Fluctuating natural selection accounts for the evolution of diversification bet hedging

Natural environments are characterized by unpredictability over all time scales. This stochasticity is expected on theoretical grounds to result in the evolution of ‘bet-hedging’ traits that maximize the long term, or geometric mean fitness even though such traits do not maximize fitness over shorter time scales. The geometric mean principle is thus central to our interpretation of optimality and adaptation; however, quantitative empirical support for bet hedging is lacking. Here, I report a quantitative test using the timing of seed germination—a model diversification bet-hedging trait—in Lobelia inflata under field conditions. In a phenotypic manipulation study, I find the magnitude of fluctuating selection acting on seed germination timing—across 70 intervals throughout five seasons—to be extreme: fitness functions for survival are complex and multimodal within seasons and significantly dissimilar among seasons. I confirm that the observed magnitude of fluctuating selection is sufficient to account for the degree of diversification behaviour characteristic of individuals of this species. The geometric mean principle has been known to economic theory for over two centuries; this study now provides a quantitative test of optimality of a bet-hedging trait in nature.     

Characterizing the multivariate physiogenomic response to environmental change

Global change is altering the climate that species have historically adapted to – in some cases at a pace not recently experienced in their evolutionary history – with cascading effects on all taxa. A central aim in global change biology is to understand how specific populations may be “primed” for global change, either through acclimation or adaptive standing genetic variation. It is therefore an important goal to link physiological measurements to the degree of stress a population experiences (Annual Review of Marine Science, 2012, 4, 39). Although “omic” approaches such as gene expression are often used as a proxy for the amount of stress experienced, we still have a poor understanding of how gene expression affects ecologically and physiologically relevant traits in non‐model organisms. In a From the Cover paper in this issue of Molecular Ecology, Griffiths, Pan and Kelley (Molecular Ecology, 2019, 28) link gene expression to physiological traits in a temperate marine coral. They discover population‐specific responses to ocean acidification for two populations that originated from locations with different histories of exposure to acidification. By integrating physiological and gene expression data, they were able to elucidate the mechanisms that explain these population‐specific responses. Their results give insight into the physiogenomic feedbacks that may prime organisms or make them unfit for ocean global change.     

Evolution in response to climate change: In pursuit of the missing evidence

Climate change is imposing intensified and novel selection pressures on organisms by altering abiotic and biotic environmental conditions on Earth, but studies demonstrating genetic adaptation to climate change mediated selection are still scarce. Evidence is accumulating to indicate that both genetic and ecological constrains may often limit populations' abilities to adapt to large scale effects of climate warming. These constraints may predispose many organisms to respond to climate change with range shifts and phenotypic plasticity, rather than through evolutionary adaptation. In general, broad conclusions about the role of evolutionary adaptation in mitigating climate change induced fitness loss in the wild are as yet difficult to make. Editor's suggested further reading in BioEssays: How will fish that evolved at constant sub‐zero temperatures cope with global warming? Notothenioids as a case study Abstract     

Evidence for evolutionary change associated with the recent range expansion of the British butterfly, Aricia agestis, in response to climate change

Poleward range expansions are widespread responses to recent climate change and are crucial for the future persistence of many species. However, evolutionary change in traits such as colonization history and habitat preference may also be necessary to track environmental change across a fragmented landscape. Understanding the likelihood and speed of such adaptive change is important in determining the rate of species extinction with ongoing climate change. We conducted an amplified fragment length polymorphism (AFLP)‐based genome scan across the recently expanded UK range of the Brown Argus butterfly, Aricia agestis, and used outlier‐based (DFDIST and BayeScan) and association‐based (Isolation‐By‐Adaptation) statistical approaches to identify signatures of evolutionary change associated with range expansion and habitat use. We present evidence for (i) limited effects of range expansion on population genetic structure and (ii) strong signatures of selection at approximately 5% AFLP loci associated with both the poleward range expansion of A. agestis and differences in habitat use across long‐established and recently colonized sites. Patterns of allele frequency variation at these candidate loci suggest that adaptation to new habitats at the range margin has involved selection on genetic variation in habitat use found across the long‐established part of the range. Our results suggest that evolutionary change is likely to affect species’ responses to climate change and that genetic variation in ecological traits across species’ distributions should be maximized to facilitate range shifts across a fragmented landscape, particularly in species that show strong associations with particular habitats.     

Phenotypic plasticity in response to environmental heterogeneity contributes to fluctuating asymmetry in plants: first empirical evidence

Fluctuating asymmetry (FA) is widely used to quantify developmental instability (DI) in ecological and evolutionary studies. It has long been recognized that FA may not exclusively originate from DI for sessile organisms such as plants, because phenotypic plasticity in response to heterogeneities in the environment might also produce FA. This study provides the first empirical evidence for this hypothesis. We reasoned that solar irradiance, which is greater on the southern side than on the northern side of plants growing in the temperate zone of the Northern Hemisphere, would cause systematic morphological differences and asymmetry associated with the orientation of plant parts. We used geometric morphometrics to characterize the size and shape of flower parts in Iris pumila grown in a common garden. The size of floral organs was not significantly affected by orientation. Shape and particularly its asymmetric component differed significantly according to orientation for three different floral parts. Orientation accounted for 10.4% of the total shape asymmetry within flowers in the falls, for 11.4% in the standards and for 2.2% in the style branches. This indicates that phenotypic plasticity in response to a directed environmental factor, most likely solar irradiance, contributes to FA of flowers under natural conditions. That FA partly results from phenotypic plasticity and not just from DI needs to be considered by studies of FA in plants and other sessile organisms.     

自然生态系统响应气候变化的脆弱性评价研究进展

以气候变暖为标志的全球气候变化已引起各国政府、国际组织和科学工作者的高度重视.气候变化给人类及自然生态系统带来的风险和危害日趋增大.生态系统脆弱性分析和评价是适应和减缓气候变化的关键和基础,已成为近年来气候变化领域和生态学领域的研究热点.目前国内外学者正在不同领域、不同空间尺度上开展响应气候变化的脆弱性评价,其中以自然生态系统为评价对象的脆弱性研究也有了长足的发展.本文通过对脆弱性的概念、气候变化脆弱性评价研究现状、自然生态系统响应气候变化的脆弱性定量评价方法的综述,探讨了该研究领域存在的问题和未来的发展前景.     

Genetic variation in Breviolum antillogorgium,a coral reef symbiont,in response to temperature and nutrients

Symbionts within the family Symbiodiniaceae are important on coral reefs because they provide significant amounts of carbon to many different reef species. The breakdown of this mutualism that occurs as a result of increasingly warmer ocean temperatures is a major threat to coral reef ecosystems globally. Recombination during sexual reproduction and high rates of somatic mutation can lead to increased genetic variation within symbiont species, which may provide the fuel for natural selection and adaptation. However, few studies have asked whether such variation in functional traits exists within these symbionts. We used several genotypes of two closely related species, Breviolum antillogorgium and B. minutum, to examine variation of traits related to symbiosis in response to increases in temperature or nitrogen availability in laboratory cultures. We found significant genetic variation within and among symbiont species in chlorophyll content, photosynthetic efficiency, and growth rate. Two genotypes showed decreases in traits in response to increased temperatures predicted by climate change, but one genotype responded positively. Similarly, some genotypes within a species responded positively to high‐nitrogen environments, such as those expected within hosts or eutrophication associated with global change, while other genotypes in the same species responded negatively, suggesting context‐dependency in the strength of mutualism. Such variation in traits implies that there is potential for natural selection on symbionts in response to temperature and nutrients, which could confer an adaptive advantage to the holobiont.     

Rapid adaptation to climate change

In recent years, amid growing concerns that changing climate is affecting species distributions and ecosystems, predicting responses to rapid environmental change has become a major goal. In this issue, Franks and colleagues take a first step towards this objective (Franks et al. 2016). They examine genomewide signatures of selection in populations of Brassica rapa after a severe multiyear drought. Together with other authors, Franks had previously shown that flowering time was reduced after this particular drought and that the reduction was genetically encoded. Now, the authors have sequenced previously stored samples to compare allele frequencies before and after the drought and identify the loci with the most extreme shifts in frequencies. The loci they identify largely differ between populations, suggesting that different genetic variants may be responsible for reduction in flowering time in the two populations.     

山地物种海拔分布对气候变化响应的研究进展

过去1个世纪以来, 全球气候变化显著并已成为全球生物多样性面临的重要威胁之一。如何利用有限的资源最有效地保护生物多样性已成为亟待解决的最重要科学问题之一。山地因其具有较高的生境异质性、气候多样性和较低的人类活动干扰, 已成为最重要的生物多样性避难所, 也具有较高的生态服务价值, 在生物多样性保护中扮演着重要角色。但山地更容易受到气候变化的影响, 山地地区较为剧烈的气候变化将对山地生态系统的稳定性及其多样性造成严重威胁。理解山地物种海拔分布对气候变化的响应和潜在机理, 以及气候变化带来的物种海拔分布变化的负面效应, 将为全球气候变化背景下的山地生物多样性保护提供参考依据。本文综述了全球山地地区的气候变化情况, 总结了物种海拔迁移的研究进展, 重点讨论了山地物种分布最适海拔、海拔上下限和海拔分布范围变化的研究进展及不足, 比较了不同地区和不同类群物种海拔迁移的差异性, 以及物种对气候变化响应的滞后性。从生物及非生物因素等多个角度概括了物种海拔迁移响应气候变化的潜在机理, 评估并总结了气候变化引起的物种海拔分布所产生的负面效应, 主要对物种向上迁移对高海拔地区物种多样性的影响、物种迁移带来的分布区改变导致的物种灭绝风险以及物种海拔分布变化导致的种间相互作用改变等方面进行全面探讨。最后, 展望了未来在此领域研究中应注意的问题, 提出了在未来气候变化下山地生物多样性保护需要采取的措施, 强调应重点关注对气候变化较为敏感的类群及生物多样性区域, 加强中国山地物种对气候变化响应的监测网络建设和研究力度, 重点加强监测气候变化对动植物互作关系的影响。     

Investigating the eco-evolutionary response of microbiomes to environmental change

Microorganisms are the primary engines of biogeochemical processes and foundational to the provisioning of ecosystem services to human society. Free-living microbial communities (microbiomes) and their functioning are now known to be highly sensitive to environmental change. Given microorganisms' capacity for rapid evolution, evolutionary processes could play a role in this response. Currently, however, few models of biogeochemical processes explicitly consider how microbial evolution will affect biogeochemical responses to environmental change. Here, we propose a conceptual framework for explicitly integrating evolution into microbiome–functioning relationships. We consider how microbiomes respond simultaneously to environmental change via four interrelated processes that affect overall microbiome functioning (physiological acclimation, demography, dispersal and evolution). Recent evidence in both the laboratory and the field suggests that ecological and evolutionary dynamics occur simultaneously within microbiomes; however, the implications for biogeochemistry under environmental change will depend on the timescales over which these processes contribute to a microbiome's response. Over the long term, evolution may play an increasingly important role for microbially driven biogeochemical responses to environmental change, particularly to conditions without recent historical precedent.     

气候变化对野生生物类自然保护区的影响及其风险

自然保护区是禁止开发区域、生态保护红线、自然保护地等生态功能重要地区的核心组成部分,在保护生物多样性、保障国家生态安全中居于重要地位。在生态文明体系加快构建、人类活动不利影响逐渐得到遏制的背景下,气候变化及其影响将成为自然保护区建设和管理面临的主要挑战。鉴于此,分析和总结了气候变化对野生生物的影响,剖析了气候变化对野生生物类自然保护区的风险,以期为协同推进自然保护区管理与应对气候变化工作、建立完善国土空间规划体系和自然保护地体系的自然保护区管理制度等提供科学依据。结果表明,气候变化对野生动植物物种分布、生物物候、种间关系的影响更加凸显,加剧了物种灭绝风险;气候变化影响特别是气候变化引起的物种适应性迁移,将对以相对固定的空间布局、保护边界、功能分区为主要特征的自然保护区建设和管理模式提出新的挑战,使得野生生物类自然保护区保护对象、保护功能等面临风险,形成自然保护区气候变化风险;而且当前自然保护区优化调整仍然滞后于气候变化影响,将进一步加剧自然保护区气候变化风险。     

生物多样性保护适应气候变化的管理策略

应对气候变化和保护生物多样性是2大全球性热点环境问题。气候变化导致物种多样性丧失、生态系统服务降低和区域生态安全屏障功能受损,威胁到中国国土生态安全格局和生态脆弱区域的可持续发展,给生物多样性保护带来新的挑战。做好生物多样性保护适应气候变化的风险管理工作,既是生物多样性应对气候变化风险的必要措施,也是减缓气候变化的重要途径。结合爱知目标10的实现情况,分析了欧盟、澳大利亚、美国等发达国家发布的生物多样性适应气候变化技术政策制定情况、中国生物多样性应对气候变化进展情况,剖析了中国生物多样性保护适应气候变化存在的问题,包括生物多样性应对气候变化的科学认知亟待提高、生物多样性保护适应气候变化的能力建设不足、自然保护地之间缺乏适应气候变化的生态廊道网络、生物多样性保护适应气候变化的技术标准缺乏。研究提出了中国生物多样性应对气候变化的适应性管理策略,包括制定《中国生物多样性保护协同应对气候变化的国家方案》、加强生物多样性保护适应气候变化的能力建设、开展自然保护区适应气候变化的风险管理试点、强化生物多样性应对气候变化的科技支撑,以期为推进纳入气候变化风险管理的生物多样性保护工作提供决策依据。     

Evolutionary response to global change: Climate and land use interact to shape color polymorphism in a woodland salamander

Evolutionary change has been demonstrated to occur rapidly in human‐modified systems, yet understanding how multiple components of global change interact to affect adaptive evolution remains a critical knowledge gap. Climate change is predicted to impose directional selection on traits to reduce thermal stress, but the strength of directional selection may be mediated by changes in the thermal environment driven by land use. We examined how regional climatic conditions and land use interact to affect genetically based color polymorphism in the eastern red‐backed salamander (Plethodon cinereus). P. cinereus is a woodland salamander with two primary discrete color morphs (striped, unstriped) that have been associated with macroclimatic conditions. Striped individuals are most common in colder regions, but morph frequencies can be variable within climate zones. We used path analysis to analyze morph frequencies among 238,591 individual salamanders across 1,170 sites in North America. Frequency of striped individuals was positively related to forest cover in populations occurring in warmer regions (>7°C annually), a relationship that was weak to nonexistent in populations located in colder regions (≤7°C annually). Our results suggest that directional selection imposed by climate warming at a regional scale may be amplified by forest loss and suppressed by forest persistence, with a mediating effect of land use that varies geographically. Our work highlights how the complex interaction of selection pressures imposed by different components of global change may lead to divergent evolutionary trajectories among populations.     

Towards genetic markers in animal populations as biomonitors for human-induced environmental change

Genetic markers provide potentially sensitive indicators of changes in environmental conditions because the genetic constitution of populations is normally altered well before populations become extinct. Genetic indicators in populations include overall genetic diversity, genetic changes in traits measured at the phenotypic level, and evolution at specific loci under selection. While overall genetic diversity has rarely been successfully related to environmental conditions, genetically based changes in traits have now been linked to the presence of toxins and both local and global temperature shifts. Candidate loci for monitoring stressors are emerging from information on how specific genes influence traits, and from screens of random loci across environmental gradients. Drosophila research suggests that chromosomal regions under recent intense selection can be identified from patterns of molecular variation and a high frequency of transposable element insertions. Allele frequency changes at candidate loci have been linked to pesticides, pollutants and climate change. Nevertheless, there are challenges in interpreting allele frequencies in populations, particularly when a large number of loci control a trait and when interactions between alleles influence trait expression. To meet these challenges, population samples should be collected for longitudinal studies, and experimental programmes should be undertaken to link variation at candidate genes to ecological processes.     

Advancing breeding phenology in response to environmental change in a wild red deer population

Most evidence for advances in phenology of in response to recent climate warming in wild vertebrate populations has come from long‐term studies of birds. Few studies have either documented phenological advances or tested their climatic causes and demographic consequences in wild mammal systems. Using a long‐term study of red deer on the Isle of Rum, Scotland, we present evidence of significant temporal trends in six phenological traits: oestrus date and parturition date in females, and antler cast date, antler clean date, rut start date and rut end date in males. These traits advanced by between 5 and 12 days across a 28‐year study period. Local climate measures associated with plant growth in spring and summer (growing degree days) increased significantly over time and explained a significant amount of variation in all six phenological traits, largely accounting for temporal advances observed in some of the traits. However, there was no evidence for temporal changes in key female reproductive performance traits (offspring birth weight and offspring survival) in this population, despite significant relationships between these traits and female phenology. In males, average antler weights increased over time presumably as a result of improved resource availability and physiological condition through spring and summer. There was no evidence for any temporal change in average male annual breeding success, as might be expected if the timing of male rutting behaviour was failing to track advances in the timing of oestrus in females. Our results provide rare evidence linking phenological advances to climate warming in a wild mammal and highlight the potential complexity of relationships between climate warming, phenology and demography in wild vertebrates.     

Collembolan water relations and environmental change in the maritime Antarctic

The water status of the collembolan Cryptopygtus antarcticus (Willem) was investigated from April 1984 to December 1987 at Signy Island, maritime Antarctic, by monthly field sampling to determine body water content. Water content, expressed either as the weight of water per unit dry weight or as a proportion of fresh weight, exhibited both a seasonal cycle and an upward trend over the 44-month study, both of which were highly significant. On an annual basis, body water content was at a minimum (1.21 g g^?1) in July and maximal (1.98 g g^?1) in September, whilst over the entire study water contents increased from 1.3 to 2.0 g g^?1 (or 57-66% of fresh weight) calculated from the fitted linear regression line. Field water contents were below those found for this species in culture (2.9-5.9 g g^?1). Individual C. antarcticus survived experimental loss of 20% of their body water with a resultant significant rise in haemolymph osmolarity from 285 to 397 mOsm L^?1 and there was no evidence of osmoregulation under the experimental conditions of 20 °C and 35% relative humidity. The cuticular permeability (mean conductance) of individual Collembola in dry air increased exponentially with temperature over the range D-45 °C (Q₁₀= 2.0) showing no control of water loss. The physiological response of C. antarcticus suggests that it experiences water stress in its maritime Antarctic habitats with significant seasonal variations of body water content, which correlate with annual cycles of water availability. It is concluded that the significant rise in its mean body water content over the 44-month field study was associated with increased glacial ablation due to higher levels of irradiation and windspeed making available more liquid water. Analyses of climate records for Signy Island from 1947 to 1990 showed that mean monthly air temperature rose by 0.93 °C over this period and by 2.29 °C during the 1980s, both statistically significant increases. Mean monthly windspeeds also increased significantly during 1970–90, and it is suggested that this parameter is the primary climatic driving force behind the increase in glacial ablation during the last two decades. The field water status of species such as C. antarcticus may reflect changes in the patterns of atmospheric circulation, associated with the circumpolar vortex, through increased ozone depletion due to increased tropospheric concentrations of halocarbons.     

青藏高原沼泽湿地植被NDVI时空变化及其对气候变化的响应

基于2000—2017年逐旬MODIS NDVI数据和逐月气温、降水数据,分析了青藏高原不同类型沼泽湿地植被生长季NDVI时空变化特征及其对气候变化的响应。研究结果表明：青藏高原沼泽植被生长季多年平均NDVI自西北向东南逐渐增加;沼泽植被生长季平均NDVI在2000—2017年总体呈现显著上升趋势 (0.010/10a) ,生长季NDVI呈上升趋势的面积占整个研究区面积的78.25%。青藏高原沼泽植被生长季NDVI与降水量总体上呈现弱的相关性,表明降水并不是影响该地区沼泽植被生长的主要因素。青藏高原沼泽植被生长主要受气温影响,气温升高能明显促进沼泽植被的生长。此外,首次发现白天和夜晚温度升高对青藏高原沼泽植被生长具有不对称性影响,其中夜晚增温对沼泽植被生长的促进效果更加显著。在全球白天和夜晚不对称增温的背景下,白天和夜晚温度对青藏高原沼泽植被的不对称影响应当引起重视,尤其是在利用模型模拟未来气候变化对该地区沼泽植被影响时。