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Extinction of species, and even clades, is a normal part of the macroevolutionary process. However, several times in Earth history the rate of species and clade extinctions increased dramatically compared to the observed "background" extinction rate. Such episodes are global, short-lived, and associated with substantial environmental changes, especially to the carbon cycle. Consequently, these events are dubbed "mass extinctions" (MEs). Investigations surrounding the circumstances causing and/or contributing to mass extinctions are on-going, but consensus has not yet been reached, particularly as to common ME triggers or periodicities. In part this reflects the incomplete nature of the fossil and geologic record, which - although providing significant information about the taxa and paleoenvironmental context of MEs - is spatiotemporally discontinuous and preserved at relatively low resolution. Mathematical models provide an important opportunity to potentially compensate for missing linkages in data availability and resolution. Mathematical models may provide a means to connect ecosystem scale processes (i.e., the extinction of individual organisms) to global scale processes (i.e., extinction of whole species and clades). Such a view would substantially improve our understanding not only of how MEs precipitate, but also how biological and paleobiological sciences may inform each other. Here we provide suggestions for how to integrate mathematical models into ME research, starting with a change of focus from ME triggers to organismal kill mechanisms since these are much more standard across time and spatial scales. We conclude that the advantage of integrating mathematical models with standard geological, geochemical, and ecological methods is great and researchers should work towards better utilization of these methods in ME investigations.

AIM: Anti‐tropical taxa are species split by the tropics into disjunct northern and southern populations. These distributions occur throughout the Tree of Life, but the mechanisms proposed to drive this pattern are debated and generally fit into two categories: dispersal and vicariance. Here, we quantitatively test the prevalence of dispersal and vicariance as plausible drivers of anti‐tropical marine distributions using intraspecific anti‐tropical marine fishes as a model system. LOCATION: Primarily Indo‐Pacific. TAXON: Marine fishes. METHODS: To test between dispersal and vicariance in latitudinally disjunct marine fishes, we used an ecological niche modelling framework to predict the spatio‐temporal suitability of tropical habitats during contemporary and glacial time periods. Three different model configurations were used per species to test: (a) presence of contemporary tropical suitable habitat for northern populations, (b) the same for southern populations and (c) presence of tropical suitable habitat during the last glacial maximum for the entire species. These models were examined in an evolutionary context to determine if there was any phylogenetic signal in biogeographic predictions. Additionally, we tested if life history traits could account for biogeographic predictions. RESULTS: Our analyses resulted in 87 strongly supported models for 29 anti‐tropical fishes across the fish Tree of Life (northern population model, southern population model, and full species model for each taxon). Model projections consistently matched predictions of vicariance in 13 fishes and 10 fishes matched predictions of dispersal regardless of thresholding approach. We failed to find any phylogenetic signal for anti‐tropicality in general, or for dispersal and vicariant species specifically. Furthermore, dispersal and vicariant tendencies were not found to be correlated with life history traits. MAIN CONCLUSIONS: These data quantitatively support both dispersal and vicariance as active mechanisms driving disjunct distributions in marine systems and suggest that they occur stochastically across the fish Tree of Life. This novel approach for examining dispersal and vicariance hypotheses supports the species‐specific nature of biogeographic mechanisms structuring distributions, and that a “one‐size‐fits‐all” prediction for current and future species’ responses to environmental change is unlikely to be informative.

The field of distributional ecology has seen considerable recent attention, particularly surrounding the theory, protocols, and tools for Ecological Niche Modeling (ENM) or Species Distribution Modeling (SDM). Such analyses have grown steadily over the past two decades—including a maturation of relevant theory and key concepts—but methodological consensus has yet to be reached. In response, and following an online course taught in Spanish in 2018, we designed a comprehensive English-language course covering much of the underlying theory and methods currently applied in this broad field. Here, we summarize that course, ENM2020, and provide links by which resources produced for it can be accessed into the future. ENM2020 lasted 43 weeks, with presentations from 52 instructors, who engaged with >2500 participants globally through >14,000 hours of viewing and >90,000 views of instructional video and question-and-answer sessions. Each major topic was introduced by an “Overview” talk, followed by more detailed lectures on subtopics. The hierarchical and modular format of the course permits updates, corrections, or alternative viewpoints, and generally facilitates revision and reuse, including the use of only the Overview lectures for introductory courses. All course materials are free and openly accessible (CC-BY license) to ensure these resources remain available to all interested in distributional ecology.

Oceanic anoxic events (OAEs) are contemporaneous with 11 of the 18 largest Phanerozoic extinction events, but the magnitude and selectivity of their paleoecological impact remains disputed. OAEs are associated with abrupt, rapid warming and increased CO2flux to the atmosphere; thus, insights from this study may clarify the impact of current anthropogenic climate change on the biosphere. We investigated the influence of the Late Cretaceous Bonarelli event (OAE2; Cenomanian/Turonian stage boundary; ~94 Ma) on generic- and species-level molluscan diversity, extinction rates, and ecological turnover. Cenomanian/Turonian results were compared with changes across all Cretaceous stage boundaries, some of which are coincident with less severe OAEs. We found increased generic turnover, but not species-level turnover, associated with several Cretaceous OAEs. The absence of a species-level pattern may reflect species occurrence data that are too temporally coarse to robustly detect patterns. Five hypotheses of ecological selectivity relating anoxia to survivorship were tested across stage boundaries with respect to faunality, mobility, and diet using generalized linear models. Interestingly, benthic taxa were consistently selected against throughout the Cretaceous regardless of the presence or absence of OAEs. These results suggest that: (1) the Cenomanian/Turonian boundary (OAE2) was associated with a decline in molluscan diversity and increase in extinction rate that were significantly more severe than Cretaceous background levels; and (2) no differential ecological selectivity was associated with OAE-related diversity declines among the variables tested here.

Aim. Tropical species are thought to experience and be adapted to narrow ranges of abiotic conditions. This idea has been invoked to explain a broad array of biological phenomena, including the latitudinal diversity gradient and differential rates of speciation and extinction. However, debate continues regarding the broad-scale applicability of this pattern and potential processes responsible. Here, we use a simulation approach to test two propositions: (1) strong geographic patterns of variation in realized niche breadth can arise in the absence of variance in the size of fundamental niches, and (2) realized niche breadths can show latitudinal patterns as a consequence of spatio-temporal climate change, even when fundamental niche breadths are unrelated to latitude, and dispersal abilities are held constant. \ud Location. Global.\ud Time period. Simulations were conducted using climate models from over the last 120 Ka, with trait dynamics captured at 95 Ka and present-day. \ud Major taxa studied. We used virtual species with traits based loosely on plants. \ud Methods. We simulated latitudinal trends of niche breadth and range size for virtual species using a cellular automaton algorithm that linked a gridded geographic domain with a three-dimensional environmental landscape. \ud Results. In all simulations, strong spatial patterns in realized niches were obtained in the absence of niche evolution, and realized niches showed geographic patterns deriving only from real-world spatiotemporal variation in climate. We noted contrasting patterns of niche breadth in different environmental dimensions, with temperature breadth increasing with latitude, but precipitation breadth decreasing with latitude. Overall, simulation outcomes mimicked real-world pattern of latitudinal range extent covarying with amount of land area.\ud Main conclusions. Tropical species can have narrower niche breadths for maximum and minimum temperature ranges compared to temperate species solely as the result of the spatial arrangement of environments. We therefore suggest that the complex spatiotemporal distribution of global abiotic environments has strong potential for structuring observed latitudinal gradients of niche breadths.

We report on new collections of cephalopods (ammonites and nautilids) from the Cretaceous-Paleogene (K-Pg) successions of the Corsicana and Kincaid formations exposed along the Brazos River in Falls County, Texas. An abundant fauna of eight species comprising four genera of ammonites is described from the Corsicana Formation, including Discoscaphites mullinaxorum n. sp. The presence of abundant aptychi (probably lower jaws) of Discoscaphites and Eubaculites, as well as juvenile specimens, indicates a living population that experienced little postmortem drift. The lytoceratid genus Gaudryceras is also reported for the first time from the Brazos River area. Presence of the index taxon Discoscaphites iris (Conrad, 1858) indicates that the fauna belongs to the D. iris Range Zone, the highest ammonite range zone in North America. Correlation with new and existing microfossil data indicates that the fauna represents the uppermost Maastrichtian, and comparison with published records further suggests that this is the most diverse D. iris Zone fauna yet reported from the Gulf and Atlantic Coastal Plains of North America. Three ammonite genera are recorded from the basal units of the K-Pg event deposit at Brazos, which likely represents deposition in the immediate aftermath of the Chicxulub impact event. A single specimen of the nautilid Eutrephoceras is reported from the Danian Kincaid Formation, less than 300 kyr after the K-Pg boundary. These data provide new information on the differing fate of these cephalopod groups during the K-Pg mass extinction and add to the picture of diverse and abundant Maastrichtian ammonite faunas prior to the Chicxulub impact event.

We present evidence of exceptional preservation in the nacre and prismatic layers of a 66 Ma bivalve shell using photoemission electron spectromicroscopy (PEEM). PEEM is a novel method to assess in situ the quality of mineralogical and organic preservation. The analysis is non-invasive and non-destructive, providing spatially explicit maps of microstructure, organics and mineral components, and the crystallographic orientation in mollusk shells. Comparison of a Late Cretaceous and a modern shell demonstrates that the 66 Ma shell (1) preserves original aragonite and calcite crystals in nacre and prismatic layers, respectively, (2) maintains nearly identical mineral microstructure and crystal orientations, and (3) preserves interprismatic proteins. Remarkably, interprismatic proteins are preserved with intact peptide bonds, and suggest an abundance of the amino acid glycine. These findings in a 66 Ma shell support the exceptional quality of organic preservation documented here, which may prove to be relatively common among fossil shells that preserve nacre. PEEM analysis is useful for understanding taphonomic processes influencing shell and molecular fossil preservation over geologic time scales, and contributes to our knowledge of molluscan physiology, biomineralization, evolution, and diagenesis.

Upper Cretaceous marine sequences in the Gulf Coastal Plain (USA) span the Cretaceous–Paleogene (K–Pg) transition, allowing for detailed studies of one of the most severe extinction events of the Phanerozoic. To improve the temporal resolution of the stratigraphic record that represents environmental change leading up to the K–Pg boundary, we constructed a high-resolution chemostratigraphy and cyclostratigraphy of upper Maastrichtian shallow marine deposits located in the state of Mississippi (USA). Upper Maastrichtian strata in this area consist of alternating decimeter scale chalk and marl rhythmites deposited in a hemipelagic setting. New geochemical proxy records were used to test whether rhythmic sedimentation was driven by Milankovitch cycles. Stable isotopes (δ13Ccarb, δ18Ocarb), carbonate content (wt% CaCO3), and elemental concentrations (Ti, K, Fe) integrated with microfossil and ammonite biostratigraphy reveal astronomical forcing in the studied record. Spectral estimation suggests that rhythmic bedding was associated with climate change driven by precession (~20 kyr). Obliquity signals are also apparent in our analysis, and short eccentricity (~100 kyr) is inferred from amplitude modulation of precession. Studied sections were correlated at the precession scale with the recently tuned K–Pg succession near Morello, Italy which is stratigraphically equivalent to the well-characterized K–Pg sites in Gubbio, Italy (Bottaccione, Contessa Highway). Additionally, carbon isotope records from the study area exhibit large scale trends throughout the latest Maastrichtian, similar to those observed in the Morello and Bottaccione sections. Thus, we show that Milankovitch-scale climatic signals and low-amplitude carbon isotope shifts (

The latitudinal diversity gradient (LDG), where the number of species increases from the poles to the Equator, ranks among the broadest and most notable biodiversity patterns on Earth. The pattern of species-rich tropics relative to species-poor temperate areas has been recognized for well over a century, but the generative mechanisms are still debated vigorously. We use simulations to test whether spatio-temporal climatic changes could generate large-scale patterns of biodiversity as a function of only three biological processes—speciation, extinction and dispersal—omitting adaptive niche evolution, diversity-dependence and coexistence limits. In our simulations, speciation resulted from range disjunctions, whereas extinction occurred when no suitable sites were accessible to species. Simulations generated clear LDGs that closely match empirical LDGs for three major vertebrate groups. Higher tropical diversity primarily resulted from higher low-latitude speciation, driven by spatio-temporal variation in precipitation rather than in temperature. This suggests that spatio-temporal changes in low-latitude precipitation prompted geographical range disjunctions over Earth’s history, leading to high rates of allopatric speciation that contributed to LDGs. Overall, we show that major global biodiversity patterns can derive from interactions of species’ niches (fixed a priori in our simulations) with dynamic climate across complex, existing landscapes, without invoking biotic interactions or niche-related adaptations.

The Cretaceous outcrop belt of the Mississippi Embayment in the Gulf Coastal Plain (GCP) spans the Cretaceous/Paleogene (K/Pg) boundary. A detailed reconstruction of this time interval is critical for understanding the nature of biotic and environmental changes preceding the end-Cretaceous Mass Extinction event and for deciphering the likely extinction mechanism (i.e., bolide impact versus volcanism). Eight sections encompassing the K/Pg succession across the Mississippi Embayment were analyzed using biostratigraphic sampling of ammonites, dinoflagellates, and nannofossils. An upper Maastrichtian ammonite zonation is proposed as follows, from oldest to youngest: Discoscaphites conradi Zone, D. minardi Zone, and D. iris Zone. Our study documents that the ammonite zonation established in the Atlantic Coastal Plain (ACP) extends to the GCP. This zonation is integrated with nannofossil and dinoflagellate biostratigraphy to provide a framework to more accurately determine the age relationships in this region. We demonstrate that ammonites and dinoflagellates are more reliable stratigraphic indicators in this area than nannofossils because age-diagnostic nannofossils are not consistently present within the upper Maastrichtian in the GCP. This biostratigraphic framework has the potential to become a useful tool for correlation of strata both within the GCP and between the GCP, Western Interior, and ACP. The presence of the uppermost Maastrichtian ammonite D. iris, calcareous nannofossil Micula prinsii, and dinoflagellates Palynodinium grallator and Disphaerogena carposphaeropsis suggests that the K/Pg succession in the GCP is nearly complete. Consequently, the GCP is an excellent setting for investigating fine scale temporal changes across the K/Pg boundary and ultimately elucidating the mechanisms causing extinction.

We report major, trace, and volatile element (CO2, H2O, F, Cl, S) contents and Sr, Nd, and Pb isotopes of mid-ocean ridge basalt (MORB) glasses from the Northern East Pacific Rise (NEPR) off-axis seamounts, the Quebrada-Discovery-GoFar (QDG) transform fault system, and the Macquarie Island. The incompatible trace element (ITE) contents of the samples range from highly depleted (DMORB, Th/La ⩽ 0.035) to enriched (EMORB, Th/La ⩾ 0.07), and the isotopic composition spans the entire range observed in EPR MORB. Our data suggest that at the time of melt generation, the source that generated the EMORB was essentially peridotitic, and that the composition of NMORB might not represent melting of a single upper mantle source (DMM), but rather mixing of melts from a two-component mantle (depleted and enriched DMM or D-DMM and E-DMM, respectively). After filtering the volatile element data for secondary processes (degassing, sulfide saturation, assimilation of seawater-derived component, and fractional crystallization), we use the volatiles to ITE ratios of our samples and a two-component mantle melting-mixing model to estimate the volatile content of the D-DMM (CO2 = 22 ppm, H2O = 59 ppm, F = 8 ppm, Cl = 0.4 ppm, and S = 100 ppm) and the E-DMM (CO2 = 990 ppm, H2O = 660 ppm, F = 31 ppm, Cl = 22 ppm, and S = 165 ppm). Our two-component mantle melting-mixing model reproduces the kernel density estimates (KDE) of Th/La and 143Nd/144Nd ratios for our samples and for EPR axial MORB compiled from the literature. This model suggests that: (1) 78% of the Pacific upper mantle is highly depleted (D-DMM) while 22% is enriched (E-DMM) in volatile and refractory ITE, (2) the melts produced during variable degrees of melting of the E-DMM controls most of the MORB geochemical variation, and (3) a fraction (∼65% to 80%) of the low degree EMORB melts (produced by ∼1.3% melting) may escape melt aggregation by freezing at the base of the oceanic lithosphere, significantly enriching it in volatile and trace element contents. Our results are consistent with previously proposed geodynamical processes acting at mid-ocean ridges and with the generation of the E-DMM. Our observations indicate that the D-DMM and E-DMM have (1) a relatively constant CO2/Cl ratio of ∼57 ± 8, and (2) volatile and ITE element abundance patterns that can be related by a simple melting event, supporting the hypothesis that the E-DMM is a recycled oceanic lithosphere mantle metasomatized by low degree melts. Our calculation and model give rise to a Pacific upper mantle with volatile content of CO2 = 235 ppm, H2O = 191 ppm, F = 13 ppm, Cl = 5 ppm, and S = 114 ppm.

Unusual decimeter-scale structures occur in the sediment-hosted Black Butte Copper Mine Project deposit within lower Mesoproterozoic strata of the Belt Supergroup, Montana. These low domal and stratiform lenses are made up of millimeter-scale, hollow or mineral-filled tubes bounded by pyrite walls. X-ray micro−computed tomography (micro-CT) shows that the tube structures are similar to the porous fabric of modern diffuse hydrothermal vents, and they do not resemble textures associated with the mineralization of known microbial communities. We determined the sulfur isotopic composition of sulfide minerals with in situ secondary ion mass spectrometry (SIMS) and of texture-specific sulfate phases with multicollector−inductively coupled plasma−mass spectrometry (MC-ICP-MS). The sedimentological setting, ore paragenesis, sulfur isotope systematics, and porosity structure of these porous precipitates constrain the site of their formation to above the sediment-water interface where metalliferous hydrothermal fluids vented into the overlying water column. These data constrain the geochemistry of the Mesoproterozoic sediment-water interface and the site of deposition for copper-cobalt-silver mineralization. Metals in the hydrothermal fluids titrated sulfide in seawater to create tortuous fluid-flow conduits. Pyrite that precipitated at the vent sites exhibits large sulfur isotope fractionation (>50‰), which indicates a close association between the vents and sulfate-reducing microbiota. In the subsurface, base metal sulfides precipitated from sulfide formed during the reduction of early diagenetic barite, also ultimately derived from seawater. This model suggests dynamic bottom-water redox conditions at the vent site driven by the interplay between sulfate-reducing organisms and metalliferous fluid effluence.

Ecological niche modeling (ENM) is a quantitative approach to predict species’ abiotic requirements. It is a correlative technique, requiring geographically explicit information on species occurrences and the suites of environmental conditions experienced at each occurrence point. The output of these models is a set of environmental suitability rules that can be projected geographically and through time to test biogeographic, ecologic, and evolutionary hypotheses. Although developed by biologists and used extensively in the modern, ENM is in its early stages of application to the deep-time fossil record (hence PaleoENM). In part its limited use in the fossil record thus far reflects the methodological challenge of constructing paleoenvironmental layers needed for PaleoENM analysis, whereas in the modern these layers are available from large public databases (e.g., WorldClim). This paper provides a contextual and methodological framework for appropriately applying PaleoENM, including best practices for developing species occurrence and paleoenvironmental data sets for PaleoENM analyses.

Abundance and other aspects of population ecology have long been known to con- tribute to shaping the geography of species' distributions. In particular, abundance patterns have recently been shown to negatively correlate with environmental distance from conditions in the center of a species' abiotic niche, rather than vary with distance from the geographic center of a species' distribution. We tested for such associations across 8 species of endangered or threatened bird species in North America using population trend data derived from >4 decades of North Amer- ican Breeding Bird Surveys. Although we found no consistent overall pattern, we did observe nega- tive population trends at conditions that were the most extreme within species' niches. This suggests that niche peripherality is a relevant factor to consider in conservation planning. Specifi- cally, environmentally peripheral sites may be poor places in which to protect populations of endan- gered and threatened species, irrespective of how centrally they may occur within species' geo- graphic distributions.

© 2016 Elsevier B.V. Nacre, the iridescent outer lining of pearls and inner lining of many mollusk shells, is composed of periodic, parallel, organic sheets alternating with aragonite (CaCO3) tablet layers. Nacre tablet thickness (TT) generates both nacre's iridescence and its remarkable resistance to fracture. Despite extensive studies on how nacre forms, the mechanisms controlling TT remain unknown, even though they determine the most conspicuous of nacre's characteristics, visible even to the naked eye. Thermodynamics predicts that temperature (T) will affect both physical and chemical components of biomineralized skeletons. The chemical composition of biominerals is well-established to record environmental parameters, and has therefore been extensively used in paleoclimate studies. The physical structure, however, has been hypothesized but never directly demonstrated to depend on the environment. Here we observe that the physical TT in nacre from modern and fossil shallow-water shells of the bivalves Pinna and Atrina correlates with T as measured by the carbonate clumped isotope thermometer. Based on the observed TT vs. T correlation, we anticipate that TT will be used as a paleothermometer, useful to estimate paleotemperature in shallow-water paleoenvironments. Here we successfully test the proposed new nacre TT thermometer on two Jurassic Pinna shells. The increase of TT with T is consistent with greater aragonite growth rate at higher T, and with greater metabolic rate at higher T. Thus, it reveals a complex, T-dependent biophysical mechanism for nacre formation.

Many modern paleobiological analyses are conducted at the generic level, a practice predicated on the validity of genera as meaningful proxies for species. Uncritical application of genera in such analyses, however, has led—perhaps inadvertently—to the unjustified reification of genera in an evolutionary context. While the utility of genera as proxies for species in evolutionary studies should be evaluated as an empirical issue, in practice it is increasingly assumed (rather than demonstrated) that genera are suitable proxies for species. This is problematic on both ontological and epistemological grounds. Genera are arbitrarily circumscribed, non-equivalent, often paraphyletic, and sometimes polyphyletic collections of species. They are useful tools for communication but have no theoretical or biological reality of their own and, whether monophyletic or not, cannot themselves operate in the evolutionary process. Attributes considered important for understanding macroevolution—e.g., geographic ranges, niche breadths, and taxon durations—are frequently variable among species within genera and will be inflated at the generic level, especially in species-rich genera. Consequently, the meaning(s) of results attained at the generic level may not “trickle down” in any obvious way that elucidates our understanding of evolution at the species level. Ideally, then, evolutionary studies that are actually about species should be pursued using species-level data rather than proxy data tabulated using genera. Where genera are used, greater critical attention should be focused on the degree to which attributes tabulated at the generic level reflect biological properties and processes at the species level.

Correlational models of species’ ecological niches are commonly used to transfer model rules onto other sets of conditions to evaluate species’ distributional potential. As with any model fitting exercise, however, interpretation of model predictions outside the range of the independent variables on which models were calibrated is perilous, herein denoted as strict extrapolation to distinguish from extrapolation onto novel combinations of variables. We use novel visualization techniques to characterize model response surfaces for several niche modeling algorithms for a virtual species (wherein the truth is known) and for two transfer-based studies published by one of our group. All modeling algorithms for each species showed strict extrapolation, such that biologically unrealistic response surfaces were reconstructed. We discuss the implications of these results for calibration and interpretation of niche models and analysis of ecological niche evolution. We present Mobility-Oriented Parity (MOP), a modification and extension of the Multivariate Environmental Similarity Surface (MESS) metric currently in use, as a means of both quantifying environmental similarity between calibration and transfer regions and highlighting regions in geographic space where strict extrapolation occurs.

Significant warming of Earth's climate in the near term seems increasingly likely. If significant enough, this climatic regime could, in the long term, come to resemble previous greenhouse intervals in earth history. Consequently, analysis of the fossil record during periods of extreme warmth may provide important lessons for species biology, including biogeography, in a much warmer world. To explore this issue, we analyzed the biogeographic response of 63 molluscan species to the long-term global warmth in the Late Cretaceous Western Interior Seaway (WIS) of North America, using Geographic Information Systems (GIS) to quantitatively measure changes in range size and distribution throughout this interval. We specifically considered the role that geographic range size played in mediating extinction resistance and invasion potential of these WIS species. We found no relationship between geographic range size and survivorship. However, endemic species with small range sizes were more likely to become invasive. Finally, mollusks did not experience a poleward shift in range out of the tropics during this warm regime. To the extent that these patterns are representative, and the WIS and taxa considered constitute a reasonable ancient analogue to a warmer future world, these results suggest that some biogeographic “rules” may not prevail under greenhouse conditions of long-term, equable warmth. They also suggest that other factors beyond geographic range size, including distinctive niche characteristics, may play quite important roles in species survival and invasion potential. This potentially complicates predictions regarding the future responses of extant species to long-term warming.

We describe a spatially explicit simulation experiment designed to assess relative impacts of macroecological traits on patterns of biological diversification under changing environmental conditions. Using a simulation framework, we assessed impacts of species' niche breadth (i.e., the range of their abiotic tolerances) and dispersal ability on resulting patterns of speciation and extinction and evaluated how these traits, in conjunction with environmental change, shape biological diversification. Simulation results supported both niche breadth and dispersal ability as important drivers of diversification in the face of environmental change, and suggested that the rate of environmental change influences how species interact with the extrinsic environment to generate diversity. Niche breadth had greater effects on speciation and extinction than dispersal ability when climate changed rapidly, whereas dispersal ability effects were elevated when climate changed slowly. Our simulations provide a bottom-up perspective on the generation and maintenance of diversity under climate change, offering a better understanding of potential interactions between species' intrinsic macroecological characteristics and a dynamic extrinsic environment in the process of biological diversification.

Ecological niche models and species distribution models are becoming important elements in the toolkit of biogeographers and ecologists. Although burgeoning in use, much variation exists in implementation of these techniques, leading to considerable diversity of methodology and discussion of what is the ‘best’ approach. In this analysis, we explore implications of different configurations of major factors that constrain species’ distributions—abiotic factors and dispersal limitation—for the success or failure of these models. We analyze variation in performance among modeling approaches as a function of the relative configuration of these two factors and the spatial extent of training region, with the result that a clear understanding of the abiotic-dispersal configuration is a prerequisite to effective model implementations; the effects of spatial extent of the training region are less consistent and clear. Model development will be powerful only when set in an appropriate and explicit biogeographic and population ecological context.

One way the effects of both ecology and environment on species can be observed in the fossil record is as changes in geographical distribution and range size. The prevalence of competitive interactions and species replacements in the fossil record has long been investigated and many evolutionary perspectives, including those of Darwin, have emphasized the importance of competitive interactions that ultimately lead one species to replace another. However, evidence for such phenomena in the fossil record is not always manifest. Here we use new quantitative analytical techniques based on Geographical Information Systems and PaleoGIS tectonic reconstructions to consider this issue in greater detail. The abundant, well-preserved fossil marine vertebrates of the Late Cretaceous Western Interior Seaway of North America provide the component data for this study. Statistical analysis of distributional and range size changes in taxa confirms earlier ideas that the relative frequency of competitive replacement in the fossil record is limited to non-existent. It appears that typically, environmental gradients played the primary role in determining species distributions, with competitive interactions playing a more minor role.