Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 3.733
Filtrar
1.
Zootaxa ; 4804(1): zootaxa.4804.1.1, 2020 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-33055999

RESUMO

The Cambrian (Marjuman-Steptoean; Guzhangian-Paibian) kingstoniid trilobite Blountia Walcott, 1916 is distributed widely in shelf strata of Laurentian North America. Species known from Marjuman formations were lost at the mass extinction at the end of that stage. New species entered the succession during and after the extinction interval, only to disappear within the Aphelaspis Zone of the lower part of the Steptoean Stage. Steptoean species and several uppermost Marjuman (Crepicephalus Zone) species are treated in this monograph. New collections and revision of type and other archival material increase the number of species in Steptoean strata from two to six. Phylogenetic analysis supports monophyly of Blountia and Maryvillia Walcott, 1916; Blountina Lochman, in Lochman Duncan, 1944 is retained as a monotypic taxon. Steptoean species do not form a single subclade within the cladogram, so there is no evidence for a simple monophyletic radiation following the end-Marjuman extinction. New species are Blountia angelae, B. morgancreekensis, B. nevadensis, B. newfoundlandensis, and B. tennesseensis.


Assuntos
Extinção Biológica , Fósseis , Animais , Humanos , Invertebrados , América do Norte , Filogenia , Sobreviventes
2.
Nat Commun ; 11(1): 5069, 2020 10 22.
Artigo em Inglês | MEDLINE | ID: mdl-33093493

RESUMO

Ongoing climate change is predicted to trigger major shifts in the geographic distribution of marine plankton species. However, it remains unclear whether species will successfully track optimal habitats to new regions, or face extinction. Here we show that one significant zooplankton group, the radiolaria, underwent a severe decline in high latitude species richness presaged by ecologic reorganization during the late Neogene, a time of amplified polar cooling. We find that the majority (71%) of affected species did not relocate to the warmer low latitudes, but went extinct. This indicates that some plankton species cannot track optimal temperatures on a global scale as assumed by ecologic models; instead, assemblages undergo restructuring and extinction once local environmental thresholds are exceeded. This pattern forewarns profound diversity loss of high latitude radiolaria in the near future, which may have cascading effects on the ocean food web and carbon cycle.


Assuntos
Mudança Climática/história , Ecossistema , Rhizaria/fisiologia , Zooplâncton/fisiologia , Aclimatação/fisiologia , Animais , Regiões Antárticas , Biodiversidade , Evolução Biológica , Extinção Biológica , História Antiga , Modelos Biológicos , Oceanos e Mares , Oceano Pacífico , Temperatura
3.
PLoS One ; 15(10): e0232993, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33052917

RESUMO

In pre-colonial and colonial times Côte d'Ivoire probably hosted one of the largest elephant populations in West Africa, resulting in the country's name Côte d'Ivoire (in English Ivory Coast) by French settlers. Numbers declined and by the early 90s it was estimated that the total number of both savannah and forest elephants had reached 63 to 360 elephants in the entire country. Here we present updated information on the distribution and conservation status of forest elephant in Côte d'Ivoire based on multiple sources-dung counts on line transects, records of human-elephant conflict, media reports, sign and interview surveys-obtained during the period 2011-2017. We used Pearson correlation to determine the correlation between the presence of forest elephant and site variables (size of the forest, percentage of area converted into plantation, size of the forest left, size of human population inside the PA, poaching index, distance to the nearest road, population density in the Department, level of protection of the PA). To examine the effect of ecological traits on elephant extirpation, we used Principal Components Analysis (PCA) to check for multicollinearity among variables. Based on dung count elephant presence was confirmed in only 4 of the 25 protected areas surveyed. PAs with higher level of protection have higher probability to be home of elephant population. The viability of these populations is uncertain, since they have a small size and are isolated. Aggressive conservation actions including law enforcement for the protection of their remaining habitat and ranger patrolling are needed to protect the remaining forest elephant populations.


Assuntos
Conservação dos Recursos Naturais/métodos , Elefantes/crescimento & desenvolvimento , Animais , Costa do Marfim , Extinção Biológica , Humanos , Densidade Demográfica , Análise de Componente Principal , Inquéritos e Questionários
5.
Science ; 370(6513): 220-222, 2020 10 09.
Artigo em Inglês | MEDLINE | ID: mdl-33033218

RESUMO

Environmental change is transforming ecological assemblages into new configurations, resulting in novel communities. We developed a robust methodology to detect novel communities, examine patterns of emergence, and quantify probabilities of local demographic turnover in transitions to and from novel communities. Using a global dataset of Cenozoic marine plankton communities, we found that the probability of local extinction, origination, and emigration during transitions to a novel community increased two to four times that of background community changes. Although rare, novel communities were five times more likely than chance to shift into another novel state. For marine plankton communities at a 100,000-year time grain, novel communities were sensitive to further extinctions and substantial community change.


Assuntos
Biodiversidade , Extinção Biológica , Plâncton , Conjuntos de Dados como Assunto , Especiação Genética , Espécies Introduzidas , Probabilidade
6.
Nat Commun ; 11(1): 4394, 2020 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-32879314

RESUMO

The Earth's biota is changing over time in complex ways. A critical challenge is to test whether specific biomes, taxa or types of species benefit or suffer in a time of accelerating global change. We analysed nearly 10,000 abundance time series from over 2000 vertebrate species part of the Living Planet Database. We integrated abundance data with information on geographic range, habitat preference, taxonomic and phylogenetic relationships, and IUCN Red List Categories and threats. We find that 15% of populations declined, 18% increased, and 67% showed no net changes over time. Against a backdrop of no biogeographic and phylogenetic patterning in population change, we uncover a distinct taxonomic signal. Amphibians were the only taxa that experienced net declines in the analysed data, while birds, mammals and reptiles experienced net increases. Population trends were poorly captured by species' rarity and global-scale threats. Incorporation of the full spectrum of population change will improve conservation efforts to protect global biodiversity.


Assuntos
Biodiversidade , Vertebrados , Anfíbios , Animais , Mudança Climática , Conservação dos Recursos Naturais , Ecossistema , Extinção Biológica , Dinâmica Populacional/tendências
7.
Curr Biol ; 30(17): R969-R971, 2020 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-32898490

RESUMO

As environmental scientists working in countries whose COVID-linked deaths already exceed their military casualties from all campaigns since 1945, we believe there are significant messages from the handling of this horrific disease for efforts addressing the enormous challenges posed by the ongoing extinction and climate emergencies.


Assuntos
Betacoronavirus , Mudança Climática , Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/prevenção & controle , Extinção Biológica , Pandemias/prevenção & controle , Pneumonia Viral/epidemiologia , Pneumonia Viral/prevenção & controle , Emergências , Humanos , Saúde Pública
8.
Nat Commun ; 11(1): 4904, 2020 09 29.
Artigo em Inglês | MEDLINE | ID: mdl-32994391

RESUMO

Mammalian frugivores are critical seed dispersers, but many are under threat of extinction. Futhermore, the impact of past and future defaunation on plant assemblages has yet to be quantified at the global scale. Here, we integrate palm and mammalian frugivore trait and occurrence data and reveal a global positive relationship between fruit size and frugivore body size. Global variation in fruit size is better explained by present-day frugivore assemblages than by Late Pleistocene assemblages, suggesting ecological and evolutionary reorganization after end-Pleistocene extinctions, except in the Neotropics, where some large-fruited palm species may have outlived their main seed dispersers by thousands of years. Our simulations of frugivore extinction over the next 100 years suggest that the impact of defaunation will be highest in the Old World tropics, and an up to 4% assemblage-level decrease in fruit size would be required to maintain the global body size-fruit size relationship. Overall, our results suggest that while some palm species may be able to keep pace with future defaunation through evolutionary changes in fruit size, large-fruited species may be especially vulnerable to continued defaunation.


Assuntos
Arecaceae/fisiologia , Coevolução Biológica , Conservação dos Recursos Naturais , Frutas/anatomia & histologia , Mamíferos/fisiologia , Animais , Arecaceae/anatomia & histologia , Tamanho Corporal/genética , Conjuntos de Dados como Assunto , Extinção Biológica , Frutas/genética , Herbivoria/fisiologia , Mamíferos/anatomia & histologia , Tamanho do Órgão/genética , Locos de Características Quantitativas , Dispersão de Sementes/fisiologia
9.
PLoS One ; 15(9): e0238767, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32898173

RESUMO

AIM: Exotic species' introductions together with extinction of native species represent the main mechanisms driving biotic homogenization of freshwater fish assemblages around the world. While generally ichtyofaunistic realms transit towards biotic homogenization, for conservation purposes it is essential to understand what specific mechanisms are promoting it on particular areas or regions. Here, we report the occurrence of biotic homogenization in 29 Chilean watersheds, analyzing its ß-diversity (including turnover and nestedness) and predicting future trends. LOCATION: Continental Chile (18o-56o S). METHODS: We determined fish composition per basin for historical and current assemblages; extant native, exotic, and extinct species were recorded as 1 (presence) or 0 (absence) in two matrices basins × species. For each matrix, we calculated the turnover (ßsim), nestedness (ßnes), and ß-diversity (ßsor); then, we obtained Δßsim, Δßnes, and Δßsor, as the arithmetical difference between basin pairs over time. In addition, we search for explanatory variables correlating Δßsim, Δßnes, and Δßsor with geographical and land use variables. Finally, simulating events of species introduction (i.e., invasion) and extinction, we generated 15 hypothetical assemblages, looking to establish future trends towards biotic change in Chilean basins. RESULTS: Species turnover and ß-diversity significantly decreased from historical to current assemblages (Δßsim = -0.084; Δßsor = -0.061, respectively), while the species nestedness did not show significant changes (Δßnes = 0.08). Biotic changes have been driven mainly by the introduction of 28 exotic species, with a minor role of extinctions (one species) and translocations (0 species) of native species. Changes in ß-diversity were negatively correlated with area, elevation, and geographical distance between basins but not with land-use nor human population. Finally, the analysis of 15 future assemblages predicts a significant decrease of ß-diversity and turnover, and an increase for species nestedness, this time promoted by an increase in the extinction of native species. MAIN CONCLUSION: Chilean basins show a significant decrease of the distributional ß-diversity and species turnover of the freshwater fish fauna, evidencing a trend towards biotic homogenization. This trend is shared with other Neotropical basins; however, specific mechanisms driving it show different magnitude. Changes in the ß-diversity components do not show correlation with variables associated to land use, thus suggesting that casual introductions of freshwater fishes in Chile follow an opportunistic mode related to commercial use. According to future scenarios simulated, biotic homogenization should increase further, mainly as consequence of increased native extinctions.


Assuntos
Biodiversidade , Extinção Biológica , Peixes/classificação , Água Doce , Espécies Introduzidas/estatística & dados numéricos , Animais , Chile
11.
Ecol Lett ; 23(12): 1849-1861, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32981202

RESUMO

We develop a novel approach to analyse trophic metacommunities, which allows us to explore how progressive habitat loss affects food webs. Our method combines classic metapopulation models on fragmented landscapes with a Bayesian network representation of trophic interactions for calculating local extinction rates. This means that we can repurpose known results from classic metapopulation theory for trophic metacommunities, such as ranking the habitat patches of the landscape with respect to their importance to the persistence of the metacommunity as a whole. We use this to study the effects of habitat loss, both on model communities and the plant-mammal Serengeti food web dataset as a case study. Combining straightforward parameterisability with computational efficiency, our method permits the analysis of species-rich food webs over large landscapes, with hundreds or even thousands of species and habitat patches, while still retaining much of the flexibility of explicit dynamical models.


Assuntos
Ecossistema , Extinção Biológica , Animais , Teorema de Bayes , Cadeia Alimentar , Modelos Biológicos , Plantas , Dinâmica Populacional
12.
Science ; 369(6506): 928, 2020 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-32820116
13.
PLoS Biol ; 18(8): e3000801, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32810126

RESUMO

The evolutionary radiation of birds has produced incredible morphological variation, including a huge range of skull form and function. Investigating how this variation arose with respect to non-avian dinosaurs is key to understanding how birds achieved their remarkable success after the Cretaceous-Paleogene extinction event. Using a high-dimensional geometric morphometric approach, we quantified the shape of the skull in unprecedented detail across 354 extant and 37 extinct avian and non-avian dinosaurs. Comparative analyses reveal fundamental differences in how skull shape evolved in birds and non-avian dinosaurs. We find that the overall skull shape evolved faster in non-avian dinosaurs than in birds across all regions of the cranium. In birds, the anterior rostrum is the most rapidly evolving skull region, whereas more posterior regions-such as the parietal, squamosal, and quadrate-exhibited high rates in non-avian dinosaurs. These fast-evolving elements in dinosaurs are strongly associated with feeding biomechanics, forming the jaw joint and supporting the jaw adductor muscles. Rapid pulses of skull evolution coincide with changes to food acquisition strategies and diets, as well as the proliferation of bony skull ornaments. In contrast to the appendicular skeleton, which has been shown to evolve more rapidly in birds, avian cranial morphology is characterised by a striking deceleration in morphological evolution relative to non-avian dinosaurs. These results may be due to the reorganisation of skull structure in birds-including loss of a separate postorbital bone in adults and the emergence of new trade-offs with development and neurosensory demands. Taken together, the remarkable cranial shape diversity in birds was not a product of accelerated evolution from their non-avian relatives, despite their frequent portrayal as an icon of adaptive radiations.


Assuntos
Evolução Biológica , Aves/anatomia & histologia , Dinossauros/anatomia & histologia , Crânio/anatomia & histologia , Animais , Fenômenos Biomecânicos , Aves/classificação , Aves/fisiologia , Dinossauros/classificação , Dinossauros/fisiologia , Extinção Biológica , Comportamento Alimentar/fisiologia , Fósseis/anatomia & histologia , Filogenia , Crânio/fisiologia
15.
Proc Biol Sci ; 287(1933): 20200730, 2020 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-32811315

RESUMO

Sexual selection often favours investment in expensive sexual traits that help individuals compete for mates. In a rapidly changing environment, however, allocation of resources to traits related to reproduction at the expense of those related to survival may elevate extinction risk. Empirical testing of this hypothesis in the fossil record, where extinction can be directly documented, is largely lacking. The rich fossil record of cytheroid ostracods offers a unique study system in this context: the male shell is systematically more elongate than that of females, and thus the sexes can be distinguished, even in fossils. Using mixture models to identify sex clusters from size and shape variables derived from the digitized valve outlines of adult ostracods, we estimated sexual dimorphism in ostracod species before and after the Cretaceous/Palaeogene mass extinction in the United States Coastal Plain. Across this boundary, we document a substantial shift in sexual dimorphism, driven largely by a pronounced decline in the taxa with dimorphism indicating both very high and very low male investment. The shift away from high male investment, which arises largely from evolutionary changes within genera that persist through the extinction, parallels extinction selectivity previously documented during the Late Cretaceous under a background extinction regime. Our results suggest that sexual selection and the allocation of resources towards survival versus reproduction may be an important factor for species extinction during both background and mass extinctions.


Assuntos
Crustáceos , Extinção Biológica , Preferência de Acasalamento Animal , Caracteres Sexuais , Animais , Evolução Biológica , Feminino , Fósseis , Masculino
16.
Science ; 369(6507)2020 08 28.
Artigo em Inglês | MEDLINE | ID: mdl-32855310

RESUMO

Strategies for 21st-century environmental management and conservation under global change require a strong understanding of the biological mechanisms that mediate responses to climate- and human-driven change to successfully mitigate range contractions, extinctions, and the degradation of ecosystem services. Biodiversity responses to past rapid warming events can be followed in situ and over extended periods, using cross-disciplinary approaches that provide cost-effective and scalable information for species' conservation and the maintenance of resilient ecosystems in many bioregions. Beyond the intrinsic knowledge gain such integrative research will increasingly provide the context, tools, and relevant case studies to assist in mitigating climate-driven biodiversity losses in the 21st century and beyond.


Assuntos
Biodiversidade , Mudança Climática/história , Conservação dos Recursos Naturais , Extinção Biológica , Animais , Arquivos , História Antiga , Paleontologia
17.
Proc Biol Sci ; 287(1932): 20201144, 2020 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-32752990

RESUMO

Substantial environmental change can force a population onto a path towards extinction, but under some conditions, adaptation by natural selection can rescue the population and allow it to persist. This process, known as evolutionary rescue, is believed to be less likely to occur with greater magnitudes of random environmental fluctuations because environmental variation decreases expected population size, increases variance in population size and increases evolutionary lag. However, previous studies of evolutionary rescue in fluctuating environments have only considered scenarios in which evolutionary rescue was likely to occur. We extend these studies to assess how baseline extinction risk (which we manipulated via changes in the initial population size, degree of environmental change or mutation rate) influences the effects of environmental variation on evolutionary rescue following an abrupt environmental change. Using a combination of analytical models and stochastic simulations, we show that autocorrelated environmental variation hinders evolutionary rescue in low-extinction-risk scenarios but facilitates rescue in high-risk scenarios. In these high-risk cases, the chance of a run of good years counteracts the otherwise negative effects of environmental variation on evolutionary demography. These findings can inform the development of effective conservation practices that consider evolutionary responses to abrupt environmental changes.


Assuntos
Evolução Biológica , Extinção Biológica , Adaptação Fisiológica , Meio Ambiente , Densidade Demográfica , Seleção Genética
18.
Proc Biol Sci ; 287(1932): 20201039, 2020 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-32781952

RESUMO

The 'social distancing' that occurred in response to the COVID-19 pandemic in humans provides a powerful illustration of the intimate relationship between infectious disease and social behaviour in animals. Indeed, directly transmitted pathogens have long been considered a major cost of group living in humans and other social animals, as well as a driver of the evolution of group size and social behaviour. As the risk and frequency of emerging infectious diseases rise, the ability of social taxa to respond appropriately to changing infectious disease pressures could mean the difference between persistence and extinction. Here, we examine changes in the social behaviour of humans and wildlife in response to infectious diseases and compare these responses to theoretical expectations. We consider constraints on altering social behaviour in the face of emerging diseases, including the lack of behavioural plasticity, environmental limitations and conflicting pressures from the many benefits of group living. We also explore the ways that social animals can minimize the costs of disease-induced changes to sociality and the unique advantages that humans may have in maintaining the benefits of sociality despite social distancing.


Assuntos
Doenças Transmissíveis Emergentes , Comportamento Social , Isolamento Social , Animais , Comportamento Animal , Doenças Transmissíveis/psicologia , Doenças Transmissíveis/veterinária , Doenças Transmissíveis Emergentes/psicologia , Comunicação , Extinção Biológica , Gorilla gorilla/psicologia , Gorilla gorilla/virologia , Humanos , Relações Interpessoais , Marsupiais , Xenofobia/psicologia
19.
Proc Natl Acad Sci U S A ; 117(35): 21008-21010, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32817482

RESUMO

The Late Devonian was a protracted period of low speciation resulting in biodiversity decline, culminating in extinction events near the Devonian-Carboniferous boundary. Recent evidence indicates that the final extinction event may have coincided with a dramatic drop in stratospheric ozone, possibly due to a global temperature rise. Here we study an alternative possible cause for the postulated ozone drop: a nearby supernova explosion that could inflict damage by accelerating cosmic rays that can deliver ionizing radiation for up to [Formula: see text] ky. We therefore propose that the end-Devonian extinctions were triggered by supernova explosions at [Formula: see text], somewhat beyond the "kill distance" that would have precipitated a full mass extinction. Such nearby supernovae are likely due to core collapses of massive stars; these are concentrated in the thin Galactic disk where the Sun resides. Detecting either of the long-lived radioisotopes [Formula: see text] or [Formula: see text] in one or more end-Devonian extinction strata would confirm a supernova origin, point to the core-collapse explosion of a massive star, and probe supernova nucleosynthesis. Other possible tests of the supernova hypothesis are discussed.


Assuntos
Radiação Cósmica/efeitos adversos , Extinção Biológica , Fósseis/história , Biodiversidade , Meio Ambiente Extraterreno/química , História Antiga , Astros Celestes
20.
Int J Syst Evol Microbiol ; 70(8): 4432-4450, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32735208

RESUMO

The genus Chryseobacterium in the family Weeksellaceae is known to be polyphyletic. Amino acid identity (AAI) values were calculated from whole-genome sequences of species of the genus Chryseobacterium, and their distribution was found to be multi-modal. These naturally-occurring non-continuities were leveraged to standardise genus assignment of these species. We speculate that this multi-modal distribution is a consequence of loss of biodiversity during major extinction events, leading to the concept that a bacterial genus corresponds to a set of species that diversified since the Permian extinction. Transfer of nine species (Chryseobacterium arachidiradicis, Chryseobacterium bovis, Chryseobacterium caeni, Chryseobacterium hispanicum, Chryseobacterium hominis, Chryseobacterium hungaricum,, Chryseobacterium pallidum and Chryseobacterium zeae) to the genus Epilithonimonas and eleven (Chryseobacterium anthropi, Chryseobacterium antarcticum, Chryseobacterium carnis, Chryseobacterium chaponense, Chryseobacterium haifense, Chryseobacterium jeonii, Chryseobacterium montanum, Chryseobacterium palustre, Chryseobacterium solincola, Chryseobacterium treverense and Chryseobacterium yonginense) to the genus Kaistella is proposed. Two novel species are described: Kaistella daneshvariae sp. nov. and Epilithonimonas vandammei sp. nov. Evidence is presented to support the assignment of Planobacterium taklimakanense to a genus apart from Chryseobacterium, to which Planobacterium salipaludis comb nov. also belongs. The novel genus Halpernia is proposed, to contain the type species Halpernia frigidisoli comb. nov., along with Halpernia humi comb. nov., and Halpernia marina comb. nov.


Assuntos
Chryseobacterium/classificação , Filogenia , Aminoácidos/química , Extinção Biológica
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA