The Effects of Biogeography and Biotic Interactions on Lemur Community Assembly

Geographic patterns of biodiversity result from broad-scale biogeographic and present-day ecological processes. The aim of this study was to investigate the relative importance of biogeographic history and ecology driving patterns of diversity in modern primate communities in Madagascar. I collected data on endemic lemur species co-occurrence from range maps and survey literature for 100 communities in protected areas. I quantified and compared taxonomic, phylogenetic, and functional dimensions of intra- and intersite diversity. I tested environmental and geographic predictors of diversity and endemism. I calculated deforestation rates within protected areas between the years 2000 and 2014, and tested if diversity is related to forest cover and loss. I found the phylogenetic structure of lemur communities could be explained primarily by remotely sensed plant productivity, supporting the hypothesis that there was ecological differentiation among ecoregions, while functional-trait disparity was not strongly related to environment. Taxonomic and phylogenetic diversity also increased with increasing topographic heterogeneity. Beta diversity was explained by both differences in ecology among localities and potential river barriers. Approximately 3000 km² were deforested in protected areas since the year 2000, threatening the most diverse communities (up to 31%/park). The strong positive association of plant productivity and topographic heterogeneity with lemur diversity indicates that high productivity, rugged landscapes support greater diversity. Both ecology and river barriers influenced lemur community ecology and biogeography. These results underscore the need for focused conservation efforts to slow the loss of irreplaceable evolutionary and ecological diversity.     

Signal Molecules for Plant Defense Responses to Biotic Stress

Plants are capable of recognizing the penetrating pathogens and of responding to their attack by the activation of the defense systems. Signal transduction from the receptor to the cell genome is required for this activation. Recently, signal molecules have been found, which are involved in the signal transduction triggered in response to biotic stress. The data accumulated imply the presence of a complex and well-coordinated signal network in plant cells. This net controls plant defense responses to pathogen attacks.     

Understanding Plant Community Responses to Combinations of Biotic and Abiotic Factors in Different Phases of the Plant Growth Cycle

Understanding plant community responses to combinations of biotic and abiotic factors is critical for predicting ecosystem response to environmental change. However, studies of plant community regulation have seldom considered how responses to such factors vary with the different phases of the plant growth cycle. To address this deficit we studied an aquatic plant community in an ecosystem subject to gradients in mute swan (Cygnus olor) herbivory, riparian shading, water temperature and distance downstream of the river source. We quantified abundance, species richness, evenness, flowering and dominance in relation to biotic and abiotic factors during the growth-, peak-, and recession-phases of the plant growth cycle. We show that the relative importance of biotic and abiotic factors varied between plant community properties and between different phases of the plant growth cycle. Herbivory became more important during the later phases of peak abundance and recession due to an influx of swans from adjacent pasture fields. Shading by riparian vegetation also had a greater depressing effect on biomass in later seasons, probably due to increased leaf abundance reducing light intensity reaching the aquatic plants. The effect of temperature on community diversity varied between upstream and downstream sites by altering the relative competitiveness of species at these sites. These results highlight the importance of seasonal patterns in the regulation of plant community structure and function by multiple factors.     

Biotic Interactions in the Face of Climate Change: A Comparison of Three Modelling Approaches

Climate change is expected to alter biotic interactions, and may lead to temporal and spatial mismatches of interacting species. Although the importance of interactions for climate change risk assessments is increasingly acknowledged in observational and experimental studies, biotic interactions are still rarely incorporated in species distribution models. We assessed the potential impacts of climate change on the obligate interaction between Aeshna viridis and its egg-laying plant Stratiotes aloides in Europe, based on an ensemble modelling technique. We compared three different approaches for incorporating biotic interactions in distribution models: (1) We separately modelled each species based on climatic information, and intersected the future range overlap (‘overlap approach’). (2) We modelled the potential future distribution of A. viridis with the projected occurrence probability of S. aloides as further predictor in addition to climate (‘explanatory variable approach’). (3) We calibrated the model of A. viridis in the current range of S. aloides and multiplied the future occurrence probabilities of both species (‘reference area approach’). Subsequently, all approaches were compared to a single species model of A. viridis without interactions. All approaches projected a range expansion for A. viridis. Model performance on test data and amount of range gain differed depending on the biotic interaction approach. All interaction approaches yielded lower range gains (up to 667% lower) than the model without interaction. Regarding the contribution of algorithm and approach to the overall uncertainty, the main part of explained variation stems from the modelling algorithm, and only a small part is attributed to the modelling approach. The comparison of the no-interaction model with the three interaction approaches emphasizes the importance of including obligate biotic interactions in projective species distribution modelling. We recommend the use of the ‘reference area approach’ as this method allows a separation of the effect of climate and occurrence of host plant.     

Examining Plant Physiological Responses to Climate Change through an Evolutionary Lens

Integrating knowledge from physiological ecology, evolutionary biology, phylogenetics, and paleobiology provides novel insights into factors driving plant physiological responses to both past and future climate change.Since the Industrial Revolution began approximately 200 years ago, global atmospheric carbon dioxide concentration ([CO₂]) has increased from 270 to 401 µL L⁻¹, and average global temperatures have risen by 0.85°C, with the most pronounced effects occurring near the poles (IPCC, 2013). In addition, the last 30 years were the warmest decades in 1,400 years (PAGES 2k Consortium, 2013). By the end of this century, [CO₂] is expected to reach at least 700 µL L⁻¹, and global temperatures are projected to rise by 4°C or more based on greenhouse gas scenarios (IPCC, 2013). Precipitation regimes also are expected to shift on a regional scale as the hydrologic cycle intensifies, resulting in greater extremes in dry versus wet conditions (Medvigy and Beaulieu, 2012). Such changes already are having profound impacts on the physiological functioning of plants that scale up to influence interactions between plants and other organisms and ecosystems as a whole (Fig. 1). Shifts in climate also may alter selective pressures on plants and, therefore, have the potential to influence evolutionary processes. In some cases, evolutionary responses can occur as rapidly as only a few generations (Ward et al., 2000; Franks et al., 2007; Lau and Lennon, 2012), but there is still much to learn in this area, as pointed out by Franks et al. (2014). Such responses have the potential to alter ecological processes, including species interactions, via ecoevolutionary feedbacks (Shefferson and Salguero-Gómez, 2015). In this review, we discuss microevolutionary and macroevolutionary processes that can shape plant responses to climate change as well as direct physiological responses to climate change during the recent geologic past as recorded in the fossil record. We also present work that documents how plant physiological and evolutionary responses influence interactions with other organisms as an example of how climate change effects on plants can scale to influence higher order processes within ecosystems. Thus, this review combines findings in plant physiological ecology and evolutionary biology for a comprehensive view of plant responses to climate change, both past and present.Open in a separate windowFigure 1.A, Abiotic conditions directly affect plant physiological traits. Also, the probability that a given species persists with climate change (both in the past and future) is influenced by the degree of phenotypic plasticity in these traits, the ability of populations to migrate and track environmental conditions in space, and the potential for populations to evolve traits that are adaptive in the novel environment. Interactions between plants and other organisms also affect plant physiology, the strength of selection on plant traits, and the probability of persistence. Climate change alters species interactions via direct effects on plant antagonists and mutualists and via changes in plant traits that influence the dynamics of these interactions. B, Following an environmental perturbation (vertical dashed line), plant populations with low genetic and/or phenotypic variability are unlikely to persist (red line). Phenotypic plasticity can facilitate the tolerance of environmental change over the short term (blue line). Migration to a more favorable environment and/or the evolution of adaptive traits (including greater plasticity) can facilitate long-term responses to environmental change (orange line).Due to rapid climate change, plants have become increasingly exposed to novel environmental conditions that are outside of their physiological limits and beyond the range to which they are adapted (Ward and Kelly, 2004; Shaw and Etterson, 2012). Plant migration may not keep pace with the unprecedented rate of current climate change (Loarie et al., 2009); therefore, rapid evolutionary responses may be the major process by which plants persist in the future (Franks et al., 2007; Alberto et al., 2013). In addition, although plants may have evolved physiological plasticity that produces a fitness advantage in novel environments, climate change may be so extreme as to push plants beyond tolerance ranges even in the most plastic of genotypes (Anderson et al., 2012).

ADVANCES

• Rapid climate change is disrupting long-standing patterns of natural selection on plant physiological traits. Microevolutionary responses to these changes can occur over time scales relevant to ecological processes.
• Emerging macroevolutionary analyses using large, time-calibrated phylogenies provide insight into evolutionary changes in plant physiology and species diversification rates following past climate change events.
• Past conditions, such as low [CO₂] during glacial cycles, likely produced lingering adaptations that could limit plant physiological responses to current and future climate change.
• Climate change can affect plant traits, fitness, and survival indirectly via shifts in biotic interactions. The ecoevolutionary consequences of altered species interactions can be as important as the direct effects of climate change on plant physiology.

Understanding the potential for evolutionary responses at the physiological level is a key challenge that must be met in order to improve predictions of plant response to climate change. A focus on physiology is critical because these processes scale from individual to ecosystem levels. For example, [CO₂] rise and climate change that alter photosynthetic rates may shift plant growth rates, overall productivity, and resource use (Ainsworth and Rogers, 2007; Norby and Donald, 2011; Medeiros and Ward, 2013). Other physiological responses to altered climate include increasing leaf sugars with elevated [CO₂], which may influence major life history traits such as flowering time and fitness via sugar-sensing mechanisms (Springer et al., 2008; Wahl et al., 2013). At higher scales, shifts in source/sink relationships of photosynthate can influence seedling survival, whole-plant growth, competitive ability within the broader plant community, symbiotic interactions, and fitness. Therefore, the potential for physiological functioning to evolve in response to climate change will be a key indicator of plant resiliency (or lack thereof) in future environments. Defining physiological components that correlate with fitness, particularly in newly emerging environments, will allow us to identify candidate processes that may be under strong selection in future environments and to predict the composition and functioning of future plant populations and communities (Kimball et al., 2012).It is clear that long-term changes in the environment spanning millions of years of plant evolution have shaped the major physiological pathways that are present in modern plants (Edwards et al., 2010; Sage et al., 2012), and these pathways will determine the range of physiological tolerances for the response to novel environments of the future. In addition, relatively recent conditions in the geologic record have shaped selective pressures on plant physiology (Ward et al., 2000) and may influence the ability of plants to respond to future conditions. For example, the peak of the last glacial period (20,000 years ago) represents a fascinating time when low [CO₂] (180–200 µL L⁻¹) likely constrained the physiological functioning of C₃ plants. During that period, [CO₂] was among the lowest values that occurred during the evolution of land plants (Berner, 2006). Modern C₃ annuals grown at glacial [CO₂] exhibit an average 50% reduction in photosynthesis and growth as well as high levels of mortality and reproductive failure relative to plants grown at modern [CO₂] (Polley et al., 1993; Dippery et al., 1995; Sage and Coleman, 2001; Ward and Kelly, 2004). Thus, this period likely imposed strong selective pressures on plants, as evidenced directly by artificial selection experiments (Ward et al., 2000) and in the recent geologic record (Gerhart and Ward, 2010).A series of key questions have now emerged. (1) How will plants evolve in response to rapid climate change? (2) How will evolutionary history and species interactions influence this evolutionary trajectory? (3) How have past responses to climate change in the geologic record influenced current and potentially future responses to a rapidly changing environment? To address these questions, we report on emerging concepts in the broad field of evolutionary physiology, paying specific attention to processes ranging from microevolution to macroevolution, the influence of species interactions on these processes, and insights from paleobiology (where we provide new findings). This review is not intended to cover all of the current ground-breaking work in this area but rather to provide an overview of how a multitude of approaches can influence our overall understanding of how plant physiological evolution has altered past ecosystems as well as those that will emerge during the Anthropocene Epoch.     

Stomata Prioritize Their Responses to Multiple Biotic and Abiotic Signal Inputs

Stomata are microscopic pores in leaf epidermis that regulate gas exchange between plants and the environment. Being natural openings on the leaf surface, stomata also serve as ports for the invasion of foliar pathogenic bacteria. Each stomatal pore is enclosed by a pair of guard cells that are able to sense a wide spectrum of biotic and abiotic stresses and respond by precisely adjusting the pore width. However, it is not clear whether stomatal responses to simultaneously imposed biotic and abiotic signals are mutually dependent on each other. Here we show that a genetically engineered Escherichia coli strain DH5α could trigger stomatal closure in Vicia faba, an innate immune response that might depend on NADPH oxidase-mediated ROS burst. DH5α-induced stomatal closure could be abolished or disguised under certain environmental conditions like low [CO₂], darkness, and drought, etc. Foliar spraying of high concentrations of ABA could reduce stomatal aperture in high humidity-treated faba bean plants. Consistently, the aggressive multiplication of DH5α bacteria in Vicia faba leaves under high humidity could be alleviated by exogenous application of ABA. Our data suggest that a successful colonization of bacteria on the leaf surface is correlated with stomatal aperture regulation by a specific set of environmental factors.     

Suitable Days for Plant Growth Disappear under Projected Climate Change: Potential Human and Biotic Vulnerability

Ongoing climate change can alter conditions for plant growth, in turn affecting ecological and social systems. While there have been considerable advances in understanding the physical aspects of climate change, comprehensive analyses integrating climate, biological, and social sciences are less common. Here we use climate projections under alternative mitigation scenarios to show how changes in environmental variables that limit plant growth could impact ecosystems and people. We show that although the global mean number of days above freezing will increase by up to 7% by 2100 under “business as usual” (representative concentration pathway [RCP] 8.5), suitable growing days will actually decrease globally by up to 11% when other climatic variables that limit plant growth are considered (i.e., temperature, water availability, and solar radiation). Areas in Russia, China, and Canada are projected to gain suitable plant growing days, but the rest of the world will experience losses. Notably, tropical areas could lose up to 200 suitable plant growing days per year. These changes will impact most of the world’s terrestrial ecosystems, potentially triggering climate feedbacks. Human populations will also be affected, with up to ~2,100 million of the poorest people in the world (~30% of the world’s population) highly vulnerable to changes in the supply of plant-related goods and services. These impacts will be spatially variable, indicating regions where adaptations will be necessary. Changes in suitable plant growing days are projected to be less severe under strong and moderate mitigation scenarios (i.e., RCP 2.6 and RCP 4.5), underscoring the importance of reducing emissions to avoid such disproportionate impacts on ecosystems and people.     

Plant Responses to Water Stress

This Special Issue comprises a series of papers that developsthe theme of plant responses to water stress, encompassing recentdevelopments at the molecular level, through responses of photosynthesisand metabolism, to their application in crop selection and yield.The consideration of water deficits is particularly timely,given the huge developments in this area in the past decade.This issue specifically sets out to place molecular and physiologicalprocesses and their agronomic applications in an environmentalcontext.     

Biotic and Climatic Velocity Identify Contrasting Areas of Vulnerability to Climate Change

Metrics that synthesize the complex effects of climate change are essential tools for mapping future threats to biodiversity and predicting which species are likely to adapt in place to new climatic conditions, disperse and establish in areas with newly suitable climate, or face the prospect of extirpation. The most commonly used of such metrics is the velocity of climate change, which estimates the speed at which species must migrate over the earth’s surface to maintain constant climatic conditions. However, “analog-based” velocities, which represent the actual distance to where analogous climates will be found in the future, may provide contrasting results to the more common form of velocity based on local climate gradients. Additionally, whereas climatic velocity reflects the exposure of organisms to climate change, resultant biotic effects are dependent on the sensitivity of individual species as reflected in part by their climatic niche width. This has motivated development of biotic velocity, a metric which uses data on projected species range shifts to estimate the velocity at which species must move to track their climatic niche. We calculated climatic and biotic velocity for the Western Hemisphere for 1961–2100, and applied the results to example ecological and conservation planning questions, to demonstrate the potential of such analog-based metrics to provide information on broad-scale patterns of exposure and sensitivity. Geographic patterns of biotic velocity for 2954 species of birds, mammals, and amphibians differed from climatic velocity in north temperate and boreal regions. However, both biotic and climatic velocities were greatest at low latitudes, implying that threats to equatorial species arise from both the future magnitude of climatic velocities and the narrow climatic tolerances of species in these regions, which currently experience low seasonal and interannual climatic variability. Biotic and climatic velocity, by approximating lower and upper bounds on migration rates, can inform conservation of species and locally-adapted populations, respectively, and in combination with backward velocity, a function of distance to a source of colonizers adapted to a site’s future climate, can facilitate conservation of diversity at multiple scales in the face of climate change.     

Ionic Interactions Promote Transmembrane Helix-Helix Association Depending on Sequence Context

Folding and oligomerization of integral membrane proteins frequently depend on specific interactions of transmembrane helices. Interacting amino acids of helix-helix interfaces may form complex motifs and exert different types of molecular forces. Here, a set of strongly self-interacting transmembrane domains (TMDs), as isolated from a combinatorial library, was found to contain basic and acidic residues, in combination with polar nonionizable amino acids and C-terminal GxxxG motifs. Mutational analyses of selected sequences and reconstruction of high-affinity interfaces confirmed the cooperation of these residues in homotypic interactions. Probing heterotypic interaction indicated the presence of interhelical charge-charge interactions. Furthermore, simple motifs of an ionizable residue and GxxxG are significantly overrepresented in natural TMDs, and a specific combination of these motifs exhibits high-affinity heterotypic interaction. We conclude that intramembrane charge-charge interactions depend on sequence context. Moreover, they appear important for homotypic and heterotypic interactions of numerous natural TMDs.     

Plant Responses to Drought,Acclimation, and Stress Tolerance

At the whole plant level, the effect of stress is usually perceived as a decrease in photosynthesis and growth. That is why this review is focused mainly on the effect of drought on photosynthesis, its injury, and mechanisms of adaptation. The analysed literature shows that plants have evolved a number of adaptive mechanisms that allow the photochemical and biochemical systems to cope with negative changes in environment, including increased water deficit. In addition, the acquisition of tolerance to drought includes both phenotypic and genotypic changes. The approaches were made to identify those metabolic steps that are most sensitive to drought. Some studies also examined the mechanisms controlling gene expression and putative regulatory pathways.     

Responses of Terrestrial Antarctic Ecosystems to Climate Change

Antarctic terrestrial biota are generally limited by the inexorably linked environmental factors of low summer temperature and lack of available water. However, in parts of the Antarctic, both these factors are changing rapidly on contemporary timescales. Terrestrial biota have concurrently been faced with changes in the timing of UV-B maxima associated with spring ozone depletion. The region of the Antarctic Peninsula and Scotia Arc has experienced one of the most rapid rates of environmental warming seen worldwide over the last 30–50 years. Together with local changes in precipitation, this has resulted in a rapid reduction in extent and thinning of many ice-fields and glaciers, exposing new terrain for colonisation while, at the same time, altering patterns of water availability in terrestrial habitats. The rapid development of communities on newly-exposed ground is also facilitated by the existence of soil propagule banks, which contain propagules of both local and exotic origin. In this paper we collate and review evidence from a range of observational and manipulative studies that investigate the effect of climate change, especially increased temperature, on the processes of colonisation and subsequent community development by plants in the Antarctic. Biological changes that have been associated with climate change are visible in the form of expansions in range and local population numbers amongst elements of the flora. Environmental manipulation experiments further demonstrate the possibility of large and rapid species and community responses to climate amelioration, with many resident biota responding positively, at least in the absence of increased competition from exotic colonists. Manipulation studies are also starting to elucidate more subtle responses to climate changes, at levels ranging from cell biochemistry to habitat and food web structure. Integrating such subtle responses is vital to improving our ability to understand the consequences of climate change, as these may lead to much greater consequential impacts on communities and ecosystems.      

miR482介导的植物生物胁迫响应

植物在生长发育过程中会遇到各种生物胁迫,根据响应过程的不同,可将之分为基于蛋白质的生物胁迫和基于RNA的生物胁迫。miR482是一种植物特有的、已在23个物种中被证实存在的小RNA。miR482参与指导植物次级phasiRNA的合成,其主要靶标为植物庞大的Ⅳ=日§三R尺类家族抗病基因。本文通过整理近年来ETI（effector-triggeredimmunity）相关的NBS-LRR类抗病基因和抗RNA沉默抑制相关miR482级联调控的研究成果,总结出了miR482介导植物两类生物胁迫响应的调控机制。