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[PMID]: 29273953 [Au] Autor: Coutinho MCL; Teixeira VL; Santos CSG [Ad] Endereço: Department of Marine Biology, Institute of Biology, Federal Fluminense University, Outeiro São João Batista, s/no, P.O. Box 100.644, Niterói, RJ, 24020-150, Brazil. marinacoutinho88@gmail.com. [Ti] Título: A Review of "Polychaeta" Chemicals and their Possible Ecological Role. [So] Source: J Chem Ecol;44(1):72-94, 2018 Jan. [Is] ISSN: 1573-1561 [Cp] País de publicação: United States [La] Idioma: eng [Ab] Resumo: Despite the many publications concerning the isolation of substances and the many reviews of marine natural products, some groups of organisms remain poorly studied, including "Polychaeta". In response, this review covers articles published through December 2016 that address marine natural products produced from polychaetes, with a focus on antipredatory strategies, competitors, fouling, and pathogens. A total of 121 compounds were isolated from 1934 to 2016, which includes halogenated aromatics, proteins, amino acids and Lumazine derivatives most notably-with a defensive function were found in the literature, most frequently in the families Sabellidae, Terebellidae, Glyceridae, and Nereididae. The period of highest discovery of natural products in defensive actions for the group was the 2000s. Polychaetes were addressed in 26 revisions of the total 51 articles analyzed and are less reported than other marine invertebrates such as sponges, cnidarians, mollusks, and tunicates. In sum, the present review provides a basis for future research on the marine chemical ecology of polychaetes. [Mh] Termos MeSH primário: Organismos Aquáticos/química Produtos Biológicos/química [Mh] Termos MeSH secundário: Animais Organismos Aquáticos/metabolismo Produtos Biológicos/isolamento & purificação Cnidários/química Cnidários/metabolismo Comportamento Consumatório/fisiologia Equinodermos/química Equinodermos/metabolismo Fenômenos Ecológicos e Ambientais Moluscos/química Moluscos/metabolismo Urocordados/química Urocordados/metabolismo [Pt] Tipo de publicação: JOURNAL ARTICLE; REVIEW [Nm] Nome de substância: 0 (Biological Products) [Em] Mês de entrada: 1802 [Cu] Atualização por classe: 180221 [Lr] Data última revisão: 180221 [Sb] Subgrupo de revista: IM [Da] Data de entrada para processamento: 171224 [St] Status: MEDLINE [do] DOI: 10.1007/s10886-017-0915-z

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[PMID]: 28919504 [Au] Autor: Starrett J; Hayashi CY; Derkarabetian S; Hedin M [Ad] Endereço: Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA; Department of Biological Sciences, Auburn University, 101 Rouse Life Sciences, Auburn, AL 36849, USA. Electronic address: jamesstarrett10@gmail.com. [Ti] Título: Cryptic elevational zonation in trapdoor spiders (Araneae, Antrodiaetidae, Aliatypus janus complex) from the California southern Sierra Nevada. [So] Source: Mol Phylogenet Evol;118:403-413, 2018 Jan. [Is] ISSN: 1095-9513 [Cp] País de publicação: United States [La] Idioma: eng [Ab] Resumo: The relative roles of ecological niche conservatism versus niche divergence in promoting montane speciation remains an important topic in biogeography. Here, our aim was to test whether lineage diversification in a species complex of trapdoor spiders corresponds with riverine barriers or with an ecological gradient associated with elevational tiering. Aliatypus janus was sampled from throughout its range, with emphasis on populations in the southern Sierra Nevada Mountains of California. We collected multi-locus genetic data to generate a species tree for A. janus and its close relatives. Coalescent based hypothesis tests were conducted to determine if genetic breaks within A. janus conform to riverine barriers. Ecological niche models (ENM) under current and Last Glacial Maximum (LGM) conditions were generated and hypothesis tests of niche conservatism and divergence were performed. Coalescent analyses reveal deeply divergent genetic lineages within A. janus, likely corresponding to cryptic species. Two primary lineages meet along an elevational gradient on the western slopes of the southern Sierra Nevada Mountains. ENMs under both current and LGM conditions indicate that these groups occupy largely non-overlapping niches. ENM hypothesis testing rejected niche identity between the two groups, and supported a sharp ecological gradient occurring where the groups meet. However, the niche similarity test indicated that the two groups may not inhabit different background niches. The Sierra Nevada Mountains provide a natural laboratory for simultaneously testing ecological niche divergence and conservatism and their role in speciation across a diverse range of taxa. Aliatypus janus represents a species complex with cryptic lineages that may have diverged due to parapatric speciation along an ecological gradient, or been maintained by the evolution of ecological niche differences following allopatric speciation. [Mh] Termos MeSH primário: Aranhas/classificação [Mh] Termos MeSH secundário: Animais California Fenômenos Ecológicos e Ambientais Complexo IV da Cadeia de Transporte de Elétrons/química Complexo IV da Cadeia de Transporte de Elétrons/classificação Complexo IV da Cadeia de Transporte de Elétrons/genética Especiação Genética Nevada Filogenia RNA Ribossômico 28S/química RNA Ribossômico 28S/classificação RNA Ribossômico 28S/genética Aranhas/genética [Pt] Tipo de publicação: JOURNAL ARTICLE [Nm] Nome de substância: 0 (RNA, Ribosomal, 28S); EC 1.9.3.1 (Electron Transport Complex IV) [Em] Mês de entrada: 1802 [Cu] Atualização por classe: 180220 [Lr] Data última revisão: 180220 [Sb] Subgrupo de revista: IM [Da] Data de entrada para processamento: 170919 [St] Status: MEDLINE

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[PMID]: 28912577 [Au] Autor: Maley CC; Aktipis A; Graham TA; Sottoriva A; Boddy AM; Janiszewska M; Silva AS; Gerlinger M; Yuan Y; Pienta KJ; Anderson KS; Gatenby R; Swanton C; Posada D; Wu CI; Schiffman JD; Hwang ES; Polyak K; Anderson ARA; Brown JS; Greaves M; Shibata D [Ad] Endereço: Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University, 1001 S. McAllister Ave, Tempe, Arizona 85287, USA. [Ti] Título: Classifying the evolutionary and ecological features of neoplasms. [So] Source: Nat Rev Cancer;17(10):605-619, 2017 Oct. [Is] ISSN: 1474-1768 [Cp] País de publicação: England [La] Idioma: eng [Ab] Resumo: Neoplasms change over time through a process of cell-level evolution, driven by genetic and epigenetic alterations. However, the ecology of the microenvironment of a neoplastic cell determines which changes provide adaptive benefits. There is widespread recognition of the importance of these evolutionary and ecological processes in cancer, but to date, no system has been proposed for drawing clinically relevant distinctions between how different tumours are evolving. On the basis of a consensus conference of experts in the fields of cancer evolution and cancer ecology, we propose a framework for classifying tumours that is based on four relevant components. These are the diversity of neoplastic cells (intratumoural heterogeneity) and changes over time in that diversity, which make up an evolutionary index (Evo-index), as well as the hazards to neoplastic cell survival and the resources available to neoplastic cells, which make up an ecological index (Eco-index). We review evidence demonstrating the importance of each of these factors and describe multiple methods that can be used to measure them. Development of this classification system holds promise for enabling clinicians to personalize optimal interventions based on the evolvability of the patient's tumour. The Evo- and Eco-indices provide a common lexicon for communicating about how neoplasms change in response to interventions, with potential implications for clinical trials, personalized medicine and basic cancer research. [Mh] Termos MeSH primário: Evolução Biológica Neoplasias/classificação Neoplasias/fisiopatologia [Mh] Termos MeSH secundário: Antígenos de Neoplasias/imunologia Fenômenos Ecológicos e Ambientais Expressão Gênica Variação Genética Seres Humanos Microbiota Neoplasias/genética Neoplasias/patologia Fenótipo Espécies Reativas de Oxigênio Fatores de Tempo Hipóxia Tumoral Microambiente Tumoral [Pt] Tipo de publicação: CONSENSUS DEVELOPMENT CONFERENCE; JOURNAL ARTICLE; REVIEW [Nm] Nome de substância: 0 (Antigens, Neoplasm); 0 (Reactive Oxygen Species) [Em] Mês de entrada: 1710 [Cu] Atualização por classe: 171004 [Lr] Data última revisão: 171004 [Sb] Subgrupo de revista: IM [Da] Data de entrada para processamento: 170916 [St] Status: MEDLINE [do] DOI: 10.1038/nrc.2017.69

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[PMID]: 28791504 [Au] Autor: Panayiotou E; Dimou M; Monokrousos N [Ad] Endereço: Department of Biological Applications and Technology, University of Ioannina, 45110, Ioannina, Greece. [Ti] Título: The effects of grazing intensity on soil processes in a Mediterranean protected area. [So] Source: Environ Monit Assess;189(9):441, 2017 Aug 08. [Is] ISSN: 1573-2959 [Cp] País de publicação: Netherlands [La] Idioma: eng [Ab] Resumo: We investigated the temporal and among-site differentiation of soil functionality properties in fields under different grazing intensities (heavy and light) and compared them to those found in their adjacent hedgerows, consisting either of wooden shrubs (Rubus canescens) or of high trees (Populus sp.), during the cold and humid seasons of the year. We hypothesized that greater intensity of grazing would result in higher degradation of the soil system. The grazing factor had a significant effect on soil organic C and N, microbial biomass C, microbial biomass N, microbial activity, and ß-glucosidase, while acid phosphatase and urease activity were not found to differ significantly among the management systems. The intensity of grazing affected mostly the chemical properties of soil (organic C and N) and altered significantly the composition of the soil microbial community, as lower C:N ratio of the microbial biomass indicates the dominance of bacteria over fungi in the heavily grazed fields. All estimated biological variables presented higher values in the humid period, although the pattern of differentiation was similar at both sampling times, revealing that site-specific variations were more pronounced than the time-specific ones. Our results indicate that not all C, N, and P dynamics were equally affected by grazing. Management plans applied to pastures, in order to improve soil quality properties and accelerate passive reforestation, should aim at the improvement of soil parameters related primarily to C and secondly to N cycle. [Mh] Termos MeSH primário: Fenômenos Ecológicos e Ambientais Monitoramento Ambiental Herbivoria Microbiologia do Solo Solo/química [Mh] Termos MeSH secundário: Bactérias/efeitos dos fármacos Biomassa Carbono/análise Fungos/efeitos dos fármacos Região do Mediterrâneo Estações do Ano Árvores [Pt] Tipo de publicação: JOURNAL ARTICLE [Nm] Nome de substância: 0 (Soil); 7440-44-0 (Carbon) [Em] Mês de entrada: 1710 [Cu] Atualização por classe: 171116 [Lr] Data última revisão: 171116 [Sb] Subgrupo de revista: IM [Da] Data de entrada para processamento: 170810 [St] Status: MEDLINE [do] DOI: 10.1007/s10661-017-6161-6

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[PMID]: 28787437 [Au] Autor: Di Palo F; Fornara DA [Ad] Endereço: School of Geography and Environmental Sciences, University of Ulster, Coleraine, United Kingdom. [Ti] Título: Plant and soil nutrient stoichiometry along primary ecological successions: Is there any link? [So] Source: PLoS One;12(8):e0182569, 2017. [Is] ISSN: 1932-6203 [Cp] País de publicação: United States [La] Idioma: eng [Ab] Resumo: Ecological stoichiometry suggests that plant Nitrogen (N)-to-Phosphorus (P) ratios respond to changes in both soil N:P stoichiometry and soil N and P availability. Thus we would expect that soil and plant N:P ratios be significantly related along natural gradients of soil development such as those associated with primary ecological successions. Here we explicitly search for linkages between plant and soil N:P stoichiometry along four primary successions distributed across Europe. We measured N and P content in soils and plant compartments (leaf, stem and root) of 72 wild plant species distributed along two sand dune and two glacier successions where soil age ranges from few to thousand years old. Overall we found that soil N:P ratios strongly increased along successional stages, however, plant N:P ratios were neither related to soil N:P stoichiometry nor to changes in soil N and P availability. Instead changes in plant nutrient stoichiometry were "driven" by plant-functional-group identity. Not only N:P ratios differed between legumes, grasses and forbs but each of these plant functional groups maintained N:P ratios relatively constant across pioneer, middle and advanced successional stages. Our evidence is that soil nutrient stoichiometry may not be a good predictor of changes in plant N:P stoichiometry along natural primary ecological successions, which have not reached yet a retrogressive stage. This could be because wild-plants rely on mechanisms of internal nutrient regulation, which make them less dependent to changes in soil nutrient availability under unpredictable environmental conditions. Further studies need to clarify what underlying evolutionary and eco-physiological mechanisms determine changes in nutrient stoichiometry in plant species distributed across natural environmental gradients. [Mh] Termos MeSH primário: Fenômenos Ecológicos e Ambientais Nitrogênio/análise Fósforo/análise Plantas/química Solo/química [Mh] Termos MeSH secundário: Fatores de Tempo [Pt] Tipo de publicação: JOURNAL ARTICLE [Nm] Nome de substância: 0 (Soil); 27YLU75U4W (Phosphorus); N762921K75 (Nitrogen) [Em] Mês de entrada: 1709 [Cu] Atualização por classe: 171116 [Lr] Data última revisão: 171116 [Sb] Subgrupo de revista: IM [Da] Data de entrada para processamento: 170809 [St] Status: MEDLINE [do] DOI: 10.1371/journal.pone.0182569

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[PMID]: 28678881 [Au] Autor: Halpern BS; Frazier M; Afflerbach J; O'Hara C; Katona S; Stewart Lowndes JS; Jiang N; Pacheco E; Scarborough C; Polsenberg J [Ad] Endereço: National Center for Ecological Analysis and Synthesis, University of California Santa Barbara, Santa Barbara, California, United States of America. [Ti] Título: Drivers and implications of change in global ocean health over the past five years. [So] Source: PLoS One;12(7):e0178267, 2017. [Is] ISSN: 1932-6203 [Cp] País de publicação: United States [La] Idioma: eng [Ab] Resumo: Growing international and national focus on quantitatively measuring and improving ocean health has increased the need for comprehensive, scientific, and repeated indicators to track progress towards achieving policy and societal goals. The Ocean Health Index (OHI) is one of the few indicators available for this purpose. Here we present results from five years of annual global assessment for 220 countries and territories, evaluating potential drivers and consequences of changes and presenting lessons learned about the challenges of using composite indicators to measure sustainability goals. Globally scores have shown little change, as would be expected. However, individual countries have seen notable increases or declines due in particular to improvements in the harvest and management of wild-caught fisheries, the creation of marine protected areas (MPAs), and decreases in natural product harvest. Rapid loss of sea ice and the consequent reduction of coastal protection from that sea ice was also responsible for declines in overall ocean health in many Arctic and sub-Arctic countries. The OHI performed reasonably well at predicting near-term future scores for many of the ten goals measured, but data gaps and limitations hindered these predictions for many other goals. Ultimately, all indicators face the substantial challenge of informing policy for progress toward broad goals and objectives with insufficient monitoring and assessment data. If countries and the global community hope to achieve and maintain healthy oceans, we will need to dedicate significant resources to measuring what we are trying to manage. [Mh] Termos MeSH primário: Conservação dos Recursos Naturais/estatística & dados numéricos Fenômenos Ecológicos e Ambientais Ecossistema Pesqueiros/estatística & dados numéricos [Mh] Termos MeSH secundário: Algoritmos Mudança Climática Conservação dos Recursos Naturais/métodos Conservação dos Recursos Naturais/tendências Pesqueiros/tendências Geografia Seres Humanos Concentração de Íons de Hidrogênio Internacionalidade Biologia Marinha/métodos Biologia Marinha/estatística & dados numéricos Biologia Marinha/tendências Modelos Teóricos Oceanos e Mares Água do Mar/química [Pt] Tipo de publicação: JOURNAL ARTICLE [Em] Mês de entrada: 1710 [Cu] Atualização por classe: 171006 [Lr] Data última revisão: 171006 [Sb] Subgrupo de revista: IM [Da] Data de entrada para processamento: 170706 [St] Status: MEDLINE [do] DOI: 10.1371/journal.pone.0178267

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[PMID]: 28655863 [Au] Autor: Michael AJ [Ad] Endereço: Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park, Dallas, TX 75390, U.S.A. anthony.michael@utsouthwestern.edu. [Ti] Título: Evolution of biosynthetic diversity. [So] Source: Biochem J;474(14):2277-2299, 2017 Jun 27. [Is] ISSN: 1470-8728 [Cp] País de publicação: England [La] Idioma: eng [Ab] Resumo: Since the emergence of the last common ancestor from which all extant life evolved, the metabolite repertoire of cells has increased and diversified. Not only has the metabolite cosmos expanded, but the ways in which the same metabolites are made have diversified. Enzymes catalyzing the same reaction have evolved independently from different protein folds; the same protein fold can produce enzymes recognizing different substrates, and enzymes performing different chemistries. Genes encoding useful enzymes can be transferred between organisms and even between the major domains of life. Organisms that live in metabolite-rich environments sometimes lose the pathways that produce those same metabolites. Fusion of different protein domains results in enzymes with novel properties. This review will consider the major evolutionary mechanisms that generate biosynthetic diversity: gene duplication (and gene loss), horizontal and endosymbiotic gene transfer, and gene fusion. It will also discuss mechanisms that lead to convergence as well as divergence. To illustrate these mechanisms, one of the original metabolisms present in the last universal common ancestor will be employed: polyamine metabolism, which is essential for the growth and cell proliferation of archaea and eukaryotes, and many bacteria. [Mh] Termos MeSH primário: Biodiversidade Enzimas/metabolismo Evolução Molecular Modelos Moleculares Biossíntese de Proteínas [Mh] Termos MeSH secundário: Animais Biocatálise Fenômenos Ecológicos e Ambientais Enzimas/química Enzimas/genética Deleção de Genes Duplicação Gênica Fusão Gênica Transferência Genética Horizontal Seres Humanos Poliaminas/metabolismo Dobramento de Proteína Homologia Estrutural de Proteína Simbiose [Pt] Tipo de publicação: JOURNAL ARTICLE; REVIEW [Nm] Nome de substância: 0 (Enzymes); 0 (Polyamines) [Em] Mês de entrada: 1707 [Cu] Atualização por classe: 170707 [Lr] Data última revisão: 170707 [Sb] Subgrupo de revista: IM [Da] Data de entrada para processamento: 170629 [St] Status: MEDLINE [do] DOI: 10.1042/BCJ20160823

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[PMID]: 28636615 [Au] Autor: Griesser M; Drobniak SM; Nakagawa S; Botero CA [Ad] Endereço: Department of Anthropology, University of Zurich, Zurich, Switzerland. [Ti] Título: Family living sets the stage for cooperative breeding and ecological resilience in birds. [So] Source: PLoS Biol;15(6):e2000483, 2017 Jun. [Is] ISSN: 1545-7885 [Cp] País de publicação: United States [La] Idioma: eng [Ab] Resumo: Cooperative breeding is an extreme form of cooperation that evolved in a range of lineages, including arthropods, fish, birds, and mammals. Although cooperative breeding in birds is widespread and well-studied, the conditions that favored its evolution are still unclear. Based on phylogenetic comparative analyses on 3,005 bird species, we demonstrate here that family living acted as an essential stepping stone in the evolution of cooperative breeding in the vast majority of species. First, families formed by prolonging parent-offspring associations beyond nutritional independency, and second, retained offspring began helping at the nest. These findings suggest that assessment of the conditions that favor the evolution of cooperative breeding can be confounded if this process is not considered to include 2 steps. Specifically, phylogenetic linear mixed models show that the formation of families was associated with more productive and seasonal environments, where prolonged parent-offspring associations are likely to be less costly. However, our data show that the subsequent evolution of cooperative breeding was instead linked to environments with variable productivity, where helpers at the nest can buffer reproductive failure in harsh years. The proposed 2-step framework helps resolve current disagreements about the role of environmental forces in the evolution of cooperative breeding and better explains the geographic distribution of this trait. Many geographic hotspots of cooperative breeding have experienced a historical decline in productivity, suggesting that a higher proportion of family-living species could have been able to avoid extinction under harshening conditions through the evolution of cooperative breeding. These findings underscore the importance of considering the potentially different factors that drive different steps in the evolution of complex adaptations. [Mh] Termos MeSH primário: Aves/fisiologia Fenômenos Ecológicos e Ambientais Ecossistema Comportamento de Nidação/fisiologia [Mh] Termos MeSH secundário: Animais Evolução Biológica Aves/classificação Aves/genética Cruzamento Filogenia Reprodução/fisiologia Comportamento Social Meio Social [Pt] Tipo de publicação: JOURNAL ARTICLE [Em] Mês de entrada: 1710 [Cu] Atualização por classe: 171002 [Lr] Data última revisão: 171002 [Sb] Subgrupo de revista: IM [Da] Data de entrada para processamento: 170622 [St] Status: MEDLINE [do] DOI: 10.1371/journal.pbio.2000483

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[PMID]: 28222542 [Au] Autor: Marquez de la Plata C; Qualls D; Plenger P; Malec JF; Hayden ME [Ad] Endereço: Pate Rehabilitation Medical Center, Dallas, TX, USA. [Ti] Título: Ecologically relevant outcome measure for post-inpatient rehabilitation. [So] Source: NeuroRehabilitation;40(2):187-194, 2017. [Is] ISSN: 1878-6448 [Cp] País de publicação: Netherlands [La] Idioma: eng [Ab] Resumo: BACKGROUND: Transfer of skills learned within the clinic environment to patients' home or community is important in post-inpatient brain injury rehabilitation (PBIR). Outcome measures used in PBIR assess level of independence during functional tasks; however, available functional instruments do not quantitate the environment in which the behaviors occur. OBJECTIVE: To examine the reliability and validity of an instrument used to assess patients' functional abilities while quantifying the amount of structure and distractions in the environment. METHODS: 2501 patients who sustained a traumatic brain injury (TBI) or cerebrovascular accident (CVA) and participated in a multidisciplinary PBIR program between 2006 and 2014 were identified retrospectively for this study. The PERPOS and MPAI-4 were used to assess functional abilities at admission and at discharge. Construct validity was assessed using a bivariate Spearman rho analysis A subsample of 56 consecutive admissions during 2014 were examined to determine inter-rater reliability. Intra-class correlation coefficient (ICC) and Kappa coefficients assessed inter-rater agreement of the total PERPOS and PERPOS subscales respectively. RESULTS: The PERPOS and MPAI-4 demonstrated a strong negative association among both TBI and CVA patients. Kappa scores for the three PERPOS scales each demonstrated good to excellent inter-rater agreement. The ICC for overall PERPOS scores fell in the good agreement range. CONCLUSION: The PERPOS can be used reliably in PBIR to quantify patients' functional abilities within the context of environmental demands. [Mh] Termos MeSH primário: Lesões Encefálicas/reabilitação Fenômenos Ecológicos e Ambientais Avaliação de Resultados (Cuidados de Saúde)/métodos Alta do Paciente/normas Reabilitação do Acidente Vascular Cerebral/normas Acidente Vascular Cerebral/terapia [Mh] Termos MeSH secundário: Atividades Cotidianas Adulto Lesões Encefálicas/diagnóstico Feminino Seres Humanos Masculino Meia-Idade Alta do Paciente/tendências Reprodutibilidade dos Testes Estudos Retrospectivos Acidente Vascular Cerebral/diagnóstico Reabilitação do Acidente Vascular Cerebral/tendências Adulto Jovem [Pt] Tipo de publicação: JOURNAL ARTICLE [Em] Mês de entrada: 1705 [Cu] Atualização por classe: 170523 [Lr] Data última revisão: 170523 [Sb] Subgrupo de revista: IM [Da] Data de entrada para processamento: 170223 [St] Status: MEDLINE [do] DOI: 10.3233/NRE-161403

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[PMID]: 28189668 [Au] Autor: Capitán JA; Cuenda S; Alonso D [Ad] Endereço: Department of Applied Mathematics, Technical University of Madrid, Madrid, Spain; Center for Advanced Studies (CEAB-CSIC), Blanes, Catalunya, Spain. Electronic address: ja.capitan@upm.es. [Ti] Título: Stochastic competitive exclusion leads to a cascade of species extinctions. [So] Source: J Theor Biol;419:137-151, 2017 Apr 21. [Is] ISSN: 1095-8541 [Cp] País de publicação: England [La] Idioma: eng [Ab] Resumo: Community ecology has traditionally relied on the competitive exclusion principle, a piece of common wisdom in conceptual frameworks developed to describe species assemblages. Key concepts in community ecology, such as limiting similarity and niche partitioning, are based on competitive exclusion. However, this classical paradigm in ecology relies on implications derived from simple, deterministic models. Here we show how the predictions of a symmetric, deterministic model about the way extinctions proceed can be utterly different from the results derived from the same model when ecological drift (demographic stochasticity) is explicitly considered. Using analytical approximations to the steady-state conditional probabilities for assemblages with two and three species, we demonstrate that stochastic competitive exclusion leads to a cascade of extinctions, whereas the symmetric, deterministic model predicts a multiple collapse of species. To test the robustness of our results, we have studied the effect of environmental stochasticity and relaxed the species symmetry assumption. Our conclusions highlight the crucial role of stochasticity when deriving reliable theoretical predictions for species community assembly. [Mh] Termos MeSH primário: Algoritmos Ecossistema Extinção Biológica Modelos Teóricos Processos Estocásticos [Mh] Termos MeSH secundário: Fenômenos Ecológicos e Ambientais Dinâmica Populacional [Pt] Tipo de publicação: JOURNAL ARTICLE [Em] Mês de entrada: 1709 [Cu] Atualização por classe: 170925 [Lr] Data última revisão: 170925 [Sb] Subgrupo de revista: IM [Da] Data de entrada para processamento: 170213 [St] Status: MEDLINE

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