Scale-free extinction dynamics in spatially structured host-parasitoid systems

Much of the work on extinction events has focused on external perturbations of ecosystems, such as climatic change, or anthropogenic factors. Extinction, however, can also be driven by endogenous factors, such as the ecological interactions between species in an ecosystem. Here we show that endogenously driven extinction events can have a scale-free distribution in simple spatially structured host-parasitoid systems. Due to the properties of this distribution there may be many such simple ecosystems that, although not strictly permanent, persist for arbitrarily long periods of time. We identify a critical phase transition in the parameter space of the host-parasitoid systems, and explain how this is related to the scale-free nature of the extinction process. Based on these results, we conjecture that scale-free extinction processes and critical phase transitions of the type we have found may be a characteristic feature of many spatially structured, multi-species ecosystems in nature. The necessary ingredient appears to be competition between species where the locally inferior type disperses faster in space. If this condition is satisfied then the eventual outcome depends subtly on the strength of local superiority of one species versus the dispersal rate of the other.     

Ecological constraints, life history traits and the evolution of cooperative breeding

The ecological constraints hypothesis is widely accepted as an explanation for the evolution of delayed dispersal in cooperatively breeding birds. Intraspecific studies offer the strongest support. Observational studies have demonstrated a positive association between the severity of ecological constraints and the prevalence of cooperation, and experimental studies in which constraints on independent breeding were relaxed resulted in helpers moving to adopt the vacant breeding opportunities. However, this hypothesis has proved less successful in explaining why cooperative breeding has evolved in some species or lineages but not in others. Comparative studies have failed to identify ecological factors that differ consistently between cooperative and noncooperative species. The life history hypothesis, which emphasizes the role of life history traits in the evolution of cooperative breeding, offers a solution to this difficulty. A recent analysis showed that low adult mortality and low dispersal predisposed certain lineages to show cooperative behaviour, given the right ecological conditions. This represents an important advance, not least by offering an explanation for the patchy phylogenetic distribution of cooperative breeding. We discuss the complementary nature of these two hypotheses and suggest that rather than regarding life history traits as predisposing and ecological factors as facilitating cooperation, they are more likely to act in concert. While acknowledging that different cooperative systems may be a consequence of different selective pressures, we suggest that to identify the key differences between cooperative and noncooperative species, a broad constraints hypothesis that incorporates ecological and life history traits in a single measure of 'turnover of breeding opportunities' may provide the most promising avenue for future comparative studies. Copyright 2000 The Association for the Study of Animal Behaviour.     

Community Biomass and Bottom up Multivariate Nutrient Complementarity Mediate the Effects of Bioturbator Diversity on Pelagic Production

Tests of the biodiversity and ecosystem functioning (BEF) relationship have focused little attention on the importance of interactions between species diversity and other attributes of ecological communities such as community biomass. Moreover, BEF research has been mainly derived from studies measuring a single ecosystem process that often represents resource consumption within a given habitat. Focus on single processes has prevented us from exploring the characteristics of ecosystem processes that can be critical in helping us to identify how novel pathways throughout BEF mechanisms may operate. Here, we investigated whether and how the effects of biodiversity mediated by non-trophic interactions among benthic bioturbator species vary according to community biomass and ecosystem processes. We hypothesized that (1) bioturbator biomass and species richness interact to affect the rates of benthic nutrient regeneration [dissolved inorganic nitrogen (DIN) and total dissolved phosphorus (TDP)] and consequently bacterioplankton production (BP) and that (2) the complementarity effects of diversity will be stronger on BP than on nutrient regeneration because the former represents a more integrative process that can be mediated by multivariate nutrient complementarity. We show that the effects of bioturbator diversity on nutrient regeneration increased BP via multivariate nutrient complementarity. Consistent with our prediction, the complementarity effects were significantly stronger on BP than on DIN and TDP. The effects of the biomass-species richness interaction on complementarity varied among the individual processes, but the aggregated measures of complementarity over all ecosystem processes were significantly higher at the highest community biomass level. Our results suggest that the complementarity effects of biodiversity can be stronger on more integrative ecosystem processes, which integrate subsidiary “simpler” processes, via multivariate complementarity. In addition, reductions in community biomass may decrease the strength of interspecific interactions so that the enhanced effects of biodiversity on ecosystem processes can disappear well before species become extinct.     

Phyllostomid Bat Occurrence in Successional Stages of Neotropical Dry Forests

Tropical dry forests (TDFs) are highly endangered tropical ecosystems being replaced by a complex mosaic of patches of different successional stages, agricultural fields and pasturelands. In this context, it is urgent to understand how taxa playing critical ecosystem roles respond to habitat modification. Because Phyllostomid bats provide important ecosystem services (e.g. facilitate gene flow among plant populations and promote forest regeneration), in this study we aimed to identify potential patterns on their response to TDF transformation in sites representing four different successional stages (initial, early, intermediate and late) in three Neotropical regions: México, Venezuela and Brazil. We evaluated bat occurrence at the species, ensemble (abundance) and assemblage level (species richness and composition, guild composition). We also evaluated how bat occurrence was modulated by the marked seasonality of TDFs. In general, we found high seasonal and regional specificities in phyllostomid occurrence, driven by specificities at species and guild levels. For example, highest frugivore abundance occurred in the early stage of the moistest TDF, while highest nectarivore abundance occurred in the same stage of the driest TDF. The high regional specificity of phyllostomid responses could arise from: (1) the distinctive environmental conditions of each region, (2) the specific behavior and ecological requirements of the regional bat species, (3) the composition, structure and phenological patterns of plant assemblages in the different stages, and (4) the regional landscape composition and configuration. We conclude that, in tropical seasonal environments, it is imperative to perform long-term studies considering seasonal variations in environmental conditions and plant phenology, as well as the role of landscape attributes. This approach will allow us to identify potential patterns in bat responses to habitat modification, which constitute an invaluable tool for not only bat biodiversity conservation but also for the conservation of the key ecological processes they provide.     

Diversity and distribution pattern of epiphyllous liverworts and its ecological determinants

Epiphyllous liverworts form a special group of bryophytes that primarily grow on leaves of understory vascular plants, occurring in constantly moist and warm evergreen forest in tropical and subtropical regions. Epiphyllous liverworts may influence ecosystem processes including carbon, nitrogen and water cycles. Furthermore, they are very sensitive to climate change and forest fragmentation, and can be used as bioindicators for changes in ecological conditions and escalating loss of biodiversity. In this paper, we reviewed studies on morphological traits, species diversity, geographical distribution and environmental conditions (including characteristics of hosts and habitats) of epiphyllous liverworts, discussed the possible reasons for the mechanisms underlying the diversity pattern of epiphyllous liverworts. According to these studies, we proposed that further ecological studies on epiphyllous liverworts should be more focused on their formation, mechanisms of matter exchange and energy flux, ecological functions in forest ecosystem, the response to climate changes and their broader-scale ecology.     

叶附生苔植物物种多样性分布格局及生态成因

叶附生苔植物(以下简称叶附生苔)是一类附生在维管植物叶片表面的、一般只出现在热带雨林和常绿阔叶林中的苔类植物。它们具有重要的生态功能, 如影响碳、氮、水循环, 对气候变化和森林破碎化反应敏感, 可用作环境变化的指示植物。该文对叶附生苔的形态特性、物种多样性的研究历史和进展、地理分布格局, 以及对环境的要求(附主和生境的特性)等进行了综述, 探讨了叶附生苔多样性分布格局形成的可能原因, 即环境(空气湿度高、林冠层发育好、干扰少)和适应特征(无性繁殖、形体微小)的选择。根据全球叶附生苔研究进展状况及所存在的问题提出未来可开展的研究方向, 如叶附生苔的形成原因、与附主间的物质交换和能量流动机制、在森林生态系统中的生态功能、气候变化指示作用研究等, 大尺度上的研究也值得关注。     

Predicting the likely response of data‐poor ecosystems to climate change using space‐for‐time substitution across domains

Predicting ecological response to climate change is often limited by a lack of relevant local data from which directly applicable mechanistic models can be developed. This limits predictions to qualitative assessments or simplistic rules of thumb in data‐poor regions, making management of the relevant systems difficult. We demonstrate a method for developing quantitative predictions of ecological response in data‐poor ecosystems based on a space‐for‐time substitution, using distant, well‐studied systems across an inherent climatic gradient to predict ecological response. Changes in biophysical data across the spatial gradient are used to generate quantitative hypotheses of temporal ecological responses that are then tested in a target region. Transferability of predictions among distant locations, the novel outcome of this method, is demonstrated via simple quantitative relationships that identify direct and indirect impacts of climate change on physical, chemical and ecological variables using commonly available data sources. Based on a limited subset of data, these relationships were demonstrably plausible in similar yet distant (>2000 km) ecosystems. Quantitative forecasts of ecological change based on climate‐ecosystem relationships from distant regions provides a basis for research planning and informed management decisions, especially in the many ecosystems for which there are few data. This application of gradient studies across domains – to investigate ecological response to climate change – allows for the quantification of effects on potentially numerous, interacting and complex ecosystem components and how they may vary, especially over long time periods (e.g. decades). These quantitative and integrated long‐term predictions will be of significant value to natural resource practitioners attempting to manage data‐poor ecosystems to prevent or limit the loss of ecological value. The method is likely to be applicable to many ecosystem types, providing a robust scientific basis for estimating likely impacts of future climate change in ecosystems where no such method currently exists.     

Ecosystem engineering in space and time

The ecosystem engineering concept focuses on how organisms physically change the abiotic environment and how this feeds back to the biota. While the concept was formally introduced a little more than 10 years ago, the underpinning of the concept can be traced back to more than a century to the early work of Darwin. The formal application of the idea is yielding new insights into the role of species in ecosystems and many other areas of basic and applied ecology. Here we focus on how temporal, spatial and organizational scales usefully inform the roles played by ecosystem engineers and their incorporation into broader ecological contexts. Two particular, distinguishing features of ecosystem engineers are that they affect the physical space in which other species live and their direct effects can last longer than the lifetime of the organism – engineering can in essence outlive the engineer. Together, these factors identify critical considerations that need to be included in models, experimental and observational work. The ecosystem engineering concept holds particular promise in the area of ecological applications, where influence over abiotic variables and their consequent effects on biotic communities may facilitate ecological restoration and counterbalance anthropogenic influences.     

The Value of Animal Behavior in Evaluations of Restoration Success

Animals are key members of ecosystems, contributing to processes like pollination, seed dispersal, and herbivory. Incorporating measures of animal behavior into evaluations of restoration success will provide critical information that is not available from animal species composition and richness estimates derived from the documentation of species presence and absence. Behavioral studies will (1) allow comparisons of the habitat quality of target and reference sites based on behaviors that have fitness consequences for organisms; (2) provide valuable information about reasons for differences in habitat quality; (3) identify critical resources that make a site suitable or not for particular species; and/or (4) provide information on the mechanisms through which species contribute to ecosystem functions. When resources for the evaluation of restoration success are available, practitioners should carefully consider the costs and benefits of the different variables they could quantify. In some cases, it may be more important to compare the behavior of one or a few critical animal species that contribute to ecosystem function rather than try to document the presence or absence of all species.     

Linking ecological theory with stream restoration

1. Faced with widespread degradation of riverine ecosystems, stream restoration has greatly increased. Such restoration is rarely planned and executed with inputs from ecological theory. In this paper, we seek to identify principles from ecological theory that have been, or could be, used to guide stream restoration. 2. In attempts to re‐establish populations, knowledge of the species’ life history, habitat template and spatio‐temporal scope is critical. In many cases dispersal will be a critical process in maintaining viable populations at the landscape scale, and special attention should be given to the unique geometry of stream systems 3. One way by which organisms survive natural disturbances is by the use of refugia, many forms of which may have been lost with degradation. Restoring refugia may therefore be critical to survival of target populations, particularly in facilitating resilience to ongoing anthropogenic disturbance regimes. 4. Restoring connectivity, especially longitudinal connectivity, has been a major restoration goal. In restoring lateral connectivity there has been an increasing awareness of the riparian zone as a critical transition zone between streams and their catchments. 5. Increased knowledge of food web structure – bottom‐up versus top‐down control, trophic cascades and subsidies – are yet to be applied to stream restoration efforts. 6. In restoration, species are drawn from the regional species pool. Having overcome dispersal and environmental constraints (filters), species persistence may be governed by local internal dynamics, which are referred to as assembly rules. 7. While restoration projects often define goals and endpoints, the succession pathways and mechanisms (e.g. facilitation) by which these may be achieved are rarely considered. This occurs in spite of a large of body of general theory on which to draw. 8. Stream restoration has neglected ecosystem processes. The concept that increasing biodiversity increases ecosystem functioning is very relevant to stream restoration. Whether biodiversity affects ecosystem processes, such as decomposition, in streams is equivocal. 9. Considering the spatial scale of restoration projects is critical to success. Success is more likely with large‐scale projects, but they will often be infeasible in terms of the available resources and conflicts of interest. Small‐scale restoration may remedy specific problems. In general, restoration should occur at the appropriate spatial scale such that restoration is not reversed by the prevailing disturbance regime. 10. The effectiveness and predictability of stream ecosystem restoration will improve with an increased understanding of the processes by which ecosystems develop and are maintained. Ideas from general ecological theory can clearly be better incorporated into stream restoration projects. This will provide a twofold benefit in providing an opportunity both to improve restoration outcomes and to test ecological theory.     

Animal behaviour shapes the ecological effects of ocean acidification and warming: moving from individual to community‐level responses

Biological communities are shaped by complex interactions between organisms and their environment as well as interactions with other species. Humans are rapidly changing the marine environment through increasing greenhouse gas emissions, resulting in ocean warming and acidification. The first response by animals to environmental change is predominantly through modification of their behaviour, which in turn affects species interactions and ecological processes. Yet, many climate change studies ignore animal behaviour. Furthermore, our current knowledge of how global change alters animal behaviour is mostly restricted to single species, life phases and stressors, leading to an incomplete view of how coinciding climate stressors can affect the ecological interactions that structure biological communities. Here, we first review studies on the effects of warming and acidification on the behaviour of marine animals. We demonstrate how pervasive the effects of global change are on a wide range of critical behaviours that determine the persistence of species and their success in ecological communities. We then evaluate several approaches to studying the ecological effects of warming and acidification, and identify knowledge gaps that need to be filled, to better understand how global change will affect marine populations and communities through altered animal behaviours. Our review provides a synthesis of the far‐reaching consequences that behavioural changes could have for marine ecosystems in a rapidly changing environment. Without considering the pervasive effects of climate change on animal behaviour we will limit our ability to forecast the impacts of ocean change and provide insights that can aid management strategies.     

An anthropogenic habitat within a suboptimal colonized ecosystem provides improved conditions for a range‐shifting species

Many species are shifting their ranges in response to the changing climate. In cases where such shifts lead to the colonization of a new ecosystem, it is critical to establish how the shifting species itself is impacted by novel environmental and biological interactions. Anthropogenic habitats that are analogous to the historic habitat of a shifting species may play a crucial role in the ability of that species to expand or persist in suboptimal colonized ecosystems. We tested if the anthropogenic habitat of docks, a likely mangrove analog, provides improved conditions for the range‐shifting mangrove tree crab Aratus pisonii within the colonized suboptimal salt marsh ecosystem. To test if docks provided an improved habitat, we compared the impact of the salt marsh and dock habitats on ecological and life history traits that influence the ability of this species to persist and expand into the salt marsh and compared these back to baselines in the historic mangrove ecosystem. Specifically, we examined behavior, physiology, foraging, and the thermal conditions of A. pisonii in each habitat. We found that docks provide a more favorable thermal and foraging habitat than the surrounding salt marsh, while their ability to provide conditions which improved behavior and physiology was mixed. Our study shows that anthropogenic habitats can act as analogs to historic ecosystems and enhance the habitat quality for range‐shifting species in colonized suboptimal ecosystems. If the patterns that we document are general across systems, then anthropogenic habitats may play an important facilitative role in the range shifts of species with continued climate change.     

Embryo and early larval stages of the Humboldt Current krill Euphausia mucronata (Crustacea: Euphausiacea)

The Humboldt Current krill, Euphausia mucronata (Crustacea: Euphausiacea), is an endemic and keystone species in the food web of this highly productive eastern border current ecosystem. The morphology and ontogeny of E. mucronata is known from calyptopis I to the adult phase, but the embryonic and early‐life stages (nauplius and metanauplius) of this broadcast spawning species are unknown. We describe the morphology and development time of these life stages to complete the knowledge of its life cycle. Embryos were obtained from purple‐gonad gravid females collected off Dichato, central Chile, during November 2012. Eight gravid females (mean=16 mm total length) were incubated in seawater at 12°C under laboratory conditions. The average development time from single‐cell embryos to the metanauplius stage was 2.2 d and hatching occurred between 20 and 25 h. The average growth rate was 0.35 mm d^?1 from the late limb bud to the metanauplius stage (range=0.21–0.48 mm d^?1). Embryos of E. mucronata had a mean chorion diameter of 0.460 mm, embryo diameter of 0.343 mm, and perivitelline space of 0.056 mm. Our biological information reported here constitutes a baseline for future ecological studies on distribution and temporal variability of spawning activity and reproductive strategies of E. mucronata in the highly variable and productive Humboldt Current ecosystem.     

A general multi-trait-based framework for studying the effects of biodiversity on ecosystem functioning

Environmental change is as multifaceted as are the species and communities that respond to these changes. Current theoretical approaches to modeling ecosystem response to environmental change often deal only with single environmental drivers or single species traits, simple ecological interactions, and/or steady states, leading to concern about how accurately these approaches will capture future responses to environmental change in real biological systems. To begin addressing this issue, we generalize a previous trait-based framework to incorporate aspects of frequency dependence, functional complementarity, and the dynamics of systems composed of species that are defined by multiple traits that are tied to multiple environmental drivers. The framework is particularly well suited for analyzing the role of temporal environmental fluctuations in maintaining trait variability and the resultant effects on community response to environmental change. Using this framework, we construct simple models to investigate two ecological problems. First, we show how complementary resource use can significantly enhance the nutrient uptake of plant communities through two different mechanisms related to increased productivity (over-yielding) and larger trait variability. Over-yielding is a hallmark of complementarity and increases the total biomass of the community and, thus, the total rate at which nutrients are consumed. Trait variability also increases due to the lower levels of competition associated with complementarity, thus speeding up the rate at which more efficient species emerge as conditions change. Second, we study systems in which multiple environmental drivers act on species defined by multiple, correlated traits. We show that correlations in these systems can increase trait variability within the community and again lead to faster responses to environmental change. The methodological advances provided here will apply to almost any function that relates species traits and environmental drivers to growth, and should prove useful for studying the effects of climate change on the dynamics of biota.     

Ecosystems off track: rate‐induced critical transitions in ecological models

Theory suggests that gradual environmental change may erode the resilience of ecosystems and increase their susceptibility to critical transitions. This notion has received a lot of attention in ecology in recent decades. An important question receiving far less attention is whether ecosystems can cope with the rapid environmental changes currently imposed. The importance of this question was recently highlighted by model studies showing that elevated rates of change may trigger critical transitions, whereas slow environmental change would not. This paper aims to provide a mechanistic understanding of these rate‐induced critical transitions to facilitate identification of rate sensitive ecosystems. Analysis of rate sensitive ecological models is challenging, but we demonstrate how rate‐induced transitions in an elementary model can still be understood. Our analyses reveal that rate‐induced transitions 1) occur if the rate of environmental change is high compared to the response rate of ecosystems, 2) are driven by rates, rather than magnitudes, of change and 3) occur once a critical rate of change is exceeded. Disentangling rate‐induced transitions from classical transitions in observations would be challenging. However, common features of rate‐sensitive models suggest that ecosystems with coupled fast–slow dynamics, exhibiting repetitive catastrophic shifts or displaying periodic spatial patterns are more likely to be rate sensitive. Our findings are supported by experimental studies showing rate‐dependent outcomes. Rate sensitivity of models suggests that the common definition of ecological resilience is not suitable for a subset of real ecosystems and that formulating limits to magnitudes of change may not always safeguard against ecosystem degradation. Synthesis Understanding and predicting ecosystem response to environmental change is one of the key challenges in ecology. Model studies have suggested that slow, gradual environmental change beyond some critical threshold can trigger so‐called critical transitions and abrupt ecosystem degradation. An important question remains however whether ecosystems can cope with the ongoing rapid anthropogenic environmental changes to which they are currently imposed. In this study we demonstrate that in some ecological models elevated rates of change can trigger critical transitions even if slow environmental change of the same magnitude would not. Such rateinduced critical transitions in models suggest that concepts like resilience and planetary boundaries may not always be sufficient to explain and prevent ecosystem degradation.     

Adapt or disperse: understanding species persistence in a changing world

The majority of studies on environmental change focus on the response of single species and neglect fundamental biotic interactions, such as mutualism, competition, predation, and parasitism, which complicate patterns of species persistence. Under global warming, disruption of community interactions can arise when species differ in their sensitivity to rising temperature, leading to mismatched phenologies and/or dispersal patterns. To study species persistence under global climate change, it is critical to consider the ecology and evolution of multispecies interactions; however, the sheer number of potential interactions makes a full study of all interactions unfeasible. One mechanistic approach to solving the problem of complicated community context to global change is to (i) define strategy groups of species based on life‐history traits, trophic position, or location in the ecosystem, (ii) identify species involved in key interactions within these groups, and (iii) determine from the interactions of these key species which traits to study in order to understand the response to global warming. We review the importance of multispecies interactions looking at two trait categories: thermal sensitivity of metabolic rate and associated life‐history traits and dispersal traits of species. A survey of published literature shows pronounced and consistent differences among trophic groups in thermal sensitivity of life‐history traits and in dispersal distances. Our approach increases the feasibility of unraveling such a large and diverse set of community interactions, with the ultimate goal of improving our understanding of community responses to global warming.     

A general biodiversity–function relationship is mediated by trophic level

Species diversity affects the functioning of ecosystems, including the efficiency by which communities capture limited resources, produce biomass, recycle and retain biologically essential nutrients. These ecological functions ultimately support the ecosystem services upon which humanity depends. Despite hundreds of experimental tests of the effect of biodiversity on ecosystem function (BEF), it remains unclear whether diversity effects are sufficiently general that we can use a single relationship to quantitatively predict how changes in species richness alter an ecosystem function across trophic levels, ecosystems and ecological conditions. Our objective here is to determine whether a general relationship exists between biodiversity and standing biomass. We used hierarchical mixed effects models, based on a power function between species richness and biomass production (Y = a × S^b), and a database of 374 published experiments to estimate the BEF relationship (the change in biomass with the addition of species), and its associated uncertainty, in the context of environmental factors. We found that the mean relationship (b = 0.26, 95% CI: 0.16, 0.37) characterized the vast majority of observations, was robust to differences in experimental design, and was independent of the range of species richness levels considered. However, the richness–biomass relationship varied by trophic level and among ecosystems; in aquatic systems b was nearly twice as large for consumers (herbivores and detritivores) compared to primary producers; in terrestrial ecosystems, b for detritivores was negative but depended on few studies. We estimated changes in biomass expected for a range of changes in species richness, highlighting that species loss has greater implications than species gains, skewing a distribution of biomass change relative to observed species richness change. When biomass provides a good proxy for processes that underpin ecosystem services, this relationship could be used as a step in modeling the production of ecosystem services and their dependence on biodiversity.     

Linking species diversity to the functioning of ecosystems: on the importance of environmental context

There is currently much interest in understanding how loss of biodiversity might alter ecological processes vital to the functioning of ecosystems. Unfortunately, ecologists have reached little consensus regarding the importance of species diversity to ecosystem functioning because empirical studies have not demonstrated any consistent relationship between the number of species in a system and the rates of ecological processes. We present the results of a simple model that suggests there may be no single, generalizable relationship between species diversity and the productivity of an ecosystem because the relative contributions of species to productivity change with environmental context. The model determined productivity for landscapes varying in species diversity (the number of species in the colonist pool), spatial heterogeneity (the number of habitat types composing the landscape), and disturbance regimes (+/? a non‐selective mortality). Linear regressions were used to relate species diversity and productivity for each of the environmental contexts. Disturbance changed the form of the diversity/productivity relationship by reducing the slope (i.e. the change in productivity per species added to the colonist pool), but spatial heterogeneity increased or decreased this slope depending on the particular habitat types composing the landscape. The cause of the diversity/productivity relationship also changed with environmental context. The amount of variation in productivity explained by species diversity always increased with spatial heterogeneity, while the amount of variation explained by species composition (i.e. the particular species composing the colonist pool) tended to increase with disturbance. These results lead us to conclude that the form and cause of the relationship between species diversity and productivity may be highly dynamic‐changing over both time and space. Because the trends resulted from well‐known mechanisms by which environmental variation alters the absolute and relative abundances of taxa, we suspect this conclusion may be applicable to many different systems.     

植物遗传多样性与生态系统功能关系的研究进展

全球变化和人类活动导致物种生境的萎缩, 造成很多植物种群数量缩减, 遗传多样性快速丧失。对于物种多样性低的生态系统, 优势种的遗传多样性可能比物种多样性对生态系统功能产生更大的影响。因此, 了解遗传多样性和生态系统功能的关系(GD-EF)及其机制对生物多样性保护、应对环境变化和生态修复具有指导意义。该文综述了植物遗传多样性对生态系统结构(高营养级生物群落结构)和生态系统功能(初级生产力、养分循环和稳定性)的影响及机制、功能多样性对GD-EF的影响、遗传多样性效应和物种多样性效应的比较, 以及GD-EF在生态修复等实际应用的研究进展。最后指出当前研究的不足之处, 以期为后续研究提供参考: 1)还需深入研究GD-EF机制; 2)未评估遗传多样性对生态系统多功能性的影响; 3)不同遗传多样性测度对生态系统功能的影响不明确; 4)缺少长期的和多空间尺度结合的GD-EF实验; 5)遗传多样性效应相对于其他因子的作用不清楚。     

Scaling up evolutionary responses to elevated CO2: lessons from Arabidopsis

Results from norm of reaction studies and selection experiments indicate that elevated CO₂ will act as a selective agent on natural plant populations, especially for C₃ species that are most sensitive to changes in atmospheric CO₂ concentration. Evolutionary responses to CO₂ may alter plant physiology, development rate, growth, and reproduction in ways that cannot be predicted from single generation studies. Moreover, ecological and evolutionary changes in plant communities will have a range of consequences at higher spatial scales and may cause substantial deviations from ecosystem level predictions based on short‐term responses to elevated CO₂. Therefore, steps need to be taken to identify the plant traits that are most likely to evolve at elevated CO₂, and to understand how these changes may affect net primary productivity within ecosystems. These processes may range in scale from molecular and physiological changes that occur among genotypes at the individual and population levels, to changes in community‐ and ecosystem‐level productivity that result from the integrative effects of different plant species evolving simultaneously. In this review, we (1) synthesize recent studies investigating the role of atmospheric CO₂ as a selective agent on plants, (2) discuss possible control points during plant development that may change in response to selection at elevated CO₂ with an emphasis at the primary molecular level, and (3) provide a quantitative framework for scaling the evolutionary effects of CO₂ on plants in order to determine changes in community and ecosystem productivity. Furthermore, this review points out that studies integrating the effects of plant evolution in response to elevated CO₂ are lacking, and therefore more attention needs be devoted to this issue among the global change research community.