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1.
New Zealand, like many other islands, has suffered extinctions of native species and successful introductions of exotic species. It has been uncertain whether the introductions caused the extinctions or whether the extinctions permitted the introductions. On New Zealand's Hauraki Gulf islands, which are unusual in their near lack of introduced mammalian predators and complete lack of mammalian browsers, exotic bird species abundant in mainland New Zealand forest and reaching these islands are virtually absent from unmodified forest. Exotic bird species disappeared from Cuvier Island's forest after elimination of mammalian predators and browsers. Hence extinctions of native species were not due to competition from introduced species but to other factors (such as mammalian predators and habitat alteration). Only after decimation of native species and forest alteration by browsing mammals could exotic birds invade forest. 相似文献
2.
舟山群岛鸟类生态地理学研究 总被引：5，自引：0，他引：5
本文在对舟山岛屿鸟类区系和生态分布研究基础上进行了岛屿间鸟类区系的相似性、多样性、稳定性、种群数量和优势种的测定,并对鸟类数量与岛屿面积的关系进行了分析。结果表明,舟山群岛自南向北,水文、气象、植被景观、鸟类种数存在梯度变化;海岛鸟类群落的空间分布不仅取决于岛屿面积大小和岛屿离大陆的远近,也取决于地理纬度、植被、气象变异、食物、海洋隔离以及人为干扰较大陆少等因素。本文对造成岛屿鸟类密度较大陆高的原因也进行了讨论。 相似文献
3.
张义浩 《农业图书情报学刊》2007,19(12):79-82
通过对浙江省海岛涉海专业院校图书馆工作人员调查分析，指出了问题和不足，从海岛实际出发，提出要“就地取材”培养海岛型图书馆人才，并采取加强进修提高、在岗培训提高、组织自学提高等对策措施，从而解决海岛院校图书馆工作人员的文化技能问题。 相似文献
4.
The worldwide distribution of volcanic ash has been determinmined from 320 deep-sea sections drilled during the Deep Sea Drilling Project. The ash distribution in the deep-sea sections, which span the last 20 million years, indicates that there has been a much higher rate of explosive volcanism from both island arc and hot spot volcanoes during the last 2 million years. This episode, and perhaps another in the Middle Miocene cprrelates with previously reported widespread synchronism in increased volcanicity in certain oceanic islands. Increased Quaternary volcanism coincides approximately with that episode of the Cenozoic marked by major and rapidly fluctuating climatic change. 相似文献
5.
Steadman DW 《Science (New York, N.Y.)》1995,267(5201):1123-1131
On tropical Pacific islands, a human-caused "biodiversity crisis" began thousands of years ago and has nearly run its course. Bones identified from archaeological sites show that most species of land birds and populations of seabirds on those islands were exterminated by prehistoric human activities. The loss of birdlife in the tropical Pacific may exceed 2000 species (a majority of which were species of flightless rails) and thus represents a 20 percent worldwide reduction in the number of species of birds. The current global extinction crisis therefore has historic precedent. 相似文献
6.
Distributions and densities of orb spiders on small islands are extremely variable. Species occurrences are far more irregular for spiders than vertebrates on the same islands. Much variation in spider density is explainable by distance from the presumed source of colonists and presence or absence of vertebrate predators. As has been predicted for passive dispersers, densities decline exponentially with distance. For a given distance, spider densities are about ten times greater on islands without vertebrate predators than on those with such predators. 相似文献
7.
Reductions in bird numbers could hamper ecosystem services such as pollination, but experimental proof is lacking. We show that functional extinction of bird pollinators has reduced pollination, seed production, and plant density in the shrub Rhabdothamnus solandri (Gesneriaceae) on the North Island ("mainland") of New Zealand but not on three nearby island bird sanctuaries where birds remain abundant. Pollen limitation of fruit set is strong [pollen limitation index (PLI) = 0.69] and significant on the mainland but small (PLI = 0.15) and nonsignificant on islands. Seed production per flower on the mainland is reduced 84%. Mainland sites have similar adult densities, but 55% fewer juvenile plants per adult, than island sites. Seed addition experiments near adult R. solandri plants on the mainland found strong seed limitation 5 years after sowing for R. solandri but not for two other co-occurring woody species. This demonstrates a terrestrial trophic cascade. 相似文献
8.
Diamond JM 《Science (New York, N.Y.)》1974,184(4138):803-806
After volcanic explosions or tidal waves had defaunated several islands near New Guinea, bird species number rapidly returned to equilibrium on coral islets and rapidly returned to quasi-steady-state values limited by regrowth of vegetation in lowland forest of larger islands. However, reequilibration in montane forest has been limited by slow dispersal of the birds. Colonists have been drawn disproportionately from r-selected "supertramrip" species, which maintain much higher population densities than do K-selected faunas, perhaps due to selection for resource overexploitation by the latter. 相似文献
9.
Diamond JM 《Science (New York, N.Y.)》1973,179(4075):759-769
The concepts by which MacArthur and Wilson have transformed the science of ecology in the past decade, and the results of ecological studies such as mine on New Guinea bird communities, have implications for conservation policies. For example, primary tropical rain forest, the most species-rich and ecologically complex habitat on earth, has for millions of years served as the ultimate evolutionary source of the world's dominant plant and animal groups. Throughout the tropics today, the rain forests are being destroyed at a rate such that little will be left in a few decades. When the rain forests have been reduced to isolated tracts separated by open country, the distribution of obligate rain forest species will come to resemble bird distributions on New Guinea land-bridge islands after severing of the land bridges. The smaller the tract, the more rapidly will forest species tend to disappear and be replaced by the widespread second-growth species that least need protection (13). This ominous process is illustrated by Barro Colorado Island, a former hill in Panama that became an island when construction of the Panama Canal flooded surrounding valleys to create Gatun Lake. In the succeeding 60 years several forest bird species have already disappeared from Barro Colorado and been unable to recolonize across the short intervening water gap from the forest on the nearby shore of Gatun Lake. The consequences of the species-area relation (Fig. 1) should be taken into consideration during the planning of tropical rain forest parks (13). In a geographical area that is relatively homogeneous with regard to the fauna, one large park would be preferable to an equivalent area in the form of several smaller parks. Continuous nonforest strips through the park (for example, wide highway swaths) would convert one rain forest "island" into two half-size islands and should be avoided. If other considerations require that an area be divided into several small parks, connecting them by forest corridors might significantly improve their conservation function at little further cost in land withdrawn from development. Modern ecological studies may also be relevant to the understanding of human populations. For instance, during a long period of human evolution there appear to have been not one but two coexistent hominid lines in Africa, the Australopithecus robustus-A. boisei ("Zinjanthropus") line, which became extinct, and the Australopithecus africanus-A. habilis line, which led to Homo sapiens (27). The need to maintain niche differences between these lines must have provided one of the most important selective pressures on the ancestors of modern man in the late Pliocene and early Pleistocene. Thus, any attempt to understand human evolution must confront the problem of what these ecological segregating mechanisms were. To what extent were contemporaneous species of the two lines separated by habitat, by diet, by size difference, or by foraging technique, and were their local spatial distributions broadly overlapping or else sharpened by behavioral interactions as in the case of the Crateroscelis warblers of Fig. 6? To take another example, there are striking parallels between the present distributions of human populations and of bird populations on the islands of Vitiaz and Dampier straits between New Guinea and New Britain. Some of these islands were sterilized by cataclysmic volcanic explosions within the last several centuries. The birds that recolonized these islands have been characterized as coastal and small-island specialists of high reproductive potential, high dispersal powers, and low competitive ability, unlike the geographically closer, competitively superior, slowly dispersing, and breeding birds of mainland New Guinea (10, 11, 13). It remains to be seen whether the people of the Vitiaz-Dampier islands, the Polynesians, and other human populations that colonize insular or unstable habitats also have distinctive population ecologies. 相似文献
10.
Coral reefs resemble islands of productive habitats where fishes aggregate, forage, and spawn. Although it has been suggested that some reef fishes use biogenic chemicals as aggregation cues, specific chemicals have not been identified. Dimethylsulfoniopropionate (DMSP), a secondary metabolite of many marine algal species, is released during foraging by higher-order consumers. DMSP has been studied intensively for its role in oceanic sulfur cycles and global climate regulation, but its ecological importance to marine fishes is unknown. We present evidence that planktivorous reef fishes will aggregate to experimental deployments of DMSP over coral reef habitats in the wild. 相似文献
11.
通过对舟山群岛野生植物资源的调查，筛选出野生木本观赏植物350种，隶属于75科183属。部分种类蕴藏量大，群落面积大于50hm^2的有14种。其中海岛特有植物12种，滨海特有植物16种，国家级珍稀濒危植物4种，浙江省省级珍稀濒危植物11种。资源在各海岛的分布从南到北逐渐递减，其中在舟山备县（区）普遍分布的有92种，分布在岱山岛、长涂岛及以南岛屿的50种，分布在舟山岛及其以南以东岛屿的94种，仪局限在该区域个别岛屿的多达160余种；生长环境以丘陵山坡为主，基岩海岸次之，少数种类见于沙砾质海岸和淤泥质海岸，表现出分布区域不平衡，生态幅度差异大，生境多样化等特征。 相似文献
12.
海南岛外来入侵生物分析 总被引：2，自引：0，他引：2
据调查,海南岛外来入侵生物已达近200种,对当地生物多样性和农林牧渔业造成了严重的影响。随着旅游、商贸和工农业等的迅速发展,外来入侵生物将会越来越多,对生态系统的影响将会更加严重。 相似文献
13.
To assay the effect of area and predators on invasion success, spiders were introduced onto islands that were large, with lizard predators; large, without lizard predators; or small, without lizard predators. Short-term survival was greater on islands without than with predators; area had no effect. Spiders initially increased substantially on both groups of islands without lizards, but after 5 years they nearly died off on small islands while persisting on most large islands; populations in the presence of predators never increased above initial sizes. Results show how predators as well as area are important in determining invasion success. 相似文献
14.
近岛礁海域距离大陆较远,风浪较小,已经成为发展水产养殖业的重点区域。研究发现,岛礁附近强烈的波浪反射会导致波浪能量的相对集中,进而造成养殖结构破坏。目前,有关养殖结构动力响应的研究大多集中在平坦海床海域,针对近岛礁海域的研究相对较少。为此,本文通过物理模型试验研究了一种布置在岛礁附近的铰接式多体浮式渔场平台在自存工况下的动力响应。结果表明,在自存工况下,岛礁地形增大了渔场平台的纵荡运动,其功率谱峰值相比平坦海床增加61.78%;平台迎浪侧系缆力的有效值增大为平坦海床的2.03倍。同时,岛礁地形引起的波浪反射使平台垂荡运动最大的位置由迎浪侧网箱转移至中间网箱,平台整体的纵摇运动减弱,但中间网箱与两侧网箱的相对转动增大。研究结果为近岛礁海域养殖设施及其系泊系统的设计提供理论参考。 相似文献
15.
Population phenomena, which provide much of the underlying basis for the theoretical structure of island biogeography, have received little direct study. We determined a key population trait-survival-in the Bahamian lizard Anolis sagrei on islands with an experimentally introduced predatory lizard and on neighboring unmanipulated islands. On unmanipulated islands, survival declined with several variables, most notably vegetation height: The island with the shortest vegetation had nearly the highest survival recorded for any lizard. On islands with the introduced predator, which forages mostly on the ground, A. sagrei shifted to taller vegetation; unlike on unmanipulated islands, its survival was very low on islands with the shortest vegetation but was higher on the others. Thus, species introduction radically changed a resident species' relation of survival to a key island-biogeographical variable. 相似文献
16.
Examples of sympatric speciation in nature are rare and hotly debated. We describe the parallel speciation of finches on two small islands in the Tristan da Cunha archipelago in the South Atlantic Ocean. Nesospiza buntings are a classic example of a simple adaptive radiation, with two species on each island: an abundant small-billed dietary generalist and a scarce large-billed specialist. Their morphological diversity closely matches the available spectrum of seed sizes, and genetic evidence suggests that they evolved independently on each island. Speciation is complete on the smaller island, where there is a single habitat with strongly bimodal seed size abundance, but is incomplete on the larger island, where a greater diversity of habitats has resulted in three lineages. Our study suggests that the buntings have undergone parallel ecological speciation. 相似文献
17.
Variation in numbers of land plant species on islands in the Galapagos Archipelago can be predicted on the basis of elevation, area of the adjacent island, distance from the nearest island, and distance from the center of the archipelago, but not on the basis of the area of the host island. Multiple linear regression (y = bx(1) + bx(2) . . .) gives better "goodness of fit" than curvilinear analysis (y = bx(z)). The variation in number of species on large islands can be predicted more accurately than the variation on small ones. Ecologic diversity and isolation are the natural regulators of species abundance. 相似文献
18.
Wilcox BA 《Science (New York, N.Y.)》1978,199(4332):996-998
Lizard faunas on post-Pleistocene land-bridge islands in the region of Baja California were examined for the effect of island age on species diversity. Species diversity and age are significantly correlated; and when the variation in species diversity attributable to area and latitude are removed, the corrected species diversity plotted against island age produces a relaxation or extinction curve. These results provide evidence for supersaturated faunas which are relaxing to lower levels of species diversity consistent with the equilibrium theory of island biogeography. 相似文献
19.
Simpson BB 《Science (New York, N.Y.)》1974,185(4152):698-700
Analyses of the floras of the high north Andean habitat islands (paramos) and the Galápagos Islands show that plant species diversity conforms to the MacArthur and Wilson model of island biogeography but that immigration occurred primarily during glacial periods. Modern plant species diversity is more significantly correlated with area and distance measures of the glacial forms of the islands than with similar measures of the present-day islands. 相似文献
20.
景观破碎化经常引起生态系统的边缘效应.千岛湖典型破碎化景观中岛屿灌木层植物的边缘效应,在10个孤立岛屿上选取灌木层植物物种作为研究对象,采用样方法调查其种类和数量.对野外调查的物种数据进行单因素方差分析,结果显示,F=23.386,P=0.000＜0.01,表明物种丰富度差异显著.用Shannon指数、Simpson指数和Pielou均匀度指数对两种环境中的植物种类多样性进行定性分析,在边缘样地,H=2.304、D=0.883、E=0.880;在内部样地,H=1.716、D:0.751、E=0.755.表明岛屿边缘的物种多样性在各个样地中都高于内部.而且岛屿边缘存在特有种,例如牡荆(Vitex negundo L.var.cannabi folia)和木莓(Rubus swinhoei Hcnce).物种相似性系数的变化范围较大(B=[0.300,0.800]),表明植物种类对景观破碎化影响的反应比较缓慢,但这种反应在某些岛屿已经表现出来.进一步的Spearman相关性分析表明,岛屿面积和灌木层物种无论在边缘样地还是内部样地的相关性都不显著. 相似文献