly known. Usually less than one percent of the bacteria from natural communities can be grown in the laboratory. This has caused us to underestimate bacterial diversity and biased our view of bacterial communities. The tools are now available to estimate the number of bacterial species in a community and to estimate the difference between communities. Using what data are available, I have estimated that thirty grams of forest soil contains over half a million species. The species difference between related communities suggests that the number of species of bacteria may be more than a thousand million. I suppose that the explanation for such a large number of bacterial species is simply that speciation in bacteria is easy and extinction difficult, giving a rate of speciation higher than the rate of extinction, leading to an ever increasing number of species over time. The idea that speciation is easy is justified from the results of recent experimental work in bacterial evolution.     

为什么在物种概念上难以达成共识?

生物学家通常认为物种是生命多样性的基本单位。然而, 尽管近一个世纪以来生物学家们不断地讨论物种概念问题, 但到目前为止仍然难以形成共识。大多数生物学家关注如何定义物种主要是因为它有非常重要的实践意义, 所以, 不同学者提出的物种概念在很大程度上是基于实践应用上的可操作性, 并且其视角难免受其专业见地以及对形成新物种的进化过程的认识所影响。物种代表了进化过程的一个阶段, 而且不同的“物种”可能处于物种形成这个进化过程的不同阶段。鉴于“定义”实际上是一种类似协议的约定或界定, 任何定义都是一种带有局限性的概括, 因此我们可能很难建立一个与分类实践中千变万化的情况都能完全匹配协调的物种定义。已经提出来的那些物种概念或定义都有其合理性, 但是也没有一个是完美无缺的。认识到这一点很重要, 否则就可能会因为固执地坚持某一特定的物种概念而在物种界定和进化研究中自觉或不自觉地引入错误甚至制造混乱。     

Is regional species diversity bounded or unbounded?

Two conflicting hypotheses have been proposed to explain large‐scale species diversity patterns and dynamics. The unbounded hypothesis proposes that regional diversity depends only on time and diversification rate and increases without limit. The bounded hypothesis proposes that ecological constraints place upper limits on regional diversity and that diversity is usually close to its limit. Recent evidence from the fossil record, phylogenetic analysis, biogeography, and phenotypic disparity during lineage diversification suggests that diversity is constrained by ecological processes but that it is rarely asymptotic. Niche space is often unfilled or can be more finely subdivided and still permit coexistence, and new niche space is often created before ecological limits are reached. Damped increases in diversity over time are the prevalent pattern, suggesting the need for a new ‘damped increase hypothesis'. The damped increase hypothesis predicts that diversity generally increases through time but that its rate of increase is often slowed by ecological constraints. However, slowing due to niche limitation must be distinguished from other possible mechanisms creating similar patterns. These include sampling artifacts, the inability to detect extinctions or declines in clade diversity with some methods, the distorting effects of correlated speciation‐extinction dynamics, the likelihood that opportunities for allopatric speciation will vary in space and time, and the role of undetected natural enemies in reducing host ranges and thus slowing speciation rates. The taxonomic scope of regional diversity studies must be broadened to include all ecologically similar species so that ecological constraints may be accurately inferred. The damped increase hypothesis suggests that information on evolutionary processes such as time‐for‐speciation and intrinsic diversification rates as well as ecological factors will be required to explain why regional diversity varies among times, places and taxa.     

History and diversity: explorations at the intersection of ecology and evolution

Phylogenetic analysis provides an important tool for assessing the influence of historical and evolutionary processes on the structure of contemporary ecological systems. Patterns of diversity, for example, represent the regional buildup of species through immigration and diversification, their loss through extinction, and the sorting of species ecologically within the region. Colonization-extinction dynamics on islands can be inferred from lineage accumulation through time. Lineage branching within clades can be used to estimate rates of speciation and extinction. However, simulations of these processes show potential ambiguities in the interpretation of data. Clade size is unrelated to age in many studies, suggesting that speciation and extinction might be in long-term equilibrium and raising questions about unobserved past diversity. Among passerine birds and other groups, the size of similar-aged clades is positively related to the size of the region within which they have diversified, and it is greater in tropical than in temperate regions. There is no consensus on the causes of these patterns. Finally, the ecological interactions between populations within regions brings the timescale of species sorting and species production close to each other and emphasizes the important interaction of ecological and evolutionary processes in shaping ecological systems.     

The cladistic solution to the species problem

The correct explanation of why species, in evolutionary theory, are individuals and not classes is the cladistic species concept. The cladistic species concept defines species as the group of organisms between two speciation events, or between one speciation event and one extinction event, or (for living species) that are descended from a speciation event. It is a theoretical concept, and therefore has the virtue of distinguishing clearly the theoretical nature of species from the practical criteria by which species may be recognized at any one time. Ecological or biological (reproductive) criteria may help in the practical recognition of species. Ecological and biological species concepts are also needed to explain why cladistic species exist as distinct lineages, and to explain what exactly takes place during a speciation event. The ecological and biological species concepts work only as sub-theories of the cladistic species concept and if taken by themselves independently of cladism they are liable to blunder. The biological species concept neither provides a better explanation of species indivudualism than the ecological species concept, nor, taken by itself, can the biological species concept even be reconciled with species individualism. Taking the individuality of species seriously requires subordinating the biological, to the cladistic, species concept.