Adaptation and evolutionary rescue in metapopulations experiencing environmental deterioration

It is not known whether evolution will usually be rapid enough to allow a species to adapt and persist in a deteriorating environment. We tracked the eco-evolutionary dynamics of metapopulations with a laboratory model system of yeast exposed to salt stress. Metapopulations experienced environmental deterioration at three different rates and their component populations were either unconnected or connected by local dispersal or by global dispersal. We found that adaptation was favored by gradual deterioration and local dispersal. After further abrupt deterioration, the frequency of evolutionary rescue depended on both the prior rate of deterioration and the rate of dispersal. Adaptation was surprisingly frequent and rapid in small peripheral populations. Thus, evolutionary dynamics affect both the persistence and the range of a species after environmental deterioration.     

Rapid temporal reversal in predator-driven natural selection

As the environment changes, will species be able to adapt? By conducting experiments in natural environments, biologists can study how evolutionary processes such as natural selection operate through time. We predicted that the introduction of a terrestrial predator would first select for longer-legged lizards, which are faster, but as the lizards shifted onto high twigs to avoid the predator, selection would reverse toward favoring the shorter-legged individuals better able to locomote there. Our experimental studies on 12 islets confirmed these predictions within a single generation, thus demonstrating the rapidity with which evolutionary forces can change during times of environmental flux.     

Microbial biogeography: from taxonomy to traits

The biogeographic variation of life has predominantly been studied using taxonomy, but this focus is changing. There is a resurging interest in understanding patterns in the distribution not only of taxa but also of the traits those taxa possess. Patterns of trait variation shed light on fundamental questions in biology, including why organisms live where they do and how they will respond to environmental change. Technological advances such as environmental genomics place microbial ecology in a unique position to move trait-based biogeography forward. We anticipate that as trait-based biogeography continues to evolve, micro- and macroorganisms will be studied in concert, establishing a science that is informed by and relevant to all domains of life.     

Cancer biomarkers--an invitation to the table

The allure of the emerging genomic technologies in cancer is their ability to generate new biomarkers that predict how individual cancer patients will respond to various treatments. However, productive implementation of cancer biomarkers into patient care will require fundamental changes in how we consider approvals for cancer indications and how we track patient responses. Here we briefly describe ongoing efforts to identify and to validate cancer biomarkers, discuss the technological hurdles that lie ahead, and then focus on the more pressing political and cultural issues that, if left unheeded, could derail many of the anticipated benefits of biomarker research.     

The shifting ground of swidden agriculture on Palawan Island,the Philippines

Recent literature describing the process and pathways of the agrarian transition in Southeast Asia suggests that the rise of agricultural intensification and the growth of commodity markets will lead to the demise of swidden agriculture. This paper offers a longitudinal overview of the conditions that drive the agrarian transition amongst indigenous swidden cultivators and migrant paddy farmers in central Palawan Island, the Philippines. In line with regional agrarian change, we describe how a history of conservation policies has criminalized and pressured swidden farmers to adopt more intensive “modern” agricultural practices. We examine how indigenous swidden cultivators adjust their practice in response to recent changes in policies, security of harvests, and socio-cultural values vis-à-vis intensification. Rather than suggest that this transition will lead to the demise of swidden, results reveal that farmers instead negotiate a shifting ground in which they lean on and value swidden as a means of negotiating agrarian change.     

Climate change, keystone predation, and biodiversity loss

Climate change can affect organisms both directly via physiological stress and indirectly via changing relationships among species. However, we do not fully understand how changing interspecific relationships contribute to community- and ecosystem-level responses to environmental forcing. I used experiments and spatial and temporal comparisons to demonstrate that warming substantially reduces predator-free space on rocky shores. The vertical extent of mussel beds decreased by 51% in 52 years, and reproductive populations of mussels disappeared at several sites. Prey species were able to occupy a hot, extralimital site if predation pressure was experimentally reduced, and local species richness more than doubled as a result. These results suggest that anthropogenic climate change can alter interspecific interactions and produce unexpected changes in species distributions, community structure, and diversity.     

Cosmic rays,clouds, and climate

It has been proposed that Earth's climate could be affected by changes in cloudiness caused by variations in the intensity of galactic cosmic rays in the atmosphere. This proposal stems from an observed correlation between cosmic ray intensity and Earth's average cloud cover over the course of one solar cycle. Some scientists question the reliability of the observations, whereas others, who accept them as reliable, suggest that the correlation may be caused by other physical phenomena with decadal periods or by a response to volcanic activity or El Ni?o. Nevertheless, the observation has raised the intriguing possibility that a cosmic ray-cloud interaction may help explain how a relatively small change in solar output can produce much larger changes in Earth's climate. Physical mechanisms have been proposed to explain how cosmic rays could affect clouds, but they need to be investigated further if the observation is to become more than just another correlation among geophysical variables.     

兴安落叶松（Larix gmelinii Rupr）针叶解剖结构变化体现其光合能力对气候变化的适应性

叶片易受环境因子影响，其形态解剖结构特征不但与叶片的生理功能密切相关，而且反映树木对环境变化的响应和适应。叶片结构的改变势必会改变树木的生理功能。同一树种长期生长在异质环境条件下，经过自然选择和适应，会在形态和生理特性等方面产生变异，形成特定的地理种群。另外，母体所经受的环境胁迫也会影响到其子代的生长、发育和生理等特征。因此，了解植物叶片形态结构对环境变化的响应与适应是探索植物对环境变化的响应适应机制的基础。兴安落叶松(Larix gmelinii Rupr.)是我国北方森林的优势树种，主要分布在我国东北地区，但日益加剧的气候变化可能会改变其现有的分布区。为了区分叶片对气候变化的可塑性和适应性，本研究采用同质园法比较测定了6个不同气候条件下的兴安落叶松种源的32年生树木的针叶解剖结构和光合生理相关因子，利用石蜡切片方法分析了针叶的解剖结构特征、光合能力（Pmax-a）、水分利用效率（WUE）之间的关系及其对气候变化的适应性。结果表明：表皮细胞厚度、叶肉细胞厚度、传输组织厚度、维管束厚度、内皮层厚度以及叶片总厚度均存在显著的种源间差异（P < 0.05）。叶肉细胞厚度与Pmax-a、气孔导度和WUE之间均存在显著的正相关关系（P < 0.05）。叶肉细胞厚度、表皮细胞厚度、叶片总厚度以及叶肉细胞厚度和表皮细胞厚度在叶片总厚度中所占比例均与种源地的干燥度指数（即年蒸发量与年降水量之比）呈正线性关系。这些结果说明：不同种源兴安落叶松针叶解剖结构因对种源原地气候条件的长期适应而产生显著的差异，从而引起其针叶光合作用、水分利用等生理功能发生相应的变化,从而有利于该树种在气候变化的情景下得以生存和繁衍。     

Ecological change, group territoriality, and population dynamics in Serengeti lions

Territorial behavior is expected to buffer populations against short-term environmental perturbations, but we have found that group living in African lions causes a complex response to long-term ecological change. Despite numerous gradual changes in prey availability and vegetative cover, regional populations of Serengeti lions remained stable for 10- to 20-year periods and only shifted to new equilibria in sudden leaps. Although gradually improving environmental conditions provided sufficient resources to permit the subdivision of preexisting territories, regional lion populations did not expand until short-term conditions supplied enough prey to generate large cohorts of surviving young. The results of a simulation model show that the observed pattern of "saltatory equilibria" results from the lions' grouping behavior.     

From signals to patterns: space, time, and mathematics in developmental biology

We now have a wealth of information about the molecular signals that act on cells in embryos, but how do the control systems based on these signals generate pattern and govern the timing of developmental events? Here, I discuss four examples to show how mathematical modeling and quantitative experimentation can give some useful answers. The examples concern the Bicoid gradient in the early Drosophila embryo, the dorsoventral patterning of a frog embryo by bone morphogenetic protein signals, the auxin-mediated patterning of plant meristems, and the Notch-dependent somite segmentation clock.     

Climate extremes: observations, modeling, and impacts

One of the major concerns with a potential change in climate is that an increase in extreme events will occur. Results of observational studies suggest that in many areas that have been analyzed, changes in total precipitation are amplified at the tails, and changes in some temperature extremes have been observed. Model output has been analyzed that shows changes in extreme events for future climates, such as increases in extreme high temperatures, decreases in extreme low temperatures, and increases in intense precipitation events. In addition, the societal infrastructure is becoming more sensitive to weather and climate extremes, which would be exacerbated by climate change. In wild plants and animals, climate-induced extinctions, distributional and phenological changes, and species' range shifts are being documented at an increasing rate. Several apparently gradual biological changes are linked to responses to extreme weather and climate events.     

Human genome. Finally, the book of life and instructions for navigating it

The race is over. On 26 June, to much fanfare, two rival teams announced that they had each completed a version of the "book of life"--a rough draft of the complete human genetic code. So what, exactly, is in these two different volumes, and how will they fine-tune it so that everyone from workaday biologists to pharmaceutical giants can mine its gold?     

Risk, anti-reflexivity, and ethical neutralization in industrial food processing

While innovations have fostered the mass production of food at low costs, there are externalities or side effects associated with high-volume food processing. We focus on foodborne illness linked to two commodities: ground beef and bagged salad greens. In our analysis, we draw from the concepts of risk, reflexive modernization, and techniques of ethical neutralization. For each commodity, we find that systems organized for industrial goals overlook how production models foster cross-contamination and widespread outbreaks. Responses to outbreaks tend to rely on technological fixes, which do not constitute the reflexive change needed to holistically and effectively address foodborne illness in the long term. We contend that powerful anti-reflexivity movements resist calls for reform and successfully maintain industrial goals and organization. Actions that thwart changes in agrifood systems to better protect consumers are unethical, yet they continue to be successful. We argue that specific techniques of ethical neutralization play an important part in their success. Research on anti-reflexivity and techniques of neutralization will serve to further expose the ethical issues associated with the industrial agrifood system and foster new guiding principles and organizational designs for food production.     

Light-driven changes in energy metabolism directly entrain the cyanobacterial circadian oscillator

Circadian clocks are self-sustained biological oscillators that can be entrained by environmental cues. Although this phenomenon has been studied in many organisms, the molecular mechanisms of entrainment remain unclear. Three cyanobacterial proteins and adenosine triphosphate (ATP) are sufficient to generate oscillations in phosphorylation in vitro. We show that changes in illumination that induce a phase shift in cultured cyanobacteria also cause changes in the ratio of ATP to adenosine diphosphate (ADP). When these nucleotide changes are simulated in the in vitro oscillator, they cause phase shifts similar to those observed in vivo. Physiological concentrations of ADP inhibit kinase activity in the oscillator, and a mathematical model constrained by data shows that this effect is sufficient to quantitatively explain entrainment of the cyanobacterial circadian clock.     

Reciprocal TH17 and regulatory T cell differentiation mediated by retinoic acid

The cytokine transforming growth factor-beta (TGF-beta) converts na?ve T cells into regulatory T (Treg) cells that prevent autoimmunity. However, in the presence of interleukin-6 (IL-6), TGF-beta has also been found to promote the differentiation of na?ve T lymphocytes into proinflammatory IL-17 cytokine-producing T helper 17 (T(H)17) cells, which promote autoimmunity and inflammation. This raises the question of how TGF-beta can generate such distinct outcomes. We identified the vitamin A metabolite retinoic acid as a key regulator of TGF-beta-dependent immune responses, capable of inhibiting the IL-6-driven induction of proinflammatory T(H)17 cells and promoting anti-inflammatory Treg cell differentiation. These findings indicate that a common metabolite can regulate the balance between pro- and anti-inflammatory immunity.     

Internal behavior in fish schools

Structural changes within fish schools correlate with declines in environmental oxygen. The changes may result from the responses of individual fish to the environmental consequences of group metabolism. Individual behaviors are adaptive to the school in that they tend to maintain stability between school members and their environment.     

Seasonality in ocean microbial communities

Ocean warming occurs every year in seasonal cycles that can help us to understand long-term responses of plankton to climate change. Rhythmic seasonal patterns of microbial community turnover are revealed when high-resolution measurements of microbial plankton diversity are applied to samples collected in lengthy time series. Seasonal cycles in microbial plankton are complex, but the expansion of fixed ocean stations monitoring long-term change and the development of automated instrumentation are providing the time-series data needed to understand how these cycles vary across broad geographical scales. By accumulating data and using predictive modeling, we gain insights into changes that will occur as the ocean surface continues to warm and as the extent and duration of ocean stratification increase. These developments will enable marine scientists to predict changes in geochemical cycles mediated by microbial communities and to gauge their broader impacts.     

稳定性碳同位素在揭示环境变化中的应用

植物组织中的稳定性碳同位素组成(δ13C)整合记录了气候因子和影响植物碳同化以及气孔导度的生理因子的相关信息。应用稳定碳同位素技术可以揭示环境变化中的一些相关信息。回顾了不同的环境因子和植物δ13C的关系,以及这些关系在气候变化研究中的应用,同时进一步讨论了这项技术在重建历史气候和预测未来气候变化中的作用。     

Division of labor with a workforce of one: challenges in specifying effector and memory T cell fate

In the course of the immune response against microbes, na?ve T cells proliferate and generate varied classes of effector cells, as well as memory cells with distinct properties and functions. Owing to recent technological advances, some of the most imposing questions regarding effector and memory T cell differentiation are now becoming experimentally soluble: How many classes of antigen-specific T cells exist, and how malleable are they in their fate and in their functional state? How might a spectrum of cell fates be imparted to the clonal descendants of a single lymphocyte? Where, when, and how does pathogen-associated information refine the instruction, selection, and direction of newly activated T cells as they perform their tasks in different locations and times? Some surprising new glimpses ahead on these subjects and other yet-unanswered questions are discussed.