Spatial Environmental Variation Research Articles

Prediction of coastal barren plant species richness and functional diversity by environmental variability across scales

AbstractQuestionsThe relationships between environmental heterogeneity and plant diversity may be negative or neutral at fine spatial scales but positive across broader areas. How do the relationships between spatial environmental variability and mean environmental conditions, plant species richness and functional diversity change across spatial scales?LocationCoastal barrens landscape in Nova Scotia, eastern Canada.MethodsWe sampled plant species composition and environmental variables in nested areas at three scales: 0.25 m2, 1 m2 and 50 m2. At each scale, subsamples of environmental variables (including elevation, soil moisture and depth) were used to calculate average and standard deviation; plant species richness was also determined for each sample. Plant traits at the species level were used to calculate functional dispersion for each of five traits (specific leaf area, leaf dry matter content, leaf thickness, plant height and canopy width) and a combined index of total functional dispersion. Functional dispersion and species richness were predicted at each scale by environmental variables using linear mixed models.ResultsEnvironmental heterogeneity had low predictive power for plant diversity at the 0.25‐m2 scale but was unimodally related to species richness and functional‐diversity variables at the 1‐m2 scale. The shape of the unimodal relationships suggested a leveling off of diversity at higher levels of environmental variability rather than a decline in diversity (monotonic or asymptotic). There was a strong positive relationship between elevation (topographic) variability and species richness at the 50‐m2 scale. Functional dispersion was most strongly related to environmental variables at the 1‐m2 scale.ConclusionsPositive or non‐linear asymptotic relationships between environmental heterogeneity, richness and functional diversity at the 1‐m2 scale provide some support for niche‐based explanations of species coexistence in plant neighborhoods. At broader sampling extents, greater topographic heterogeneity may allow distinct plant communities to co‐occur within a sample, increasing richness but not functional diversity because functional diversity in leaf and canopy traits are already high within each plant community.

Remotely-Sensed Game Trails Are a Behavioral Footprint That Explains Patterns of Herbivore Habitat Use.

Trade-offs between food acquisition and predator avoidance shape the landscape-scale movements of herbivores. These movements create landscape features, such as game trails, which are paths that animals use repeatedly to traverse the landscape. As such, these trails integrate behavioral trade-offs over space and time. Here, we used remotely sensed imagery to analyze the density of game trails with spatial environmental variables to understand landscape-scale patterns of herbivore habitat use in an African savanna. Woody plant cover was the best predictor of game trail density, with the highest densities correlating with intermediate woody plant cover. We also explored how patterns of game trail density compared to two known measures of herbivore habitat use (i.e., dung counts and maximum entropy modeling) and found strong quantitative fits. To understand the patterns revealed by the density of game trails, we explored the trade-off between food acquisition and perceived predation risk across a woody plant cover gradient. Using behavioral observations, we found that the relationship between woody plant cover and the distribution of game trails was likely driven by the risk and reward trade-off, with less vigilance and more feeding occurring in areas with a high density of game trails and intermediate woody cover. Ultimately, we show that game trails are a novel data source that can be used to identify broadly-occurring patterns of herbivore habitat use over large spatial scales.

The effect of shallow water bathymetry on swash and surf zone modelled by SWASH

Submerged topography in shallow waters is fundamental in the propagation and dissipation of ocean waves in the surf and swash zones. However, obtaining accurate bathymetric data in this region is challenging due to the high temporal and spatial environmental variability. The bottom boundary condition can directly affect the accuracy of numerical models used for shallow water simulations. In this study, the performance of the SWASH numerical model in describing wave runup in the swash zone is assessed using different bathymetric boundary conditions. The first method involves using data measured in the surf zone obtained by a Unmanned Aerial Vehicle (UAV), and analyzing it using the cBathy algorithm. The second method utilizes a regular bathymetric mesh generated from Dean’s equilibrium profile combined with beach topography data. The third method relies exclusively on interpolation methods using data from deep waters and beach profiles. This interpolation approach is the most used among SWASH users when detailed or updated surf zone bathymetry is unavailable. Based on the numerical simulations performed, not incorporating data from the surf zone resulted in a 4% increase in the runup estimated and approximately a 2% difference in identifying the swash zone position. The method to obtain bathymetry through the cBathy algorithm, used in this article, is cost-effective and can be used to reduce uncertainties in surf zone numerical simulations, induced by the lack of knowledge about the bottom conditions.

Temporal and spatial variation in reproductive benefits in a partial migrant.

In partial migrant systems, where residents and migrants coexist within a population, residents are commonly predicted to gain a reproductive advantage over migrants through priority access to high-quality territories and an earlier breeding start. Annual variation in reproductive benefits has been suggested to be important for the coexistence of both strategies in a population, as differences in wintering conditions experienced by the two strategies may result in a periodic reproductive advantage for migrants. However, the importance of spatial environmental variation for reproductive output in partially migrant populations remains largely unexplored. We investigated variation in the reproductive output of migrants and residents in a population of Swiss red kites (Milvus milvus) both temporally, across and within years, and spatially, along an elevational gradient. We gathered 4 years of reproductive data combined with 183 GPS-derived full annual cycles from individuals breeding in the Swiss Alpine foothills. At low, but not high, elevations, residents produced more fledglings than migrants. We also found evidence for annual variation in the reproductive advantage of the two strategies. Furthermore, while reproductive output did decline with a later breeding start, there was no difference in the start of breeding between the two migration strategies. The results of this study suggest that differences in reproductive output between migrants and residents in partial migrant populations can vary both due to the use of spatially distinct overwintering grounds and because the strategies are differently affected by spatial variables in the breeding area, such as elevation. The study emphasizes that spatial and temporal variation in reproductive benefits must be considered when predicting how migratory species will respond to future environmental change.

Small topographical variations controlling trace maker community: Combining palaeo- and neoichnological data at the Porcupine Abyssal Plain

Ichnological research has generally assumed that abyssal plains are dominated by quiescent, homogenous environmental conditions. Thus, deep-sea trace fossil assemblage changes have been usually linked to significant spatial and temporal environmental variations. Here, we conducted a comparative ichnological analysis between a small abyssal hill (50 m elevation) and the surrounding abyssal plain; this modest bathymetric variation is known to generate substantial environmental heterogeneity for the benthic fauna community of the Porcupine Abyssal Plain (c. 4850 m depth), Northeast Atlantic. Based on X-ray data from a 5 × 5 core grid emplaced in two box cores, we compared hill and plain bioturbational sedimentary structures, including trace fossil assemblages (e.g., ichnotaxonomy) and biodeformational structures (e.g., mixed-layer depth). We observed that topographically-enhanced near-bottom currents over the hill likely produce significant changes in depositional dynamics and sediment properties (e.g., grain size, organic matter content and degradation), and control specificities of bioturbational sedimentary structures (e.g., trace fossils, mixed layer attributes such as thickness, mottled background, discrete traces). Palaeoichnological data suggested that the abyssal plain had experienced consistent conditions during the last thousands of years while the abyssal hill recorded improving environmental conditions for the trace maker community. Our results highlight the complexity of the deep-sea environment, demonstrating that small changes in bioturbated sedimentary assemblages appear even within the same box core (m-scale), and that substantial changes can occur due to environmental heterogeneity (e.g., subtle topographic variations) at the local scale (km-scale). Considering the vast global extent of abyssal hill terrain, we suggest that their influence on the bioturbational sedimentary record may be significantly under-appreciated and require more attention in palaeoenvironmental reconstructions.

Plant beta-turnover rather than nestedness shapes overall taxonomic and phylogenetic beta-diversity triggered by favorable spatial-environmental conditions in large-scale Chinese grasslands.

Although it is widely acknowledged that biodiversity maintains plant community assembly processes, exploring the patterns and drivers of beta-diversity (β-diversity; species variation among local plant communities) has received much less attention compared to alpha-diversity (α-diversity; species variation within a local plant community). Here, we aim to examine the patterns and spatial-environmental drivers of taxonomic and phylogenetic β-diversity, and their components such as species turnover and nestedness, in large-scale Leymus chinensis grassland communities. We collected plant community data from 166 sites across widely distributed L. chinensis communities in northern China, and then calculated the taxonomic and phylogenetic β-diversity indices (overall, turnover and nestedness) using a pairwise dissimilarity approach. To assess the effects and to explain the variation in the patterns of β-diversity, we collected data on geospatial, climate and soil conditions. We applied descriptive statistics, Mental correlations, and multiple linear regression models to assess the patterns and spatial-environmental drivers of β-diversity. The β-turnover, as compared to β-nestedness, exhibited a predominant influence, constituting 92.6% of the taxonomic β-diversity and 80.4% of the phylogenetic β-diversity. Most of the spatial-environmental variables were significantly positively correlated with the overall taxonomic and phylogenetic β-diversity and β-turnover, but not with β-nestedness. Climatic factors such as MAP and MAT were the strongest predictors of both taxonomic and phylogenetic β-diversity and β-turnover. The variance partitioning analysis showed that the combined effects of spatial and environmental factors accounted for 19% and 16% of the variation in the taxonomic and phylogenetic β-diversity (overall), 17% and 12% of the variation in the β-turnover, and 7% and 1% of the variation in the β-nestedness, respectively, which were higher than independent effects of either spatial or environmental factors. At larger spatial scales, the turnover component of β-diversity may be associated with the species complementarity effect, but dominant or functionally important species can vary among communities due to the species selection effect. By incorporating β-diversity into grassland management strategies, we can enhance the provision of vital ecosystem services that bolster human welfare, serving as a resilient barrier against the adverse effects of climate change at regional and global scales.

Temporal and Spatial Variability of the Electron Environment at the Orbit of Ganymede as Observed by Juno

AbstractThe thermal and energetic electrons along Ganymede's orbit not only weather the surface of the icy moon, but also represent a major threat to spacecraft. In this article, we rely on Juno plasma measurements to characterize the temporal and spatial variability of the electron environment upstream of Ganymede. In particular, we find that electron spectra observed by Juno have fluxes larger by a factor of 2–9 at energies above 10 keV than what was measured two decades earlier by Galileo. This result will advance our understanding of the surface weathering and may be a concern for the radiation safety of the JUICE mission. Furthermore, the June 2021 close fly‐by of Ganymede through the moon's wake reveals that the open field line regions of its magnetosphere attenuate electron fluxes at all energies by a factor of 1.6–5, thereby offering a natural shelter to visiting spacecraft crossing this region.

Evolution and plasticity of physiological traits in the collembolan Orchesella villosa at fine spatial scales within the city

Abstract Divergent natural selection caused by spatial environmental variation can lead to local adaptation and evolutionary divergence between populations, even those within close proximity to one another. This, however, is only one possibility among other outcomes, such as the evolution of adaptive phenotypic plasticity or local maladaptation. Cities, as fragmented landscapes with high environmental variability across microgeographic scales, present an excellent venue to explore these possible outcomes. Here, we use common garden experiments to explore the potential for microgeographic divergence of physiological traits among populations of a collembolan, Orchesella villosa, living within the footprint of a single city. We assessed if intra-urban variation in the intensity of the heat island effect and soil salinity has led to evolutionary divergence in heat tolerance and salinity tolerance, respectively. While we found little variation in salinity tolerance among populations, there was evidence for both plasticity and evolutionary divergence among populations in response to variation in the urban heat island. Although the adaptive nature of these specific responses is not known, we suggest that cities, and human modified habitats in general, promote evolutionary divergence at small spatial scales by creating barriers to dispersal and imposing divergent selective environments within previously contiguous habitats.

Spatial factors overcome seasonality regulating the consumption of allochthonous food resources by fishes from tropical lotic ecosystems

Abstract In lotic ecosystems, a higher availability of allochthonous food resources is expected during floods and rainfall events, which may yield a higher consumption of these resources by consumers. However, allochthonous input and seasonality in environmental conditions are locally dependent. Thus, dietary responses of freshwater consumers to seasonality should also be locally dependent. Herein, we applied a meta‐analytical approach to identify the spatial and seasonal environmental variables associated with the relative consumption of allochthonous food resources by fishes from tropical lotic ecosystems in different seasons. We gathered 566 observations of the diet of fish populations (i.e., restricted to the same sampling event) from 38 studies conducted in 70 localities across the tropics during flood and drought periods (hereafter, high‐water and low‐water periods, respectively). We retrieved latitude, seasonal channel width, elevation and two proxies for allochthonous input for each locality: terrestrial biomass (without considering seasonality) and the normalised difference vegetation index (NDVI; considering seasonality). Then, we applied meta‐regression models using these environmental variables as predictors and the proportion of allochthonous food resources in each consumer's diet (%Allo) as the response variable. Our models revealed that the diet of fishes from tropical lotic ecosystems is mostly autochthonous‐based, independent of the hydrological period (high‐water or low‐water), and aquatic invertebrates were the most consumed food items. Terrestrial vegetation biomass and elevation predicted increasing allochthony in the diet of tropical fishes for high‐water, but only terrestrial biomass predicted allochthony at low‐water periods. We found no relationship between latitude, channel width or NDVI with allochthony. Our study highlights the importance of considering the hierarchical level of biological organisation and fish trophic guilds for understanding seasonal patterns of relative consumption of allochthonous and autochthonous food resources by fishes. We also argue that variations in seasonality across the tropics are likely to have undermined its influence on allochthony in fish diets. The absence of a non‐relationship between channel width and allochthony provides evidence that the River Continuum Concept is better suited to temperate lotic ecosystems. Our results provide novel insights and the big‐picture of seasonal pattern in the diets of tropical fishes for use in future local empirical studies, improving forecasting of the relationship between the factors underpinning the availability of allochthonous and autochthonous food resources, and the diet of freshwater fishes.

Fine-scale spatial variability of marine acoustic environment corresponds with habitat utilization of Indo-Pacific humpback dolphins in Hong Kong waters

Acoustic properties of the underwater environment are important in maintaining biological processes of various marine organisms. However, with the increasing level of underwater noise in the global ocean, there is a growing need to better understand how marine animals use soundscape cues in their habitat selection. Indo-Pacific humpback dolphins (Sousa chinensis) inhabiting the Pearl River Estuary, southeast China, live in one of world’s most developed and noisiest coastal environment and are subjected to many sources of anthropogenic noise. To investigate whether spatial variability of underwater soundscape corresponds with their habitat utilization, we collected daytime underwater recordings in western Hong Kong waters from mid-2016 to mid-2018, and quantified the spatial pattern of marine acoustic environment and its differing characteristics in a fine spatial scale. We developed a framework of soundscape information retrieval to investigate spectral features that may facilitate identification of dolphins’ core habitats. Our findings reveal that a spectral feature, which peaks at 2 kHz, is a reliable predictor of humpback dolphin core habitat. Further modelling of spatial and seasonal variations of underwater soundscape demonstrates that the relative strength of this spectral feature is positively correlated with the sighting rates of humpback dolphins throughout the year. Although the source of the 2 kHz feature remains unknown, it is likely associated with humpback dolphins’ prey. We suggest that underwater acoustic environment represents an important component in evaluating the quality and suitability of coastal habitats for the daily needs of this threatened dolphin species. Local and regional conservation authorities should include habitat-specific baseline soundscape data when developing conservation management strategies.

Effects of seagrass restoration on coastal fish abundance and diversity.

Restoration is accelerating to reverse global declines of key habitats and recover lost ecosystem functions, particularly in coastal ecosystems. However, there is high uncertainty about the long-term capacity of restored ecosystems to provide habitat and increase biodiversity and the degree to which these ecosystem services are mediated by spatial and temporal environmental variability. We addressed these gaps by sampling fishes biannually for 5-7 years (2012-2018) at 16 sites inside and outside a rapidly expanding restored seagrass meadow in coastal Virginia (USA). Despite substantial among-year variation in abundance and species composition, seine catches in restored seagrass beds were consistently larger (6.4 times more fish, p<0.001) and more speciose (2.6 times greater species richness, p<0.001; 3.1 times greater Hill-Shannon diversity, p=0.03) than seine catches in adjacent unvegetated areas. Catches were particularly larger during summer than autumn (p<0.01). Structural equation modeling revealed that depth and water residence time interacted to control seagrass presence, leading to higher fish abundance and richness in shallow, well-flushed areas that supported seagrass. Together, our results indicate that seagrass restoration yields large and consistent benefits for many coastal fishes, but that restoration and its benefits are sensitive to the dynamic seascapes in which restoration is conducted. Consideration of how seascape-scale environmental variability affects the success of habitat restoration and subsequent ecosystem function will improve restoration outcomes and the provisioning of ecosystem services.

Background matching through fast and reversible melanin-based pigmentation plasticity in tadpoles comes with morphological and antioxidant changes

Facultative colour change is widespread in the animal kingdom, and has been documented in many distantly related amphibians. However, experimental data testing the extent of facultative colour change, and associated physiological and morphological implications are comparatively scarce. Background matching in the face of spatial and temporal environmental variation is thought to be an important proximate function of colour change in aquatic amphibian larvae. This is particularly relevant for species with long larval periods such as the western spadefoot toad, Pelobates cultripes, whose tadpoles spend up to six months developing in temporary waterbodies with temporally variable vegetation. By rearing tadpoles on different coloured backgrounds, we show that P. cultripes larvae can regulate pigmentation to track fine-grained differences in background brightness, but not hue or saturation. We found that colour change is rapid, reversible, and primarily achieved through changes in the quantity of eumelanin in the skin. We show that this increased eumelanin production and/or maintenance is also correlated with changes in morphology and oxidative stress, with more pigmented tadpoles growing larger tail fins and having an improved redox status.

Relationships between phenotypic plasticity and epigenetic variation in two Caribbean Acropora corals.

The plastic ability for a range of phenotypes to be exhibited by the same genotype allows organisms to respond to environmental variation and may modulate fitness in novel environments. Differing capacities for phenotypic plasticity within a population, apparent as genotype by environment interactions (GxE), can therefore have both ecological and evolutionary implications. Epigenetic gene regulation alters gene function in response to environmental cues without changes to the underlying genetic sequence and likely mediates phenotypic variation. DNA methylation is currently the most well described epigenetic mechanism and is related to transcriptional homeostasis in invertebrates. However, evidence quantitatively linking variation in DNA methylation with that of phenotype is lacking in some taxa, including reef-building corals. In this study, spatial and seasonal environmental variation in Bonaire, Caribbean Netherlands was utilized to assess relationships between physiology and DNA methylation profiles within genetic clones across different genotypes of Acropora cervicornis and A. palmata corals. The physiology of both species was highly influenced by environmental variation compared to the effect of genotype. GxE effects on phenotype were only apparent in A. cervicornis. DNA methylation in both species differed between genotypes and seasons and epigenetic variation was significantly related to coral physiological metrics. Furthermore, plastic shifts in physiology across seasons were significantly positively correlated with shifts in DNA methylation profiles in both species. These results highlight the dynamic influence of environmental conditions and genetic constraints on the physiology of two important Caribbean coral species. Additionally, this study provides quantitative support for the role of epigenetic DNA methylation in mediating phenotypic plasticity in invertebrates.

Can spatial and temporal differences in fish assemblage structure inform conservation of an endangered sucker in a large western reservoir?

AbstractObjectiveConversion of lotic to lentic habitat after river impoundment can lead to habitat loss and threats from introduced species to native aquatic organisms. Some native species can persist in reservoirs despite these alterations. Some of the largest reservoirs in North America were constructed in the Colorado River basin and are used by endangered Razorback Sucker Xyrauchen texanus. This species successfully spawns in several reservoirs and recruits to adulthood in Lake Mead, whereas recruitment in other reservoirs and altered river habitats is limited or nonexistent. Hypothesized mechanisms for the general lack of recruitment include flow and habitat alteration as well as competition and predation from nonnative fishes.MethodsWe analyzed 16 years of netting data from Lake Mead to assess spatial and temporal patterns in fish assemblage structure and the size structure of Razorback Sucker across four sites.ResultThere was a substantial shift in assemblage structure across all sites after the establishment of Gizzard Shad Dorosoma cepedianum in 2010–2011 and an apparent decline in Threadfin Shad D. petenense. Captures of juvenile Razorback Sucker (&lt;450 mm total length in Lake Mead) were higher at sites where overall fish abundance was also higher, suggesting that all fishes might be responding to similar spatial and temporal environmental variation. We identified differences in Razorback Sucker size structure that varied over time and among sites, largely driven by the presence of juvenile Razorback Sucker at some sites in some years.ConclusionRazorback Sucker was among the top‐10 most abundant species at all sites sampled, but assemblages were dominated by abundant nonnative fishes. Razorback Sucker continue to recruit in Lake Mead in the face of abundant and diverse nonnative fishes, but the adult population size remains relatively small (&lt;1000). Further investigation of limiting factors will be necessary to understand which actions might be successful at improving recruitment conditions.

Characterizing tree trait variance over spatiotemporal scales.

Beyond the study of the mean, functional ecology lacks a concise characterization of trait variance patterns across spatiotemporal scales. Traits are measured in different ways, using different metrics, and at different spatial (and rarely temporal) scales. This study expands on previous research by applying a ubiquitous and widely used empirical model-Taylor's Power Law-to functional trait variance with the goal of identifying general patterns of trait variance scaling (the behavior of trait variance across scales). We compiled data on tree seedling communities monitored over 10 years across 213 2 m2 plots and functional trait data from a subtropical forest in Puerto Rico. We examined trait-based Taylor's Power Law at nested spatial and temporal scales. The scaling of variance with the mean was idiosyncratic across traits suggesting that the drivers of variation are likely to differ across traits that may make variance scaling theory elusive. However, slopes varied more in space than through time, suggesting that spatial environmental variability may have a larger role in driving trait variance than temporal variability. Empirical models that characterize taxonomic patterns across spatiotemporal scales, like Taylor's Power Law, can provide an insight into the scaling of functional traits, a necessary next step toward a more predictive trait-based ecology.

Effects of climate, spatial and hydrological processes on shaping phytoplankton community structure and β-diversity in an estuary-ocean continuum (Amazon continental shelf, Brazil)

This study investigated the influence of the estuarine plume from the Maranhense Gulf on the phytoplankton community structure and β-diversity. To understand the effects of the regulation mechanisms on shaping phytoplankton community structure and β-diversity along an estuary-ocean continuum in the eastern sector of the Amazon shelf, this study considered spatiotemporal analyses of physical, chemical, and biological variables from May 2019 to June 2020. High temporal environmental heterogeneity was identified in Cumã Bay and significant spatial environmental variability in the estuary-ocean continuum. Based on the thermohaline properties, an estuarine plume was observed alongshore at a distance of approximately 60 km from the coastline. Both phytoplankton community structure and β-diversity varied in time and space. From 189 taxa, thirty-nine indicator species were selected based on their functional traits and indicator value. Skeletonema costatum was considered the best phytoplankton indicator of the estuarine water influence. Turnover was the main component responsible for boosting β-diversity at spatial and temporal scales. The present study was the first performed on an Amazon estuary-ocean continuum which applied diversity metrics (β-diversity) to generate new information about loss of taxon richness and provided important information about spatiotemporal changes in phytoplankton community and environmental heterogeneity.

Coexistence in spatiotemporally fluctuating environments

Ecologists have put forward many explanations for coexistence, but these are only partial explanations; nature is complex, so it is reasonable to assume that in any given ecological community, multiple mechanisms of coexistence are operating at the same time. Here, we present a methodology for quantifying the relative importance of different explanations for coexistence, based on an extension of the Modern Coexistence Theory. Current versions of Modern Coexistence Theory only allow for the analysis of communities that are affected by spatial or temporal environmental variation, but not both. We show how to analyze communities with spatiotemporal fluctuations, how to parse the importance of spatial variation and temporal variation, and how to measure everything with either mathematical expressions or simulation experiments. Our extension of Modern Coexistence Theory shows that many more species can coexist than originally thought. More importantly, it allows empiricists to use realistic models and more data to better infer the mechanisms of coexistence in real communities.

Biotic homogenisation and differentiation as directional change in beta diversity: synthesising driver-response relationships to develop conceptual models across ecosystems.

Biotic homogenisation is defined as decreasing dissimilarity among ecological assemblages sampled within a given spatial area over time. Biotic differentiation, in turn, is defined as increasing dissimilarity over time. Overall, changes in the spatial dissimilarities among assemblages (termed 'beta diversity') is an increasingly recognised feature of broader biodiversity change in the Anthropocene. Empirical evidence of biotic homogenisation and biotic differentiation remains scattered across different ecosystems. Most meta-analyses quantify the prevalence and direction of change in beta diversity, rather than attempting to identify underlying ecological drivers of such changes. By conceptualising the mechanisms that contribute to decreasing or increasing dissimilarity in the composition of ecological assemblages across space, environmental managers and conservation practitioners can make informed decisions about what interventions may be required to sustain biodiversity and can predict potential biodiversity outcomes of future disturbances. We systematically reviewed and synthesised published empirical evidence for ecological drivers of biotic homogenisation and differentiation across terrestrial, marine, and freshwater realms to derive conceptual models that explain changes in spatial beta diversity. We pursued five key themes in our review: (i) temporal environmental change; (ii) disturbance regime; (iii) connectivity alteration and species redistribution; (iv) habitat change; and (v) biotic and trophic interactions. Our first conceptual model highlights how biotic homogenisation and differentiation can occur as a function of changes in local (alpha) diversity or regional (gamma) diversity, independently of species invasions and losses due to changes in species occurrence among assemblages. Second, the direction and magnitude of change in beta diversity depends on the interaction between spatial variation (patchiness) and temporal variation (synchronicity) of disturbance events. Third, in the context of connectivity and species redistribution, divergent beta diversity outcomes occur as different species have different dispersal characteristics, and the magnitude of beta diversity change associated with species invasions also depends strongly on alpha and gamma diversity prior to species invasion. Fourth, beta diversity is positively linked with spatial environmental variability, such that biotic homogenisation and differentiation occur when environmental heterogeneity decreases or increases, respectively. Fifth, species interactions can influence beta diversity via habitat modification, disease, consumption (trophic dynamics), competition, and by altering ecosystem productivity. Our synthesis highlights the multitude of mechanisms that cause assemblages to be more or less spatially similar in composition (taxonomically, functionally, phylogenetically) through time. We consider that future studies should aim to enhance our collective understanding of ecological systems by clarifying the underlying mechanisms driving homogenisation or differentiation, rather than focusing only on reporting the prevalence and direction of change in beta diversity, per se.

A guide and tools for selecting and accessing microclimate data for mechanistic niche modeling

AbstractMost ecological analyses and forecasts use weather station data or coarse interpolated, gridded air temperature data. Yet, these products often poorly capture the microclimates experienced by organisms that respond to fine‐scale spatial and temporal environmental variation near the surface. Sources of historic and projected future data with finer spatial and temporal resolution are proliferating. We qualitatively and quantitatively review and evaluate the available data on three core issues central to microclimate modeling: the quality of the input environmental data, the ability of algorithms to capture microclimatic processes given environmental forcing data, and how best to access microclimatic data. We show how differences between observed environmental conditions and those estimated using environmental forcing data, microclimate algorithms, and precomputed microclimate datasets can be substantial depending on the variable, location, and season. The choice of environmental dataset to parameterize biophysical models has ramifications for biological estimates, such as the duration of potential activity and incidence of thermal stress. New data sources offering high temporal and spatial resolution correspond well to observational data and have the potential to revolutionize understanding of the ecological implications of microclimate variability. We provide resources to help users select and access appropriate environmental data for biological applications, including users' guides and interactive visualization, to better infer how organisms experience climate variability and change.

Biodiversity transformations in the global ocean: A climate change and conservation management perspective.

Understanding the biological diversity of different communities and evaluating the risks to biological sustainability in a time of rapid environmental change is a key challenge for providing an adapting management approach for biodiversity transformations in the ocean linked to human well-being. (Photo credit: Andrea Belgrano).