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The end-Permian mass extinction (252.3 Ma) was an abrupt and severe loss of diversity on land and in the oceans, the largest extinction of the Phanerozoic. Recent palaeontological, geochemical and modelling studies link the extinction with eruption of the Siberian Traps flood basalts, which would have caused global warming, ocean acidification and shallow-marine anoxia. On land, global warming and aridification were mostly responsible for the vertebrate and plant extinction. Although almost no marine group emerged unscathed, selectivity favoured more active animals, whereas sessile and heavily calcified taxa such as corals and reef-building sponges suffered heavily. The recovery interval was unusually long, likely because of continuing stress, and the extinction resulted in permanent shifts in marine ecosystem composition and structure, giving rise to the mollusc-rich communities that still dominate today. Key Concepts: The end-Permian mass extinction was a severe crisis for nearly every plant and animal group, on land and in the oceans. The extinction was abrupt, apparently synchronous on land and in the sea, with the majority of taxonomic losses occurring over a few tens of thousands of years, approximately 252.3 Ma. In the marine realm, more actively motile animal groups fared relatively better during the extinction. Although low-oxygen waters were widespread and contributed to the marine extinction, the primary cause most likely was global warming and ocean acidification from CO2 released by Siberia Traps flood basalt volcanism. The terrestrial extinction was also caused by global warming and, among plants, the resulting dry conditions. It took an unusually long time (5–7 million years) for most marine and terrestrial ecosystems to recover from the extinction, likely because of continuing intermittent stress. The extinction triggered permanent changes in the composition and structure of marine ecosystems, giving rise to mollusc-dominated communities that remain dominant today. Keywords: Permian; Triassic; extinction; ocean acidification; climate change; reefs; evolution

The main paradigm for protection of biodiversity, focusing on maintaining or restoring conditions where humans leave no or little impact, risks overlooking anthropogenic landscapes harboring a rich native biodiversity. An example is northern European agricultural landscapes with traditionally managed semi-natural grasslands harboring an exceptional local richness of many taxa, such as plants, fungi and insects. During the last century these grasslands have declined by more than 95%, i.e. in the same magnitude as other, internationally more recognized declines of natural habitats. In this study, data from the Swedish Red List was used to calculate tentative extinction rates for vascular plants, insects (Lepidoptera, Coleoptera, Hymenoptera) and fungi, given a scenario where such landscapes would vanish. Conservative estimates suggest that abandonment of traditional management in these landscapes would result in elevated extinction rates in all these taxa, between two and three orders of magnitude higher than global background extinction rates. It is suggested that the species richness in these landscapes reflects a species pool from Pleistocene herbivore-structured environments, which, after the extinction of the Pleistocene megafauna, was rescued by the introduction of pre-historic agriculture. Maintaining traditionally managed agricultural landscapes is of paramount importance to prevent species loss. There is no inherent conflict between preservation of anthropogenic landscapes and remaining ‘wild’ areas, but valuating also anthropogenic landscapes is essential for biodiversity conservation.

The first “complete” paradigm of extinction was proposed as “the multigenerational, attritional loss of reproductive fitness,” for which MALF is a suitable acronym. A “complete” paradigm mu...

We document a positive and strong correlation between speciation and extinction rates in the Paleozoic zooplankton graptoloid clade, between 481 and 419 Ma. This correlation has a magnitude of ~0.35–0.45 and manifests at a temporal resolution of We infer that this correlation reflects approximately synchronous coupling of speciation and extinction in the graptoloids on timescales of a few tens of thousands of years. Almost half of graptoloid species in our data set have durations of

Species selection, the effect of heritable traits in generating between-lineage diversification rate differences, provides a valuable conceptual framework for understanding the relationship between traits, diversification, and phylogenetic tree shape. An important challenge, however, is that the nature of real diversification landscapes—curves or surfaces which describe the propensity of species-level lineages to diversify as a function of one or more traits—remains poorly understood. Here, we present a novel, time-stratified extension of the QuaSSE model in which speciation/extinction rate is specified as a static or temporally shifting Gaussian or skewed-Gaussian function of the diversification trait. We then use simulations to show that the generally imbalanced nature of real phylogenetic trees, as well as their generally greater than expected frequency of deep branching events, are typical outcomes when diversification is treated as a dynamic, trait-dependent process. Focusing on four basic models (Gaussian-speciation with and without background extinction; skewed-speciation; Gaussian-extinction), we also show that particular features of the species selection regime produce distinct tree shape signatures and that, consequently, a combination of tree shape metrics has the potential to reveal the species selection regime under which a particular lineage diversified. We evaluate this idea empirically by comparing the phylogenetic trees of plant lineages diversifying within climatically and geologically stable environments of the Greater Cape Floristic Region, with those of lineages diversifying in environments that have experienced major change through the Late Miocene-Pliocene. Consistent with our expectations, the trees of lineages diversifying in a dynamic context are less balanced, show a greater concentration of branching events close to the present, and display stronger diversification rate-trait correlations. We suggest that species selection plays an important role in shaping phylogenetic trees but recognize the need for an explicit probabilistic framework within which to assess the likelihoods of alternative diversification scenarios as explanations of a particular tree shape. [Cape flora; diversification landscape; environmental change; gamma statistic; species selection; time-stratified QuaSSE model; trait-dependent diversification; tree imbalance.]

“Earth provides enough to satisfy every man’s needs, but not every man’s greed” - Mahatma Gandhi The vast number of species prevailing on planet Earth is the result of evolutionary processes that have been operating since life originated about 3.5 billion years ago. As new species evolved, a small number of species that became misfits in the prevailing environment became extinct (background extinction). However, the rapid increase in human population and humanity’s greed for luxurious living have resulted in marked environmental degradation, particularly in the recent decades, increasing species extinction hundred or even thousand-fold compared to background extinctions, thus precipitating the ‘sixth mass extinction’ crisis. Unlike the past five mass extinctions that were due to natural catastrophes, the sixth mass extinction would be exclusively the result of human activities. Habitat loss and its degradation, overex-ploitation of bioresources and climate change have been the main drivers of the sixth mass extinction crisis. Amongst human-induced environmental changes, climate change is going to affect humanity more than any other changes. Apart from exterminating a large number of both terrestrial and aquatic species, these changes bring down crop productivity and quality substantially, thus seriously compromising ecosystem services essential for human welfare. Mitigating human-induced environmental changes has become one of the highest priorities for the humanity to sustain biodiversity and human welfare.

Whether mass extinctions and their associated recoveries represent an intensification of background extinction and origination dynamics versus a separate macroevolutionary regime remains a central debate in evolutionary biology. The previous focus has been on extinction, but origination dynamics may be equally or more important for long-term evolutionary outcomes. The evolution of animal body size is an ideal process to test for differences in macroevolutionary regimes, as body size is easily determined, comparable across distantly related taxa and scales with organismal traits. Here, we test for shifts in selectivity between background intervals and the ‘Big Five’ mass extinction events using capture–mark–recapture models. Our body-size data cover 10 203 fossil marine animal genera spanning 10 Linnaean classes with occurrences ranging from Early Ordovician to Late Pleistocene (485–1 Ma). Most classes exhibit differences in both origination and extinction selectivity between background intervals and mass extinctions, with the direction of selectivity varying among classes and overall exhibiting stronger selectivity during origination after mass extinction than extinction during the mass extinction. Thus, not only do mass extinction events shift the marine biosphere into a new macroevolutionary regime, the dynamics of recovery from mass extinction also appear to play an underappreciated role in shaping the biosphere in their aftermath.

The decline in background extinction rates of marine animals through geologic time is an established but unexplained feature of the Phanerozoic fossil record. There is also growing consensus that the ocean and atmosphere did not become oxygenated to near-modern levels until the mid-Paleozoic, coinciding with the onset of generally lower extinction rates. Physiological theory provides us with a possible causal link between these two observations-predicting that the synergistic impacts of oxygen and temperature on aerobic respiration would have made marine animals more vulnerable to ocean warming events during periods of limited surface oxygenation. Here, we evaluate the hypothesis that changes in surface oxygenation exerted a first-order control on extinction rates through the Phanerozoic using a combined Earth system and ecophysiological modeling approach. We find that although continental configuration, the efficiency of the biological carbon pump in the ocean, and initial climate state all impact the magnitude of modeled biodiversity loss across simulated warming events, atmospheric oxygen is the dominant predictor of extinction vulnerability, with metabolic habitat viability and global ecophysiotype extinction exhibiting inflection points around 40% of present atmospheric oxygen. Given this is the broad upper limit for estimates of early Paleozoic oxygen levels, our results are consistent with the relative frequency of high-magnitude extinction events (particularly those not included in the canonical big five mass extinctions) early in the Phanerozoic being a direct consequence of limited early Paleozoic oxygenation and temperature-dependent hypoxia responses.

Most people can name a mammal or bird that has become extinct in recent centuries, but few can name a recently extinct plant. We present a comprehensive, global analysis of modern extinction in plants. Almost 600 species have become extinct, at a higher rate than background extinction, but almost as many have been erroneously declared extinct and then been rediscovered. Reports of extinction on islands, in the tropics and of shrubs, trees or species with narrow ranges are least likely to be refuted by rediscovery. Plant extinctions endanger other organisms, ecosystems and human well-being, and must be understood for effective conservation planning.

Subtropical islands are often viewed as refuges where Quaternary climatic shifts driving global episodes of extinction were buffered. Island biodiversity, however, may have been impacted by climatic fluctuations at local scales, particularly in spatially heterogeneous island systems. In this study, we generated a conceptual framework for predicting the potential impact of Pleistocene extinctions on the biogeographical pattern of the Canarian spermatophyte flora, with a focus on the easternmost Canarian islands (ECI). Then, we performed an exhaustive bibliographic revision (270 studies) to examine whether taxonomic, phylogenetic and phylogeographical data support our predictions. Although molecular information is limited for many lineages, the available data suggest that the majority of extant ECI plant taxa may be the result of relatively recent (, C. G.V. was funded by project SV‐17‐GIJON‐BOTANICO. J.P. was funded by the MINECO through the Ramón y Cajal Program (RYC‐2016‐20506), and Marie Sklodowska‐Curie COFUND, Researchers' Night and Individual Fellowships Global (MSCA grant agreement No 747238, 'UNISLAND').

D. Jablonski [Proc. Natl. Acad. Sci. U.S.A. 99, 8139-8144 (2002)] coined the term "dead clades walking" (DCWs) to describe marine fossil orders that experience significant drops in genus richness during mass extinction events and never rediversify to previous levels. This phenomenon is generally interpreted as further evidence that the macroevolutionary consequences of mass extinctions can continue well past the formal boundary. It is unclear, however, exactly how long DCWs are expected to persist after extinction events and to what degree they impact broader trends in Phanerozoic biodiversity. Here we analyze the fossil occurrences of 134 skeletonized marine invertebrate orders in the Paleobiology Database (paleobiodb.org) using a Bayesian method to identify significant change points in genus richness. Our analysis identifies 70 orders that experience major diversity losses without recovery. Most of these taxa, however, do not fit the popular conception of DCWs as clades that narrowly survive a mass extinction event and linger for only a few stages before succumbing to extinction. The median postdrop duration of these DCW orders is long (>30 Myr), suggesting that previous studies may have underestimated the long-term taxonomic impact of mass extinction events. More importantly, many drops in diversity without recovery are not associated with mass extinction events and occur during background extinction stages. The prevalence of DCW orders throughout both mass and background extinction intervals and across phyla (>50% of all marine invertebrate orders) suggests that the DCW pattern is a major component of macroevolutionary turnover.

Selectivity of mass extinctions is thought to play a major role in coupling or decoupling of taxonomic, morphological, and ecological diversity, yet these measures have never been jointly evaluated within a single clade over multiple mass extinctions. We investigate extinction selectivity and changes in taxonomic diversity, morphological disparity, and functional ecology over the ~160-million-year evolutionary history of diplobathrid crinoids (Echinodermata), which spans two mass extinctions. Whereas previous studies documented extinction selectivity for crinoids during background extinction, we find no evidence for selectivity during mass extinctions. Despite no evidence for extinction selectivity, disparity remains strongly correlated with richness over extinction events, contradicting expected patterns of disparity given nonselective extinction. Results indicate that (i) disparity and richness can remain coupled across extinctions even when selective extinction does not occur, (ii) simultaneous decreases in taxonomic diversity and disparity are insufficient evidence for extinction selectivity, and (iii) selectivity differs between background and mass extinction regimes.

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. National Museum of Natural History, Smithsonian Institution National Science FoundationNational Science Foundation (NSF) [NSF-EAR 1424906] info:eu-repo/semantics/publishedVersion

The half-billion-year history of animal evolution is characterized by decreasing rates of background extinction. Earth's increasing habitability for animals could result from several processes: (i) a decrease in the intensity of interactions among species that lead to extinctions; (ii) a decrease in the prevalence or intensity of geological triggers such as flood basalt eruptions and bolide impacts; (iii) a decrease in the sensitivity of animals to environmental disturbance; or (iv) an increase in the strength of stabilizing feedbacks within the climate system and biogeochemical cycles. There is no evidence that the prevalence or intensity of interactions among species or geological extinction triggers have decreased over time. There is, however, evidence from palaeontology, geochemistry and comparative physiology that animals have become more resilient to an environmental change and that the evolution of complex life has, on the whole, strengthened stabilizing feedbacks in the climate system. The differential success of certain phyla and classes appears to result, at least in part, from the anatomical solutions to the evolution of macroscopic size that were arrived at largely during Ediacaran and Cambrian time. Larger-bodied animals, enabled by increased anatomical complexity, were increasingly able to mix the marine sediment and water columns, thus promoting stability in biogeochemical cycles. In addition, body plans that also facilitated ecological differentiation have tended to be associated with lower rates of extinction. In this sense, Cambrian solutions to Cambrian problems have had a lasting impact on the trajectory of complex life and, in turn, fundamental properties of the Earth system.

The flora of the island of St Helena provides an amplified system for the study of extinction by reason of the island’s high endemism, small size, vulnerable biota, length of time of severe disturbance (since 1502) and severity of threats. Endemic plants have been eliminated from 96.5% of St Helena by habitat loss. There are eight recorded extinctions in the vascular flora since 1771 giving an extinction rate of 581 extinctions per million species per year (E/MSY). This is considerably higher than background extinction rates, variously estimated at 1 or 0.1 E/MSY. We have no information for plant extinctions prior to 1771 but applying the same extinction rate to the period 1502 to 1771 suggests that there may be around ten unrecorded historical extinctions. We use census data and population decline estimates to project likely extinction forward in time. The projected overall extinction rate for the next 200 years is somewhat higher at 625 E/MSY. However, our data predict an extinction crunch in the next 50 years with 4 species out of the remaining 48 likely to become extinct during this period. It is interesting that during a period when the native plant areas dropped to 3.5% of the original, the extinction rate appears to have remained shallowly linear with under 30% of the endemic flora becoming extinct.

We present an analysis of the invertebrates of St Helena using an invertebrate conservation evaluation framework, to review invertebrate data, highlight knowledge gaps and prioritise invertebrate conservation needs that perhaps could be applied to other regions of the world. St Helena’s invertebrate fauna has 891 genera and 1133 species. The fauna has a high level of endemism with 450 species (equal to 96% of all native species) but the total species richness now comprises many introduced species (664) with 93 species in 24 orders that are entirely novel to St Helena. The elevation ranges of native species appear to be narrow, most being confined to higher elevations above 500 m. St Helena has had a large number of probable extinction events; 30 insects, and 19 molluscs, and the threat of further extinctions remains high. The cumulative invertebrate extinctions on St Helena exceed the global background extinction rate on an island barely covering 122 km2. We present actions and timelines to focus invertebrate conservation on St Helena; taxonomy, ecology, long term monitoring and invasive species control are priority areas to reduce extinction risk.

Extinction of species has been a recurrent phenomenon in the history of our planet, but it was generally outweighed in the course of quite a long geological time by the appearance of new species, except, especially, for the five geologically short times when the so-called “Big Five” mass extinctions occurred. Could the current decline in biodiversity be considered as a signal of an ongoing, human-driven sixth mass extinction? This note briefly examines some issues related to: (i) The hypothesized current extinction rate and the magnitude of contemporary global biodiversity loss; (ii) the challenges of comparing them to the background extinction rate and the magnitude of the past Big Five mass extinction events; (iii) briefly considering the effects of the main anthropogenic stressors on ecosystems, including the risk of the emergence of pandemic diseases. A comparison between the Pleistocene fauna dynamics with the present defaunation process and the cascading effects of recent anthropogenic actions on ecosystem structure and functioning suggests that habitat degradation, ecosystem fragmentation, and alien species introduction are important stressors increasing the negative impact on biodiversity exerted by anthropogenic-driven climate changes and their connected effects. In addition, anthropogenic ecological stressors such as urbanization, landscapes, and wildlife trade, creating new opportunities for virus transmission by augmenting human contact with wild species, are among the main factors triggering pandemic diseases.

Hierarchy theory recognises that ecological and evolutionary units occur in a nested and interconnected hierarchical system, with cascading effects occurring between hierarchical levels. Different biological disciplines have routinely come into conflict over the primacy of different forcing mechanisms behind evolutionary and ecological change. These disconnects arise partly from differences in perspective (with some researchers favouring ecological forcing mechanisms while others favour developmental/historical mechanisms), as well as differences in the temporal framework in which workers operate. In particular, long-term palaeontological data often show that large-scale (macro) patterns of evolution are predominantly dictated by shifts in the abiotic environment, while short-term (micro) modern biological studies stress the importance of biotic interactions. We propose that thinking about ecological and evolutionary interactions in a hierarchical framework is a fruitful way to resolve these conflicts. Hierarchy theory suggests that changes occurring at lower hierarchical levels can have unexpected, complex effects at higher scales due to emergent interactions between simple systems. In this way, patterns occurring on short- and long-term time scales are equally valid, as changes that are driven from lower levels will manifest in different forms at higher levels. We propose that the dual hierarchy framework fits well with our current understanding of evolutionary and ecological theory. Furthermore, we describe how this framework can be used to understand major extinction events better. Multi-generational attritional loss of reproductive fitness (MALF) has recently been proposed as the primary mechanism behind extinction events, whereby extinction is explainable solely through processes that result in extirpation of populations through a shutdown of reproduction. While not necessarily explicit, the push to explain extinction through solely population-level dynamics could be used to suggest that environmentally mediated patterns of extinction or slowed speciation across geological time are largely artefacts of poor preservation or a coarse temporal scale. We demonstrate how MALF fits into a hierarchical framework, showing that MALF can be a primary forcing mechanism at lower scales that still results in differential survivorship patterns at the species and clade level which vary depending upon the initial environmental forcing mechanism. Thus, even if MALF is the primary mechanism of extinction across all mass extinction events, the primary environmental cause of these events will still affect the system and result in differential responses. Therefore, patterns at both temporal scales are relevant.

Four substantial tetrapod extinctions have been identified during the Permian, but only one of these is an apparent mass extinction. Analyses of global compilations of the family-level diversity of Permian tetrapods have been confounded by incorrect and compiled correlations. Instead, analyzing diversity patterns at the genus level in “best sections” identifies only one apparent mass extinction of Permian tetrapods. Much evolutionary turnover took place among tetrapods during the latter part of the early Permian and had been identified as a single mass extinction at the Artinskian-Kungurian boundary. However, the only stratigraphically dense tetrapod record of the late early Permian, from the southwestern USA, indicates a succession of extinctions spread out from Redtankian through Littlecrontonian (Kungurian) time, not a single mass extinction. Olson's gap remains a hiatus in the global record of Permian tetrapods equivalent to part of the Kungurian-Roadian. Across the gap, eupelycosaur-dominated assemblages were replaced by therapsid-dominated assemblages, but the claim that this is associated with a mass extinction (“Olson's extinction”) has been based on compressing all of the extinctions of the Redtankian-Littlecrotonian and Olson's gap into one event. Recognition of Olson's gap does not preclude the possibility of an extinction at the early-middle Permian boundary (“Olson's extinction”). However, the gap in the tetrapod fossil record makes it impossible to establish the magnitude, precise timing and structure of the extinctions that took place across Olson's gap. The only Permian mass extinction of tetrapods is the dinocephalian extinction event during the Gamkan (near the end of the Guadalupian), which saw the total extinction of dinocephalians and major diversity drop in therocephalians. In the Karoo basin of South Africa, this extinction is the loss of at least 64% of generic diversity. The changeover from dinocephalian assemblages to assemblages without dinocephalians in other parts of Permian Pangea suggests that the dinocephalian extinction event was a global event. The late Permian tetrapod extinctions are older than the end-Permian marine extinctions. Furthermore, the magnitude of the diversity drop and ecological severity of the end-Permian tetrapod extinctions have been greatly overstated. Best sections analysis in the Karoo basin indicates a stepwise late Permian tetrapod extinction during deposition of the upper Dicynodon Assemblage Zone that took at least 250,000 and perhaps more than a million years. The culmination of this stepwise extinction, across the highest occurrence of Dicynodon (= boundary of Platbergian and Lootsbergian land-vertebrate faunachrons) is a loss of genera not much above an inferred background extinction rate of Permian tetrapod genera and resembles the amount of turnover seen at several other boundaries of Permian and Triassic land-vertebrate faunachrons. The case for coeval land plant, insect and tetrapod extinctions during the Permian is a weak one. The first coeval marine and nonmarine mass extinctions of the Phanerozoic were likely the end-Guadalupian extinction. Climate change, notably greenhouse climates, may have driven Permian tetrapod extinctions, but that hypothesized relationship needs better documentation.

BackgroundExtinction-based procedures are often used to inhibit maladaptive fear responses. However, because extinction procedures show efficacy limitations, transcranial direct current stimulation (tDCS) has been suggested as a promising add-on enhancer.ObjectiveIn this study, we tested how cathodal tDCS over the right dorsolateral prefrontal cortex affects extinction and tried to unveil the processes at play that boost the effectiveness of extinction procedures and its translational potential to the treatment of anxiety disorders.MethodsWe implemented a fear conditioning paradigm whereby 41 healthy women (mean age = 20.51 +/- 5.0) were assigned to either cathodal tDCS (n = 27) or sham tDCS (n = 16). Fear responses were measured with self-reports, autonomic responses, and implicit avoidance tendencies.ResultsCathodal tDCS shows no statistically significant effect in extinction, according to selfreports, and seems to even negatively affect fear conditioned skin conductance responses. However, one to three months after the tDCS session and extinction, we found a group difference in the action tendencies towards the neutral stimuli (F (1, 41) = 12.04, p =.001,.p2 =.227), with the cathodal tDCS group (as opposed to the sham group) showing a safety learning (a positive bias towards the CS-), with a moderate effect size. This suggests that cathodal tDCS may foster stimuli discrimination, leading to a decreased generalization effect.DiscussionCathodal tDCS may have enhanced long-term distinctiveness between threatening cues and perceptively similar neutral cues through a disambiguation process of the value of the neutral stimuli-a therapeutic target in anxiety disorders. Future studies should confirm these results and extend the study of cathodal tDCS effect on short term avoidance tendencies., AGA is supported by the Foundation for Science and Technology, Portugal and Programa COMPETE [grants numbers SFRH/BD/80945/2011, PTDC/MHC-PAP/5618/2014 (POCI-01-0145FEDER-016836); http://www.poci-compete2020.pt/].JA is supported by the Foundation for Science and Technology, Portugal and Programa COMPETE [grants numbers PTDC/MHC-PAP/5618/2014 (POCI-01-0145-FEDER-016836), PTDC/MHC-PCN/3575/2012, PTDC/MHC-PCN/0522/2014, PTDC/MHC-PCN/6805/2014; https://www.fct.pt/index.phtml.en].The Cognitive and Behavioral Center for Research and Intervention of the Faculty of Psychology and Educational Sciences of the University of Coimbra is supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Education and Science through national funds and co-financed by FEDER through COMPETE2020 under the PT2020 Partnership Agreement [UID/PSI/01662/2013; https://www.portugal2020.pt].The Psychology Research Centre of the University of Minho is supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Education and Science through national funds and co-financed by FEDER through COMPETE2020 under the PT2020 Partnership Agreement (POCI-01-0145-FEDER007653). The Proaction Laboratory and the PTDC/MHC-PAP/5618/2014 (POCI-01-0145-FEDER016836) directly supported this research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Extinction was recognized as a scientific fact 200 years ago, although no adequate paradigm has emerged to explain the process. Prevailing theory has focused on ‘cause(s)’ of extinction but has neglected ‘effect’ and ‘mechanism’. These omissions preclude the formulation of a functional paradigm necessary for remedial action in response to the impending anthropogenic mediated, worldwide extinction crisis. The new paradigm is defined as the multi-generational, attritional loss of reproductive fitness. Stabilizing selection continuously adapts species to specific ecosystems, which often results in highly evolved species prone to extinction when environments shift. Some species survive by tracking the declining palaeoclimates in which they presumably evolved, often becoming relicts prior to extinction. Compelling new evidence shows that even mass extinctions are largely a result of environmental change leading to widespread, attritional reproductive decline, rather than a result of instantaneous global catastrophes.

Two distinct regimes of extinction dynamic are present in the major marine zooplankton group, the graptolites, during the Ordovician and Silurian periods (486−418 Ma). In conditions of “background” extinction, which dominated in the Ordovician, taxonomic evolutionary rates were relatively low and the probability of extinction was highest among newly evolved species (“background extinction mode”). A sharp change in extinction regime in the Late Ordovician marked the onset of repeated severe spikes in the extinction rate curve; evolutionary turnover increased greatly in the Silurian, and the extinction mode changed to include extinction that was independent of species age (“high-extinction mode”). This change coincides with a change in global climate, from greenhouse to icehouse conditions. During the most extreme episode of extinction, the Late Ordovician Mass Extinction, old species were selectively removed (“mass extinction mode”). Our analysis indicates that selective regimes in the Paleozoic ocean plankton switched rapidly (generally in

Metacommunity theory indicates that variation in local community structure can be partitioned into components including those related to local environmental conditions vs. spatial effects and that these can be quantified using statistical methods based on variation partitioning. It has been hypothesized that joint associations of community composition with environment and space could be due to patch dynamics involving colonization-extinction processes in environmentally heterogeneous landscapes but this has yet to be theoretically shown. We develop a two-patch, type-two, species competition model in such a "harlequin" landscape (where different patches have different environments) to evaluate how composition is related to environmental and spatial effects as a function of background extinction rate. Using spatially implicit analytical models, we find that the environmental association of community composition declines with extinction rate as expected. Using spatially explicit simulation models, we further find that there is an increase in the spatial structure with extinction due to spatial patterning into clusters that are not related to environmental conditions but that this increase is limited. Natural metacommunities often show both environment and spatial determination even under conditions of relatively high isolation and these could be more easily explained by our model than alternative metacommunity models.

This study is a literature review aiming to give a summary of the effects that the current anthropogenic caused climate crisis has on the biogeography and environment, and further give examples of likely future adaptations and needed conservation work. This study is based on scientific articles, primary from Web of Science and Google Scholar. The biodiversity is under pressure due to climate changes, the average species extinction is currently two to three orders of magnitude higher than the normal background extinction, and faster than the rate of origination. This development follows the predictions of The Red Queen Hypothesis that every species must constantly evolve due to environmental changes in order to avoid extinction. The natural environments are changing due to e.g. increased extreme weather events and ocean acidification. The increased heating is causing drought, and adaptations of the biota is needed, like more drought resistant flora and fauna with the ability to undergo estivation. The increased oceanic acidity can cause the shells of calcifying organisms to dissolve. These organisms will need to either spend energy on increased calcification or develop in a way so they can carry out live with lesser calcification. If organisms cannot develop, they are likely to migrate to colder regions. In the ocean this means towards polar areas and to greater depths, and in the terrestrial environment it is pole wards and to greater altitudes. Conservation is needed, and there are multiple options. Ex situ might be the only option for species whose natural habitat will be forever gone if the development of the climate change continues as present. To carry out conservation to infinity is unrealistic, and we are at a point where climate change is threatening our food security. It is possible to both slow down the current climate crisis and counteract its consequences.

The Late Triassic and Early Toarcian extinction events are both associated with greenhouse warming events triggered by massive volcanism. These Mesozoic hyperthermals were responsible for the mass extinction of marine organisms and resulted in significant ecological upheaval. It has, however, been suggested that these events merely involved intensification of background extinction rates rather than significant shifts in the macroevolutionary regime and extinction selectivity. Here, we apply a multivariate modelling approach to a vast global database of marine organisms to test whether extinction selectivity varied through the Late Triassic and Early Jurassic. We show that these hyperthermals do represent shifts in the macroevolutionary regime and record different extinction selectivity compared to background intervals of the Late Triassic and Early Jurassic. The Late Triassic mass extinction represents a more profound change in selectivity than the Early Toarcian extinction but both events show a common pattern of selecting against pelagic predators and benthic photosymbiotic and suspension-feeding organisms, suggesting that these groups of organisms may be particularly vulnerable during episodes of global warming. In particular, the Late Triassic extinction represents a macroevolutionary regime change that is characterized by (i) the change in extinction selectivity between Triassic background intervals and the extinction event itself; and (ii) the differences in extinction selectivity between the Late Triassic and Early Jurassic as a whole.

There have been five past mass extinctions during the history of Earth. We have entered a 6th mass extinction. The 6th mass extinction (also referred to as the Anthropocene extinction) is an ongoing current event where a large number of living species are threatened with extinction or are going extinct because of the environmentally destructive activities of humans. This article presents an overview of Earth's five past mass extinctions, an overview of the current 6th mass extinction, current and future rates of species extinction associated with the ongoing 6th mass extinction, and past and present human activities associated with the 6th mass extinction.

The mass extinction event that occurred at the close of the Permian Period (~ 252 million years ago) represents the most severe biodiversity loss in the ocean of the Phanerozoic. The links between the global carbon cycle, climate change and mass extinction are complex and involve a whole range of often inter-related geochemical, biological, ecologic and climatic factors. It has become widely accepted that the end-Permian mass extinction was associated with a global warming event, because the age of the Siberian Trap eruption, a potentially massive source of carbon dioxide, coincides within error with the extinction event. However, geologic data that are in support of this global warming event are relatively sparse. The chain of events and the causal relationship between the eruption of Siberian Traps and mass extinction is not well established. Global warming, in particular, has only been reported from limited proxy data and climate models, for which the pCO2 in the atmosphere just before and during the end-Permian extinction event is poorly known. This study critically assesses both the proxy climate data and the existing paleoclimate simulations with the goals of assessing our current understanding of the link between mass extinction and climate change and providing some guidance for future studies. Proxies indicate that prior to the end-Permian extinction event tropical sea surface temperatures ranged from ~ 22 to 25 °C, and possible pCO2 values ranged from ~ 500 to ~ 4000 ppm before the extinction event. During the peak extinction, tropical temperatures rose up to ~ 30 °C while pCO2 perhaps increased up to ~ 8000 ppm. Climate models that use different pre-event pCO2 values show similar amount of CO2 doubling to replicate the observed carbon isotope excursions. We find that the temperature anomaly during the end-Permian extinction is consistent with ~ 1.5 doublings of atmospheric pCO2, and that the implied climate sensitivity is 5–6 °C, within the upper range of values produced by climate models.

The Late Triassic was a prolonged interval of elevated extinction rates and low origination rates that manifested themselves in a series of extinctions during Carnian, Norian and Rhaetian time. Most of these extinctions took place in the marine realm, particularly affecting radiolarians, conodonts, bivalves, ammonoids and reef-building organisms. On land, the case for a Late Triassic mass extinction is much more tenuous and has largely focused on tetrapod vertebrates (amphibians and reptiles), though some workers advocate a sudden end-Triassic (TJB) extinction of land plants. Nevertheless, an extensive literature does not identify a major extinction of land plants at the TJB, and a comprehensive review of palynological records concluded that TJB vegetation changes were non-uniform (different changes in different places), not synchronous and not indicative of a mass extinction of land plants. Claims of a substantial perturbation of plant ecology and diversity at the TJB in East Greenland are indicative of a local change in the paleoflora largely driven by lithofacies changes resulting in changing taphonomic filters. Plant extinctions at the TJB were palaeogeographically localized events, not global in extent. With new and more detailed stratigraphic data, the perceived TJB tetrapod extinction is mostly an artifact of coarse temporal resolution, the compiled correlation effect. The amphibian, archosaur and synapsid extinctions of the Late Triassic are not concentrated at the TJB, but instead occur stepwise, beginning in the Norian and extending into the Hettangian. There was a disruption of the terrestrial ecosystem across the TJB, but it was more modest than generally claimed. The ecological severity of the end-Triassic nonmarine biotic events are relatively low on the global scale. Biotic turnover at the end of the Triassic was likely driven by the CAMP (Central Atlantic Magmatic Province) eruptions, which caused significant environmental perturbations (cooling, warming, acidification) through outgassing, but the effects on the nonmarine biota appear to have been localized, transient and not catastrophic. Long-term changes in the terrestrial biota across the TJB are complex, diachronous and likely climate driven evolutionary changes in the context of fluctuating background extinction rates, not a single, sudden or mass extinction.

Patterns of last occurrences of fossil species are often used to infer the tempo and timing of mass extinction, even though last occurrences generally precede the time of extinction. Numerical simulations with constant extinction demonstrate that last occurrences are not randomly distributed, but tend to cluster at subaerial unconformities, surfaces of forced regression, flooding surfaces and intervals of stratigraphical condensation, all of which occur in predictable stratigraphical positions. This clustering arises not only from hiatuses and non-deposition, but also from changes in water depth. Simulations with intervals of elevated extinction cause such clusters of last occurrences to be enhanced within and below the interval of extinction, suggesting that the timing and magnitude of extinctions in these instances could be misinterpreted. With the possible exception of the end-Cretaceous, mass extinctions in the fossil record are characterized by clusters of last occurrences at these sequence stratigraphical horizons. Although these clusters of last occurrences may represent brief pulses of elevated extinction, they are equally likely to form by stratigraphical processes during a protracted period (more than several hundred thousand years) of elevated extinction rate. Geochemical proxies of extinction causes are also affected similarly, suggesting that many local expressions of mass extinction should be re-evaluated for the timing of extinction and its relation to environmental change. We propose three tests for distinguishing pulses of extinction from clusters of last occurrences produced by stratigraphical processes.

To improve the performance of high-throughput surface plasmon resonance (SPR) imaging sensors, the imperfections of the conventional gold film polarization contrast method and the bare prism polarization contrast method are discussed, and a background extinction method is proposed. Thick gold film is coated as the background area, surrounding gold sensing spots, to form a “gold microwell array”. By blocking the light reflected from the background area with appropriate parameters, an opposite-oriented SPR curve is obtained, which can be exploited to achieve a high signal-to-noise ratio in trace amount detection. The contrast between the sensing spots and the background is effectively improved, and the background is inert to the change of solution. Influences of parameter errors on the SPR curve are also investigated, and results show that extinction adjustment in this method is easy to be realized. The practicability of the background extinction method is proved by an experiment using a home-built SPR imaging sensor.

Mass extinction events are recognized by increases in extinction rate and magnitude and, often, by changes in the selectivity of extinction. When considering the selective fingerprint of a particular event, not all taxon extinctions are equally informative: some would be expected even under a ‘background’ selectivity regime, whereas others would not and thus require special explanation. When evaluating possible drivers for the extinction event, the latter group is of particular interest. Here, we introduce a simple method for identifying these most surprising victims of extinction events by training models on background extinction intervals and using these models to make per-taxon assessments of ‘expected’ risk during the extinction interval. As an example, we examine brachiopod genus extinctions during the Late Ordovician Mass Extinction and show that extinction of genera in the deep-water ‘ Foliomena fauna’ was particularly unexpected given preceding Late Ordovician extinction patterns.

Rarity is a population characteristic that is usually associated with a high risk of extinction. We argue here, however, that chronically rare species (those with low population densities over many generations across their entire ranges) may have individual-level traits that make populations more resistant to extinction. The major obstacle to persistence at low density is successful fertilisation (union between egg and sperm), and chronically rare species are more likely to survive when (1) fertilisation occurs inside or close to an adult, (2) mate choice involves long-distance signals, (3) adults or their surrogate gamete dispersers are highly mobile, or (4) the two sexes are combined in a single individual. In contrast, external fertilisation and wind- or water-driven passive dispersal of gametes, or sluggish or sedentary adult life habits in the absence of gamete vectors, appear to be incompatible with sustained rarity. We suggest that the documented increase in frequency of these traits among marine genera over geological time could explain observed secular decreases in rates of background extinction. Unanswered questions remain about how common chronic rarity actually is, which traits are consistently associated with chronic rarity, and how chronically rare species are distributed among taxa, and among the world's ecosystems and regions.

Extinction rates for terrestrial rodent species from palaeontological sites in the Meade Basin of southwestern Kansas and an archaeological site in New Mexico are compared with extinction rates for modern rodents from locations affected by anthropogenic activities. Background extinction rates are defined as global extinctions occurring over proscribed intervals in the absence of significant environmental perturbations. Background rates for the Meade Basin are estimated at 0¿~1.0 E/MSY (extinctions per million species years). Elevated rates from 1.4 to 6.25 E/MSY are associated with volcanic events and Late Pleistocene environmental change. These rates are considerably less than those for rodent extinction rates promoted by human activities during the Holocene, the latter ranging from 42.3 to 50,000 E/MSY., Research in the Meade Basin was supported by grants from the National Geographic Society (5963-97, 6547-99), the National Science Foundation (EAR 0207582, EAR 1338262) and MICINN project CGL2011-28877.

The end-Permian mass extinction is widely regarded as the largest mass extinction in the past 542 million years with loss of about 95% of marine species and 75% of terrestrial species. There has been much focus and speculation on what could have caused such a catastrophe. Despite decades of study the cause or causes remain mysterious. Numerous scenarios have been proposed, including asteroid impact, Siberian flood basalt volcanism, marine anoxia and euxinia, sea-level change, thermogenic methane release and biogenic methane release due to explosive growth of a methanogenic microbe. It is now clear that a number of major environmental perturbations are approximately coincident with the end-Permian mass extinction. These include global negative excursions of both  13 Ccarb and  13 Corg near the extinction interval (see a review by [1] and a recent study by [2]); distinctive calcium isotope excursions [3]; a sudden expansion of microbialites [4]; a rapid temperature rise of ~8 o C in the extinction interval [5] followed by a long “hothouse” period in the Early Triassic [6], large regression followed by rapid transgression [7], evidence for wildfires and cyanobacteria blooms [8] etc. There remains disagreement over the nature, timing, and duration of the environmental perturbations and how they relate to detailed patterns of extinction, resolution of which are critical for understanding the causative mechanism(s).

A key measure of humanity's global impact is by how much it has increased species extinction rates. Familiar statements are that these are 100–1000 times pre-human or background extinction levels. Estimating recent rates is straightforward, but establishing a background rate for comparison is not. Previous researchers chose an approximate benchmark of 1 extinction per million species per year (E/MSY). We explored disparate lines of evidence that suggest a substantially lower estimate. Fossil data yield direct estimates of extinction rates, but they are temporally coarse, mostly limited to marine hard-bodied taxa, and generally involve genera not species. Based on these data, typical background loss is 0.01 genera per million genera per year. Molecular phylogenies are available for more taxa and ecosystems, but it is debated whether they can be used to estimate separately speciation and extinction rates. We selected data to address known concerns and used them to determine median extinction estimates from statistical distributions of probable values for terrestrial plants and animals. We then created simulations to explore effects of violating model assumptions. Finally, we compiled estimates of diversification—the difference between speciation and extinction rates for different taxa. Median estimates of extinction rates ranged from 0.023 to 0.135 E/MSY. Simulation results suggested over- and under-estimation of extinction from individual phylogenies partially canceled each other out when large sets of phylogenies were analyzed. There was no evidence for recent and widespread pre-human overall declines in diversity. This implies that average extinction rates are less than average diversification rates. Median diversification rates were 0.05–0.2 new species per million species per year. On the basis of these results, we concluded that typical rates of background extinction may be closer to 0.1 E/MSY. Thus, current extinction rates are 1,000 times higher than natural background rates of extinction and future rates are likely to be 10,000 times higher. Estimacion de la Tasa Normal de Extincion de Especies

International audience; In this paper, we show that the Triassic fossil record reflects just two great depletions of conodont diversity before the Rhaetian, which occurred in the Smithian (Olenekian, Early Triassic) and in the Julian (Carnian, Late Triassic). By exploring this context, our results highlighted that they respond to different origination?extinction dynamics. Thus, while the Smithian diversity depletion can be interpreted as a consequence of elevated extinction, the Julian diversity depletion was triggered by fluctuations in origination regime. This evidence suggests that, despite the role of extinction on diversity losses, conodonts suffered crucial changes on the origination regimes during the Late Triassic which triggered these events. Notwithstanding, our results indicate that the end-Triassic diversity depletion of conodonts was produced by background extinction levels in a context of lower origination. This suggests that several biological factors, rather than a unique, environmental and/or cyclic cause, could have influenced the evolutionary history of conodonts during the Triassic.

This study used the dense late Cenozoic rodent record of south-western Kansas to test for an equilibrium in species richness through millions of years, identify and clarify historical influences on species richness, determine the relative contribution of immigration, speciation and local extinction to species originations at the community level, and calculate background extinction rates to compare with modern species losses due to anthropogenic activities. The Meade Basin rodent community has been in equilibrium, with an average of about 17 species, for almost 5 million years. No speciation events were identified in the Meade Basin rodent record; although speciation ultimately contributes to the regional species pool, local speciation events contributed little to community structure. Extinctions and immigrations continued through the study period, with elevated bouts of turnover correlated with global cooling events and lowered sea level associated with the Beringian land bridge. Turnover was generated primarily by stochastic climatic agents at several temporal scales, possibly including rapid and devastating regional volcanic ashfalls. None of the extinction rates recorded in the Meade Basin system rivals extinction levels in modern species due to anthropogenic activities.

Studies of the end-Permian mass extinction have suggested a variety of patterns from a single catastrophic event to multiple phases. But most of these analyses have been based on fossil distributions from single localities. Although single sections may simplify the interpretation of species diversity, they are susceptible to bias from stratigraphic incompleteness and facies control of preservation. Here we use a data set of 1450 species from 18 fossiliferous sections in different paleoenvironmental settings across South China and the northern peri-Gondwanan region, and integrate it with high-precision geochronologic data to evaluate the rapidity of the largest Phanerozoic mass extinction. To reduce the Signor-Lipps effect, we applied constrained optimization (CONOP) to search for an optimal sequence of first and last occurrence datums for all species and generate a composite biodiversity pattern based on multiple sections. This analysis indicates that an abrupt extinction of 62% of species took place within 200 Kyr. The onset of the sudden extinction is around 252.3 Ma, just below Bed 25 at the Meishan section. Taxon turnover and diversification rates suggest a deterioration of the living conditions nearly 1.2 Myr before the sudden extinction. The magnitude of the extinction was such that there was no immediate biotic recovery. Prior suggestions of highly variable, multi-phased extinction patterns reflect the impact of the Signor-Lipps effect and facies-dependent occurrences, and are not supported following appropriate statistical treatment of this larger data set.

The kind and duration of phylogenetic topological "signatures" left in the wake of macroevolutionary events remain poorly understood. To this end, we examined a broad range of simulated phylogenies generated using trait-biased, heritable speciation probabilities and mass extinction that could be either random or selective on trait value, but also using background extinction and diversity-dependence to constrain clade sizes. In keeping with prior results, random mass extinction increased imbalance of clades that recovered to pre-extinction size, but was a relatively weak effect. Mass extinction that was selective on trait values tended to produce clades of similar or greater balance compared to random extinction or controls. Allowing evolution to continue past the point of clade-size recovery resulted in erosion and eventual erasure of this signal, with all treatments converging on similar values of imbalance, except for very intense extinction regimes targeted at taxa with high speciation rates. Return to a more balanced state with extended post-extinction evolution was also associated with loss of the previous phylogenetic root in most treatments. These results further demonstrate that while a mass extinction event can produce a recognizable phylogenetic signal, its effects become increasingly obscured the further an evolving clade gets from that event, with any sharp imbalance due to unrelated evolutionary factors.

A key aspect of the current debate about the Anthropocene focuses on defining a new geological epoch. Features of the Anthropocene include a biodiversity crisis with the potential to reach ‘mass extinction’ status alongside increasing global CO2 and temperature. Previous geological boundaries associated with mass extinctions, rises in atmospheric CO2 and rises in global temperature are more usually associated with transitions between geological periods. The current rapid increase in species extinctions suggest that a new mass extinction event is most likely imminent in the near-term future. Although CO2 levels are currently low in comparison with the rest of the Phanerozoic, they are rising rapidly along with global temperatures. This suggests that defining the Anthropocene as a new geological period, rather than a new epoch, may be more consistent with previous geological boundaries in the Phanerozoic.

A major criticism of the "overkill" theory for the late Pleistocene extinction in the Americas has been the seeming implausibility of a relatively small number of humans selectively killing off millions of large-bodied mammals. Critics argue that early Paleoindian hunters had to be extremely selective to have produced the highly size-biased extinction pattern characteristic of this event. Here, we derive a probabilistic extinction model that predicts the extinction risk of mammals at any body mass without invoking selective human harvest. The new model systematically analyzes the variability in life-history characteristics, such as the instantaneous mortality rate, age of first reproduction, and the maximum net reproductive rate. It captures the body size-biased extinction pattern in the late Pleistocene and precisely predicts the percentage of unexpectedly persisting large mammals and extinct small ones. A test with a global late Quaternary mammal database well supports the model. The model also emphasizes that quantitatively analyzing patterns of variability in ecological factors can shed light on diverse behaviors and patterns in nature. From a macro-scale conservation perspective, our model can be modified to predict the fate of biota under the pressures from both climate change and human impacts.

This is the first American Fisheries Society conservation assessment of freshwater gastropods (snails) from Canada and the United States by the Gastropod Subcommittee (Endangered Species Committee). This review covers 703 species representing 16 families and 93 genera, of which 67 species are considered extinct, or possibly extinct, 278 are endangered, 102 are threatened, 73 are vulnerable, 157 are currently stable, and 26 species have uncertain taxonomic status. Of the entire fauna, 74% of gastropods are imperiled (vulnerable, threatened, endangered) or extinct, which exceeds imperilment levels in fishes (39%) and crayfishes (48%) but is similar to that of mussels (72%). Comparison of modern to background extinction rates reveals that gastropods have the highest modern extinction rate yet observed, 9,539 times greater than background rates. Gastropods are highly susceptible to habitat loss and degradation, particularly narrow endemics restricted to a single spring or short stream reaches. Compil...

Freshwater habitats make up only ∼0.01% of available aquatic habitat and yet harbor 40% of all fish species, whereas marine habitats comprise >99% of available aquatic habitat and have only 60% of fish species. One possible explanation for this pattern is that diversification rates are higher in freshwater habitats than in marine habitats. We investigated diversification in marine and freshwater lineages in the New World silverside fish clade Menidiinae (Teleostei, Atherinopsidae). Using a time-calibrated phylogeny and a state-dependent speciation‐extinction framework, we determined the frequency and timing of habitat transitions in Menidiinae and tested for differences in diversification parameters between marine and freshwater lineages. We found that Menidiinaeisanancestrallymarinelineagethatindependentlycolonizedfreshwaterhabitatsfourtimesfollowedbythreereversals to the marine environment. Our state-dependent diversification analyses showed that freshwater lineages have higher speciation and extinction rates than marine lineages. Net diversification rates were higher (but not significant) in freshwater than marine environments. The marine lineage-through time (LTT) plot shows constant accumulation, suggesting that ecological limits to clade growth have not slowed diversification in marine lineages. Freshwater lineages exhibited an upturn near the recent in their LTT plot, which is consistent with our estimates of high background extinction rates. All sequence data are currently being archived on Genbank and phylogenetic trees archived on Treebase.

Procedures introduced here make it possible, first, to show that background (piecemeal) extinction is recorded throughout geologic stages and substages (not all extinction has occurred suddenly at the ends of such intervals); second, to separate out background extinction from mass extinction for a major crisis in earth history; and third, to correct for clustering of extinctions when using the rarefaction method to estimate the percentage of species lost in a mass extinction. Also presented here is a method for estimating the magnitude of the Signor–Lipps effect, which is the incorrect assignment of extinctions that occurred during a crisis to an interval preceding the crisis because of the incompleteness of the fossil record. Estimates for the magnitudes of mass extinctions presented here are in most cases lower than those previously published. They indicate that only ∼81% of marine species died out in the great terminal Permian crisis, whereas levels of 90–96% have frequently been quoted in the literature. Calculations of the latter numbers were incorrectly based on combined data for the Middle and Late Permian mass extinctions. About 90 orders and more than 220 families of marine animals survived the terminal Permian crisis, and they embodied an enormous amount of morphological, physiological, and ecological diversity. Life did not nearly disappear at the end of the Permian, as has often been claimed.

Background Extinction of fear memory depends on the environmental and emotional cues. Furthermore, consolidation of extinction is also dependent on the environmental exposure. But, the relationship of the time of the exposure to a variety of environmental cues is not well known. The important region involved in facilitation of extinction of fear memory is through diversion of the flow of information leaving the lateral nucleus of amygdala. Purpose The study aimed to address a question to explain how these brain regions react to environmental stimulation during the retention and extinction of fear memory. Methods An enriched environment (EE) is assumed to mediate extinction of fear memory, we examined the apparent discrepancy between the effects of defensive response, the freezing behavior induced by Pavlovian classical fear conditioning by subjecting them to variance in the timing to EE. The different timing of EE exposure was 10 days of EE either before fear conditioning and/or after extinction training to the rats. The local field potentials was recorded from CA1 hippocampus, lateral nucleus of amygdala and infralimbic region of medial prefrontal cortex (mPFC) during the fear learning and extinction from the control rats and rats exposed to EE before and after fear conditioning. Results Exposure to EE before the fear conditioning and after extinction training was more effective in the extinction fear memory. In addition, we also found switching from exploratory locomotion to freezing during retention of contextual fear memory which was associated with decreased theta power and reduced synchronized theta oscillations in CA1-hippocampus, lateral nucleus of amygdala, and infralimbic region of mPFC. Conclusion Thus, we propose that the timing of exposure to EE play a key role in the extinction of fear memory.