Global imprint of historical connectivity on freshwater fish biodiversity

The relative importance of contemporary and historical processes is central for understanding biodiversity patterns. While several studies show that past conditions can partly explain the current biodiversity patterns, the role of history remains elusive. We reconstructed palaeo‐drainage basins under lower sea level conditions (Last Glacial Maximum) to test whether the historical connectivity between basins left an imprint on the global patterns of freshwater fish biodiversity. After controlling for contemporary and past environmental conditions, we found that palaeo‐connected basins displayed greater species richness but lower levels of endemism and beta diversity than did palaeo‐disconnected basins. Palaeo‐connected basins exhibited shallower distance decay of compositional similarity, suggesting that palaeo‐river connections favoured the exchange of fish species. Finally, we found that a longer period of palaeo‐connection resulted in lower levels of beta diversity. These findings reveal the first unambiguous results of the role played by history in explaining the global contemporary patterns of biodiversity.     

First multi-proxy record of Jurassic wildfires from Gondwana: Evidence from the Middle Jurassic of the Neuquén Basin,Argentina

Wildfires play a crucial role in recent and ancient ecosystem modeling but their detailed history on the Earth is still not well recorded or understood. The co-occurrence of charcoal and pyrolytic polycyclic aromatic hydrocarbons (PAHs) is used for the recognition of wildfires in geological record that may have implications for the analysis of the terrestrial environment, ecosystems, climate and the level of atmospheric oxygen. Here we present the first multi-proxy evidence of wildfires on the Gondwana continent during the Jurassic, based on the occurrence of charcoal and pyrolytic PAHs in the Middle Jurassic of the Neuquén Basin, Argentina. This is the first evidence of wildfire in the Aalenian, the lowest stage of the Middle Jurassic, and one of the few records of wildfires in the Bathonian. Temperature interpretations, derived from charcoal reflectance data, show that charcoals formed in low temperature surface fires that only sporadically reached the higher temperatures, possibly related to crown fires. The occurrence of charcoals in the Middle Jurassic deposits confirms recent results that the atmospheric oxygen level reached at least 15% during the Middle Jurassic times.     

Wildfires in the Early Triassic of northeastern Pangaea: Evidence from fossil charcoal in the Bogda Mountains,northwestern China

Fires are an integral part of modern and ancient ecosystems, serving as friends for renewal or foes for complete destruction and extinction. Indicators of palaeowildfire were so far absent from the Lower Triassic. Lack of plants in the Early Triassic due to the end-Permian mass extinction event and low atmospheric oxygen levels were proposed as the major reasons for the scarcity of wildfires. We present macroscopic charcoals from the Olenekian (Lower Triassic) in northwestern China, indicating probable ground/smoldering fires occurred on landscapes in mid-latitudes of northeastern Pangaea. Atmospheric oxygen concentration during the Olenekian would have been above 18.5%. These findings demonstrate that wildfires continued to be a source of disturbance of terrestrial ecosystems in Bogda Mountains after the end-Permian marine biotic crisis. There were adequate supplies of fuels and oxygen during this critical time period in the Earth history.     

Niche expansion and temperature sensitivity of tropical African montane forests

Aim Climate and land‐use change will have a dramatic impact on future ecosystems through alterations to species ranges and community composition. When forming conservation strategies, correlative species distribution models are often created to assess risks for individual species. These models are based on the assumption of climatic equilibrium, such that the modern range is representative of the full range of conditions under which species could thrive. However, the palaeo‐ecological record illustrates examples of disequilibrium in species today, and recent studies suggest that many species could occur in much broader climatic settings than previously thought. Montane ecosystems are thought to be at disproportionate risk due to temperature sensitivity and restricted geographical ranges. However, in the Afrotropics the palaeo‐ecological record shows that montane forest taxa expanded into the lowlands numerous times, suggesting a possible tolerance to warm temperatures. Location Africa. Methods We integrate palaeo‐ecological and palaeo‐climatic data in order to compare climate conditions in which species are currently found with those in the past. We use species distribution models to construct potential modern ranges for Afromontane species based on modern distributions and distributions in the palaeo‐ecological record in order to evaluate the equilibrium of species ranges. Results We show that many Afromontane trees have occupied warmer climates in the past, which suggests that the current low‐elevation boundaries are not set by climate. Interestingly, the species with the largest disequilibrium between palaeo‐ and modern distributions are those whose modern distributions show the least temperature sensitivity. Mapping of species potential ranges based on modern and palaeo‐ distributions clearly shows that suitable climate conditions exist today in the lowlands for less temperature‐sensitive species. Main conclusions These results imply that the current range of these forest trees does not necessarily inform risk from climatic change, and that human land use may be the major pressure for many species in the future.     

Patterns and processes of global riverine fish endemism

Aim To explore global patterns of riverine fish endemism by applying an island biogeography framework to river drainage basins and highlight evolutionary mechanisms producing two kinds of endemism: neo‐endemism, arising from within‐drainage cladogenetic speciation, and palaeo‐endemism, arising from species range contraction or anagenetic speciation. Location World‐wide. Methods We use a uniquely comprehensive data set of riverine fish species distributions to map global fish endemism patterns. We then use the relationships between (1) total species richness and proportions of endemic species and (2) total species richness and a measure of in situ (i.e. within‐drainage basin) probability of speciation by cladogenesis, to identify the two distinct forms of endemism. After separating drainage basins into two different sets according to dominance of one of these two forms, we apply a model averaging procedure to highlight, for both datasets, the environmental and historical variables that better explain endemism patterns. We finally analyse the effect of biotic components related to dispersal ability on the percentages of both kinds of endemism among lineages. Results Our results indicate that the two types of endemism are distributed differently across space and taxonomic lineages: (1) neo‐endemism, positively related to the overall richness of the drainage basin, is essentially linked to in situ cladogenetic speciation and is positively related to drainage basin area, negatively related to climate variability since glacial periods and negatively related to all proxies of dispersal ability; and (2) palaeo‐endemism, not directly contributing to drainage basin richness, is a pure process of extinction through range contraction and/or isolation through time and is mostly related to geographic isolation, glacial history and positively related to marine‐derived origin of families. Main conclusions The non‐random spatial and taxonomic distribution of neo‐endemism and palaeo‐endemism sharply reflects the role of evolutionary processes and provides a way to identify areas of high conservation interest based on their high present and future diversification potential.     

Ribosomal RNA gene fragments from fossilized cyanobacteria identified in primary gypsum from the late Miocene,Italy

Earth scientists have searched for signs of microscopic life in ancient samples of permafrost, ice, deep‐sea sediments, amber, salt and chert. Until now, evidence of cyanobacteria has not been reported in any studies of ancient DNA older than a few thousand years. Here, we investigate morphologically, biochemically and genetically primary evaporites deposited in situ during the late Miocene (Messinian) Salinity Crisis from the north‐eastern Apennines of Italy. The evaporites contain fossilized bacterial structures having identical morphological forms as modern microbes. We successfully extracted and amplified genetic material belonging to ancient cyanobacteria from gypsum crystals dating back to 5.910–5.816 Ma, when the Mediterranean became a giant hypersaline brine pool. This finding represents the oldest ancient cyanobacterial DNA to date. Our clone library and its phylogenetic comparison with present cyanobacterial populations point to a marine origin for the depositional basin. This investigation opens the possibility of including fossil cyanobacterial DNA into the palaeo‐reconstruction of various environments and could also be used to quantify the ecological importance of cyanobacteria through geological time. These genetic markers serve as biosignatures providing important clues about ancient life and begin a new discussion concerning the debate on the origin of late Miocene evaporites in the Mediterranean.     

全球变化背景下野火研究进展

野火是森林和多种植被生态系统面临的最重要自然干扰,也是一种重要的自然灾害;而人类活动已在全球范围内显著影响了野火的发生与分布,因此野火成为全球变化及其环境影响研究的关键议题之一。本文基于国际野火研究的文献搜索和统计分析,从野火的观测-评估-预警技术、野火时空格局研究、气候变化和人类活动对野火的影响、野火的环境-生态-进化效应等方面入手,综述了自21世纪以来的国际野火研究进展。概括起来,遥感技术的快速发展,推动了野火观测的时空分辨率不断提高,对野火时空格局的刻画从单一因子向多重指标的火烧体系评估转变。气候变化在某些区域已经显著影响了野火的发生频率,预计随着全球变暖野火风险将进一步加大,并且极端大火的发生机制和生态影响越来越受到关注。人类活动一方面通过增加火源提高了野火频率,另一方面又通过提高生态系统管理的强度、扑救火灾以及降低可燃物的连通性抑制了野火的发生。植被在长期演化过程中形成了一系列适应火的功能机制,这些功能属性影响着生态系统对野火的响应,并对火后生态恢复和重建具有科学指导价值。未来野火研究将向跨时空尺度、观测和模拟深度融合、典型机制和大尺度效应相结合的方向发展。     

Life conditions on the early Earth after 4.0 Ga

The organization level of Precambrian fossils is the most reliable indicator of the state and parameters of the biosphere, such as the atmosphere composition, average temperature of the earth’s surface, and others. At present, cyanobacteria, unicellular and multicellular eukaryotes, and coelomates are considered to appear in the geological history of the Earth much earlier than it was supposed previously. Our knowledge and ideas of the early Earth are very important for considering the problems of the origin of life. A key boundary of the earliest period was probably about 4 Ga. This boundary is between the periods documented and undocumented by the geological record. The Earth history and probable surface conditions before 4 Ga are considered by L.M. Mukhina, A.V. Vityazeva, G.V. Pechernikova, and L.V. Ksanfomaliti in this volume.     

Land management: data availability and process understanding for global change studies

In the light of daunting global sustainability challenges such as climate change, biodiversity loss and food security, improving our understanding of the complex dynamics of the Earth system is crucial. However, large knowledge gaps related to the effects of land management persist, in particular those human‐induced changes in terrestrial ecosystems that do not result in land‐cover conversions. Here, we review the current state of knowledge of ten common land management activities for their biogeochemical and biophysical impacts, the level of process understanding and data availability. Our review shows that ca. one‐tenth of the ice‐free land surface is under intense human management, half under medium and one‐fifth under extensive management. Based on our review, we cluster these ten management activities into three groups: (i) management activities for which data sets are available, and for which a good knowledge base exists (cropland harvest and irrigation); (ii) management activities for which sufficient knowledge on biogeochemical and biophysical effects exists but robust global data sets are lacking (forest harvest, tree species selection, grazing and mowing harvest, N fertilization); and (iii) land management practices with severe data gaps concomitant with an unsatisfactory level of process understanding (crop species selection, artificial wetland drainage, tillage and fire management and crop residue management, an element of crop harvest). Although we identify multiple impediments to progress, we conclude that the current status of process understanding and data availability is sufficient to advance with incorporating management in, for example, Earth system or dynamic vegetation models in order to provide a systematic assessment of their role in the Earth system. This review contributes to a strategic prioritization of research efforts across multiple disciplines, including land system research, ecological research and Earth system modelling.     

Analysis of ancient human genomes

High‐capacity sequencing technologies have dramatically reduced both the cost and time required to generate complete human genome sequences. Besides expanding our knowledge about existing diversity, the nature of these technologies makes it possible to extend knowledge in yet another dimension: time. Recently, the complete genome sequence of a 4,000‐year‐old human from the Saqqaq culture of Greenland was determined to 20‐fold coverage. These data make it possible to investigate the population affinities of this enigmatic culture and, by identifying several phenotypic traits of this individual, provide a limited glimpse into how these people may have looked. While undoubtedly a milestone in ancient DNA research, the cost to generate an ancient genome, even from such an exceptionally preserved specimen, remains out of reach for most. Nonetheless, recently developed DNA capture methods, already applied to Neanderthal and fossil human mitochondrial DNA, may soon make large‐scale genome‐wide analysis of ancient human diversity a reality, providing a fresh look at human population history.     

Signal transduction in cells of the immune system in microgravity

Life on Earth developed in the presence and under the constant influence of gravity. Gravity has been present during the entire evolution, from the first organic molecule to mammals and humans. Modern research revealed clearly that gravity is important, probably indispensable for the function of living systems, from unicellular organisms to men. Thus, gravity research is no more or less a fundamental question about the conditions of life on Earth. Since the first space missions and supported thereafter by a multitude of space and ground-based experiments, it is well known that immune cell function is severely suppressed in microgravity, which renders the cells of the immune system an ideal model organism to investigate the influence of gravity on the cellular and molecular level. Here we review the current knowledge about the question, if and how cellular signal transduction depends on the existence of gravity, with special focus on cells of the immune system. Since immune cell function is fundamental to keep the organism under imnological surveillance during the defence against pathogens, to investigate the effects and possible molecular mechanisms of altered gravity is indispensable for long-term space flights to Earth Moon or Mars. Thus, understanding the impact of gravity on cellular functions on Earth will provide not only important informations about the development of life on Earth, but also for therapeutic and preventive strategies to cope successfully with medical problems during space exploration.     

Ecosystem memory of wildfires affects resilience of boreal mixedwood biodiversity after retention harvest

The extent to which past states influence present and future ecosystem characteristics (ecosystem memory (EM)) is challenging to assess because signals of past ecological conditions fade with time. Using data about seven different taxa, we show that ecological gradients initiated by wildfires up to three centuries earlier affect biotic recovery after variable retention harvest in the boreal mixedwood forest. First, we show that fire history over the last 300 years is reflected in pre‐harvest species‐specific stand basal area (BA), with longer times since high severity fire associated with proportionally higher BA of shade‐tolerant softwood species than shade‐intolerant hardwoods. Second, using patterns in the BA of pre‐harvest tree species we link fire history to species composition of pre‐harvest assemblages of bryophytes, herbs, shrubs, regenerated trees, songbirds, spiders and carabid beetles. Finally, we use variance partitioning to compare the importance of species‐specific pre‐ versus post‐harvest BA for explaining the structure of these seven biotic assemblages two, five and ten years after harvest. We detected persistent significant effects of pre‐harvest BA in all post‐harvest biotic assemblages up to ten years after harvest. Pre‐harvest BA was more strongly associated with early post‐harvest understory plant and carabid beetle assemblages than was post‐harvest BA, but the opposite was true for spiders, songbirds and regenerated trees. EM effects were detected two, five and ten years after harvest but temporal patterns varied according to taxa. Thus, EM of fire history can persist at least ten years after variable retention harvest and such effects appear to be stronger for understory plants than for animals. We conclude that management of biological legacies to increase post‐disturbance EM will increase overall resilience and sustainability of these mixedwood forests.     

Holocene vertebrate fossils aid the management and restoration of Australian ecosystems

European‐settlement‐related impacts over the past 200 years pose many challenges for the conservation and restoration of Australia's ecosystems. Landscape modification, associated habitat loss and the introduction of exotic species have caused the extinction and mainland extirpation of numerous vertebrates. This process happened so quickly that many species became locally or functionally extinct before their presence was documented. A growing body of research on Holocene fossil accumulations is providing insights into the composition and biogeography of Australian ecosystems prior to European settlement. This review explores the similarities between palaeo‐ and neo‐ecology and how Holocene (last 10,000 years) assemblages can be used by neo‐ecologists, conservation managers and policy makers to identify and fill gaps in knowledge and contribute to the management and restoration of Australia's degraded ecosystems.     

A Scientific Look at Spaghetti

The United States is currently experiencing its worst man-made environmental disaster, the BP Deepwater Horizon oil leak. The Gulf of Mexico oil spill is severe in its impact, but it is only one of several global oil spill disasters in history. Students can utilize the technology of Google Earth to explore the spatial and temporal distribution of oil spills. In addition to increasing content knowledge of oil spills, Google Earth assists in developing student geographic and technologic literacy. Designed for a middle school science class, this activity may also be used in English, history, math, art, and poster-making.     

Postwildfire seeding to restore native vegetation and limit exotic annuals: an evaluation in juniper‐dominated sagebrush steppe

Reestablishment of perennial vegetation is often needed after wildfires to limit exotic species and restore ecosystem services. However, there is a growing body of evidence that questions if seeding after wildfires increases perennial vegetation and reduces exotic plants. The concern that seeding may not meet restoration goals is even more prevalent when native perennial vegetation is seeded after fire. We evaluated vegetation cover and density responses to broadcast seeding native perennial grasses and mountain big sagebrush (Artemisia tridentata Nutt. spp. vaseyana [Rydb.] Beetle) after wildfires in the western United States in six juniper (Juniperus occidentalis ssp. occidentalis Hook)‐dominated mountain big sagebrush communities for 3 years postfire. Seeding native perennial species compared to not seeding increased perennial grass and sagebrush cover and density. Perennial grass cover was 4.3 times greater in seeded compared to nonseeded areas. Sagebrush cover averaged 24 and less than 0.1% in seeded and nonseeded areas at the conclusion of the study, respectively. Seeding perennial species reduced exotic annual grass and annual forb cover and density. Exotic annual grass cover was 8.6 times greater in nonseeded compared to seeded areas 3 years postfire. Exotic annual grass cover increased over time in nonseeded areas but decreased in seeded areas by the third‐year postfire. Seeded areas were perennial‐dominated and nonseeded areas were annual‐dominated at the end of the study. Establishing perennial vegetation may be critical after wildfires in juniper‐dominated sagebrush steppe to prevent the development of annual‐dominated communities. Postwildfire seeding increased perennial vegetation and reduced exotic plants and justifies its use.     

Palaeo‐islands as refugia and sources of genetic diversity within volcanic archipelagos: the case of the widespread endemic Canarina canariensis (Campanulaceae)

Geographical isolation by oceanic barriers and climatic stability has been postulated as some of the main factors driving diversification within volcanic archipelagos. However, few studies have focused on the effect that catastrophic volcanic events have had on patterns of within‐island differentiation in geological time. This study employed data from the chloroplast (cpDNA haplotypes) and the nuclear (AFLPs) genomes to examine the patterns of genetic variation in Canarina canariensis, an iconic plant species associated with the endemic laurel forest of the Canary Islands. We found a strong geographical population structure, with a first divergence around 0.8 Ma that has Tenerife as its central axis and divides Canarian populations into eastern and western clades. Genetic diversity was greatest in the geologically stable ‘palaeo‐islands’ of Anaga, Teno and Roque del Conde; these areas were also inferred as the ancestral location of migrant alleles towards other disturbed areas within Tenerife or the nearby islands using a Bayesian approach to phylogeographical clustering. Oceanic barriers, in contrast, appear to have played a lesser role in structuring genetic variation, with intra‐island levels of genetic diversity larger than those between‐islands. We argue that volcanic eruptions and landslides after the merging of the palaeo‐islands 3.5 Ma played key roles in generating genetic boundaries within Tenerife, with the palaeo‐islands acting as refugia against extinction, and as cradles and sources of genetic diversity to other areas within the archipelago.     

A reconstruction of Palaeo‐Macaronesia,with particular reference to the long‐term biogeography of the Atlantic island laurel forests

Macaronesia is a biogeographical region comprising five Atlantic Oceanic archipelagos: the Azores, Madeira, Selvagen (Savage Islands), Canaries and Cape Verde. It has strong affinities with the Atlantic coast of the Iberian Peninsula and the north‐western fringes of Africa. This paper re‐evaluates the biogeographical history and relationships of Macaronesia in the light of geological evidence, which suggests that large and high islands may have been continuously available in the region for very much longer than is indicated by the maximum surface area of the oldest current island (27 Ma) – possibly for as long as 60 million years. We review this literature, attempting a sequential reconstruction of Palaeo‐Macaronesia from 60 Ma to the present. We consider the implications of these geological dynamics for our understanding of the history of colonization of the present islands of Macaronesia. We also evaluate the role of these archipelagos as stepping stones and as both repositories of palaeo‐endemic forms and crucibles of neo‐endemic radiations of plant and animal groups. Our principal focus is on the laurel forest communities, long considered impoverished relicts of the Palaeotropical Tethyan flora. This account is therefore contextualized by reference to the long‐term climatic and biogeographical history of Southern Europe and North Africa and by consideration of the implications of changes in land–sea configuration, climate and ocean circulation for Macaronesian biogeography. We go on to provide a synthesis of the more recent history of Macaronesian forests, which has involved a process of impoverishment of the native elements of the biota that has accelerated since human conquest of the islands. We comment briefly on these processes and on the contemporary status and varied conservation opportunities and threats facing these forests across the Macaronesian biogeographical region.     

Fire resilience of a rare,freshwater crustacean in a fire‐prone ecosystem and the implications for fire management

Understanding species’ responses to fire regimes, particularly rare or threatened species, is important for land managers tasked with managing for biodiversity. Hickman's Allanaspides (Allanaspides hickmani, Anaspidesidae) is a rare, primitive, shrimp‐like crustacean, with high conservation value. It is restricted to a single catchment in the island state of Tasmania, Australia, where it occurs within moorland pools typically containing crayfish (Ombrastacoides spp.) burrows. Although its moorland habitat has a long history of firing, adverse fire regimes are a potential threat to the species. A large part of its range is subject to planned burning to help manage the detrimental effects of high‐intensity wildfires. The resilience of A. hickmani to low–moderate‐intensity fires was investigated over 13 years using a replicated before‐after‐control‐impact design. The fires resulted in an initial reduction in vegetation cover and surface water and an increase in water temperature. There was no effect of fire on A. hickmani captures 4 months after small‐scale, low‐intensity autumn burns. However, 5 months later, following an unintended larger‐scale, medium‐intensity spring burn, there was an 80–90% reduction in A. hickmani captures and their numbers did not recover until 6–9 years post‐fire. It is not known whether the reduced catch was due to a reduction in the number of A. hickmani or their movement from pools into crayfish burrows. These findings together with evidence of a varied fire history, including high‐intensity wildfires, within their range suggests that A. hickmani and its habitat are resilient to a range of fire frequencies and intensities provided that the fire regime does not degrade or lead to a complete loss of peat. Climate change predictions for warmer and drier summers in western Tasmania will increase the risk of peat loss. Planned burning is likely to be important for the protection of A. hickmani habitat from predicted adverse fire regimes.     

Combining limnological and palaeolimnological data to disentangle the effects of nutrient pollution and climate change on lake ecosystems: problems and potential

1. As long‐term observational lake records continue to lengthen, the historical overlap with lake sediment records grows, providing increasing opportunities for placing the contemporary ecological status of lakes in a temporal perspective. 2. Comparisons between long‐term data sets and sediment records, however, require lake sediments to be accurately dated and for sediment accumulation rates to be sufficiently rapid to allow precise matching with observational data. 3. The critical role of the sediment record in this context is its value in tracking the changing impact of human activity on a lake from a pre‐disturbance reference through to the present day. 4. Here, we use data from a range of lakes across Europe presented as case studies in this Special Section. The seven sites considered all possess both long‐term observational records and high‐quality sediment records. Our objective is to assess whether recent climate change is having an impact on their trophic status and in particular whether that impact can be disentangled from the changes associated with nutrient pollution. 5. The palaeo‐data show clear evidence for the beginning of nutrient pollution varying from the mid‐nineteenth century at Loch Leven to the early and middle twentieth century at other sites. The monitoring data show different degrees of recovery when judged against the palaeo‐reference. 6. The reason for limited recovery is attributed to continuing high nutrient concentrations related to an increase in diffuse nutrient loading or to internal P recycling, but there is some evidence that climate change may be playing a role in offsetting recovery at some sites. If this is the case, then lake ecosystems suffering from eutrophication may not necessarily return to their pre‐eutrophication reference status despite the measures that have been taken to reduce external nutrient loading. 7. The extent to which future warming might further limit such recovery can be evaluated only by continued monitoring combined with the use of palaeo‐records that set the pre‐eutrophication reference.     

Understanding how nature works: Five pathways towards a more ecologically literate world – A perspective

The sustainability of human life on Earth depends upon the integrity of the relationship between humanity and nature. Natural systems support humanity, and knowledge and understanding of how nature works form the foundation of ecological literacy. It is ecological literacy, and science literacy in general, that underpins our capacity as humans to make well‐informed decisions about how to live in sustainable ways. It is of concern that levels of ecological knowledge and understanding within many contemporary human communities may be too low to enable effective decision‐making in support of sustainable human settlements. Our concern led to an exploration of the concept of ecological literacy and the assessment of a sample of South Australian adults. We found that while ecological literacy can vary significantly in correlation with a range of socio‐demographic and psychographic characteristics, no one factor is necessarily more critical than another. Based on this work, we have identified five pathways for growing eco‐literate communities. While the patterns and drivers of ecological knowledge and understanding naturally vary between cultures and communities, our findings certainly invite serious consideration for a society, and indeed a world, that aspires to cultivate informed citizenry, leadership and governance with capacity for building sustainable human settlements.