Exoplanet Biosignatures: Future Directions

Astrobiology, Год журнала: 2018, Номер 18(6), С. 779 - 824

Опубликована: Июнь 1, 2018

We introduce a Bayesian method for guiding future directions detection of life on exoplanets. describe empirical and theoretical work necessary to place constraints the relevant likelihoods, including those emerging from better understanding stellar environment, planetary climate geophysics, geochemical cycling, universalities physics chemistry, contingencies evolutionary history, properties as an emergent complex system, mechanisms driving emergence life. provide examples how formalism could guide search strategies, determining observations prioritize or deciding between targeted searches larger lower resolution surveys generate ensemble statistics address methodology constrain prior probability with without positive detection. Key Words: Exoplanets—Biosignatures—Life detection—Bayesian analysis. Astrobiology 18, 779–824. 1. Introduction 2. Setting Stage: What Is Life? Biosignature? 3. Detecting Unknown Biology Worlds: A Framework 3.1. Habitability in framework biosignatures 4. P(data|abiotic) 4.1. Stellar environment 4.2. Climate geophysics 4.2.1. Coupled tectonic–climate models 4.2.2. Community GCM projects generating P(data|life) 4.3. Geochemical 4.3.1. Anticipating unexpected: statistical approaches characterizing atmospheres non-Earth-like worlds 5. 5.1. Black-box living processes 5.1.1. Type classification Seager et al. (2013a) 5.1.1.1. Energy capture (type I) 5.1.1.2. Biomass II) 5.1.1.3. Other uses III) 5.1.1.4. Products modification gases IV) 5.1.2. Alternatives type 5.1.2.1. I, energy 5.1.2.2. II, biomass 5.1.2.3. III, "other uses" 5.1.2.4. IV 5.1.3. When is it appropriate deconstruct black box? 5.2. Life improbable chemistry 5.3. process 5.3.1. coevolution its planet: Earth example 5.3.2. Calculating conditional probabilities biological evolution past biogeochemical states 5.4. Insights universal biology 5.4.1. Network 5.4.2. Universal scaling laws, applicable other worlds? 6. P(life) 6.1. P(emerge): constraining origins 6.2. Biological innovations 7. Example: Atmospheric Oxygen 8. Tuning Search Strategies Based 9. Conclusions Acknowledgments Author Disclosure Statement References Abbreviations Used

Язык: Английский

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Equal fitness paradigm explained by a trade-off between generation time and energy production rate

Nature Ecology & Evolution, Год журнала: 2017, Номер 2(2), С. 262 - 268

Опубликована: Дек. 27, 2017

Язык: Английский

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Extreme rainfall events alter the trophic structure in bromeliad tanks across the Neotropics

Nature Communications, Год журнала: 2020, Номер 11(1)

Опубликована: Июнь 25, 2020

Abstract Changes in global and regional precipitation regimes are among the most pervasive components of climate change. Intensification rainfall cycles, ranging from frequent downpours to severe droughts, could cause widespread, but largely unknown, alterations trophic structure ecosystem function. We conducted multi-site coordinated experiments show how variation quantity evenness modulates 210 natural freshwater microcosms (tank bromeliads) across Central South America (18°N 29°S). The biomass smaller organisms (detritivores) was higher under more stable hydrological conditions. Conversely, predators highest when uneven, resulting top-heavy pyramids. These results illustrate extremes precipitation, localized droughts or flooding, can erode base food webs, with negative implications for stability dynamics.

Язык: Английский

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Global drivers of population density in terrestrial vertebrates

Global Ecology and Biogeography, Год журнала: 2018, Номер 27(8), С. 968 - 979

Опубликована: Авг. 1, 2018

Abstract Aim Although the effects of life history traits on population density have been investigated widely, how spatial environmental variation influences for a large range organisms and at broad scale is poorly known. Filling this knowledge gap crucial global species management conservation planning to understand potential impact changes multiple species. Location Global. Time period Present. Major taxa studied Terrestrial amphibians, reptiles, birds mammals. Methods We collected estimates terrestrial vertebrates, including 364 850 5,667 7,651 contrasted importance predictors using mixed models tested different hypotheses explain in four groups. assessed predictive accuracy through cross‐validation mapped partial response vertebrate variables globally. Results Amphibians were more abundant wet areas with high productivity levels, whereas reptiles showed relatively higher densities arid low stable temperatures. The mammals was typically temperate intermediate levels productivity. good abilities, pseudo‐ R 2 ranging between 0.68 (birds) 0.83 (reptiles). Main conclusions Traits determine most across species, conditions intraspecific populations. Species traits, resource availability climatic stability influence These can be used predict average over explore macroecological patterns inform analyses.

Язык: Английский

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Pyramids and cascades: a synthesis of food chain functioning and stability

Ecology Letters, Год журнала: 2018, Номер 22(2), С. 405 - 419

Опубликована: Дек. 17, 2018

Abstract Food chain theory is one of the cornerstones ecology, providing many its basic predictions, such as biomass pyramids, trophic cascades and predator–prey oscillations. Yet, ninety years into this theory, conditions under which these patterns may occur persist in nature remain subject to debate. Rather than address each pattern isolation, we propose that they must be understood together, calling for synthesis a fragmented landscape theoretical empirical results. As first step, minimal combines long‐standing energetic dynamical approaches food chains. We chart predictions on concise map, where two main regimes emerge: across various functioning stability metrics, regime characterised by pyramidal other cascade patterns. The axes map combine key physiological ecological variables, metabolic rates self‐regulation. A quantitative comparison with data sheds light conflicting puzzles, from size spectra causes strength. conclude drawing systematic connections between existing chains, their stability, crucial step confronting real ecosystems.

Язык: Английский

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Feeding ecological knowledge: the underutilised power of faecal DNA approaches for carnivore diet analysis

Mammal Review, Год журнала: 2018, Номер 49(2), С. 97 - 112

Опубликована: Дек. 22, 2018

Abstract Accurate analyses of the diets predators are key to understand trophic interactions and defining conservation strategies. Diets commonly assessed through analysis non‐invasively collected scats, use faecal DNA ( fDNA ) can reduce species misidentifications that could lead biased ecological inference. We review scientific literature since publication first paper on amplifying , in order assess trends genetic non‐invasive sampling gNIS for predator identification scat‐based diet studies North American European terrestrial mammalian carnivores (Carnivora). quantify error rates morphology‐based identification. then provide an overview how applying would improve research other areas carnivore ecology. found identity was verified by using only 8% 400 based scats. The median percentage false positives (i.e. samples wrongly identified as belonging target species) 18%, consistent regardless species’ body size. did not find increasing trend over time, despite existing technical capability identify almost all species. New directions include employing high‐throughput sequencing HTS metabarcoding species, individual predator, entire assemblage consumed items, microbiome pathogens. conclude protocols metagenomic approaches hold great promise elevating a fundamental cornerstone future ecology biology mammals.

Язык: Английский

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The adaptive cycle: More than a metaphor

Ecological Complexity, Год журнала: 2019, Номер 39, С. 100767 - 100767

Опубликована: Июнь 18, 2019

The adaptive cycle and its extension to panarchy (nested cycles) has been a useful metaphor conceptual model for understanding long-term dynamics of change in ecological social–ecological systems. We argue that cycles are ubiquitous complex systems because they reflect endogenously generated as result processes self-organization evolution. synthesize work from wide array fields support this claim. If growth, conservation, collapse renewal endogenous systems, then there ought be signals system over time this. describe series largely thermodynamically based indicators have developed purpose, we add critical heretofore missing component–namely, (adaptive at objectively identified spatial temporal scales nested within each system, instead solely the level. explicit consideration scales, when coupled with selective indicators, may circumvent need multiple capture will provide richer picture trajectory than offered by single-scale analysis. feasible ways which researchers could systematically quantitatively look signatures ecosystems, rather relying on qualitative descriptions.

Язык: Английский

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Regime shifts occur disproportionately faster in larger ecosystems

Nature Communications, Год журнала: 2020, Номер 11(1)

Опубликована: Март 10, 2020

Abstract Regime shifts can abruptly affect hydrological, climatic and terrestrial systems, leading to degraded ecosystems impoverished societies. While the frequency of regime is predicted increase, fundamental relationships between spatial-temporal scales their underlying mechanisms are poorly understood. Here we analyse empirical data from ( n = 4), marine 25) freshwater 13) environments show positive sub-linear size shift duration systems. Each additional unit area an ecosystem provides increasingly smaller time taken for that system collapse, meaning large systems tend more slowly than small but disproportionately faster. We substantiate these findings with five computational models reveal importance structure in controlling duration. The imply Earth occur over ‘human’ timescales years decades, collapse vulnerable ecosystems, such as Amazon rainforest Caribbean coral reefs, may take only a few decades once triggered.

Язык: Английский

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The global ocean size spectrum from bacteria to whales

Science Advances, Год журнала: 2021, Номер 7(46)

Опубликована: Ноя. 10, 2021

It has long been hypothesized that aquatic biomass is evenly distributed among logarithmic body mass size classes. Although this community structure observed regionally, mostly plankton groups, its generality never formally tested across all marine life over the global ocean, nor have impacts of humans on it globally assessed. Here, we bring together data at scale to test hypothesis from bacteria whales. We find within most order magnitude classes indeed remarkably constant, near 1 gigatonne (Gt) wet weight (1015 g), but and large mammals are markedly above below value, respectively. Furthermore, human appear significantly truncated upper one-third spectrum. This dramatic alteration what possibly life’s largest-scale regularity underscores extent activities.

Язык: Английский

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Inferring ecosystem networks as information flows

Scientific Reports, Год журнала: 2021, Номер 11(1)

Опубликована: Март 29, 2021

The detection of causal interactions is great importance when inferring complex ecosystem functional and structural networks for basic applied research. Convergent cross mapping (CCM) based on nonlinear state-space reconstruction made substantial progress about network inference by measuring how well historical values one variable can reliably estimate states other variables. Here we investigate the ability a developed optimal information flow (OIF) model to infer bidirectional causality compare that CCM. Results from synthetic datasets generated simple predator-prey model, data real-world sardine-anchovy-temperature system multispecies fish highlight proposed OIF performs better than CCM predict population community patterns. Specifically, provides larger gradient inferred interactions, higher point-value accuracy smaller fluctuations [Formula: see text]-diversity including their characteristic time delays. We propose an threshold maximize in predicting effective text]-diversity, defined as count model-inferred interacting species. Overall outperforms all models assessing predictive (also terms computational complexity) due explicit consideration synchronization, divergence diversity events define sensitivity, uncertainty complexity. Thus, offers broad ecological extracting ecosystems time-series space-time continuum. accurate species at any biological scale organization highly valuable because it allows biodiversity changes, instance function climate anthropogenic stressors. This has practical implications defining management design, such stock prioritization delineation marine protected areas derived collective assembly. be used evaluation design where should considered non-linear predictability diverse populations or communities.

Язык: Английский

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