Pioneer Organisms Research Articles

A promising application of biodegradable glue to improve the efficiency of biocrust inoculation on mining tailings in Brazil

The Fundão dam failure in Brazil stands as one of the most significant environmental disasters in global mining, causing extensive harm to soils and native vegetation. Despite ongoing restoration efforts, the potential of photosynthetic cryptogamic pioneer organisms, such as biocrusts, remains largely untapped. This study explores the inoculation of moss‐dominated biocrusts in mining tailings using a novel biodegradable glue technique. We began by assessing the diversity of mosses naturally occurring in these tailings, identifying six species. Among them, Hyophila involuta (Hook.) A. Jaeger emerged as the most suitable species for inoculation experiments. We compared the inoculation of biocrusts within the biodegradable glue bed to direct soil inoculation. Our findings revealed that 94.5% of the inoculated biocrusts adhered to the glue bed after 75 days, demonstrating the technique's global potential in overcoming challenges associated with moss inoculation. We emphasize the need for further research into the long‐term effects of biodegradable glue‐bed application on biocrust sustainability across different ecosystems, while also implementing habitat improvements to mitigate other environmental stress.

Moss flora of two Alpine glacial and periglacial sites on crystalline and carbonatic bedrock

Mosses are important pioneer organisms in cold and wet habitats, such as glacial and periglacial habitats of the European Alps. These habitats include glaciers and rock glaciers, respectively, and are of increasing interest for being directly threatened by climate change and for hosting a specialized and often rare and endemic biodiversity (EU Habitats Directive, habitat code 8340, Natura 2000 network). However, the moss flora of rock glaciers was never studied, and, in general, few studies were performed specifically on mosses of ice-related landforms in the European Alps. The aim of this work is to give a first comparative checklist from two Alpine sites, the rock glacier of Lazaunkar (Bolzano, Italy) and the debris-cover glacier and rock glacier of Cima Uomo (Trento, Italy), with different bedrock compositions. Threatened species (according to IUCN red lists) and extremely specialized high-elevation species were found in both sites, but mostly on crystalline bedrock in Lazaunkar. This biodiversity is the most threatened by climate change. These findings highlight how these habitats still need to be studied and monitored in the future.

Phytoplankton and zooplankton paleocommunity change before and during the onset of the Lau Extinction Event (Ludlow, Silurian)

The Ludlow epoch of the Silurian period was a time of significant geobiological perturbations, the most significant being the mid-Ludfordian Lau Event and associated huge positive carbon isotopic excursion. On the other hand, the impact of the Lau Event on ecosystems is far from understood, with the majority of studies being concentrated on conodonts, graptolites, and brachiopods. Therefore, here we present the high-resolution Gorstian to mid-Ludfordian Baubliai-2 core section record of the phytoplankton (acritarch and green algae) change from the deep shelfal facies belt of the Silurian Baltic Sedimentary Basin. Seven distinct phytoplankton assemblages are distinguished. The general feature of the assemblage change is an overarching trend toward higher relative abundances of the green algae disaster taxon Leiosphaeridia spp., which peaked during the Lau Event. The absolute abundance variability of the various components of the plankton including the hyper-abundant Leiosphaeridia spp. and Tasmanites spp. revealed the presence of consistent 0.93 Ma cyclicity. The diversity of phytoplankton is directly correlated with graptolite species diversity, which suggests common driving mechanisms of evolution for different components of the plankton community. The recurrence and joint recurrence plots and recurrence quantification analysis revealed a coordinated evolution of phytoplankton and graptolite diversities. The Lau Event interval stood out as a distinct coordinated low diversity state in both phytoplankton and in graptolites. Similar anomalous community states were previously detected in benthic communities (brachiopods), and in communities of pelagic predators (conodonts). Therefore, the current evidence suggests that the Lau Event had a significant impact across the whole range of communities and ecosystems.

Terrestrial algae: pioneer organisms of carbonate rock solutional weathering in South China karst.

The formation of soil in karst ecosystem has always been a scientific problem of great concern to human beings. Algae can grow on the exposed and non-nutrition carbonate surface, inducing and accelerating weathering of rock substrates, thus promoting soil formation. Yet the actual contribution of algae to solutional weathering intensity remains unclear. In this study, we performed weathering simulation experiment on two algae species (Klebsormidium dissectum (F.Gay) H.Ettl & G.Gärtner and Chlorella vulgaris Beijerinck), which were screened from carbonated rock surfaces from a typical karst region in South China. The results showed: (1) both algae have solutional weathering effect on carbonate rock, (2) there is no difference of solutional intensity observed, yet the solutional modes are different, suggesting different ecological adaptative strategies, (3) algae on carbonate rocks have higher carbonic anhydrase activity (CAA) and secrete more extracellular polysaccharide (EPS), accelerating rock weathering. (4) The absolute dissolution amount of carbonate rock with algae participation is 3 times of that of without algae. These results indicate the significant impact of terrestrial algae on carbonate rock solutional weathering and provides quantitative evidence that terrestrial algae are pioneer species. It also contributes to our further understanding of soil formation in karst ecosystems in South China.

Terrestrial Fern Diversity in Palak Siring Waterfall and Its Potential to Support Junior High School Science learning

The Palak Siring Waterfall is a natural tourism object located in Kemumu Village, Armajaya District, North Bengkulu Regency were the area have variety of vegetation. This research aims to analyze the Terrestrial Fern Diversity in that area. The benefits of ferns in an ecosystem are as one of the pioneer organisms that open and start a new life in an ecosystem, food sources, and planting media. The method used is transect by forming (five) plots based on the slope of the land, consist of flat, sloping, rather steep, steep, and very steep areas. Plot size of 20 x 20 m placed along the transect line. Based on the survey was found 22 species with 13 types of family ferns in the Palak Siring Waterfall. The Diversity Index value of ferns (pteridophyta) belongs to the medium category. This certainly indicates that there is a fern that can adapt to the environment as well as other plants in area. Diversity of fern have the potential to be applied to junior high school science learning through several Basic competencies, materials, and forms of learning activities.

Siliciclastic input controlling carbonate deposition on a low-angle ramp system: New insight from the Upper Triassic Luning Formation (Western-Central Nevada)

Although more than one century has passed since the first studies, knowledge about the Upper Triassic shallow-water carbonates from the Panthalassa Ocean remains lower than their Tethyan counterparts. Characterising these sedimentary rocks represents a unique way to deepen our understanding of the biosphere's evolution and recovery after the major Permian–Triassic biological crisis. The Triassic Luning Formation in Western–Central Nevada is a crucial sedimentary succession due to its considerable thickness and areal extent. Among the three members forming the Luning Formation, the present study has only described the upper one in detail due to the minor areal distribution of the Lower Member and the pure siliciclastic nature of the middle Member. All accessible localities in this region, 21 in total, have been extensively sampled for facies and micropalaeontological analyses, including conodonts and poorly preserved foraminifera, leading to new insights about the depositional conditions and exact age of the Luning Formation's Upper Member. A depositional model is proposed for the first time, corresponding to a low-angle ramp with homogeneous bathymetric and hydrodynamic conditions subjected to frequent siliciclastic input from the continent. The regular terrigenous influx causes a significant cyclicity in this portion of the formation, comprising heterogeneously thick limestone beds. The environment-diagnostic fauna is characterised by pioneer organisms that regenerate carbonate production after the main break related to the pure siliciclastic Middle Member's deposition. Numerous conodont specimens indicate that the entire Upper Member is middle Norian in age. Identifying the observed organisms, tied to a reliable stratigraphic interval, allows comparing the Luning Formation with other Upper Triassic carbonates from the Panthalassa Ocean, now cropping out at different latitudes on the eastern and western coasts of the Pacific Ocean. Despite some faunal affinities, especially with carbonate build-ups developed at middle-palaeolatitudes, the Luning Formation differs from most other East Panthalassa carbonates because of its short palaeo-distance from the continent (i.e. the American craton), being deposited near the mainland coast instead of on an isolated volcanic arc.

Fern Macroflora Identified in the Basal Danian of the Raton Formation Supports Palynological Signal of a Widespread “Postdisaster” Fern Flora

Premise of research. From a purely palynological perspective, lowest Danian fern-dominated assemblages of the Williston Basin (North Dakota and southwestern Saskatchewan) and the Raton Basin (northeastern New Mexico and southeastern Colorado) appear indistinguishable, although this perspective has yet to be corroborated by macrofloral studies across this same region. No ferns have been collected from the lowest Danian barren series of the Raton Formation in more than a century, and this section remains sparsely sampled.Methodology. New collections of fossil ferns from the basal portion of the barren series or informal middle member of the Raton Formation, which directly overlies the K/Pg boundary, are compared with contemporaneous assemblages in other North American depositional basins.Pivotal results. Dennastra sorimarginata McIver and Basinger (Dennstaedtiaceae Lotsy) and Woodwardia arctica (Heer) Brown (Blechnaceae Newman) that produce Cyathidites diaphana (Wilson and Webster) Nichols and JL Brown and Laevigatosporites haardtii (Potonié and Venitz) Thomson and Pflug, respectively, are recognized as characteristic ferns in the basal portion of the barren series, in addition to Osmunda macrophylla Penhallow.Conclusions. In accordance with palynological perspectives, lowest Danian fern macrofossil assemblages from the Raton Basin support the concept of a geographically widespread “postdisaster” pteridophyte flora represented predominantly by Dennstaedtiaceae and Blechnaceae, with other minor components of more northern assemblages. The enigmatic hypothesis of a landscape dominated by anemiaceous or schizaeaceous ferns is rejected on the basis of this new evidence, which suggests that Cyathidites diaphana–producing dennstaedtiaceous ferns were the K/Pg boundary “disaster taxon” and among those that flourished in the Raton Basin.

Decrypting the stream periphyton physical habitat of recently deglaciated floodplains

The rapid recession of glaciers is exposing large zones to the development of embryonic phototrophic ecosystems and eventual ecological succession. Traditionally, succession patterns in glacial forefields have been seen as a response to time since deglaciation, but nowadays forefield exposure is so rapid that this theory may be less applicable. In this succession process, periphyton are potential pioneer organisms because of their role in modifying the local environment (e.g. access to water) to create conditions conducive to plant colonization. In this paper, we aim to decrypt the physical properties of the habitats that define the spatial and temporal assemblage of periphyton during the melt-season of an Alpine temperate glacier in the context of rapid climate change. We show that periphyton develop in glacial floodplains throughout the melt-season and could extend to cover significant surfaces. However, development is only possible when the combined conditions of stability and water accessibility are met. In glacial floodplains, stable zones exist and are typically located on terraces; but they can also be locally found for much shorter periods in the more active, glacial-stream reworked zone. On terraces, water accessibility can be a limit due to well-drained sediments, but when present, often aided by the role that biofilms play in creating an impermeable layer, it provides a stable and clear water source that biofilms could exploit. In the active part of the braid plain, whilst water availability is very high, the water is harsh (low temperature, high turbidity) and erosive. Therein, periphyton can rapidly exploit short windows of opportunity but the habitat conditions rarely remain stable for long enough for continuous periphyton cover to develop. Thus, the role of periphyton in ecosystem succession is strongly conditioned by the spatial extent of the active zone, itself a function of high rates of glacier melt and sediment supply associated with rapid glacier retreat.

Variations of Soil Cyanobacteria Communities Accompanied by Different Habitat Types in Abandoned Ion-Absorbed Rare Earth Tailings

Soil fertility declined, companied with the poor capacity of water holding, after rare earth mining for a long time, mine tailings remediation produced in conventional rare earth elements REEs exploitation are currently urgent issues. Cyanobacteria are prokaryotic oxygenic phototrophs, played a vital role in the biogeochemical cycling of carbon (C) and nitrogen (N), reducing soil loss, are the pioneer organisms of biological soil crusts BSCs. However, studies on cyanobacteria inoculation in abandoned ionic rare earth mines were still insufficient. The abundance and composition of microorganisms in the topsoil of abandoned ionic rare earth mines were analyzed using high-throughput sequencing of the 16S rRNA V4 gene in this study. Fifteen samples were selected in and around rare earth mine tailings based on five different habitat types to assess the difference of main bacteria component and the dominant cyanobacteria caused by environmental factors. A total of 713,057 effective 16S rRNA genes were classified into 30 bacteria phyla, and 7 cyanobacterial genera were determined in phyla of Cyanobacteria. Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, Planctomycetes, and Cyanobacteria were dominant groups in all samples (>5% of total effective sequences). Only Microcoleus, Leptolyngbya, Microcystis, Stigonema, Chroococcidiopsis, Phormidium, and Lyngbya were determined in rare earth mine tailings. Leptolyngbya was wildly distributed in rare earth tailings except for natural woodland, while Microcoleus was found in all of the studying areas in this study. Mining activities could cause the amount of unknown cyanobacteria specie pnr_Chloroplast abnormal. Additionally, results showed that cyanobacteria community composition was not correlated with soil organic matter SOM, but cyanobacteria richness and diversity were limited by the high content of ammonia nitrogen, and Leptolyngbya and Microcoleus could apply to abandoned ion-absorbed rare earth mining tailings repairment.

The Jurassic epiphytic macrolichen Daohugouthallus reveals the oldest lichen-plant interaction in a Mesozoic forest ecosystem

Lichens are well known as pioneer organisms or stress-tolerant extremophiles, potentially playing a core role in the early formation of terrestrial ecosystems. Epiphytic macrolichens are known to contribute to the water- and nutrient cycles in forest ecosystem. But due to the scarcity of fossil record, the evolutionary history of epiphytic macrolichens is poorly documented. Based on new fossil of Jurassic Daohugouthallus ciliiferus, we demonstrate the hitherto oldest known macrolichen inhabited a gymnosperm branch. We applied energy dispersive X-ray spectroscopy and geometric morphometric analysis to complementarily verify lichen affinity of D. ciliiferus and quantitatively assess the potential relationships with extant lichenized lineages, providing new approaches for study of this lichen adpression fossil. Considering the results, and the inferred age of D. ciliiferus, a new family, Daohugouthallaceae, is established. This work updates current knowledge to the early evolution of epiphytic macrolichens and reveals more complex lichen-plant interactions in a Jurassic forest ecosystem.

Revisiting R.H. Tschudy’s fern-spore spike concept 40 years later: connecting Tschudy’s ‘disaster taxon’ concept with paleopolyploidization in Stenochlaena J. Sm

The Cretaceous/Paleogene (K/Pg) boundary fern-spore spike concept was first introduced by R.H. Tschudy 40 years ago and established the precept that ferns are so-called ‘disaster taxa’ that flourish after natural disasters because of the high colonization potential of their wind-blown spores. Among the least understood topics at the crux of contemporary K/Pg boundary fern-spike studies is whether Stenochlaena-like or other stem blechnaceous ferns were among those that flourished after the K/Pg event, contributing to the Laevigatosporites-dominated phase of the fern-spore spike. For instance, dispersed Stenochlaena-like spores – e.g. Polypodiisporites usmensis (van der Hammen) Khan & Martin – first appear in the upper Eocene stratigraphic record of South America, whereas megafossils of Stenochlaena-like ferns are first known from the upper Paleocene strata of this same region. Beyond this traditional focus on taphonomic and taxonomic uncertainty regarding the identity of dispersed spore producers, however, there is further discordance between contemporary paleobotanical and molecular phylogenetic perspectives on the timing of diversification of stem lineages of blechnaceous ferns in relation to the K/Pg boundary. This investigation reconciles these two perspectives by constraining molecular clock divergence time estimates using contemporary fossil data. If this reconciliation is correct, then paleopolyploidization (whole genome duplication or WGD) associated with the origin of the genus Stenochlaena J. Sm. predated evolution of polocytic stomata, a heavily ornamented exospore, and a hemi-epiphytic to epiphytic habit observed in the crown lineage. Critically, this novel perspective elicits a merger of the K/Pg boundary fern spike and K/Pg boundary-WGD concepts, suggesting a link between polyploidy and the ‘disaster taxon’ concept.

An experimental protocol using N. commune as pioneer organism to induce bio-deterioration of surfaces: comparison between new and soiled surfaces

ABSTRACT Biological growth on building surfaces can be responsible for degradation of their aesthetical and functional properties. This is damaging for solar reflective materials (SRM), which are characterised by the ability to reflect solar radiation in the whole wavelength spectrum. SRM represent one of the most efficient countermeasures to the urban heat Island effect. The present study compares different experimental setups to expose SRM samples to laboratory bio-ageing and define which setup is the most repeatable in terms of biodegradation on surfaces.

Silica-Carbonate of Ba(II) and Fe2+/Fe3+ Complex as Study Models to Understand Prebiotic Chemistry.

The Precambrian era is called the first stage of the Earth history and is considered the longest stage in the geological time scale. Despite its duration, several of its environmental and chemical characteristics are still being studied. It is an era of special relevance not only for its duration but also because it is when a set of conditions gave rise to the first organism. This pioneer organism has been proposed to have been formed by a mineral and an organic part. A chemical element suggested to have been part of the structure of this cell is iron. However, what special characteristic does iron have with respect to other chemical elements to be proposed as part of this first cell? To answer this and other questions, it is indispensable to have a model that will allow extrapolating the first chemical structures of the pioneer organism formed in the Precambrian. In this context, for several decades, in vitro structures chemically formed by silica-carbonates have been synthetized, called biomorphs, because they could emulate living organisms and might resemble primitive organisms. It has been inferred that because biomorphs form structures with characteristic morphologies, they could resemble the microfossils found in the cherts of the Precambrian. Aiming at providing some insight on how iron contributed to the formation of the chemical structures of the primitive organism, we evaluated how iron contributes to the morphology and chemical–crystalline structure during the synthesis of these compounds under different conditions found in the primitive atmosphere. Experimentally, synthesis of biomorphs was performed at four different atmospheric conditions including UV light, nonionizing microwave radiation (NIR-mw), water steam (WS), and CO2 in the presence of Fe2+, Fe3+, and Fe2+/Fe3+, obtaining 48 different conditions. The produced biomorphs were observed under scanning electron microscopy (SEM). Afterward, their chemical composition and crystalline structure were analyzed through Raman and IR spectroscopy.

Evaluation of Soil Evolution After a Fire in the Southeast of Spain: A Multiproxy Approach

Fire is considered as part of the ecological dynamic in Mediterranean forests and is strongly related to an anthropogenic origin. The aim of this study is to evaluate the evolution of soil properties after a fire in the short term (20 months) by the use of soil quality indicators. The work is based on a multiproxy approach about three basic aspects: 1) the study of changes in soil properties; 2) the estimation of erosion rates; and 3) the evaluation of colonization evolution by soil arthropods through ichnological analysis. Three sectors were selected for this study: a burned and intervened area, a burned and not intervened area, and a reference area. Soil samples were taken randomly from each plot and their main physico-chemical properties analyzed. The assessment of soil erosion was estimated for each plot from three transects (20 m in length) perpendicular to the maximum slope, and the same transects were used for the ichnological study to identify the different bioturbations and the producers. An increase in pH and K values and C/N ratio, and a decrease in total N, available P, CEC, and respiration rate were observed among the fire-affected areas and the reference area; however, there were no significant differences in soil organic carbon. According to erosion, the hydrological correction measures based on the construction of barriers with trunks and branches favored higher runoff and erosion rates in the intervened areas with respect to the not intervened areas. The ichnological analysis showed that arthropods of Formicidae family and Lycosidae sp. genre were the main organisms that recolonized post-fire scenarios; moreover, a lower ichnodiversity is observed in the not intervened area, although with a greater abundance, with respect to the intervened and reference area. According to our results, 20 months after the fire most soil physical-chemical properties did not experiment significant differences in relation to unburned reference area. Our erosion estimation suggested the hydrological correction measures were not appropriate to reduce erosion rates and led to higher soil losses. Moreover, our ichnological study supports the domination by pioneer and opportunist organisms in the recolonization of burned areas.

Small RNAs Worm Up Transgenerational Epigenetics Research.

DNA is central to the propagation and evolution of most living organisms due to the essential process of its self-replication. Yet it also encodes factors that permit epigenetic (not included in DNA sequence) flow of information from parents to their offspring and beyond. The known mechanisms of epigenetic inheritance include chemical modifications of DNA and chromatin, as well as regulatory RNAs. All these factors can modulate gene expression programs in the ensuing generations. The nematode Caenorhabditis elegans is recognized as a pioneer organism in transgenerational epigenetic inheritance research. Recent advances in C. elegans epigenetics include the discoveries of control mechanisms that limit the duration of RNA-based epigenetic inheritance, periodic DNA motifs that counteract epigenetic silencing establishment, new mechanistic insights into epigenetic inheritance carried by sperm, and the tantalizing examples of inheritance of sensory experiences. This review aims to highlight new findings in epigenetics research in C. elegans with the main focus on transgenerational epigenetic phenomena dependent on small RNAs.

Diversity and activities of pioneer bacteria, algae, and fungi colonizing ceramic roof tiles during the first year of outdoor exposure

Like other building materials, ceramic roof tiles are biodeteriorated over time. Natural conditions affect deterioration processes, but the development of a biofilm composed of many types of microorganisms also plays a critical role in biodeterioration. However, the pioneering stages of biofilm formation remain poorly studied, whereas they determine the development of the well-characterized mature biofilms. To further characterize this pioneering microbial diversity, the bacterial, algal, and fungal colonization of new tiles exposed to outdoor conditions over one full year was monitored, combining fluorimetry, biofilm imaging (SEM, confocal macroscopy), culture-based, and high-throughput sequencing approaches. For all the samples, pioneering biofilms were found to be extremely diverse but dominated by Actinobacteria (Pantoea sp. - up to 90% of the bacterial diversity -, and Pseudomonas sp. -up to 75%-), Chlorophyta (Trebouxiophyceae -100% of the algal diversity-), and Pleosporales (Alternaria sp. -up to 75% of the fungal diversity-). Interestingly, if biofilm development was highly heterogeneous between tiles and exposition sites, microbial colonization patterns succession remained comparable regardless of tile type and exposure site. Additionally, we investigated whether microbial isolates collected in this study harbor some physiological traits related to their pioneer character. This work revealed that pioneer organisms colonizing tiles harbored interesting features like the ability to produce biofilm matrix and anti-quorum sensing and antimicrobial compounds, highlighting the intense competition between the microbial players during the priming of the tile colonization. Altogether, our results emphasize the necessity to taxonomically and functionally characterize the key pioneering microorganisms involved in biofilm formation to design innovative antifouling solutions for ceramic roof tiles.

Triassic Foraminifera from the Great Bank of Guizhou, Nanpanjiang Basin, south China: taxonomic account, biostratigraphy, and implications for recovery from end-Permian mass extinction

AbstractForaminifera are important components of tropical marine benthic ecosystems and their recovery pattern from the end-Permian mass extinction can yield insights into the Mesozoic history of this group. Here we report the calcareous and agglutinated foraminifera recovered from five measured stratigraphic sections on the Great Bank of Guizhou, an uppermost Permian to Upper Triassic isolated carbonate platform in the Nanpanjiang Basin, south China. The material contains >100 Triassic species, including three that are newly described (Arenovidalina weiin. sp.,Meandrospira?enosin. sp., andSpinoendotebanella lehrmannin. gen., n. sp.), ranging from Griesbachian (Induan) to Cordevolian (Carnian) age. The species belong to the classes Miliolata, Textulariata, Fusulinata, Nodosariata, and to an unknown class housing all aragonitic forms of the orders Involutinida and Robertinida. Based on previously established conodont zones and carbon isotope chemostratigraphy, the Griesbachian (early Induan) through Illyrian (late Anisian) interval has been subdivided into 12 foraminiferal zones and two unnamed intervals devoid of foraminifera. Following the extinction at the Permian-Triassic boundary, habitable ecological niches of Griesbachian age were invaded by disaster taxa that subsequently became extinct during the Dienerian (late Induan) and left no younger descendants. The disaster taxa were replaced by Lazarus taxa with Permian origins, which were then decimated by the Smithian-Spathian (mid-Olenekian) boundary crisis. The tempo of recovery appears to have been modulated by environmental changes during the Griesbachian through Smithian that involved both climate change and expansion of anoxic ocean bottom waters. Uninterrupted and lasting recovery of benthic foraminifera did not begin until the Spathian.UUID:http://zoobank.org/2a6e9061-b163-402a-9098-8765a80576b3

Evidence from South Africa for a protracted end-Permian extinction on land

Earth's largest biotic crisis occurred during the Permo-Triassic Transition (PTT). On land, this event witnessed a turnover from synapsid- to archosauromorph-dominated assemblages and a restructuring of terrestrial ecosystems. However, understanding extinction patterns has been limited by a lack of high-precision fossil occurrence data to resolve events on submillion-year timescales. We analyzed a unique database of 588 fossil tetrapod specimens from South Africa's Karoo Basin, spanning ∼4 My, and 13 stratigraphic bin intervals averaging 300,000 y each. Using sample-standardized methods, we characterized faunal assemblage dynamics during the PTT. High regional extinction rates occurred through a protracted interval of ∼1 Ma, initially co-occurring with low origination rates. This resulted in declining diversity up to the acme of extinction near the Daptocephalus-Lystrosaurus declivis Assemblage Zone boundary. Regional origination rates increased abruptly above this boundary, co-occurring with high extinction rates to drive rapid turnover and an assemblage of short-lived species symptomatic of ecosystem instability. The "disaster taxon" Lystrosaurus shows a long-term trend of increasing abundance initiated in the latest Permian. Lystrosaurus comprised 54% of all specimens by the onset of mass extinction and 70% in the extinction aftermath. This early Lystrosaurus abundance suggests its expansion was facilitated by environmental changes rather than by ecological opportunity following the extinctions of other species as commonly assumed for disaster taxa. Our findings conservatively place the Karoo extinction interval closer in time, but not coeval with, the more rapid marine event and reveal key differences between the PTT extinctions on land and in the oceans.

A brachiopod fauna from latest Permian to Induan of northern Guizhou, South China and its evolutionary pattern

A new brachiopod fauna is reported from the Bozhou section spanning the latest Permian and Early Induan in Zunyi, northern Guizhou, South China. The brachiopods were collected from the Changhsingian Changhsing Formation and the Lower Induan Yelang Formation. The Changhsing Formation is composed of limestone and bioclastic limestone. The lower part of the Yelang Formation is composed of calcareous mudstone and argillaceous limestone intercalated with clay, and the upper part of the Yelang Formation comprises limestone intercalated with calcareous mudstone. After applying cluster analysis on the occurrence data of brachiopod species, three communities are recognized. FAS community mainly includes Fusichonetes, Acosarina, Spinomarginifera, and Araxathyris individuals. LP community mainly contains several Permian holdovers including Paracrurithyris, Orbicoelia, and Araxathyris, and disaster taxa like Lingularia. AP community is composed of Abrekia?, Paracrurithyris, and Prelissorhynchia. Shift of brachiopods from FAS community to LP community represents the extinction stage. LP community represents the survival stage. AP community is in the survival‐initial recovery stage. In the extinction stage, global brachiopod faunas showed similar patterns in that most brachiopod species and genera disappeared. In the survival stage, Lingularia quickly occupied the vacant ecospace and dominated the brachiopod community in the shallow‐water environment with soft substrate. In the survival‐initial recovery stage, Mesozoic‐type brachiopods appeared and were sporadically found in various environments.

The Disaster Taxon Lystrosaurus: A Paleontological Myth

The term “disaster species” was a term originally conceived to describe marine microfossils that exhibited profound abundances in the wake of a biological crisis. The term was expanded in the 1990s to describe (as “disaster taxa”) opportunistic taxa that dominated their biota numerically (“bloomed”) during the survival interval of a mass extinction event. The Permo-Triassic tetrapod genus Lystrosaurus has been cited regularly as a “disaster taxon” of the end-Permian mass extinction. A review of the definitions that have been developed for disaster taxa, and data from recent biostratigraphic and phylogenetic studies that include species of Lystrosaurus, leads to the conclusion that the genus is not a “disaster taxon”. Further, the known biostratigraphy and tree topologies of species of Lystrosaurus do not satisfy more recent definitions that attribute diversification to disaster species. At most, species of Lystrosaurus that form the informal “Lystrosaurus abundant zone” in the lower Katberg Formation, Lower Triassic of South Africa, could be described as opportunistic species.