物种灭绝机制

对灭绝类型、灭绝率、灭绝特点等物种灭绝的基本概念进行了阐述,从灭绝与进化,灭绝与系统发育历程之间的关系等方面探讨了灭绝的内在机制,并从生物学、物理学及人类影响三方面对物种灭绝的外在机制进行了系统的说明。     

Trends in Extinction Risk for Imperiled Species in Canada

Protecting and promoting recovery of species at risk of extinction is a critical component of biodiversity conservation. In Canada, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) determines whether species are at risk of extinction or extirpation, and has conducted these assessments since 1977. We examined trends in COSEWIC assessments to identify whether at-risk species that have been assessed more than once tended to improve, remain constant, or deteriorate in status, as a way of assessing the effectiveness of biodiversity conservation in Canada. Of 369 species that met our criteria for examination, 115 deteriorated, 202 remained unchanged, and 52 improved in status. Only 20 species (5.4%) improved to the point where they were ‘not at risk’, and five of those were due to increased sampling efforts rather than an increase in population size. Species outcomes were also dependent on the severity of their initial assessment; for example, 47% of species that were initially listed as special concern deteriorated between assessments. After receiving an at-risk assessment by COSEWIC, a species is considered for listing under the federal Species at Risk Act (SARA), which is the primary national tool that mandates protection for at-risk species. We examined whether SARA-listing was associated with improved COSEWIC assessment outcomes relative to unlisted species. Of 305 species that had multiple assessments and were SARA-listed, 221 were listed at a level that required identification and protection of critical habitat; however, critical habitat was fully identified for only 56 of these species. We suggest that the Canadian government should formally identify and protect critical habitat, as is required by existing legislation. In addition, our finding that at-risk species in Canada rarely recover leads us to recommend that every effort be made to actively prevent species from becoming at-risk in the first place.     

Andean Condor (Vultur gryphus) in Ecuador: Geographic Distribution,Population Size and Extinction Risk

The Andean Condor (Vultur gryphus) in Ecuador is classified as Critically Endangered. Before 2015, standardized and systematic estimates of geographic distribution, population size and structure were not available for this species, hampering the assessment of its current status and hindering the design and implementation of effective conservation actions. In this study, we performed the first quantitative assessment of geographic distribution, population size and population viability of Andean Condor in Ecuador. We used a methodological approach that included an ecological niche model to study geographic distribution, a simultaneous survey of 70 roosting sites to estimate population size and a population viability analysis (PVA) for the next 100 years. Geographic distribution in the form of extent of occurrence was 49 725 km². During a two-day census, 93 Andean Condors were recorded and a population of 94 to 102 individuals was estimated. In this population, adult-to-immature ratio was 1:0.5. In the modeled PVA scenarios, the probability of extinction, mean time to extinction and minimum population size varied from zero to 100%, 63 years and 193 individuals, respectively. Habitat loss is the greatest threat to the conservation of Andean Condor populations in Ecuador. Population size reduction in scenarios that included habitat loss began within the first 15 years of this threat. Population reinforcement had no effects on the recovery of Andean Condor populations given the current status of the species in Ecuador. The population size estimate presented in this study is the lower than those reported previously in other countries where the species occur. The inferences derived from the population viability analysis have implications for Condor management in Ecuador. This study highlights the need to redirect efforts from captive breeding and population reinforcement to habitat conservation.     

Forest Loss in Protected Areas and Intact Forest Landscapes: A Global Analysis

In spite of the high importance of forests, global forest loss has remained alarmingly high during the last decades. Forest loss at a global scale has been unveiled with increasingly finer spatial resolution, but the forest extent and loss in protected areas (PAs) and in large intact forest landscapes (IFLs) have not so far been systematically assessed. Moreover, the impact of protection on preserving the IFLs is not well understood. In this study we conducted a consistent assessment of the global forest loss in PAs and IFLs over the period 2000–2012. We used recently published global remote sensing based spatial forest cover change data, being a uniform and consistent dataset over space and time, together with global datasets on PAs’ and IFLs’ locations. Our analyses revealed that on a global scale 3% of the protected forest, 2.5% of the intact forest, and 1.5% of the protected intact forest were lost during the study period. These forest loss rates are relatively high compared to global total forest loss of 5% for the same time period. The variation in forest losses and in protection effect was large among geographical regions and countries. In some regions the loss in protected forests exceeded 5% (e.g. in Australia and Oceania, and North America) and the relative forest loss was higher inside protected areas than outside those areas (e.g. in Mongolia and parts of Africa, Central Asia, and Europe). At the same time, protection was found to prevent forest loss in several countries (e.g. in South America and Southeast Asia). Globally, high area-weighted forest loss rates of protected and intact forests were associated with high gross domestic product and in the case of protected forests also with high proportions of agricultural land. Our findings reinforce the need for improved understanding of the reasons for the high forest losses in PAs and IFLs and strategies to prevent further losses.     

Extinction Risk: Predicting and Redressing the Threat

Predicting and redressing the threat of species extinction is not a success story. The science of estimating extinction rates and risk prediction is approached in a manner that is difficult to apply in the field, and yet current integrated ecosystem management programmes in many parts of the world, which are trying to place the conservation of species into sustainable community projects, need predictive tools for planning land use programmes. Such programmes involve US$100s of millions of multilateral and bilateral aid; many predicated on a site's biodiversity importance, the risks of extinction, sustainable extraction, production forms of land use, community livelihoods, water, and many others factors, but increasingly on ensuring that after the pump-priming funds are finished the programmes are both environmentally and economically sustainable (Swingland 2002, 2003, 2004; Swingland et al. 2003). [Swingland I.R. 2002. In: Swingland I.R., Bettelheim E.C., Grace J., Prance G.T. and Saunders L.S. (eds), Carbon Biodiversity, Conservation and Income: An Analysis of a Free Market Approach to Land-use Change and Forestry in Developing and Developed Countries. Philosophical Transactions Royal Society London A: Mathematical, Physical and Engineering Sciences, London; Swingland I.R. (ed.) 2003. Capturing Biodiversity and Conserving Biodiversity: The Market Approach. Earthscan, London; Swingland I.R. (ed.) 2004. CO² e biodiversità. Un approccio integrato a favore del clima e del patrimonio naturale. Edizioni Ambiente, Milano, Italy, 296 pp.; Swingland I.R., Bettelheim E.C. and Niles J.O. 2003. In: Swingland I.R. (ed.), Capturing Biodiversity and Conserving Biodiversity: The Market Approach. Earthscan, London] This involves predictions of ‘what if?’ what if laws are changed to prevent over utilisation and prevent ‘The Tragedy of the Commons’ where land ownership is vested in the state and people degrade the environment, and instead institute private land ownership. In places like China and much of the Far East, biodiversity is over-exploited as nearly all their species are used for food, medicine and construction purposes, and private land ownership in rural areas is rudimentary or absent. Since most species extinction is anthropocentric, research on species extinction needs to be more accessible and focussed on global problems.     

Dead Shrimp Blues: A Global Assessment of Extinction Risk in Freshwater Shrimps (Crustacea: Decapoda: Caridea)

We present the first global assessment of extinction risk for a major group of freshwater invertebrates, caridean shrimps. The risk of extinction for all 763 species was assessed using the IUCN Red List criteria that include geographic ranges, habitats, ecology and past and present threats. The Indo-Malayan region holds over half of global species diversity, with a peak in Indo-China and southern China. Shrimps primarily inhabit flowing water; however, a significant subterranean component is present, which is more threatened than the surface fauna. Two species are extinct with a further 10 possibly extinct, and almost one third of species are either threatened or Near Threatened (NT). Threats to freshwater shrimps include agricultural and urban pollution impact over two-thirds of threatened and NT species. Invasive species and climate change have the greatest overall impact of all threats (based on combined timing, scope and severity of threats).     

非胎生红树植物繁殖体特征及潮间带分带现象

研究了香港4种非胎生红树植物榄李(Lumnitzera racemosa(Jack．)Voigt．)、银叶树(Heritiera littoralis(Drgand．)Ait．)、海漆(Excoecaria agallocha L．)和老鼠筋(Acanthus ilicifotius L．)的繁殖体特征和萌发技术,并分析了其在潮间带分带的决定因素。所有直接种植的新鲜榄李繁殖体均不能萌发,但经湿润贮藏35d和50d的繁殖体能萌发,说明该物种具有种子休眠的特性。榄李萌发率随盐度升高而下降,盐度高于25则不能萌发。银叶树繁殖体果壳的去除可加速其萌发。海漆和老鼠筋的繁殖体分别在2d和3d开始萌根。在繁殖体萌发方面,老鼠筋的耐盐性比榄李强。4种非胎生红树植物对潮间带不稳定环境的适应方式有：(1)繁殖体的寿命较长,如榄李和银叶树;(2)萌根速度快,如海漆和老鼠筋;(3)具有沉性繁殖体,如榄李。繁殖体的悬浮性是决定这4种非胎生红树植物潮间带分带的最重要因素：榄李因具有沉性繁殖体而自然分布于最靠海的区域,而银叶树、海漆和老鼠筋因具有浮性繁殖体而更靠陆岸分布。对于繁殖体悬浮性相同的物种,萌根速度是影响潮间带分带的重要因素：完整的银叶树繁殖体需要108d才能萌根,因而分布于最靠陆岸的区域,而海漆和老鼠筋因萌根速度快而在相对更靠海的区域分布。环境盐度、繁殖体大小、动物啃食和幼苗大小等因素则不能解释香港非胎生红树植物在潮间带的分带现象。     

A Global Analysis of the Effectiveness of Marine Protected Areas in Preventing Coral Loss

Background

A variety of human activities have led to the recent global decline of reef-building corals [1], [2]. The ecological, social, and economic value of coral reefs has made them an international conservation priority [2], [3]. The success of Marine Protected Areas (MPAs) in restoring fish populations [4] has led to optimism that they could also benefit corals by indirectly reducing threats like overfishing, which cause coral degradation and mortality [2], [5]. However, the general efficacy of MPAs in increasing coral reef resilience has never been tested.

Methodology/Principal Findings

We compiled a global database of 8534 live coral cover surveys from 1969–2006 to compare annual changes in coral cover inside 310 MPAs to unprotected areas. We found that on average, coral cover within MPAs remained constant, while coral cover on unprotected reefs declined. Although the short-term differences between unprotected and protected reefs are modest, they could be significant over the long-term if the effects are temporally consistent. Our results also suggest that older MPAs were generally more effective in preventing coral loss. Initially, coral cover continued to decrease after MPA establishment. Several years later, however, rates of coral cover decline slowed and then stabilized so that further losses stopped.

Conclusions/Significance

These findings suggest that MPAs can be a useful tool not only for fisheries management, but also for maintaining coral cover. Furthermore, the benefits of MPAs appear to increase with the number of years since MPA establishment. Given the time needed to maximize MPA benefits, there should be increased emphasis on implementing new MPAs and strengthening the enforcement of existing MPAs.     

澳门红树林植物组成及种群分布格局的研究

调查工作于１９９２年４月～１９９４年９月在路环及凼仔红树林区内进行．路环红树林面积约７．１１５ｈｍ２,凼仔红树林面积约５７．２０５ｈｍ２．在两地区的海滩中,红树林植物计有４科４种,分属于红树科（Ｒｈｉｚｏｐｈｏｒａｃｅａｅ）、紫金牛科（Ｍｙｒｏｉｎａｃｅａｅ）、马鞭草科（Ｖｅｒｂｅｎａｃｅａｅ）和爵床科（Ａｃａｎｔｈａｃｅａｅ）．海岸半红树植物计有１５科２７种．利用样带法研究澳门红树林种群的分布格局,除秋茄为随机分布外,桐花树、白骨壤及老鼠勒均趋于集群的分布格局．结合数据分析８个研究区域种群生态位序列,只有凼仔红树林研究区最具有显著的生态位序列．     

Global Establishment Risk of Economically Important Fruit Fly Species (Tephritidae)

The global invasion of Tephritidae (fruit flies) attracts a great deal of attention in the field of plant quarantine and invasion biology because of their economic importance. Predicting which one in hundreds of potential invasive fruit fly species is most likely to establish in a region presents a significant challenge, but can be facilitated using a self organising map (SOM), which is able to analyse species associations to rank large numbers of species simultaneously with an index of establishment. A global presence/absence dataset including 180 economically significant fruit fly species in 118 countries was analysed using a SOM. We compare and contrast ranked lists from six countries selected from each continent, and also show that those countries geographically close were clustered together by the SOM analysis because they have similar fruit fly assemblages. These closely clustered countries therefore represent greater threats to each other as sources of invasive fruit fly species. Finally, we indicate how this SOM method could be utilized as an initial screen to support prioritizing fruit fly species for further research into their potential to invade a region.     

Extinction Risk: A Comparative Analysis of Central Asian Vertebrates

In 2004, IUCN listed 20% of all mammals, 12% of birds and 4% of reptiles as threatened with extinction. Why are these species, but not the others in their clades, at risk? Most comparative studies of Red List status to date have investigated the relationship between status and life history or ecology, either at a local level where species face a given situation which may be known in detail, or at a global level where threats are much more heterogeneous. The use of data at a sub-global level raises several issues, including the need to assess populations across geopolitical borders and how best to treat non-breeding phases of populations. However, regional-level data provide the opportunity to look in more detail at how threatening processes operate. We employ comparative analysis using phylogenetically independent contrasts and multiple regression to control for inter-related and confounding independent variables, to evaluate correlates of regional threat for three groups of central Asian vertebrates. We find that aspects of dispersal, area of occupancy, body mass and generation time are important in predicting the perceived risk of regional extinction.     

红雪茶基源种的鉴定及资源分布

本研究通过对红雪茶基源种进行考证,并结合品种鉴定及野外生态调查,结果表明,红雪茶的基源种应为金丝刷（Lethariella cladonioides）和金丝带（L.zahlbruckneri）,在这两个种群内,存在化学多态现象。市售的“红雪茶”主要由这两个种的四个化学宗所组成。红雪茶的分布中心主要在藏东南,滇西北及川西地区,目前红雪茶的资源已经受到了极大的破坏,日渐濒危。为加强对野生红雪茶资源的有效保护,提出了开展红雪茶种质资源保护的建议。     

Macrofaunal Loss and Microhabitat Destruction: The Impact of Trampling in a Temperate Mangrove Forest, NSW Australia

Trampling paths are a feature of estuarine habitats in southeastern Australia. An experimental investigation quantified the impact of trampling over a 3 year period on the microhabitat features and macrofaunal assemblages in a temperate mangrove forest in New South Wales, Australia. The magnitude of the impact varied between 0 and 25 passes (representing a visit by 25 people), which reduced the biomass of the Bostrychia–Caloglossa algal association by 50%. The frequency of trampling varied between one and four, simulating a single and seasonal visits by a group of people to the mangrove forest. The main impact of trampling was an alteration to the microhabitat structures of the forest floor including a decrease in the number and vertical height of pneumatophores, an increase in the proportion of bent and broken pneumatophores in trampled lanes and a decrease in the biomass of the epiphytic Bostrychia–Caloglossa algal association. The macrofauna most impacted by trampling were the gastropods most commonly associated with the pneumatophores and algal assemblages and included Ophicardelus spp. and Assiminea buccinoides. Those gastropods least impacted by trampling were commonly associated with the surface of the sediment or were known to move over the surface and included Bembicium auratum and Cassidula zonata. There was little impact on the main burrowing crab, Heloecius cordiformis. There were some indirect impacts of trampling with the recruitment of Ophicardelus spp. Assiminea buccinoides and Salinator solida reduced in the subsequent year after trampling had ceased. People can create walking paths in mangrove forests that have long term effects on the habitat. An appropriate management emphasis may lie in maintaining the structural features of the habitat.     

Reef Fishes in Biodiversity Hotspots Are at Greatest Risk from Loss of Coral Species

Coral reef ecosystems are under a variety of threats from global change and anthropogenic disturbances that are reducing the number and type of coral species on reefs. Coral reefs support upwards of one third of all marine species of fish, so the loss of coral habitat may have substantial consequences to local fish diversity. We posit that the effects of habitat degradation will be most severe in coral regions with highest biodiversity of fishes due to greater specialization by fishes for particular coral habitats. Our novel approach to this important but untested hypothesis was to conduct the same field experiment at three geographic locations across the Indo-Pacific biodiversity gradient (Papua New Guinea; Great Barrier Reef, Australia; French Polynesia). Specifically, we experimentally explored whether the response of local fish communities to identical changes in diversity of habitat-providing corals was independent of the size of the regional species pool of fishes. We found that the proportional reduction (sensitivity) in fish biodiversity to loss of coral diversity was greater for regions with larger background species pools, reflecting variation in the degree of habitat specialization of fishes across the Indo-Pacific diversity gradient. This result implies that habitat-associated fish in diversity hotspots are at greater risk of local extinction to a given loss of habitat diversity compared to regions with lower species richness. This mechanism, related to the positive relationship between habitat specialization and regional biodiversity, and the elevated extinction risk this poses for biodiversity hotspots, may apply to species in other types of ecosystems.     

Phenotypic Changes Across a Geographic Gradient: The Case of Three Sympatric Dolphin Species

Phenotypic changes in the mammalian mandible can occur at different spatial and temporal scales. We investigated mandibular size and shape variation in three extant closely related dolphins (Cetacea, Odontoceti): Tursiops truncatus, Stenella coeruleoalba and Delphinus delphis in order to test the hypothesis that similar phenotypic changes occur across the same geographical gradient. Our data included 219 specimens representative of the following geographic locations: the Mediterranean Sea, the eastern north Atlantic and the North Sea. Each mandibula was photographed laterally and spatial positioning of eight homologous 2D landmarks was recorded. After applying generalised Procrustes analysis (GPA), intraspecific variation was first investigated between sexes and among populations to allow further pooling of samples. Size and shape differences among populations and species were investigated through multivariate ordination techniques (PCA), Procrustes ANOVA and allometric analyses. In all three species, Mediterranean populations clearly differed in mandible shape from the extra-Mediterranean ones. Among the three, the direction of geographic phenotypic changes was significantly similar in the striped and common dolphin, while the bottlenose dolphin was the most divergent species, differing both in size and allometric trajectory. Shape variation of the two former species highlighted a morphological convergence in the Atlantic, and a phenotypic divergence in the Mediterranean. Shape differences among the three dolphin species were interpreted in the light of different prey preferences, feeding strategies and habitat partitioning to avoid direct competition.