抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Freshwater biodiversity is the over-riding conservation priority during the International Decade for Action - 'Water for Life' - 2005 to 2015. Fresh water makes up only 0.01% of the World's water and approximately 0.8% of the Earth's surface, yet this tiny fraction of global water supports at least 100000 species out of approximately 1.8 million - almost 6% of all described species. Inland waters and freshwater biodiversity constitute a valuable natural resource, in economic, cultural, aesthetic, scientific and educational terms. Their conservation and management are critical to the interests of all humans, nations and governments. Yet this precious heritage is in crisis. Fresh waters are experiencing declines in biodiversity far greater than those in the most affected terrestrial ecosystems, and if trends in human demands for water remain unaltered and species losses continue at current rates, the opportunity to conserve much of the remaining biodiversity in fresh water will vanish before the 'Water for Life' decade ends in 2015. Why is this so, and what is being done about it? This article explores the special features of freshwater habitats and the biodiversity they support that makes them especially vulnerable to human activities. We document threats to global freshwater biodiversity under five headings: overexploitation; water pollution; flow modification; destruction or degradation of habitat; and invasion by exotic species. Their combined and interacting influences have resulted in population declines and range reduction of freshwater biodiversity worldwide. Conservation of biodiversity is complicated by the landscape position of rivers and wetlands as 'receivers' of land-use effluents, and the problems posed by endemism and thus non-substitutability. In addition, in many parts of the world, fresh water is subject to severe competition among multiple human stakeholders. Protection of freshwater biodiversity is perhaps the ultimate conservation challenge because it is influenced by the upstream drainage network, the surrounding land, the riparian zone, and - in the case of migrating aquatic fauna - downstream reaches. Such prerequisites are hardly ever met. Immediate action is needed where opportunities exist to set aside intact lake and river ecosystems within large protected areas. For most of the global land surface, trade-offs between conservation of freshwater biodiversity and human use of ecosystem goods and services are necessary. We advocate continuing attempts to check species loss but, in many situations, urge adoption of a compromise position of management for biodiversity conservation, ecosystem functioning and resilience, and human livelihoods in order to provide a viable long-term basis for freshwater conservation. Recognition of this need will require adoption of a new paradigm for biodiversity protection and freshwater ecosystem management - one that has been appropriately termed 'reconciliation ecology'.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/96AA265E3D88C95FB802E7A73CCB4332/S1464793105006950a.pdf/div-class-title-freshwater-biodiversity-importance-threats-status-and-conservation-challenges-div.pdf

Freshwater biodiversity: importance, threats, status and conservation challenges

Protecting the world’s freshwater resources requires diagnosing threats over a broad range of scales, from global to local. Here we present the first worldwide synthesis to jointly consider human and biodiversity perspectives on water security using a spatial framework that quantifies multiple stressors and accounts for downstream impacts. We find that nearly 80% of the world’s population is exposed to high levels of threat to water security. Massive investment in water technology enables rich nations to offset high stressor levels without remedying their underlying causes, whereas less wealthy nations remain vulnerable. A similar lack of precautionary investment jeopardizes biodiversity, with habitats associated with 65% of continental discharge classified as moderately to highly threatened. The cumulative threat framework offers a tool for prioritizing policy and management responses to this crisis, and underscores the necessity of limiting threats at their source instead of through costly remediation of symptoms in order to assure global water security for both humans and freshwater biodiversity.

/pdf/global-threats-to-human-water-security-and-river-2hfichkqti.pdf

Global threats to human water security and river biodiversity

Food in the Anthropocene: the EAT–Lancet Commission on healthy diets from sustainable food systems

▪ Abstract Local habitat and biological diversity of streams and rivers are strongly influenced by landform and land use within the surrounding valley at multiple scales. However, empirical associations between land use and stream response only varyingly succeed in implicating pathways of influence. This is the case for a number of reasons, including (a) covariation of anthropogenic and natural gradients in the landscape; (b) the existence of multiple, scale-dependent mechanisms; (c) nonlinear responses; and (d) the difficulties of separating present-day from historical influences. Further research is needed that examines responses to land use under different management strategies and that employs response variables that have greater diagnostic value than many of the aggregated measures in current use. In every respect, the valley rules the stream.      H.B.N. Hynes (1975)

http://deq.idaho.gov/media/525804-Landscapes_Riverscapes_Influence_landuse_stream_ecosystems_Allan_2004.pdf

Landscapes and Riverscapes: The Influence of Land Use on Stream Ecosystems

https://science.sciencemag.org/content/sci/362/6421/1369.1.full.pdf

The freshwater biodiversity crisis.

Protected areas are a cornerstone strategy for terrestrial and increasingly marine biodiversity conservation, but their use for conserving inland waters has received comparatively scant attention. In 2010, the Convention on Biological Diversity (CBD) included a target of 17% protection for inland waters, yet there has been no meaningful way of measuring progress toward that target. Defining and evaluating “protection” is especially complicated for rivers because their integrity is intimately linked to impacts in their upstream catchments. A new generation of global hydrographic data now enables a high-resolution, standardized assessment of how upland activities may be propagated downstream. Here, we develop and apply, globally, a river protection metric that integrates both local and upstream catchment protection. We found that “integrated” river protection is highly variable across geographies and river size classes and in most basins falls short of the 17% CBD target. Around the world, about 70% of river reaches (by length) have no protected areas in their upstream catchments, and only 11.1% (by length) achieve full integrated protection. The average level of integrated protection is 13.5% globally, yet the majority of the world's largest basins show averages below 10%. Within basins, gaps are particularly severe for larger rivers.

Looking Beyond the Fenceline: Assessing Protection Gaps for the World's Rivers

Efforts to set global conservation priorities have largely ignored freshwater diversity, thereby excluding some of the world's most speciose, threatened, and valuable taxa. Using a new global map of freshwater ecoregions and distribution data for about 13,300 fish species, we identify regions of exceptional freshwater biodiversity and assess their overlap with regions of equivalent terrestrial importance. Overlap is greatest in the tropics and is higher than expected by chance. These high-congruence areas offer opportunities for integrated conservation efforts, which could be of particular value when economic conditions force conservation organizations to narrow their focus. Areas of low overlap—missed by current terrestrially based priority schemes—merit independent freshwater conservation efforts. These results provide new information to conservation investors setting priorities at global or regional scales and argue for a potential reallocation of future resources to achieve representation of overlooked biomes.

/pdf/concordance-of-freshwater-and-terrestrial-biodiversity-17lsai7n1a.pdf

Concordance of freshwater and terrestrial biodiversity

Freshwater biodiversity of Latin America and the Caribbean : a conservation assessment. Report of a workshop

Large rivers and their floodplains support a significant proportion of the world's biodiversity and provide important goods and ecological services to society, including fisheries. Riverine ecosystems and fisheries are subject to intense pressure from a wide range of anthropogenic disturbances, the main ones being impacts from altered land use, modifications to river flow regimes, riparian and physical habitat loss, water pollution, exotic species invasions and intensive exploitation of fish stocks. As a consequence, a far greater proportion of freshwater species are threatened or endangered than terrestrial or marine species in the same taxonomic groups. In this paper we review ecological processes sustaining river and floodplain biodiversity and productivity. We also outline the status of knowledge of fundamental issues in fish ecology, including fish habitat requirements, trophic ecology, life history strategies, migration, the population biology of riverine fish and modelling of fish populations and assemblages. We evaluate threats to the productivity and diversity of large river systems, as well as conservation and rehabilitation measures and discuss ecological approaches and tools for management decision support. The final summary highlights knowledge gaps and research priorities and new research frontiers that demand more attention in river ecosystem studies, conservation efforts and fisheries management.

/pdf/river-fisheries-ecological-basis-for-management-and-387xrkzlpk.pdf

Robin Abell

Papers

The freshwater biodiversity crisis.

Looking Beyond the Fenceline: Assessing Protection Gaps for the World's Rivers

Concordance of freshwater and terrestrial biodiversity

Freshwater biodiversity of Latin America and the Caribbean : a conservation assessment. Report of a workshop

River fisheries: ecological basis for management and conservation