Biotic Dynamics Research Articles

Within the boundaries of the Dnipro ice lobe: Biotic dynamics in the Middle Dnipro area (Ukraine) during deglaciation and postglacial stages

Within the boundaries of the Dnipro ice lobe: Biotic dynamics in the Middle Dnipro area (Ukraine) during deglaciation and postglacial stages

Impact of variable concentrations of sulphur dioxide exposure on biochemical contents in lens culinaris l.

The effect of Sulphur di oxide gas on crop production as well as physiological and biotic dynamics at both the individual and community scale. pulses are a remarkable source of protein in India. Plant variety that produces legume such as lentil and dry pea are negatively affected by the existence of Sulphur dioxide causing in decrease in their whole production. In present work biochemical content extracted from lentil plant leaves treated with various concentration of SO2 and prepared sample were exposed to a range of light having various wavelength and interpreted using a Spectrophotometer and calculation of chlorophyll a and b applying Arnon method (1949). It was observed that biochemical content chlorophyll and also carotenoid was higher in low concentration and depleted gradually with higher concentration.

Specific responses in soil metabolite alteration and fungal community decline to the long-term monocropping of lisianthus

Continuous cropping obstacle (CCO) is becoming a serious threat to the quality production of lisianthus (Eustoma grandiflorum). However, investigations of the causal mechanism of CCO in lisianthus are still lacking. To this end, soil biotic dynamics and metabolites alterations were illuminated using metagenomic sequencing and metabolomic profiling along a chronosequence that has cultivated lisianthus from 2 weeks to 6 years. Soil EC and nutrient contents increased significantly as the cultivation duration prolonged. Fungal community has undergone significant decline in their diversity and biomass. Nevertheless, no apparent accumulation of pathogenicity-related microbes was observed along the investigated chronosequence. The alterations of soil metabolites along the chronosequence reflect the decline of microbial activity, the accumulation of phytotoxic compounds and the loss of metabolite involved in beneficial plant-microbe interactions. As a result, lisianthus plants in the longer continuous cropping soil experienced stressful condition as evidenced by the increasing trend of stress responsive metabolites and the overall soil function deterioration as indicated by soil enzymes. Hierarchical partitioning analysis showed that the investigated factors can explain a total of 92.25 % of the variations in the soil function degradation. Of which, soil metabolite alteration was the most important factor in explaining the CCO development, covering 24.55 % of the explainable variations. Spearman's correlation results further implied that soil metabolite alteration is the main driver in the development of CCO in lisianthus, especially by mediating the plant-microbes interactions. Our findings revealed a general pattern of soil biotic and abiotic response to the continuous monocropping of lisianthus and suggest that the overcome of the CCO in lisianthus requires further studies focusing on the crucial metabolites and their interactions with microbes.

Beta diversity of restored river dike grasslands is strongly influenced by uncontrolled spatio‐temporal variability

AbstractAimsUnderstanding the spatio‐temporal patterns of restoration outcomes is crucial to improve predictability of restoration. High beta diversity of species‐rich communities is sought because it increases overall biodiversity and improves ecosystem stability and multifunctionality. For predictive restoration, it is important to identify the significance of drivers like site characteristics but also uncontrolled factors such as spatial effects, historical factors, and year effects.LocationDikes at river Danube, SE Germany.MethodsWe studied dike grasslands 4–19 years after restoration over five years (2017–2021, 41 plots in 12 sites). We calculated beta diversity indices to describe spatial variation and temporal turnover, including their additive components ‘replacement’ and ‘nestedness’, or ‘gains’ and ‘losses’. We analysed the main drivers of beta diversity like local site characteristics, landscape, and historical factors.ResultsSpatial variation of the restored dike grasslands was dominated by the replacement component and showed no homogenisation despite a significant temporal turnover. The replacement drivers changed over time, although replacement was mainly affected by slope aspect and landscape factors. Historical factors were inconsistent over time, and no statistically clear drivers of nestedness were found. The dike grasslands exhibited a year‐to‐year turnover in species composition of 37 ± 11%. Gains and losses were balanced over time, although the ratio changed and was most pronounced on south‐facing slopes.ConclusionsThe restored grasslands exhibited spatial variation by site characteristics but also by spatial factors which were not controlled by restorations. Moreover, high non‐directional temporal turnover occurred, caused most likely by weather fluctuations, slightly varying management, and stochastic biotic dynamics. Thus, flexible targets are recommended for restoration monitoring, by defining a set of desired states within a certain range. Furthermore, the dominance of the replacement component of spatial variation should move the focus from defining one precise restoration approach to defining a set of possible methods which together would foster beta diversity.

Quadrat soil pollen signal reflects plant important values in forests and shrublands from subtropical China.

Pollen analysis, a crucial tool in botany and ecology for examining historical biotic dynamics, has elicited debate owing to its complex link with vegetation. The challenge lies in discerning the ecological significance of pollen data. In this study, we conducted detailed quadrat surveys on Jinhua Mountain, subtropical China, analyzing topsoil pollen to determine whether pollen signals accurately reflect key ecological components in the forests and shrublands. We performed direct comparisons between pollen and plant compositions and calculated pollen percentages and plant Important Values (IVs) for each quadrat. The results indicate greater homogeneity in pollen composition across the study area compared to plant composition, particularly in the high percentage of Pinus pollen. However, distinct plant communities exhibited significantly different pollen compositions, as evidenced by the multi-response permutation test. This divergence aligns with variations in the dominant plant species across different communities. There were significant correlations between pollen percentages and plant IVs, with correlation coefficients of 0.55 (p < 0.001) at the quadrat level and 0.78 (p < 0.001) at the taxon level. These results support the utility of pollen analysis for representing ecologically significant values in subtropical Chinese forests and shrublands. Such correlations might also be extrapolated to pollen-based paleoecological studies.

The need of ecohydrological research in tropical forests for healthy watersheds

Tropical forests play a critical role in providing clean water and maintaining healthy watersheds, yet they face numerous threats such as deforestation, land use change, and climate change. To address these challenges, there is a growing need for ecohydrological research that can inform land use planning and management strategies for healthy watersheds. Ecohydrology is an emerging science that seeks to understand the functional interactions between hydrology and biota. It quantifies and explains the relationships between hydrological processes and biotic dynamics as well as linkages among upland, riparian, and aquatic components on a watershed scale. However, most of the ecohydrological studies have been concentrated on temperate regions, and for tropical regions, such studies are lacking. This article argues that there is a high time to launch research for identifying critical ecohydrological functions and driving forces that regulate the quality and quantity of water, and their role in providing water-based ecosystem services in tropical watersheds. The article outlines the main challenges facing tropical forests and watersheds, and highlights the importance of interdisciplinary collaboration and long-term monitoring for effective ecohydrological research. It also provides examples of successful ecohydrological research projects in tropical forests, and discusses the potential benefits of investing in ecohydrological research for tropical forest conservation and watershed management. Overall, this article emphasizes the importance of ecohydrological research in tropical forests for healthy watersheds and calls for more attention and resources to be devoted to this field.

Biotic induction and microbial ecological dynamics of Oceanic Anoxic Event 2

Understanding the causal mechanisms of past marine deoxygenation is critical to predicting the long-term Earth systems response to climate change. However, the processes and events preceding widespread carbon burial coincident with oceanic anoxic events remain poorly constrained. Here, we report a comprehensive biomarker inventory enveloping Oceanic Anoxic Event 2 that captures microbial communities spanning epipelagic to benthic environments in the southern proto-North Atlantic Ocean. We identify an abrupt, sustained increase in primary productivity that predates Oceanic Anoxic Event 2 by ∼220 ± 4 thousand years, well before other geochemical proxies register biogeochemical perturbations. During the event, recurrent photic zone euxinia triggered a major marine microbial reorganization accompanied by a decrease in primary production. These findings highlight how organic carbon burial drivers operated along a continuum in concert with microbial ecological changes, with antecedent, localized increases in primary production destabilizing carbon cycling and promoting the progressive marine deoxygenation leading to Oceanic Anoxic Event 2.

Resilient biotic response to long-term climate change in the Adriatic Sea.

Preserving adaptive capacities of coastal ecosystems, which are currently facing the ongoing climate warming and a multitude of other anthropogenic impacts, requires an understanding of long‐term biotic dynamics in the context of major environmental shifts prior to human disturbances. We quantified responses of nearshore mollusk assemblages to long‐term climate and sea‐level changes using 223 samples (~71,300 specimens) retrieved from latest Quaternary sediment cores of the Adriatic coastal systems. These cores provide a rare chance to study coastal systems that existed during glacial lowstands. The fossil mollusk record indicates that nearshore assemblages of the penultimate interglacial (Late Pleistocene) shifted in their faunal composition during the subsequent ice age, and then reassembled again with the return of interglacial climate in the Holocene. These shifts point to a climate‐driven habitat filtering modulated by dispersal processes. The resilient, rather than persistent or stochastic, response of the mollusk assemblages to long‐term environmental changes over at least 125 thousand years highlights the historically unprecedented nature of the ongoing anthropogenic stressors (e.g., pollution, eutrophication, bottom trawling, and invasive species) that are currently shifting coastal regions into novel system states far outside the range of natural variability archived in the fossil record.

A roadmap for sustaining biodiversity and ecosystem services through joint conservation and restoration of northern drainage basins

Abstract1. Freshwater ecosystems and their biota are more seriously threatened than their marine and terrestrial counterparts. A solution to halt increasing negative impacts of anthropogenic development would be to reconsider the basics of nature conservation (i.e. protection of pristine and near‐pristine areas) and restoration (i.e. returning an impacted site to as natural condition as possible) through inclusion of the knowledge on abiotic and biotic dynamics of rivers draining pristine catchments. In boreal and Arctic regions, such comparisons are still possible because in addition to harbouring strongly modified drainage basins, some of the most natural drainage basins are also situated in these high‐latitude areas.2. A suitable approach for simultaneous planning of joint river conservation and restoration would be to (i) examine how well different kinds of rivers are covered by existing protected area networks and (ii) to restore parts of degraded rivers to facilitate colonization by aquatic and riparian organisms that have found havens in existing protected areas. This joint approach is a two‐way road, as conservation and restoration benefit from each other by allowing river networks to facilitate movements of organisms and matter, thereby mimicking natural riverine meta‐systems in anthropogenically modified drainage basins, with restored sites acting as stepping‐stones between protected areas.3. We argue that existing policy instruments should consider the fact that river ecosystems are spatially and temporally dynamic meta‐systems. These characteristics should be given due attention in conservation and restoration rather than relying on a static approach where a snap‐shot classification of river reaches is thought to be enough without considering underlying ecological dynamics. Taking ecological dynamics into account would contribute to sustainable management and maintenance of biodiversity and ecosystem services.

Spatiotemporal dynamics drive synergism of land use and climatic extreme events in insect meta-populations

Ecosystems are increasingly threatened by co-occurring stressors associated with anthropogenic global change. Spatial stressor patterns range from local to regional to global, and temporal stressor patterns from discrete to continuous. To date, most multiple stressor studies covered short periods and focused on local effects and interactions. However, it remains largely unknown how stressors with different spatiotemporal patterns interact in their effects over longer periods. In particular, at higher spatial scales, biotic dynamics in ecological networks complicate the understanding of stressor interactions.We used a spatially explicit meta-population model for a generic freshwater insect, parameterized based on traits of the European damselfly Coenagrion mercuriale, to simulate scenarios of discrete climatic extreme events and continuous land use-related stress. Climatic extreme events were modeled as recurring mortality in all patches, whereas land use permanently influenced meta-populations via patch qualities and network connectivity.We found that the risk of discrete climatic extreme events to meta-populations depended strongly on the proportion of land use types, with effects ranging from negligible to extinction. Land use-related stress limited recovery in meta-populations from effects of climatic extreme events, resulting in synergistic stressor interactions. Moreover, the spatial configuration of land use type influenced the combined stressor effects with clustered configurations resulting in lower effects compared to a random configuration. Finally, we found that combined stressor effects can vary with the time point at which they were determined, indicating that inconclusive results in multiple stressor research can partly be due to differences in the time of determination.We conclude that conservation should focus on regional landscape management to mitigate risks on meta-populations from future, intensified extreme climate events. Reducing land use effects, thus improving patch quality and network connectivity, can compensate for effects of additional discrete stressors and, in turn, synergistic interactions.

Inter-annual climatic variability modulates biotic interactions on early Nothofagus pumilio community development

ABSTRACT Background: Despite extensive efforts to understand how biotic interactions and community dynamics respond to changes in environmental conditions many knowledge gaps remain. Assessing biotic interactions involving little studied organisms, such as the biological soil crust (BSC), can widen our understanding of ecosystem functioning. Aims: (1) to quantify the effects of two pioneer communities, one of shrubs and the other of BSC, on the survival and early growth of Nothofagus pumilio tree seedlings on land exposed after glacier retreat, and (2) evaluate how these biotic effects changed according to variations in environmental conditions. Methods: We conducted seedling transplants, at four glacier forelands in the Patagonian Andes across a precipitation gradient in three microsite types: bare soil, soil-covered BSC, low-stature vegetation cover by the creeping dwarf-shrub Empetrum rubrum (ER). Results: N. pumilio seedling survival was related to inter-annual climatic variations, with higher survival in cool-wet years. These effects depended on microsite conditions, with a tendency towards highest survival in BSC. Conversely, microsite type was the dominant factor affecting seedling leaf area, with a trend towards bigger leaves in bare soil. Conclusions: At regional scales, inter-annual climatic variability modulates N. pumilio colonisation. However, microenvironmental differences imposed by cover type introduce important variations. Accounting for interactions between climate and pre-existing communities is essential for predicting climate change impacts on plant community development.

Reach-Scale Model of Aquatic Vegetation Quantifies N Fate in a Bedrock-Controlled Karst Agroecosystem Stream

In-stream fate of nutrients in karst agroecosystems remains poorly understood. The significance of these streams is recognized given spring/surface water confluences have been identified as hotspots for biogeochemical transformations. In slow-moving streams high in dissolved inorganic nutrients, benthic and floating aquatic macrophytes are recognized to proliferate and drastically impact nutrient fate; however, models that quantify coupled interactions between these pools are limited. We present a reach-scale modeling framework of nitrogen dynamics in bedrock-controlled streams that accounts for coupled interactions between hydrology, hydraulics, and biotic dynamics and is validated using a multi-year, biweekly dataset. A fluvial N budget with uncertainty was developed to quantify transformation dynamics for the dissolved inorganic nitrogen (DIN) pool using a GLUE-like modeling framework, and scenario analyses were run to test for model function over variable environmental conditions. Results from a 10,000 run uncertainty analysis yielded 195 acceptable parameter sets for the calibration period (2000–2002), 47 of which were acceptable for the validation period (2003) (Nash-Sutcliffe Efficiency (NSE) &gt; 0.65; percent bias (PBIAS) &lt; ±15), with significantly different posterior parameter spaces for parameters including denitrification coefficients and duckweed growth factors. The posterior solution space yielded model runs with differing biomass controls on DIN, including both algae and duckweed, but suggested duckweed denitrifies at a rate that would place the bedrock agroecosystem stream on the high-end of rates reported in the literature, contradicting the existing paradigm about bedrock streams. We discuss broader implications for watershed-scale water quality modeling and implementation strategies of management practices for karst agroecosystems, particularly with respect to stream restoration.

Post-fire wood mulch for reducing erosion potential increases tree seedlings with few impacts on understory plants and soil nitrogen

Following high-severity wildfire, application of mulch on the soil surface is commonly used to stabilize slopes and limit soil erosion potential, protecting ecosystem values at risk. Despite the widespread use of mulch, relatively little is known about its effects on ecosystem recovery and soil processes important for plant re-establishment. Following a high-severity wildfire in a Colorado lodgepole pine forest, we studied the effects of both mulch material and application rate on plant recovery and the relative importance of soil abiotic conditions and microbial substrate availability as drivers of plant community development over the first four years of recovery. Mulches were applied to experimental plots in a randomized complete block design immediately following the High Park Fire in July 2012. Treatments included wheat straw, wood strands, and wood shreds applied at two coverage rates (standard and high). Two controls, non-mulched and a microbially-neutral synthetic mulch, were included in each block to assess the relative importance of mulch effects on abiotic versus biotic dynamics. Plant and soil monitoring occurred at least annually for four-years post fire. Understory plants increased in total cover and shifted in composition over time, but these trends were largely unaffected by mulch type or application rate. Non-native understory plant species were not abundant at the end of this experiment, but their cover was higher in plots treated with wheat straw and high-rate wood strands compared to non-mulched control. Lodgepole pine seedling densities were higher in wood shred and mulched control treatments than in wheat straw and non-mulched control treatments. Because there were few effects of mulch treatments on plant available nitrogen, it is likely that effects of mulch on soil abiotic conditions (moisture and temperature) drove ecosystem responses in this system. Our findings indicate wood mulches can provide soil protection for many years and accelerate lodgepole pine establishment following wildfire with few negative near-term effects on plant recovery. In systems such as this, post-fire application of wood mulch can help managers meet site protection goals with minimal impacts on plant recovery.

Endless Forams: &gt;34,000 Modern Planktonic Foraminiferal Images for Taxonomic Training and Automated Species Recognition Using Convolutional Neural Networks

ABSTRACTPlanktonic foraminiferal species identification is central to many paleoceanographic studies, from selecting species for geochemical research to elucidating the biotic dynamics of microfossil communities relevant to physical oceanographic processes and interconnected phenomena such as climate change. However, few resources exist to train students in the difficult task of discerning amongst closely related species, resulting in diverging taxonomic schools that differ in species concepts and boundaries. This problem is exacerbated by the limited number of taxonomic experts. Here we document our initial progress toward removing these confounding and/or rate‐limiting factors by generating the first extensive image library of modern planktonic foraminifera, providing digital taxonomic training tools and resources, and automating species‐level taxonomic identification of planktonic foraminifera via machine learning using convolution neural networks. Experts identified 34,640 images of modern (extant) planktonic foraminifera to the species level. These images are served as species exemplars through the online portal Endless Forams (endlessforams.org) and a taxonomic training portal hosted on the citizen science platform Zooniverse (zooniverse.org/projects/ahsiang/endless‐forams/). A supervised machine learning classifier was then trained with ~27,000 images of these identified planktonic foraminifera. The best‐performing model provided the correct species name for an image in the validation set 87.4% of the time and included the correct name in its top three guesses 97.7% of the time. Together, these resources provide a rigorous set of training tools in modern planktonic foraminiferal taxonomy and a means of rapidly generating assemblage data via machine learning in future studies for applications such as paleotemperature reconstruction.

Forecasted homogenization of high Arctic vegetation communities under climate change

AbstractAimClimate change results in increasing temperature and modified precipitation regimes in the High Arctic. Models can help anticipate the consequences on future biotic dynamics, e.g. vegetation. In rugged terrain, forecasts should consider fine‐scale spatial variability in environmental conditions that are proximally linked to plant performance. Here, we forecasted Arctic plant community response to future climate change using high‐resolution environmental variables.LocationZackenberg in the High Arctic of Greenland.MethodsUsing a combination of remote‐sensing data and field measurements, we interpolated soil moisture and temperature at 1 m resolution together with spatial data on snow cover and solar radiation. We calibrated stacked species distribution models (S‐SDMs) with data from 200 vegetation plots. To explore the sensitivity of Arctic communities to climate change, we forecasted these models under simulated increases in temperature and changes (positive or negative) in snow cover and soil moisture, corresponding to more winter and/or summer precipitation and higher frequencies of summer droughts.ResultsS‐SDMs associated with high‐resolution environmental variables were able to reproduce the spatial variation in species richness and plant community structure along a mountain slope in Zackenberg. Model forecasts under climate change revealed that most species reacted to a combination of changes in soil moisture and temperature, and changes in these two variables resulted in an extensive restructuring of the distributions of species assemblages. In most scenarios, a gradual homogenization of communities was forecasted due to shrub expansion.Main conclusionsIncreasing temperatures and altered soil moisture were predicted to turn the currently highly heterogeneous tundra landscape at Zackenberg into homogenous dwarf‐shrub tundra. Such homogenization of vegetation communities may have profound ramifications for species, interaction webs, and ecosystem processes via modifications to the surface albedo, energy and water balance, as well as snow accumulation and permafrost.

Megascopic processes reflected in the microscopic realm: sedimentary and biotic dynamics of the Middle Ordovician “orthoceratite limestone” at Kinnekulle, Sweden

The Middle Ordovician (Dapingian–middle Darriwilian) “orthoceratite limestone” is documented in its traditional type area at Kinnekulle in the province of Västergötland in southern Sweden. Detailed field studies combined with systematic qualitative and quantitative analyses of carbonate microfacies at high stratigraphic resolution show that this suite of cool-water carbonate rocks is more variable than is suggested by its overall homogeneous macroscopic appearance. Long-term changes in carbonate textures and fossil grain assemblages, together with pervasive rhythmic/cyclic patterns, suggest a strong influence from sea level on microfacies characteristics. Assessment of the results in light of regional facies patterns indicates that the cool-water “orthoceratite limestone” behaved much like “model” siliciclastic sedimentary systems, in that carbonate texture varied with depositional depth as particle size of siliclastics does. Carbonate texture thus appears to reflect absolute depth well, whereas grain assemblages record high-frequency cycles of changes in both sea level and substrate conditions. A relative sea level curve compiled from the collective data shows excellent agreement with previously published curves based on different proxies. The most important factor for the long-term establishment and regional dominance of the “orthoceratite limestone” throughout much of the Early and Middle Ordovician appears to have been a limited terrigenous sediment input to the Baltoscandian paleobasin. Hence, much of the regional facies zonation may reflect distance from weathering sources rather than bathymetric conditions.

Repeated flood disturbance enhances rotifer dominance and diversity in a zooplankton community of a small dammed mountain pond

&lt;p&gt;The zooplankton community in a relatively small and mountain pond was studied during the spring growing season. To investigate which factors operate in the community structure, we explored several physical conditions, such as high inflows, and the biotic dynamics of the main zooplankton groups (i.e., rotifers, cladocerans and copepods). Two extreme flood events occurred during the investigated period and caused dramatic changes in physical conditions and reduction of the planktonic community abundances. The short period between both high-flow events was enough for the recovery of microplankton, but not for the metazoan zooplankton. Our results are in agreement with the common situation in which high flood events commonly favour rotifers over crustaceans, likely due to rotifer species have great colonization ability and grow faster. However, we found that the dominance of rotifers over crustaceans in our system is evidenced by an extremely, unusual high ratio between their abundances. We observed that, at the time of the great floods, crustacean abundances as well as rotifer populations notably decreased until near zero values. Although rotifer abundance began declining before high floods, the decrease was particularly notable when the great flood happened. Our results evidenced that i) dilution rate and temperature were the main drivers which are operating in the structure of the zooplankton community; and ii) no negative biotic interactions were detected between large and small cladocerans and rotifers. Additionally, we found surprisingly that a repeated disturbance caused by high flood events does increase the species diversity of rotifers. Finally, our study also detected some cues which may indicate that diapausing egg bank is also playing an important role in the zooplankton community, favouring the dominance of rotifers; however, this phenomenon deserves further studies. &lt;/p&gt;

Towards a morphological metric of assemblage dynamics in the fossil record: a test case using planktonic foraminifera

With a glance, even the novice naturalist can tell you something about the ecology of a given ecosystem. This is because the morphology of individuals reflects their evolutionary history and ecology, and imparts a distinct ‘look’ to communities—making it possible to immediately discern between deserts and forests, or coral reefs and abyssal plains. Once quantified, morphology can provide a common metric for characterizing communities across space and time and, if measured rapidly, serve as a powerful tool for quantifying biotic dynamics. Here, we present and test a new high-throughput approach for analysing community shape in the fossil record using semi-three-dimensional (3D) morphometrics from vertically stacked images (light microscopic or photogrammetric). We assess the potential informativeness of community morphology in a first analysis of the relationship between 3D morphology, ecology and phylogeny in 16 extant species of planktonic foraminifera—an abundant group in the marine fossil record—and in a preliminary comparison of four assemblages from the North Atlantic. In the species examined, phylogenetic relatedness was most closely correlated with ecology, with all three ecological traits examined (depth habitat, symbiont ecology and biogeography) showing significant phylogenetic signal. By contrast, morphological trees (based on 3D shape similarity) were relatively distantly related to both ecology and phylogeny. Although improvements are needed to realize the full utility of community morphometrics, our approach already provides robust volumetric measurements of assemblage size, a key ecological characteristic.

Refined stratigraphy of the Late Ordovician (Katian; Richmondian) Waynesville Formation across the northeastern and northwestern margin of the Cincinnati Arch

The Late Ordovician (Katian; Richmondian) Waynesville Formation is an important unit for its juxtaposition relative to a series or paleoecological events. The Waynesville Formation includes the Richmondian Invasion and records a critical part of the transitional period between the Great Ordovician Biodiversification Event and the end Ordovician Hirnantian Extinction. The Waynesville can be correlated across the Cincinnati Arch through the use of epibole taxa and long-term invaders, including the brachiopods Glyptorthis insculpta, Catazyga headi, and Eochonetes clarksvillensis, and colonial and solitary corals. This paper subdivides theWaynesville Formation into twelve beds and submembers, which are discussed herein, with respect to lithology, sequence stratigraphic position, and paleontology, with special attention to occurrences of new or distinctive taxa. In addition, a refined, high resolution stratigraphic framework highlights the brief timing of a major phase of the Richmondian Invasion associated with the base of the Clarksville Member and herein termed the "Clarksville Phase". This study thus establishes a high-resolution stratigraphic framework within which to gage the timing and facies context of physical and biotic dynamics during an important interval of ecological turnover.

Resolving the relationships of Paleocene placental mammals.

ABSTRACTThe ‘Age of Mammals’ began in the Paleocene epoch, the 10 million year interval immediately following the Cretaceous–Palaeogene mass extinction. The apparently rapid shift in mammalian ecomorphs from small, largely insectivorous forms to many small‐to‐large‐bodied, diverse taxa has driven a hypothesis that the end‐Cretaceous heralded an adaptive radiation in placental mammal evolution. However, the affinities of most Paleocene mammals have remained unresolved, despite significant advances in understanding the relationships of the extant orders, hindering efforts to reconstruct robustly the origin and early evolution of placental mammals. Here we present the largest cladistic analysis of Paleocene placentals to date, from a data matrix including 177 taxa (130 of which are Palaeogene) and 680 morphological characters. We improve the resolution of the relationships of several enigmatic Paleocene clades, including families of ‘condylarths’. Protungulatum is resolved as a stem eutherian, meaning that no crown‐placental mammal unambiguously pre‐dates the Cretaceous–Palaeogene boundary. Our results support an Atlantogenata–Boreoeutheria split at the root of crown Placentalia, the presence of phenacodontids as closest relatives of Perissodactyla, the validity of Euungulata, and the placement of Arctocyonidae close to Carnivora. Periptychidae and Pantodonta are resolved as sister taxa, Leptictida and Cimolestidae are found to be stem eutherians, and Hyopsodontidae is highly polyphyletic. The inclusion of Paleocene taxa in a placental phylogeny alters interpretations of relationships and key events in mammalian evolutionary history. Paleocene mammals are an essential source of data for understanding fully the biotic dynamics associated with the end‐Cretaceous mass extinction. The relationships presented here mark a critical first step towards accurate reconstruction of this important interval in the evolution of the modern fauna.