试论贴近度与择近原则在放牧衰退演替系列中更替种群的识别应用

[1]文曾从生态学中引入隶属度概念,建立了模糊集及其运算,模糊关系等。[2]文又对模糊集清晰化问题进行了讨论。同时也提出了用模糊度这一概念、公式来研究生物种群间、演替阶段间的模糊性的度量问题。本文是用贴近度概念和公式,对放牧衰退演替各阶段种群更替的贴近度与择近原则的探讨与评议。用来刻划实体其特征的贴近程度,简称贴近度,     

内蒙古达茂旗腾格淖尔地区大沙鼠种群繁殖习性的调查

鼠类繁殖生态学的研究是其种群生态学研究的一个重要方面 ,它不但为研究鼠类种群数量变动规律对种群数量进行预测预报提供重要的生态学基础资料 ,也为控制鼠害措施的制定提供依据 ,同时也具有重要的流行病学意义。大沙鼠 (Ｒｈｏｍｂｍｙｓｏｐｉｍｕｓ)广泛分布于中亚细亚、哈萨克斯坦、伊朗、阿富汗和蒙古国等地 ,在我国主要分布于内蒙古西部、甘肃北部和新疆 ,是荒漠—半荒漠地区的重要害鼠。我国对其生态学方面多注重于种群分布格局的研究[1～ 5] ,在繁殖方面的研究甚少[6] 。 1 979～1 980年和 1 995～ 1 996年对内蒙古包头市达尔罕茂…     

克隆种群的有关概念在水生植物中应用和研究进展

自20世纪80年代以来,克隆植物(C lonal p lants)种群生态学的研究逐渐成为国外生态学研究的热点之一,其研究成果不断发表在各种重要的国际学术刊物上[1—3],从而引起国内学者的关注。现已在陆生植物的多个类群中展开,但是水生植物的克隆种群研究仍然相对较少。随着我国淡水生态系统环境的恶化,水生植物在一些水域逐渐退化甚至完全消失,淡水生态系统的功能受到了严重的破坏[4],与此同时很多入侵性水生植物却疯狂生长,严重影响了水生生态系统的安全与利用。克隆生长和无性繁殖在水生植物中是十分普遍的现象[5—8],因此深入开展水生植物的克隆生态学研究对水生植被的恢复及外来种的管理具有重要的意义。1克隆种群的一些概念对植物克隆现象的重视首先源自于对植物构件性的研究。20世纪70年代Harper,et a·l提出了植物种群统计的构件理论(Modu le theory)[9]。构件理论把种群划分为由遗传单位形成的个体种群和由无性繁殖形成的构件种群两种结构水平,较好地解释种群内部个体的大小和数量在同龄或异龄植株之间的差异,因此被迅速接受并广泛地运用于植物种群生态学研究的多个方面。此后,对构件植物种群,特别是对克隆植物种群的...     

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…     

描述Meta-种群动态的耦合映象格子模型

Ｍｅｔａ－种群观点为在局部种群之上的空间尺度上描述种群的生态学过程提供了一种途径。但是由于植物所拥有的若干特殊性质（如种子休眠、有限扩散和局部适应）使得对某些植物种使用原有的Ｍｅｔａ－种群概念和模型存在许多困难。因此,为了能更精确地反映植物Ｍｅｔａ－种群动态,本文将Ｍｅｔａ－种群动态分解为斑块内局部种群动态和斑块间的扩散过程两个分量。用Ｌｏｇｉｓｔｉｃ方程表述每个斑块内的局部种群动态,用扩散系数ε表示斑块间的扩散,建立了描述Ｍｅｔａ－种群动态的耦合映象格子模型。对单峰映象ｘｎ＋１＝１－ａｘ２ｎ给出了耦合映象格子的时空行为,这对Ｍｅｔａ－种群动态的研究可能是非常重要的。     

Metapopulation(复合种群)究竟是什么?

Ｍｅｔａｐｏｐｕｌａｔｉｏｎ是种群生态学、景观生态学和保护生物学诸领域中的一个重要概念,近年来,有关ｍｅｔａｐｕｌａｔｉｏｎ的中文文章频率地出现在生态学杂志和书籍中。这一现象很好地反映了国内外华人生态学者对有关ｍｅｔａｐｏｐｕｌａｔｉｏｎ的问题愈来愈感兴趣,但对同一英文词出现的多种中文译法不免给诸造成了一些概念上的混乱,同时似乎也反映了作者们对ｍｅｔａｐｏｐｕｌａｔｉｏｎ这一概念在理解上的差异,因     

西辽河平原不同利用条件下羊草无性系种群结构的研究

1　引　　言羊草 (Ｌｅｙｍｕｓｃｈｉｎｅｎｓｉｓ(Ｔｒｉｎ .)Ｔｚｖｅｌ.)是典型的无性系根茎禾草 ,营养繁殖力强 ,在我国内蒙古东部和东北西部以及黄土高原地区的天然草地有广泛分布 .羊草具有很高的营养价值 ,是我国优良的牧草之一 ,多年来一直是草地学和生态学工作者研究的热点 ,并已开展到生物学的各个层次水平[1～ 3 ,8] .但对羊草无性系种群的研究较少 ,主要集中在年龄结构及营养繁殖特性等方面[4～ 7] .本文以天然草地灰绿型和黄绿型羊草种群为研究对象 ,对种群在不同干扰地段的变化进行了现实种群与潜在种群年龄结构的分析 ,为羊…     

Metapopulaton(复合种群)究竟是什么？

 Metapopulation是种群生态学、景观生态学和保护生物学诸领域中的一个重要概念。近年来,有关metapulation的中文文章频繁地出现在生态学杂志和书籍中。这一现象很好地反映了国内外华人生态学者对有关metapopulation的问题愈来愈感兴趣,但对同一英文词出现的多种中文译法不免给读者造成了一些概念上的混乱,同时似乎也反映了作者们对metapopulation这一概念在理解上的差异。因此,本文拟对metapopulation及其有关概念的涵义和发展加以讨论,并对现有的几种译文的确切性作一分析,以与生态学同行商榷。     

尾管藻属的形态学特征研究

硅藻是一个庞大的微藻类群,不但种类多,数量大,分布也很广泛,是水体中浮游植物的重要组成类群^[1]。硅藻是浮游动物、贝类、鱼类的饵料,在水生生物生态学研究中,常被作为重要的生物指示类群,用于监测水质和评价水环境。化石硅藻也是重要的指示生物,用于石油勘探、底层划分,以及古地理、古气候等领域的研究^[2]。硅藻的分类学依据主要是其硅质细胞壁上的花纹,目前被广泛采用的分类系统是将硅藻门分为中心纲（Centrieae）和羽纹纲（Pennatae）两个纲。     

赤地区蒙古族与汉族老年人肠道微生态学研究

对种族、生活习惯不同人群的肠道菌群进行研究,寻找适宜的生态调节剂是微生态学的研究热点[1]。在我国,对汉族、彝族人群的肠道菌群研究的较多[1,2],已经能够对肠道内10余类细菌进行定量分析,同时也研制出了如促菌生、回春生、昂立1号等微生态制剂用于临床[3]。对于蒙古族人群特别是老年人的肠道微生态学研究、寻找适于本地区人群的微生态制剂,既是微生态学领域的重要任务,也是落实民族政策的必需,是开发具有针对性老年保健品的前提[4]。为此,我们于1999年8月至1999年9月对赤峰地区蒙古族、汉族老年人的肠道微生态学进行了研究。1　材料与方…     

Evaluating the metapopulation consequences of ecological traps

Ecological traps occur when environmental changes cause maladaptive habitat selection. Despite their relevance to metapopulations, ecological traps have been studied predominantly at local scales. How these local impacts scale up to affect the dynamics of spatially structured metapopulations in heterogeneous landscapes remains unexplored. We propose that assessing the metapopulation consequences of traps depends on a variety of factors that can be grouped into four categories: the probability of encounter, the likelihood of selection, the fitness costs of selection and species-specific vulnerability to these costs. We evaluate six hypotheses using a network-based metapopulation model to explore the relative importance of factors across these categories within a spatial context. Our model suggests (i) traps are most severe when they represent a large proportion of habitats, severely reduce fitness and are highly attractive, and (ii) species with high intrinsic fitness will be most susceptible. We provide the first evidence that (iii) traps may be beneficial for metapopulations in rare instances, and (iv) preferences for natal-like habitats can magnify the effects of traps. Our study provides important insight into the effects of traps at landscape scales, and highlights the need to explicitly consider spatial context to better understand and manage traps within metapopulations.     

Postfire population dynamics of a fire-dependent cypress

Plant Ecology - Tecate cypress (Hesperocyparis forbesii) is a rare species restricted to four metapopulations in southern California, USA and a few isolated populations in northern Baja California,...     

Spatial scale of local adaptation in a plant-pathogen metapopulation

The rate and scale of gene flow can strongly affect patterns of local adaptation in host-parasite interactions. I used data on regional pathogen occurrence to infer the scale of pathogen dispersal and to identify pathogen metapopulations in the interaction between Plantago lanceolata and its specialist phytopathogen, Podosphaera plantaginis. Frequent extinctions and colonizations were recorded in the metapopulations, suggesting substantial gene flow at this spatial scale. The level of pathogen local adaptation was assessed in a laboratory inoculation experiment at three different scales: in sympatric host populations, in sympatric host metapopulations and in allopatric host metapopulations. I found evidence for adaptation to sympatric host populations, as well as evidence indicating that local adaptation may extend to the scale of the sympatric host metapopulation. There was also variation among the metapopulations in the degree of pathogen local adaptation. This may be explained by regional differences in the rate of migration.     

Development of genetic differentiation and postzygotic isolation in experimental metapopulations of spider mites

We studied the development of genetic differentiation and postzygotic isolation in experimental metapopulations of the two-spotted spider mite, Tetranychus urticae Koch. A genetically diverse starter population was made by allowing six inbred sublines to interbreed. Then three migration patterns were tested: no migration, or one or three immigrants per subpopulation per generation. Variations in four traits were investigated: allozymes, acaricide resistance, diapause, and hatchability. In the allozymes, acaricide resistance, and diapause, genetic variation among subpopulations became high in metapopulations with no migration, but not in the others, which showed that one immigrant is enough to prevent genetic differentiation. Hatchability, which was decreased by interbreeding among the six sublines, gradually recovered in succeeding generations. In metapopulations with no migration, hatchability was reduced again after in-migration at the 15th generation. Different karyotypes or coadapted gene complexes can survive in different subpopulations by genetic drift, and both Wolbachia-infected and -noninfected subpopulations may be selected, which would lead to postzygotic isolation between isolated subpopulations. Our results indicate that sampling effects such as genetic drift or stochastic loss of Wolbachia produce postzygotic isolation in laboratory populations of spider mite.     

Regional structuring of genetic variation in short-lived rock pool populations of Branchipodopsis wolfi (Crustacea: Anostraca)

The genetic structure of three metapopulations of the southern African anostracan Branchipodopsis wolfi was compared by analysing allozyme variation at four loci (PGM, GPI, APK, AAT). In total, 17 local populations from three sites (metapopulations) were analysed from rock pools in south-eastern Botswana ranging from 0.2 to 21 m² in surface area. In three populations we found significant deviations from Hardy-Weinberg (H-W) equilibrium at one or more loci due to heterozygote deficiencies. Genetic variability at one site was significantly lower than at the other sites, which may be linked to a greater incidence of extinction and recolonisation, as the basins at this site are shallower and have shorter hydrocycles. Across all local populations, a significant level of population differentiation was revealed. More than 90% of this variation was explained by differentiation among sites (metapopulations), although this differentiation did not correlate with geographic distance, or with environmental variables. Genetic differentiation among populations within metapopulations was low, but significant at all sites. At only one of the sites was a significantly positive association measured between genetic and geographic distance among local populations. Our data suggest that persistent stochastic events and limited effective long-range dispersal appear to dominate genetic differentiation among populations of B. wolfi inhabiting desert rock pools. The lack of association between geographic distance and genetic or ecological differences between rock pool sites is indicative of historical stochastic events. Low heterozygosity, the significant deviations from H-W equilibrium, and the large inter- but low intra-site differentiation are suggestive of the importance of short-range dispersal. Gene flow between metapopulations of B. wolfi appears to be seriously constrained by distances of 2 km or even less. Received: 28 June 1999 / Accepted: 10 January 2000     

Stability aware spatial cut of metapopulations ecological networks

Ecological complex networks are common in the study of patched ecological systems where evolving populations interact within and among the patches. The loss of the dispersal connections between patches due to reasons such as erosion of migration corridors and road construction can cause an undesirable partitioning of such networks resulting in instability or negative impact on the metapopulations. A partitioning or spatial cut that is aware of the stability of the dynamics in the resulting daughter sub-networks can be an effective tool in dealing with the situation like proposing road alignment through a metapopulations network. This paper provides some mathematical conditions along with an heuristic graph partitioning algorithm that can help in finding ecologically suitable partitions of the metapopulations networks. Our study noted the crucial role of network connectivity (measured by Fiedler value) in stabilizing the metapopulations. That is, a sufficiently connected metapopulations network along with constrained internal patch dynamics has stable dynamics around its homogeneous co-existential equilibrium solution. With the considered mathematical model in this paper, network partitioning does not alter the internal patch dynamics around its homogeneous equilibrium point, but it can change the connectivity levels in the partitioned subnetworks. Thus, the proposed partitioning problem for an already stable metapopulations network is reduced to finding its subnetworks with desirable connectivity levels.     

Maintenance of the sexes and persistence of a clonal organism in spatially complex metapopulations

Clonal organisms persist at a range of population sex ratios, from equal numbers of males and females to single-sex systems. When intersexual competition is strong enough to drive one sex locally extinct, the maintenance of the sexes is facilitated by the semi-independent dynamics of populations within a metapopulation. These semi-independent dynamics are influenced by dispersal and recolonization rates, which are affected by the spatial arrangement of populations. To establish the quantitative relationship between spatially complex metapopulations and the maintenance of the sexes, we used a mathematical model of the liverwort Marchantia inflexa. This clonal organism is found in discrete patches on rocks and along the banks of streams, which form single-sex and two-sex metapopulations. In this system, asexual propagules mainly disperse short distances. Long-distance between-patch dispersal and recolonization mainly occurs via sexual propagules, which require both sexes to be present. Dispersal of these two types of propagules could interact with the spatial arrangement of populations to affect the maintenance of the sexes. With our mathematical model, we found that at intermediate distances between populations, metapopulations maintained both sexes, and the spatial arrangement of populations changed the threshold at which one sex was lost. On the other hand, when populations were close to one another, one sex was lost and the single-sex metapopulation persisted through dispersal of asexual propagules. When populations were far apart, one sex was lost, and the metapopulation either went extinct due to lack of recolonization by asexual propagules or persisted because clumped populations facilitated recolonization. These idealized spatial arrangements help clarify the effects of the spatial arrangement on the maintenance of the sexes and the persistence of metapopulations of clonal organisms, which can help explain geographic parthenogenesis and the distribution of asexual populations, the persistence of asexual species, and inform the conservation of clonal organisms.     

Reconciling theoretical approaches to stochastic patch-occupancy metapopulation models

There appear to be two different kinds of theoretical results about stochastic patch-occupancy metapopulation models: those recently proposed by Gyllenberg and Silvestrov about metapopulations including a very stable patch, and those by Darroch and Seneta about more general metapopulations. Based on the spectral theory of linear operators, it is shown that the results by Gyllenberg and Silvestrov are a limiting case of those by Darroch and Seneta. Taking the examples proposed by Gyllenberg and Silvestrov as a case study, the application and relevance of these results are discussed, with a particular stress to their bearing on real metapopulations.     

Refugia and connectivity sustain amphibian metapopulations afflicted by disease

Metapopulation persistence in fragmented landscapes depends on habitat patches that can support resilient local populations and sufficient connectivity between patches. Yet epidemiological theory for metapopulations has largely overlooked the capacity of particular patches to act as refuges from disease, and has suggested that connectivity can undermine persistence. Here, we show that relatively warm and saline wetlands are environmental refuges from chytridiomycosis for an endangered Australian frog, and act jointly with connectivity to sustain frog metapopulations. We coupled models of microclimate and infection probability to map chytrid prevalence, and demonstrate a strong negative relationship between chytrid prevalence and the persistence of frog populations. Simulations confirm that frog metapopulations are likely to go extinct when they lack environmental refuges from disease and lose connectivity between patches. This study demonstrates that environmental heterogeneity can mediate host–pathogen interactions in fragmented landscapes, and provides evidence that connectivity principally supports host metapopulations afflicted by facultative pathogens.