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1.
    
When temperature and other kinds of barrier divide formerly continuous populations and confine them to more restricted geographical areas, there is an evolutionary reaction that will, over time, result in the formation of endemic species. In such cases, an allopatric speciation process is considered to have taken place because reproductive isolation was caused by physical means instead of by natural selection. In contrast, when populations exist in a very high-diversity area and remain undivided by physical events, they exhibit a tendency to speciate by means of sympatry (or parapatry). This process, sometimes called competitive or ecological speciation, does involve reproductive isolation by means of natural selection. Populations that exist in geographical provinces bounded by physical barriers add to the overall diversity through the production of endemic species. This increase by species packing is relatively slow due to the very gradual tempo of the allopatric speciation process. Populations existing in centres of origin add to the general diversity through the production of species that are dominant in terms of their ability to spread over large parts of the world. It is proposed that such species are usually formed by sympatric speciation, a process that can be c. 20 times faster than species formation by allopatry. It is not suggested that sympatry is exclusive to centres of origin, nor that allopatry is confined to peripheral provinces. Both processes are widespread, but there do appear to be distinctive geographical concentrations. Considering that numbers of widespread species produced by centres of origin may eventually become subdivided by barriers, and thus give rise to descendants by allopatry, it is difficult to say how much of our present species diversity has come from one source or the other. Both speciation by sympatry from centres of origin and speciation by allopatry in peripheral provinces appear to be important sources of marine biodiversity.  相似文献   

2.
分子生态学研究与运行多样性保护   总被引:7,自引:1,他引:7  
分子生态学的发展揭开了生物多样性保护研究的新篇章,分子技术的应用克服了传统生态学法中的一些难题,如野外调查周期长,分辨率有限,实验条件不易控制等,应用各种分子标记(如:RFLP,VNTR,RAPD,DNA测序等)可以分析种群地理格局和异质种群动态,确定种群间的基因流,研究瓶颈效应对种群的影响以及确定个体间的亲缘关系等等,所有这些研究都是指导物种保护和淑危种群的恢复所必要的,种或品系特异性的分子标记技术能够解决形态分类中的模糊现象,确定基于遗传物质的谱系关系,还可以用来分析近缘种间杂交问题,这些问题的解决有助于确定物种优先保护顺序,选择保护地工,近年来引起重视的主要组织人性复合体(MHC)NDA异分析可能会在研究种群对疾病的易感性第一系列种群特异性问题方面非常有用,随着分子技术的不断发展,会有更多的保护生物学问题得到解决,尤其是结合野外调查统计数据应用多个分子标记对目标种群进行研究,所得到的结果会更精确,更有说服力。  相似文献   

3.
    
We synthesize the evolutionary implications of recent advances in the fields of phylogeography, biogeography and palaeogeography for shallow‐water marine species, focusing on marine speciation and the relationships among the biogeographic regions and provinces of the world. A recent revision of biogeographic provinces has resulted in the recognition of several new provinces and a re‐evaluation of provincial relationships. These changes, and the information that led to them, make possible a clarification of distributional dynamics and evolutionary consequences. Most of the new conclusions pertain to biodiversity hotspots in the tropical Atlantic, tropical Indo‐West Pacific, cold‐temperate North Pacific, and the cold Southern Ocean. The emphasis is on the fish fauna, although comparative information on invertebrates is utilized when possible. Although marine biogeographic provinces are characterized by endemism and thus demonstrate evolutionary innovation, dominant species appear to arise within smaller centres of high species diversity and maximum interspecies competition. Species continually disperse from such centres of origin and are readily accommodated in less diverse areas. Thus, the diversity centres increase or maintain species diversity within their areas of influence, and are part of a global system responsible for the maintenance of biodiversity over much of the marine world.  相似文献   

4.
Coastal-marine biodiversity conservation must focus increasingly at the level of the land- and seascape. Five cases illustrate discontinuities and synergisms and how system changes may take place. For Caribbean coral reefs, the result of overfishing and disease has been a shrinkage in the entire system, the effects of which may cascade through the coastal seascape. For Beringia, patterns of benthic diversity are best understood in a manner that matches the multiscale, integrated dynamics of weather, ice, marine mammal feeding, and community structure. In the case of US East Coast estuaries, oyster reefs may be keystone elements, with important effects on functional diversity. Large-scale coastal systems depend upon the connectivity of fresh and marine waters in the coastal zone, having implications for the apparent stochasticity of coastal fisheries. And, for a coastal barrier-lagoon site, a state change may be described in terms of a combination of succession, the attainment of a quasi-equilibrium state, and disturbance. A profound problem for conservation is that there is very little information about the relationship between species diversity and ecological function. Coastal-marine biodiversity conservation is best addressed at the level of the land- and seascape.  相似文献   

5.
Centrifugal speciation and centres of origin   总被引:3,自引:2,他引:3  
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6.
    
In a recent paper by D. R. Bellwood and C. P. Meyer ('Searching for heat in a marine biodiversity hotspot', Journal of Biogeography , 2009, 36 , 569–576), the authors had two evident objectives: (1) to disprove the theory that the geographical origins of reef organisms could be determined by locating concentrations of endemic species, and (2) to emphasize that the high diversity of the Coral Triangle was due to an accumulation of species from outside that area. With regard to the first point, no such theory had previously been proposed to my knowledge. Second, the accumulation theory was promoted without consideration of the facts supporting the centre of origin hypothesis, except to dismiss it by saying that it had its origin in pre-continental drift ideas. This short response outlines the properties and evidence for the operation of centres of origin in this region.  相似文献   

7.
1. North‐eastern Spain is a hot spot for the introduction of alien fish species, and its native fish fauna is one of the most endangered worldwide. We used an extensive data set from 2002 to 2003 and historical information from the area to characterize fish diversity and establish conservation priorities in river catchments. 2. Diversity indices were used to characterize fish diversity at the basin scale. An index of conservation status was applied for each species, which considers the occurrence, abundance and endemicity of each taxon. We used indirect ordination methods to test the relationship among basin features and to identify those variables most correlated with each other. To identify physical, biotic and environmental characteristics that seem to make a basin particularly susceptible to invasion, we performed a step‐wise multiple regression to examine the relationship between the number of native, translocated and introduced fish species (including the original native species richness of each basin), and landscape variables. 3. Over a period of approximately 50 years, the mean range size of native fish species has decreased by 60%. The greatest decline occurred in Gasterosteus gymnurus, Anguilla anguilla and Salaria fluviatilis, for which species over 75% of the original distribution area has been lost. The species with the highest conservation index were Gasterosteus gymnurus and Salaria fluviatilis. 4. Basin area and the catchment type explained 70% of variation in native species richness, whereas the number of dams and basin area accounted for more than 80% of variation in the number of introduced species. 5. The original native species richness and the number of introduced species at basin scale were not related, and thus there was no evidence of “biotic resistance” to invasion. The restoration of natural hydrologic processes and the development of specific management tools to protect native species, such as the prioritization of areas for fish conservation and the eradication of local populations of exotic species, are required to restore native fish fauna in these catchments.  相似文献   

8.
Mammals have incredible biological diversity, showing extreme flexibility in eco-morphology, physiology, life history and behaviour across their evolutionary history. Undoubtedly, mammals play an important role in ecosystems by providing essential services such as regulating insect populations, seed dispersal and pollination and act as indicators of general ecosystem health. However, the macroecological and macroevolutionary processes underpinning past and present biodiversity patterns are only beginning to be explored on a global scale. It is also particularly important, in the face of the global extinction crisis, to understand these processes in order to be able to use this knowledge to prevent future biodiversity loss and loss of ecosystem services. Unfortunately, efforts to understand mammalian biodiversity have been hampered by a lack of data. New data compilations on current species' distributions, ecologies and evolutionary histories now allow an integrated approach to understand this biodiversity. We review and synthesize these new studies, exploring the past and present ecology and evolution of mammalian biodiversity, and use these findings to speculate about the mammals of our future.  相似文献   

9.
Recent morphometric and breeding studies of diatoms show that the present species classification is too coarse and hides significant diversity. Many species are subdivided into phenodemes, which often differ in cell size, shape, stria density and pattern, but may also have different ultrastructural features. In raphid diatoms these can include the form of the raphe endings, details of the pore occlusions, and the structure of the girdle, while chloroplast structure can also vary. The phenodemes can be sympatric or allopatric. In Sellaphora pupula and other species, sympatric phenodemes are reproductively isolated. It is recommended that such demes are recognized as separate species; the total number of diatom species worldwide may thus be at least 2 × 105. Use of a fine-grained classification reveals that many diatom species may be endemics, some restricted to a single lake or catchment, others to wider areas. Environmental impact assessments and conservation strategies must begin to take account of endemism and rarity among microscopic algae and protists.  相似文献   

10.
Sandwiched between the Namib and Kalahari Deserts of southwestern Africa are the karooid and escarpment biotopes of Namibia which are rich in endemics of many taxa. Most plant, invertebrate, amphibian, reptile, mammal and bird species endemic to Namibia are found in a zone running through, and to the west of, Namibia's escarpment region. There is also an important region of endemism for succulent plants, reptiles and invertebrates in the Succulent Karoo biome. Congruence between endemism hotspots, particularly on rocky substrates, is remarkably high for most taxa, implying broadly similar speciation processes. Possible speciation mechanisms in different parts of the country include the spatial isolation of rupicolous taxa such as insects and reptiles by the formation of large coastal dune fields; the expansion and contraction of wooded savannas during pluvial and interpluvial periods; and global temperature shifts which created highland refugia for frost-susceptible plants and poikilotherms. Areas of endemism and species richness overlap poorly for Namibia's mainly arid-dwelling endemic vertebrates, as richness is highest in the mesic wetlands and woodlands of northeast Namibia. The overlap for succulent plants, insects and arachnids, however, is relatively high. Centres of endemism for plants and vertebrates fall mainly outside protected areas, as few parks were established with biodiversity indices in mind. Our analysis of endemism congruence provides a strong platform for the promulgation of new protected areas to safeguard Namibia's unique biota. Furthermore, analysis of speciation patterns and processes is a useful predictive tool for the identification of other biotically important sites.  相似文献   

11.
Data from 3991 records of museum collections representing 421 species of plants, arthropods, amphibians, fish, and primates were analyzed with GIS to identify areas of high species diversity and endemism in Amazonia. Of the 472 1 × 1° grid cells in Amazonia, only nine cells are included in the highest species diversity category (43–67 total species) and nine in the highest endemic species diversity category (4–13 endemic species). Over one quarter of the grid cells have no museum records of any of the organisms in our study. Little correspondence exists between the centers of species diversity identified by our collections-based data and those areas recommended for conservation in an earlier qualitative study of Amazonian biodiversity. Museum collections can play a vital role in identifying species-rich areas for potential conservation in Amazonia, but a concerted and structured effort to increase the number and distribution of collections is needed to take maximum advantage of the information they contain.  相似文献   

12.
We describe a method for applying geographical information systems (GIS) to exploring biodiversity in the wild relatives of crop species and illustrate its application to the wild common bean (Phaseolus vulgaris L.). We use the latitude, longitude and altitude of the location of origin of each accession in a germplasm collection of wild P. vulgaris, along with long-term monthly mean values of rainfall, temperature and diurnal temperature range for about 10000 stations throughout Latin America to produce maps indicating areas with bean-favouring climates. In a test case, these identify a new suitable area in Colombia where wild P. vulgaris has been reported in the literature, and two more areas which are strong candidates on other grounds. Dividing the bean-favouring climates into clusters identifies areas that have similar climates but are geographically remote, where we can expect to find wild beans with similar ecological adaptation. We discuss the implications of these results for conserving and improving the common bean, and the application of these methods to other species.  相似文献   

13.
Summary For the 70% of New Zealand under private ownership, native biodiversity conservation has to occur within a landscape that must also provide a productive return to land owners. Recent New Zealand legislation, especially the Resource Management Act 1991, promotes sustainable management on private land by allowing for the economic and cultural well-being of local communities while providing for the protection of natural resources including native biodiversity. We suggest that, to effectively conserve native biodiversity in rural landscapes, we need to consider four key issues: (i) what might be realistic goals for native biodiversity conservation; (ii) how might we better arrange different land uses to meet both native biodiversity and production goals; (iii) what is the optimum arrangement of native biodiversity; and (iv) how native biodiversity conservation can improve productive returns to land managers. Options to enhance native biodiversity conservation include a variety of incentives (e.g. management agreements, financial incentives and regulatory systems) and onsite management options (e.g. remnant management, restoration plantings, weed and pest control, use of native species for commercial and amenity purposes, use of exotic species to facilitate native biodiversity). The importance of taking a landscape-based rather than a paddock-based approach to management is emphasized.  相似文献   

14.
Aim To assess short‐term variability in the community composition and community structure of tintinnid ciliates, herbivores of the microzooplankton. Location North‐west Mediterranean Sea. Methods We sampled on 18 dates over a 4‐week period in 2004 at an open‐water site. Species were classified as ‘core species’, found on every date, or ‘occasional species’, absent on one or more dates. Species abundance distributions of the entire community, and separately the core and occasional species, were compared with geometric, log‐series and log‐normal distributions. Core and occasional species were compared in terms of the shell or lorica oral diameter (LOD), analogous to gape size. Results We found 11 core and 49 occasional species. Diversity metrics were stable compared with shifts in abundances. Core species accounted for the majority of individuals in all samples. On each date, 9–22 occasional species, representing 10–15% of the population, were found. Species richness of the occasionals was positively related to population size. The identities of the occasional species found were unrelated to the time between sampling. The species abundance distribution of the occasional population was best fit by a log‐series distribution, while that of the core species was best fit by a log‐normal distribution. The species abundance distribution of the entire community was best fit by a log‐series distribution. Most of the occasional species had LODs distinct from that of a core species and occupied size classes left empty by the core population. However, the most abundant and frequent of the occasional species had a LOD similar to that of a core species. Main conclusions Among tintinnids, which are planktonic protists, occasional species have a species abundance distribution pattern distinct from that of core species. Occasional species appeared to be composed of two groups, one of relatively abundant species and similar to core species, and a second group of ephemeral species with morphologies distinct from core species. The existence of two categories of occasional or rare species may be common: (1) those similar to, and thus perhaps able to replace, dominant species in the absence of a change in the environment; and (2) those distinct from dominant species and requiring different conditions to prosper.  相似文献   

15.
16.
The coral genus Acropora is reviewed from Indonesia for the first time, following detailed collections made at 131 sites and additional material collected from approximately 40 sites throughout the archipelago during the period 1993–6. Eighty-three species are recorded, four of these ( Acropora halmaherae, A. awi, A. plumosa and A. simplex ) new to science, six first described in 1994 and six in 1997. Records are compared with specimen-based records from localities worldwide. The species of Acrokora occurring in Indonesian waters include five recorded only from the Indian Ocean and Indonesia, seven recorded only from the Pacific Ocean, South China Sea and Indonesia, and a further 10 species apparently endemic to Indonesia, as well as widespread Indo-Pacific species. Two species ( A. jacquelineae Wallace, 1994 and A. batunai Wallace, 1996) are recorded only from north central Indonesia and Papua New Guinea, and two species ( A. russelli Wallace, 1994 and A. turaki Wallace, 1994) only from north central Indonesia and north western Australia. The findings contribute to a new view of the corals of the Indo-Pacific 'centre of diversity' as a composite fauna with origins in a number of events in space and time.  相似文献   

17.
18.
海南岛生物多样性保护优先区评价与系统保护规划   总被引:4,自引:0,他引:4  
选择海南岛140个濒危物种为指示物种,在物种栖息地评价的基础上,利用系统保护规划工具MARXAN模型进行迭代运算,提出了海南岛生物多样性保护优先区域,并对保护优先区进行评价.结果表明:海南岛保护优先区面积5383.7km2,占海南岛陆地面积的15.6%,集中分布于鹦哥岭、尖峰岭、五指山等林区和北部湿地;在保护优先区中,11个I级指示物种栖息地的保护比例均超过各自栖息地总面积的65%.通过对保护优先区与现有自然保护区的空缺分析,建议扩充尖峰岭保护区群、鹦哥岭-黎母山保护区群、五指山-吊罗山保护区群;新建抱龙林场-林鼻岭-福万岭保护体系;在海南岛北部建立以水源保护为主,同时兼顾珍稀物种保护的水源地保护带.  相似文献   

19.
20.
Twenty-five islands of different sizes were rapidly surveyed in the Andaman islands for patterns of butterfly distribution and abundance. The surveys were conducted in the dry seasons of 1992 in the South Andaman islands, 1994 in the North Andaman islands and on both these years on the Little Andaman Island. Different habitat types were identified on each island and butterflies were sampled by the line transect method in each habitat type. Sixty-five species of butterflies were recorded from six families. Fifty-one species were less common and contributed to 25 % of the total count. Six species were very common. The overall distribution patterns of the species were nested. This suggests that small islands share their species with the larger islands but not vice versa. Many uncommon species were found exclusively on large islands. The presence of evergreen forest on islands significantly influenced the species encountered. Small and medium sized islands with evergreen forests had significantly more species than those without evergreen forests. Loss of primary forests due to logging and encroachment will result in the loss of many butterfly species. It is recommended that the large patches of primary evergreen forests be protected on a priority basis on large islands.  相似文献   

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