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

The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth system. Here, we revise and update the planetary boundary framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries—climate change and biosphere integrity—have been identified, each of which has the potential on its own to drive the Earth system into a new state should they be substantially and persistently transgressed.

/pdf/planetary-boundaries-guiding-human-development-on-a-changing-5gmf909etg.pdf

Planetary boundaries: Guiding human development on a changing planet

The most unique feature of Earth is the existence of life, and the most extraordinary feature of life is its diversity. Approximately 9 million types of plants, animals, protists and fungi inhabit the Earth. So, too, do 7 billion people. Two decades ago, at the first Earth Summit, the vast majority of the world's nations declared that human actions were dismantling the Earth's ecosystems, eliminating genes, species and biological traits at an alarming rate. This observation led to the question of how such loss of biological diversity will alter the functioning of ecosystems and their ability to provide society with the goods and services needed to prosper.

/pdf/biodiversity-loss-and-its-impact-on-humanity-2d0fgc88mg.pdf

Biodiversity loss and its impact on humanity

We live amid a global wave of anthropogenically driven biodiversity loss: species and population extirpations and, critically, declines in local species abundance. Particularly, human impacts on animal biodiversity are an under-recognized form of global environmental change. Among terrestrial vertebrates, 322 species have become extinct since 1500, and populations of the remaining species show 25% average decline in abundance. Invertebrate patterns are equally dire: 67% of monitored populations show 45% mean abundance decline. Such animal declines will cascade onto ecosystem functioning and human well-being. Much remains unknown about this “Anthropocene defaunation”; these knowledge gaps hinder our capacity to predict and limit defaunation impacts. Clearly, however, defaunation is both a pervasive component of the planet’s sixth mass extinction and also a major driver of global ecological change.

/pdf/defaunation-in-the-anthropocene-46k054u5cx.pdf

Defaunation in the Anthropocene

Large carnivores face serious threats and are experiencing massive declines in their populations and geographic ranges around the world. We highlight how these threats have affected the conservation status and ecological functioning of the 31 largest mammalian carnivores on Earth. Consistent with theory, empirical studies increasingly show that large carnivores have substantial effects on the structure and function of diverse ecosystems. Significant cascading trophic interactions, mediated by their prey or sympatric mesopredators, arise when some of these carnivores are extirpated from or repatriated to ecosystems. Unexpected effects of trophic cascades on various taxa and processes include changes to bird, mammal, invertebrate, and herpetofauna abundance or richness; subsidies to scavengers; altered disease dynamics; carbon sequestration; modified stream morphology; and crop damage. Promoting tolerance and coexistence with large carnivores is a crucial societal challenge that will ultimately determine the fate of Earth's largest carnivores and all that depends upon them, including humans.

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Status and ecological effects of the world's largest carnivores.

Why don't all species overexploit?

On the implications of currently available data on population fluctuations of arctic lemmings

Background: The Fennoscandian tundra differs from other arctic regions hosting brown lemmings (Lemmus spp.) in that it supports exceptionally low numbers of avian predators. Jaegers (Stercorarius spp.) play a central role in the guild of predators exploiting lemming outbreaks, as they are long-lived and have a vast supply of marine survival resources. Collared lemmings (Dicrostonyx spp.) evolved much earlier than brown lemmings (Lemmus spp.), Hypothesis: Lemming–vegetation dynamics and summer predation are causally interconnected. Avian predators that are adapted to exploit lemming outbreaks evolved in tundra areas where lemming–vegetation interactions generate density oscillations with a mean period short enough to provide dependable breeding resources for predators. Predictions: Long-tailed jaegers (Stercorarius longicaudus), primarily exploiting collared lemmings, diverged from parasitic jaegers (S. parasiticus) more than 2 million years ago. Pomarine jaegers (S. pomarinus) evolved more recently in response to the emergence of regular oscillations of brown lemming populations. The current breeding distribution of jaegers should reflect the distribution of the two lemming genera, except for areas where the oscillations generated by lemming–plant interactions are too erratic to provide dependable breeding resources. Empirical evidence: Our hypothesis accounts for the current distributions, behaviours, and ecologies of the three jaeger species. In addition, long-tailed jaegers did diverge early from other Stercorariidae. But we still do not know whether the timing of the divergence matches the evolution of collared lemmings. Evidence suggests that either: (1) Pomarine jaegers diverged from the skua (Catharacta spp.) lineage early, before skuas had developed their distinctive morphological traits; or (2) Pomarine jaegers diverged recently from great skuas (Catharacta skua) and then reverted to the ancestral jaeger morphology. Only the latter interpretation is consistent with our hypothesis, so we need to have more reliable timing of the evolution of long-tailed and Pomarine jaegers.

Co-evolution of jaegers (Stercorarius spp.) and arctic lemmings (Dicrostonyx spp. and Lemmus spp.) and the formation of the jaeger guild: an hypothesis

Tarja Oksanen

Papers

Why don't all species overexploit?

On the implications of currently available data on population fluctuations of arctic lemmings

Co-evolution of jaegers (Stercorarius spp.) and arctic lemmings (Dicrostonyx spp. and Lemmus spp.) and the formation of the jaeger guild: an hypothesis

The paradox of searching efficiency or why are violent population cycles so uncommon in terrestrial ecosystem