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。     

狭域物种广西秋海棠传粉生物学研究

为了检验广西秋海棠（Begonia guangxiensis）的交配系统和该物种是否依赖原生境的特殊传粉昆虫进行传粉及其能否在人工生境中实现有性繁殖,展开了广西秋海棠的单花花期观察、花部特征测定、授粉、访花者观察及种子萌发测定等试验。结果显示：广西秋海棠具有较长的单花花期,不同生境下的花冠大小表现出一定差异;自交和异交之间座果率及种子萌发率和两生境之间的自然对照座果均无显著差异;访花者包括蜂类（中华蜜蜂（Apis cerana）与萃熊蜂（Bombus eximius））和食蚜蝇（黑带食蚜蝇（Episyrphus balteatus）与刺腿食蚜蝇（Ischiodon scutellaris））,不同生境和不同年份访花者组成有差异。以上结果一致表明,自交亲和的广西秋海棠依赖传粉者进行有性繁殖,但并不依赖某种特殊类型传粉者,而是具有较泛化的传粉系统,因此在非自然生境中也能成功进行有性繁殖。     

景观物种的理论与实践

结合保护生物学和景观生态学的理论发展起来的景观物种的理论,为更有效地保护物种及其生境开拓了新的视角。本文就景观物种的概念及其相关理论作一初步的介绍,并概括了对其实施保护的具体步骤。     

基于多源遥感数据的植物物种分类与识别: 研究进展与展望

物种分类与识别是生物多样性监测的基础, 明确物种的类别及其分布是解决几乎所有生态学问题的前提。为深入了解基于多源遥感数据的植物物种分类与识别相关研究的发展现状和存在的问题, 本文对2000年以来该领域的研究进行了总结分析, 发现: 当前大多数研究集中在欧洲和北美地区的温带或北方森林以及南非的热带稀树草原; 使用最多的遥感数据是机载高光谱数据, 而激光雷达作为补充数据, 通过单木分割及提供单木的三维垂直结构信息, 显著提高了分类精度; 支持向量机和随机森林作为应用最广的非参数分类算法, 平均分类精度达80%; 随着计算机技术及机器学习领域的不断成熟, 人工神经网络在物种识别领域得以迅速发展。基于此, 本文对目前基于遥感数据的植物物种分类与识别中在分类对象复杂性、多源遥感数据整合、植物物候与纹理特征整合和分类算法技术等方面面临的挑战进行了总结, 并建议通过整合多时相监测数据、高光谱和激光雷达数据、短波红外等特定波谱信息、采用深度学习等方法来提高分类精度。     

物种受威胁状况评估:研究进展与中国的案例

评估物种濒危等级,确定物种保护优先序,是生物多样性保护的一项重要工作。通过不断的修订,IUCN红色名录濒危等级标准已经趋于完善。但是,目前人们还在探索在无法获得物种的种群数量、生境、生活史数据时,如何寻找替代指标评估物种濒危等级。我们综述了国内外物种濒危状况研究的进展,提出了结合物种分布区、生活史、生态功能、人为干扰和特殊利用价值的评估物种受威胁状况的方法,并以此方法评估了中国陆生脊椎动物的生存状况。结果表明,列入灭绝级的物种有5个,功能性灭绝级的物种有30个,濒危级的物种有343个,受胁级的物种有459个,关注级的物种有439个,无危级的物种有1,032个。     

日本七鳃鳗物种特异性microRNAs及其前体的识别与验证

MicroRNAs(miRNAs)对参与多种生物代谢过程的基因在转录及转录后水平进行负调控。近年来,随着深度测序及芯片技术的应用,有关miRNA的发现和功能分析在植物和动物中得到广泛研究。文章利用第二代测序技术对日本七鳃鳗(Lampetra japonica)白细胞的小RNA进行了高通量测序,共得到5 207 787条小RNA序列,其中4 739 346条序列可以拼接为10 989种mi RNA变体。基于序列相似性分析,发现这10 989个变体序列与306个已知的保守mi RNA家族成员序列相匹配;其中,6个保守miRNA家族成员呈极高丰度表达,表明mi RNA在物种间具有保守性。70个未注释序列被预测为新的miRNA。通过miRNA微阵列技术鉴定与验证了34个新预测的mi RNA在免疫处理的日本七鳃鳗白细胞中表达,其中16个mi RNA前体的最低折叠自由能系数大于0.85,说明日本七鳃鳗存在特异性miRNA。这些物种特异性miRNAs的存在可能在日本七鳃鳗的白细胞生长、发育和对疾病的反应中发挥重要的调控作用。     

基于系统发育分析的DNA条形码技术在澄清芍药属牡丹组物种问题中的应用

清晰的物种概念是材料正确鉴定的基础,是DNA条形码技术应用的前提.本文通过芍药属牡丹组植物DNA条形码数据的系统发育分析,揭示牡丹组植物的进化谱系及其与分类上“物种”的关系.在此基础上分析DNA条形码技术在牡丹组植物中应用的可能性.同时,以芍药科芍药属牡丹组植物为例,讨论DNA条形码技术在应用中存在的问题与解决方案.研究材料包括牡丹组植物目前已知的几乎所有的变异类型（种或种下分类群）共40份.DNA序列来自叶绿体基因组ndhF,rps16-trnQ,trnL-F和trnS-G4个基因,共有（含插入/缺失）5040个位点,包含96个变异位点,其中信息位点69个;核基因组GPAT基因2093~2197bp,变异位点（含插入/缺失）总数279个,其中信息位点148个.叶绿体基因组与核基因组所揭示的包括四川牡丹、矮牡丹、卵叶牡丹和紫斑牡丹在内的进化线与根据形态所建立的物种限定不吻合：（ⅰ）叶绿体基因分化明显但核基因没有明显分化——四川牡丹和紫斑牡丹的各居群系统;（ⅱ）核基因分化显著而叶绿体基因分化很小——矮牡丹和卵叶牡丹.因为这些居群系统之间存在一定程度的地理隔离,但不存在生殖隔离,出现这种两个基因组数据背离的现象可能是由于不同居群系统在进化历史中捕获了其他居群系统的叶绿体基因组.这些基因作为牡丹组植物DNA条形码的适合性分析显示,叶绿体基因在种间或居群系统之间的变异是种或居群系统内变异的4.82倍,GPAT基因在种间或居群系统之间的变异是种或居群系统内变异的2.21倍,说明这些基因可作为牡丹组植物的DNA条形码.种间或居群系统之间完全分化位点的统计结果表明,这些种或居群系统之间存在相互区别所必需的位点.通过牡丹组植物DNA条形码分析,认为：（ⅰ）物种概念对DNA条形码技术能否成功应用有十分重要的影响,拟应用DNA条形码的类?     

物种多样性与生态系统功能的关系研究进展

物种的空前丧失促使人们越来越多地开始研究物种多样性与生态系统功能的关系,并探讨其潜在的作用机制.本文根据最新研究进展,归纳了微宇宙实验、\"生态箱\"实验、Cedar Creek草地多样性实验和欧洲草地实验等代表性实验中关于物种多样性与生产力、稳定性、抗入侵性等生态系统功能的焦点问题,介绍了去除实验在多样性与生态系统功能研究中的应用.在此基础上,提出未来研究所面临的挑战,并对研究趋势进行了展望.主要挑战和趋势有:将小尺度上开展的实验研究扩展到较大的时空尺度上;综合考虑生物因素和非生物因素对多样性变化、生态系统功能的交互作用;营养级之间的相互作用、物种共存机制对物种多样性与生态系统功能关系的影响.     

2种块菌的物种分子鉴定与系统地位分析

以采自内蒙古贺兰山地区的2种块菌为实验材料,分别运用形态学和分子生物学方法进行物种鉴定,并通过与GenBank数据库信息比对,利用Mega5.1软件构建系统进化树,分析其进化关系并确定2种块菌的进化地位。结果表明:两菌株子囊果都为地下生;其中,菌株order-a为灰黄色,近球形到不规则形,较硬,表面被覆微绒毛;菌株tuber-b呈黄褐色,质地均匀,表面有疣状物,顶端呈凹陷状,全株带有干果般特殊的香气。经分子生物学方法分析认为菌株order-a为块菌属的一种,tuber-b为冬块菌(Tuber brumale),并初步确定为内蒙古新记录种。     

啮齿类取食的物种偏好与时空格局

通过强烈消耗土壤种子库,动物取食种子对植物种群更新和群落动态产生深远的影响。一般认为种子被食概率的空间格局取决于种子密度和离母树的距离,而环境（如地形）异质性的影响则一直没有得到足够的关注,与此相关的机制及其影响程度亦不清楚。研究设计在野外埋放种子以模拟种子扩散后的情形,监测啮齿类对种子的取食,以检验种子取食受埋藏生境、时间及动物对种子种类的偏好等因素的影响。结果表明,经过1a实验,8种落叶阔叶树种子的累计取食概率为0～48．25％,平均值为20％;山顶部位的取食概率大致是其它部位概率的3倍;埋放在凋落物层中的种子被食概率大约为埋放在土壤层中概率的2倍。利用logistic回归模型进行统计分析表明,种子被食概率变化的45％可以被上述因素解释。其中,物种偏好是影响种子被取食概率的首要因素,其后依次是地形、埋藏时间和深度。啮齿类明显喜好较大的种子;其取食行为在山脊部位明显较其它部位更频繁和剧烈;对埋藏种子的取食从3月份开始加剧,到7月份以后平息下来。种子埋放深度对啮齿类的取食概率有显著影响。     

物种与物种多样性

本文首先讨论生物物种的科学概念和生物学本质,分析物种客观存在的自然属性和物种概念的局限性,认为物种的生物学属性和物种多样性的科学属性之间有着本质联系。物种多样性研究的实质是研究生物物种的生物学多样性。度量物种多样性程度有多种方法,但物种数目是物种多样性程度最直接、也是最基本的表达,估计物种多样性数目是当前国际上物种多样性研究的核心与热点内容。物种多样性产生的根源是物种形成,物种绝灭速率是维持物种多样性的关键因素。本文简要总结了物种形成与绝灭的基本模式和机制,通过分析生物地理区系与物种多样性研究的密切关系,说明物种的区系成份分析是物种多样性大尺度格局研究的重要内容。     

Natural and sexual selection against hybrid flycatchers

While sexual selection is generally assumed to quickly cause or strengthen prezygotic barriers between sister species, its role in causing postzygotic isolation, through the unattractiveness of intermediate hybrids, is less often examined. Combining 24 years of pedigree data and recently developed species-specific molecular markers from collared (Ficedula albicollis) and pied (Ficedula hypoleuca) flycatchers and their hybrids, we were able to quantify all key components of fitness. To disentangle the relative role of natural and sexual selection acting on F1 hybrid flycatchers, we estimated various fitness components, which when combined represent the total lifetime reproductive success of F1 hybrids, and then compared the different fitness components of F1 hybrids to that of collared flycatchers. Female hybrid flycatchers are sterile, with natural selection being the selective force involved, but male hybrids mainly experienced a reduction in fitness through sexual selection (decreased pairing success and increased rate of being cuckolded). To disentangle the role of sexual selection against male hybrids from a possible effect of genetic incompatibility (on the rate of being cuckolded), we compared male hybrids with pure-bred males expressing intermediate plumage characters. Given that sexual selection against male hybrids is a result of their intermediate plumage, we expect these two groups of males to have a similar fitness reduction. Alternatively, hybrids have reduced fitness owing to genetic incompatibility, in which case their fitness should be lower than that of the intermediate pure-bred males. We conclude that sexual selection against male hybrids accounts for approximately 75% of the reduction in their fitness. We discuss how natural and sexual selection against hybrids may have different implications for speciation and conclude that reinforcement of reproductive barriers may be more likely when there is sexual selection against hybrids.     

Mating behaviour of the ‘cosmopolitan’ species Phyllognathopus viguieri (Copepoda: Harpacticoida) and its systematical significance

The mating behaviour was studied and recorded on video with individuals of four cultures of Phyllognathopus viguieri from different populations obtained from the interstitial water of a slow sand filter near the river Ruhr (Germany) (Ruhr population), from a compost heap in Bethesda (Maryland, USA) (Maryland population), from a rain gauge in Windsor Campbell farm (Jamaica) (Jamaica population), and a tree trunk with moss in a forest in the municipality of Rio de Janeiro (Brazil) (Brazil population). The mating behaviour was divided into the well‐known initial phase, copula phase and postcopulatory mate guarding phase. An additional phase prior to the initial phase serves to recognize the female, the recognition phase. The mating behaviour is identical in the males of the Jamaica and Brazil populations of P. viguieri. A postcopulatory mate guarding phase is not found in these two groups. Here, we refute the hypothesis, that a postcopulatory mate guarding phase is found in taxa in which only adult males grasp adult females. The males of the Ruhr and Maryland populations differ from each other in their mating behaviour. Generally, the males of all four populations do not mate with fertilized females which are equally unattractive to the males, i.e., females mate only once in their lifetime to produce offspring. These results corroborate the view that the different populations of P. viguieri do not belong to a single cosmopolitan species.     

The genic view of the process of speciation

The unit of adaptation is usually thought to be a gene or set of interacting genes, rather than the whole genome, and this may be true of species differentiation. Defining species on the basis of reproductive isolation (RI), on the other hand, is a concept best applied to the entire genome. The biological species concept (BSC; 84 ) stresses the isolation aspect of speciation on the basis of two fundamental genetic assumptions – the number of loci underlying species differentiation is large and the whole genome behaves as a cohesive, or coadapted genetic unit. Under these tenets, the exchange of any part of the genomes between diverging groups is thought to destroy their integrity. Hence, the maintenance of each species’ genome cohesiveness by isolating mechanisms has become the central concept of species. In contrast, the Darwinian view of speciation is about differential adaptation to different natural or sexual environments. RI is viewed as an important by product of differential adaptation and complete RI across the whole genome need not be considered as the most central criterion of speciation. The emphasis on natural and sexual selection thus makes the Darwinian view compatible with the modern genic concept of evolution. Genetic and molecular analyses of speciation in the last decade have yielded surprisingly strong support for the neo‐Darwinian view of extensive genetic differentiation and epistasis during speciation. However, the extent falls short of what BSC requires in order to achieve whole‐genome ‘cohesiveness’. Empirical observations suggest that the gene is the unit of species differentiation. Significantly, the genetic architecture underlying RI, the patterns of species hybridization and the molecular signature of speciation genes all appear to support the view that RI is one of the manifestations of differential adaptation, as 34 , Chap. 8) suggested. The nature of this adaptation may be as much the result of sexual selection as natural selection. In the light of studies since its early days, BSC may now need a major revision by shifting the emphasis from isolation at the level of whole genome to differential adaptation at the genic level. With this revision, BSC would in fact be close to Darwin’s original concept of speciation.