Find research datasets worth reusing

Data from: The abiotic and biotic drivers of rapid diversification in Andean bellflowers (Campanulaceae)

The tropical Andes of South America, the world's richest biodiversity hotspot, are home to many rapid radiations. While geological, climatic, and ecological processes collectively explain such radiations, their relative contributions are seldom examined within a single clade. We explore the contribution of these factors by applying a series of diversification models that incorporate mountain building, climate change, and trait evolution to the first dated phylogeny of Andean bellflowers (Campanulaceae: Lobelioideae). Our framework is novel for its direct incorporation of geological data on Andean uplift into a macroevolutionary model. We show that speciation and extinction are differentially influenced by abiotic factors: speciation rates rose concurrently with Andean elevation, while extinction rates decreased during global cooling. Pollination syndrome and fruit type, both biotic traits known to facilitate mutualisms, played an additional role in diversification. These abiotic and biotic factors resulted in one of the fastest radiations reported to date: the centropogonids, whose 550 species arose in the last 5 Myr. Our study represents a significant advance in our understanding of plant evolution in Andean cloud forests. It further highlights the power of combining phylogenetic and Earth science models to explore the interplay of geology, climate, and ecology in generating the world's biodiversity.

Data from: Microhabitat selection in the common lizard: implications of biotic interactions, age, sex, local processes, and model transferability among populations

Modeling species' habitat requirements are crucial to assess impacts of global change, for conservation efforts and to test mechanisms driving species presence. While the influence of abiotic factors has been widely examined, the importance of biotic factors and biotic interactions, and the potential implications of local processes are not well understood. Testing their importance requires additional knowledge and analyses at local habitat scale. Here, we recorded the locations of species presence at the microhabitat scale and measured abiotic and biotic parameters in three different common lizard (Zootoca vivipara) populations using a standardized sampling protocol. Thereafter, space use models and cross-evaluations among populations were run to infer local processes and estimate the importance of biotic parameters, biotic interactions, sex, and age. Biotic parameters explained more variation than abiotic parameters, and intraspecific interactions significantly predicted the spatial distribution. Significant differences among populations in the relationship between abiotic parameters and lizard distribution, and the greater model transferability within populations than between populations are in line with effects predicted by local adaptation and/or phenotypic plasticity. These results underline the importance of including biotic parameters and biotic interactions in space use models at the population level. There were significant differences in space use between sexes, and between adults and yearlings, the latter showing no association with the measured parameters. Consequently, predictive habitat models at the population level taking into account different sexes and age classes are required to understand a specie's ecological requirements and to allow for precise conservation strategies. Our study therefore stresses that future predictive habitat models at the population level and their transferability should take these parameters into account.

Data from: Trait-mediated community assembly: distinguishing the signatures of biotic and abiotic filters

Conflicting hypotheses predict how traits mediate species establishment and community assembly. Traits of newly establishing individuals are predicted to converge, or be more similar to the resident, preexisting community, when the biotic or abiotic environment favors a single best phenotype, but are predicted to diverge when trait differences reduce competitive interactions. We tested these competing hypotheses using transplant seedlings in an old-field environment, and assessed the contribution of inter- and intra-specific transplant trait variation to community-level patterns. Using a soil moisture gradient and resident plant removals, we determined when traits of newly-establishing plants converge or diverge from the resident community by calculating community weighted mean traits for transplant and resident communities. We saw evidence of environmentally- and competitively-driven trait shifts that resulted in both trait convergence and divergence from the resident community, whose traits reflect the combined effects of both drivers. Leaf dry matter content (LDMC) of transplants diverged in the presence of competition, whereas plant height and stem-specific density (SSD) showed the opposite pattern, converging with the resident community in their presence. Specific leaf area (SLA) shifted with competition but did not reflect resident community SLA. All transplant traits were influenced by soil moisture, often in an interaction with competition, indicating that the strength of convergence or divergence is contingent on the abiotic environment. Intraspecific differences in transplant traits among treatments were evident in three of four traits; intraspecific height and SLA trends mirrored transplant community-level trends, whereas intraspecific shifts in SSD were distinct from community-level trends. Our study shows competition between plant species may cause traits of newly establishing plants to converge with the resident community, as frequently as it selects for trait divergence. These opposing effects of competition suggest that it plays a pervasive role in both intraspecific and species-level trait differences among communities.

opencc-zeroSep 2019View details →

Data from: Spatio-temporal variation of biotic and abiotic stress agents determines seedling survival in assisted oak regeneration

1. Mediterranean oak woodlands are currently undergoing considerable anthropogenic changes that globally threaten their long-term persistence. Restoration efforts via assisted regeneration depend on species traits and type of stress. However, how different sources of stress vary across space (microsites) and time (intra and inter-annual variation) for co-occurring oak species remains largely unknown. 2. We examined spatio-temporal variation of biotic (herbivory, seed predation) and abiotic (drought) stress agents to evaluate seedling survival across different regeneration microsites, and considering two climatically contrasting years. We used two co-occurring species of contrasting ecology and leaf traits in California oak woodlands: the deciduous Quercus lobata and the evergreen Q. agrifolia. 3. Most oak seedlings (98.8%) suffered from some type of stress. For both species, summer drought was the main cause of mortality, followed by rodent damage, ungulate browsing and insect damage. Rodents represented the predominant biotic stress, as all rodent-affected seedlings eventually died. Interactions among stress factors were nuanced: insect and ungulate-browsing stresses were greater during dry year, whereas rodent damage was similar in dry and average years. Intra-annually, rodent damage was the main stress agent in early spring, whereas water stress and ungulate-browsing were greater in late spring-early fall. Plant species traits were also determinant: overall, the evergreen species had greater survival probability than the deciduous one. 4. Across microsites, water stress showed higher occurrence in open grassland habitats, while rodent damage was prevalent under palatable shrubs and ungulate browsing under conspecific trees. Shrub and tree cover reduced damage attributed to water stress but increased rodent and ungulate damage, respectively. Interestingly, lower water stress but higher rodent damage was found further inside the shrub cover. 5. Synthesis and applications. Intra and inter-annual variation are critical determinants of stress type and intensity on oak recruitment. Spatial variation (microsite identity) is also informative to manipulate stress agent impact. We conclude that assisted regeneration should consider not only the predominance and lethality of each stress type and microsite, but also the interactions thereof and thus manipulate protective microsites accordingly.

opencc-zeroDec 2013View details →

Data from: Untangling interactions: do temperature and habitat fragmentation gradients simultaneously impact biotic relationships?

Gaining insight into the impact of anthropogenic change on ecosystems requires investigation into interdependencies between multiple drivers of ecological change and multiple biotic responses. Global environmental change drivers can act simultaneously to impact the abundance and diversity of biota, but few studies have also measured the impact across trophic levels. We firstly investigated whether climate (using temperature differences across a latitudinal gradient as a surrogate) interacts with habitat fragmentation (measured according to fragment area and distance to habitat edges) to impact a New Zealand tri-trophic food chain (plant, herbivore and natural enemy). Secondly, we examined how these interactions might differentially impact both the density and biotic processes of species at each of the three trophic levels. We found evidence to suggest that these drivers act non-additively across trophic levels. The nature of these interactions however varied: location synergistically interacted with fragmentation measures to exacerbate the detrimental effects on consumer density; and antagonistically interacted to ameliorate the impact on plant density and on the interactions between trophic levels (herbivory and parasitoid attack rate). Our findings indicate that the ecological consequences of multiple global change drivers are strongly interactive and vary according to the trophic level studied and whether density or ecological processes are investigated.

opencc-zeroDec 2014View details →

Data from: Biotic and climatic velocity identify contrasting areas of vulnerability to climate change

Metrics that synthesize the complex effects of climate change are essential tools for mapping future threats to biodiversity and predicting which species are likely to adapt in place to new climatic conditions, disperse and establish in areas with newly suitable climate, or face the prospect of extirpation. The most commonly used of such metrics is the velocity of climate change, which estimates the speed at which species must migrate over the earth's surface to maintain constant climatic conditions. However, "analog-based" velocities, which represent the actual distance to where analogous climates will be found in the future, may provide contrasting results to the more common form of velocity based on local climate gradients. Additionally, whereas climatic velocity reflects the exposure of organisms to climate change, resultant biotic effects are dependent on the sensitivity of individual species as reflected in part by their climatic niche width. This has motivated development of biotic velocity, a metric which uses data on projected species range shifts to estimate the velocity at which species must move to track their climatic niche. We calculated climatic and biotic velocity for the Western Hemisphere for 1961–2100, and applied the results to example ecological and conservation planning questions, to demonstrate the potential of such analog-based metrics to provide information on broad-scale patterns of exposure and sensitivity. Geographic patterns of biotic velocity for 2954 species of birds, mammals, and amphibians differed from climatic velocity in north temperate and boreal regions. However, both biotic and climatic velocities were greatest at low latitudes, implying that threats to equatorial species arise from both the future magnitude of climatic velocities and the narrow climatic tolerances of species in these regions, which currently experience low seasonal and interannual climatic variability. Biotic and climatic velocity, by approximating lower and upper bounds on migration rates, can inform conservation of species and locally-adapted populations, respectively, and in combination with backward velocity, a function of distance to a source of colonizers adapted to a site's future climate, can facilitate conservation of diversity at multiple scales in the face of climate change.

opencc-zeroFeb 2020View details →

Invasive species and biotic homogenization in temperate aquatic plant communities

Aim: Biotic homogenization (BH), a reduction in the distinctness of species composition between geographically separated ecological communities in a region, is an important but underappreciated potential consequence of biological invasions. While BH theory has always considered invasions, it has generally been in a relatively narrow context, i.e., that the cosmopolitan nature of invasive species increases BH because of their shared presence across many locations. We sought to evaluate this component of BH as well as broader effects of invasive species on BH through changes in native communities, including overall reductions in species richness or shifts in species composition. Location: Minnesota, USA Time Period: 2002-2014 Major Taxa Studied: Aquatic macrophytes, including both vascular plants and attached macroalgae. Methods: We used surveys of aquatic macrophyte communities from 1,102 shallow lakes in Minnesota, USA (including 248 lakes with repeated surveys) to evaluate relationships between invasion, native species, and BH. Results: We found that the presence of invasive species was associated with BH and that this pattern was reflected in both the total community (i.e., with invasive species included) and in the composition of the native species community alone. We found that invaded lakes were more compositionally similar to each other than uninvaded lakes, but that both groups were becoming more similar over time—despite neither group exhibiting declines in species richness. This pattern was largely driven by shifts in the native community itself, with common species becoming more widespread and rare species becoming rarer. Main Conclusions: Invasive species increase measures of community similarity through their own presence in multiple locations, and also by influencing the composition of native species. These patterns have important implications for conservation and management and suggest that BH should be considered more widely in evaluating the impacts of biological invasions and developing response strategies.

Data from: Quantifying the role of colonization history and biotic interactions in shaping communities –a community transplant approach

The role of colonization history and subsequent biotic interactions in determining the species composition in communities has long been the subject of debate in ecology. While one narrative has emphasized deterministic assembly rules, another has emphasized historical contingency. One problem lies in approach: community studies are typically either manipulative but somewhat unnatural, or observational but lacking manipulation. Furthermore, while most ecologists now recognize that both historical and biotic factors shape communities, too few studies have moved beyond qualitative descriptions of their roles. Here we use a manipulative approach that leverages natural variation to provide quantitative estimates of the relative contributions of colonization history and the subsequent biotic interactions. 384 communities were developed on artificial substrata in a homogeneous environment before undergoing reciprocal transplantation. We then compare community structure before and after transplantation as proxies for colonization history and biotic interactions. We found that the importance of history and the ensuing biotic environment differed at different times in community development. Early transplantations resulted in the local environment modifying community history faster compared to postponed transplantations. With a four-week difference in age, colonization history explained 20% more of the variation in older communities than in younger communities. Biotic interactions were able to modify colonization history at the age of 16 weeks, but older communities showed more resistance to the changing biotic environment. Our method provides a manipulative and quantitative approach for understanding the relative contributions of colonization history and biotic interactions to community in natural systems.

opencc-zeroDec 2012View details →

Data from: Consequences of climate change for biotic disturbances in North American forests

About one third of North America is forested. These forests are of incalculable value to human society in terms of harvested resources and ecosystem services and are sensitive to disturbance regimes. Epidemics of forest insects and diseases are the dominant sources of disturbance to North American forests. Here we review current understanding of climatic effects on the abundance of forest insects and diseases in North America, and of the ecological and socioeconomic impacts of biotic disturbances. We identify 27 insects (6 nonindigenous) and 22 diseases (9 nonindigenous) that are notable agents of disturbance in North American forests. The distribution and abundance of forest insects and pathogens respond rapidly to climatic variation due to their physiological sensitivity to temperature, high mobility, short generation times, and high reproductive potential. Additionally, climate affects tree defenses, tree tolerance, and community interactions involving enemies, competitors, and mutualists of insects and diseases. Recent research affirms the importance of milder winters, warmer growing seasons, and changes in moisture availability to the occurrence of biotic disturbances. Predictions from the first US National Climate Assessment of expansions in forest disturbances from climate change have been upheld - in some cases more rapidly and dramatically than expected. Clear examples are offered by recent epidemics of spruce beetles in Alaska, mountain pine beetle in high-elevation five-needle pine forests of the Rocky Mountains, and southern pine beetle in the New Jersey Pinelands. Pathogens are less studied with respect to climate but some are facilitated by warmer and wetter summer conditions. Changes in biotic disturbances have broad consequences for forest ecosystems and the services they provide to society. Climatic effects on forest insect and disease outbreaks may foster further changes in climate by influencing the exchange of carbon, water, and energy between forests and the atmosphere. Climate-induced changes in forest productivity and disturbance create opportunities as well as vulnerabilities (e.g., increases in productivity in many areas, and probably decreases in disturbance risks in some areas). There is a critical need to better understand and predict the interactions among climate, forest productivity, forest disturbance, and the socioeconomic relations between forests and people.

opencc-zeroFeb 2020View details →

The role of environmental vs. biotic filtering in the structure of European ant communities: a matter of trait type and spatial scale

Functional trait-based approaches are increasingly used for studying the processes underlying community assembly. The relative influence of different assembly rules might depend on the spatial scale of analysis, the environmental context and the type of functional traits considered. By using a functional trait-based approach, we aim to disentangle the relative role of environmental filtering and interspecific competition on the structure of European ant communities according to the spatial scale and the type of trait considered. We used a large database on ant species composition that encompasses 361 ant communities distributed across the five biogeographic regions of Europe; these communities were composed of 155 ant species, which were characterized by 6 functional traits. We then analysed the relationship between functional divergence and co-occurrence between species pairs across different spatial scales (European, biogeographic region and local) and considering different types of traits (ecological tolerance and niche traits). Three different patterns emerged: negative, positive and non-significant regression coefficients suggest that environmental filtering, competition and neutrality are at work, respectively. We found that environmental filtering is important for structuring European ant communities at large spatial scales, particularly at the scale of Europe and most biogeographic regions. Competition could play a certain role at intermediate spatial scales where temperatures are more favourable for ant productivity (i.e. the Mediterranean region), while neutrality might be especially relevant in spatially discontinuous regions (i.e. the Alpine region). We found that no ecological mechanism (environmental filtering or competition) prevails at the local scale. The type of trait is especially important when looking for different assembly rules, and multi-trait grouping works well for traits associated with environmental responses (tolerance traits), but not for traits related to resource exploitation (niche traits). The spatial scale of analysis, the environmental context and the chosen traits merit special attention in trait-based analyses of community assembly mechanisms.

opencc-zeroDec 2017View details →

Data from: Mapping the imprint of biotic interactions on β-diversity

Investigating how trophic interactions influence the β-diversity of meta-communities is of paramount importance to understanding the processes shaping biodiversity distribution. Here, we apply a statistical method for inferring the strength of spatial dependencies between pairs of species groups. Using simulated community data generated from a multi-trophic model, we showed that this method can approximate biotic interactions in multi-trophic communities based on β-diversity patterns across groups. When applied to soil multi-trophic communities along an elevational gradient in the French Alps, we found that fungi make a major contribution to the structuring of β-diversity across trophic groups. We also demonstrated that there were strong spatial dependencies between groups known to interact specifically (e.g. plant-symbiotic fungi, bacteria-nematodes) and that the influence of environment was less important than previously reported in the literature. Our method paves the way for a better understanding and mapping of multi-trophic communities through space and time.

opencc-zeroNov 2019View details →

Biotic predictors with phenological information improve range estimates for migrating monarch butterflies in Mexico

Although long-standing theory suggests that biotic variables are only relevant at local scales for explaining the patterns of species' distributions, recent studies have demonstrated improvements to species distribution models (SDMs) by incorporating predictor variables informed by biotic interactions. However, some key methodological questions remain, such as which kinds of interactions are permitted to include in these models, how to incorporate the effects of multiple interacting species, and how to account for interactions that may have a temporal dependence. We addressed these questions in an effort to model the distribution of the monarch butterfly (Danaus plexippus L. 1758) during its fall migration (September – November) through Mexico, a region with new monitoring data and uncertain range limits even for this well-studied insect. We estimated species richness of selected nectar plants (Asclepias spp.) and roosting trees (various highland species) for use as biotic variables in our models. To account for flowering phenology, we additionally estimated nectar plant richness of flowering species per month. We evaluated three types of models: climatic variables only (abiotic), plant richness estimates only (biotic), and combined (abiotic and biotic). We selected models with AICc and additionally determined if they performed better than random on spatially withheld data. We found that the combined models accounting for phenology performed best for all three months, and better than random for discriminatory ability but not omission rate. These combined models also produced the most ecologically realistic spatial patterns, but the modeled response for nectar plant richness matched ecological predictions for November only. These results represent the first model-based monarch distributional estimates for the Mexican migration route and should provide foundations for future conservation work. More generally, the study demonstrates the potential benefits of using SDM-derived richness estimates and phenological information for biotic factors affecting species distributions.

opencc-zeroDec 2013View details →

Data from: Assembly of root-associated bacteria communities: interactions between abiotic and biotic factors

Nitrogen (N) deposition in many areas of the world is over an order of magnitude greater than it would be in absence of human activity. We ask how abiotic (N) and biotic (plant host and neighborhood) effects interact to influence root-associated bacterial (RAB) community assembly. Using 454 pyrosequencing, we examined RAB communities from two dominant alpine tundra plants, Geum rossii and Deschampsia cespitosa, under control, N addition and D. cespitosa removal treatments, implemented in a factorial design. We hypothesized that host would have the strongest effect on RAB assembly, followed by N, then neighbor effects. The most dominant phyla were Proteobacteria (mostly Gammaproteobacteria), Actinobacteria, Bacteroidetes and Acidobacteria. We found RAB communities were host specific, with only 17% overlap in operational taxonomic units. Host effects on composition were over twice as strong as N effects. D. cespitosa RAB diversity declined with N, while G. rossii RAB did not. D. cespitosa removal did not influence G. rossii RAB community composition, but G. rossii RAB diversity declined with N only when D. cespitosa was absent. We conclude that RAB of both hosts are sensitive to N enrichment, and RAB response to N is influenced by host identity and plant neighborhood.

opencc-zeroDec 2017View details →

Data from: Primary rainforest amount at the landscape scale mitigates bird biodiversity loss and biotic homogenization

1.Tropical conservation strategies traditionally focus on large tracts of pristine forests, but given rapid primary forest decline, understanding the role of secondary forest remnants for biodiversity maintenance is critical. Until now, the interactive effects of changes in forest amount, configuration and disturbance history (secondary vs. primary forest) on the conservation value of tropical landscapes has remained unknown, hampering the incorporation of these global change drivers into local and global conservation planning. 2.We disentangled effects of landscape wide forest amount, fragment size, and forest age (old growth versus secondary forest) on abundance, α-diversity, β-diversity (biotic homogenisation) and community shifts of bird communities in human-dominated landscapes of southern Costa Rica. Utilizing two complementary methods, yielding 6900 individual detections and 223 species, we characterized bird communities in 49 forest fragments representing independent gradients in fragment size (<5 ha vs >30 ha) and forest amount (5%-80%) in the surrounding landscape (within 1000 m). 3.Abundance and α-diversity of forest specialists and insectivores declined by half in small fragments, but only in landscapes with little old growth forest. Conversely, secondary forest at the landscape scale showed no such compensation effect. Similarly, a null-model approach indicated significant biotic homogenisation in small versus large fragments, but only in landscapes with little old growth forest, suggesting forest amount and configuration interactively affect β-diversity in tropical human-dominated landscapes. Finally, dramatic abundance-based community shifts relative to intact forests are largely a result of landscape-scale loss of old growth rather than changes in overall forest cover. 4.Policy implications. Our study provides strong evidence that retaining old growth within tropical human modified landscapes can simultaneously curb erosion of avian forest specialist α-diversity, mitigate collapse of β-diversity (biotic homogenisation) and dampen detrimental avian community shifts. However, secondary forests play, at best, a subordinate role to mitigate these processes. To maintain tropical forest biodiversity, retaining old growth forest within landscapes should be first priority, highlighting a land-sparing approach.

Data from: Predator-guided sampling reveals biotic structure in the bathypelagic

We targeted habitat used differentially by deep-diving, air-breathing predators to empirically sample their prey's distributions off southern California. Fine-scale measurements of the spatial variability of potential prey animals from the surface to 1200 m were obtained using conventional fisheries echosounders aboard a surface ship and uniquely integrated into a deep-diving autonomous vehicle. Significant spatial variability in the size, composition, total biomass, and spatial organization of biota was evident over all spatial scales examined and was consistent with the general distribution patterns of foraging Cuvier's beaked whales (Ziphius cavirostris) observed in separate studies. Striking differences were found in prey characteristics between regions at depth, however, did not reflect differences observed in surface layers. These differences in deep pelagic structure horizontally and relative to surface structure, absent clear physical differences, change our long-held views of this habitat as uniform. The revelation that animals deep in the water column are so spatially heterogeneous at scales from 10 m to 50 km critically affects our understanding of the processes driving predator-prey interactions, energy transfer, biogeochemical cycling and other ecological processes in the deep sea, and the connections between the productive surface mixed layer and the deep water column.

Data from: Neogene sloth assemblages (Mammalia, Pilosa) of the Cocinetas Basin (La Guajira, Colombia): implications for the Great American Biotic Interchange

We describe sloth assemblages from the Cocinetas Basin (La Guajira peninsula, Colombia), found in the Neogene Castilletes and Ware formations, located in northernmost South America, documenting otherwise poorly known biotas. The tentative referral of a specimen to a small megatherioid sloth, Hyperleptus?, from the early–middle Miocene Castilletes Formation, suggests affinities of this fauna with the distant Santa Cruz Formation and documents a large latitudinal distribution for this taxon. The late Pliocene Ware Formation is much more diverse, with five distinct taxa representing every family of 'ground sloths'. This diversity is also remarkable at the ecological level, with sloths spanning over two orders of magnitude of body mass and probably having different feeding strategies. Being only a few hundred kilometres away from the Isthmus of Panama, and a few hundred thousand years older than the classically recognized first main pulse of the Great American Biotic interchange (GABI 1), the Ware Formation furthermore documents an important fauna for the understanding of this major event in Neogene palaeobiogeography. The sloths for which unambiguous affinities were recovered are not closely related to the early immigrants found in North America before GABI 1.

Data from: Disentangling biotic interactions, environmental filters, and dispersal limitation as drivers of species co-occurrence

A key focus in ecology is to search for community assembly rules. Here we compare two community modelling frameworks that integrate a combination of environmental and spatial data to identify positive and negative species associations from presence-absence matrices, and incorporate an additional comparison using joint species distribution models (JSDM). The frameworks use a dichotomous logic tree that distinguishes dispersal limitation, environmental requirements, and interspecific interactions as causes of segregated or aggregated species pairs. The first framework is based on a classical null model analysis complemented by tests of spatial arrangement and environmental characteristics of the sites occupied by the members of each species pair (Classic framework). The second framework, (SDM framework) implemented here for the first time, builds on the application of environmentally-constrained null models (or JSDMs) to partial out the influence of the environment, and includes an analysis of the geographical configuration of species ranges to account for dispersal effects. We applied these approaches to examine plot-level species co-occurrence in plant communities sampled along a wide elevation gradient in the Swiss Alps. According to the frameworks, the majority of species pairs were randomly associated, and most of the non-random positive and negative species associations could be attributed to environmental filtering and/or dispersal limitation. These patterns were partly detected also with JSDM. Biotic interactions were detected more frequently in the SDM framework, and by JSDM, than in the Classic framework. All approaches detected species aggregation more often than segregation, perhaps reflecting the important role of facilitation in stressful high-elevation environments. Differences between the frameworks may reflect the explicit incorporation of elevational segregation in the SDM framework and the sensitivity of JSDM to the environmental data. Nevertheless, all methods have the potential to reveal general patterns of species co-occurrence for different taxa, spatial scales, and environmental conditions.

Data from: Is biotic resistance enhanced by natural variation in diversity?

Theories linking diversity to ecosystem function have been challenged by the widespread observation of more exotic species in more diverse native communities. Few studies have addressed the underlying processes by dissecting how biotic resistance to new invaders may be shaped by the same environmental influences that determine diversity and other community properties. In grasslands with heterogeneous soils, we added invaders and removed competitors to analyze the causes of invasion resistance. Abiotic resistance was measured using invader success in the absence of the resident community. Biotic resistance was measured as the reduction in invader success in the presence of the resident community. Invaders were most successful where biotic resistance was lowest and abiotic resistance was highest, confirming the dominant role of biotic resistance. Contrary to theory, though, biotic resistance was highest where both species richness and functional diversity were lowest. In the multivariate framework of a structural equation model, biotic resistance was independent of community diversity, and was highest where fertile soils led to high community biomass. Seed predation slightly augmented biotic resistance without qualitatively changing the results. Soil-related genotypic variation in the invader also did not affect the results. We conclude that in natural systems, diversity may be correlated with invasibility and yet have little effect on biotic resistance to invasion. More generally, the environmental causes of variation in diversity should be considered when examining the potential functional consequences of diversity.

Data from: From success to persistence: Identifying an evolutionary regime shift in the diverse Paleozoic aquatic arthropod group Eurypterida, driven by the Devonian biotic crisis

Mass extinctions have altered the trajectory of evolution a number of times over the Phanerozoic. During these periods of biotic upheaval a different selective regime appears to operate, although it is still unclear whether consistent survivorship rules apply across different extinction events. We compare variations in diversity and disparity across the evolutionary history of a major Paleozoic arthropod group, the Eurypterida. Using these data, we explore the group's transition from a successful, dynamic clade to a stagnant persistent lineage, pinpointing the Devonian as the period during which this evolutionary regime shift occurred. The late Devonian biotic crisis is potentially unique among the 'Big Five' mass extinctions in exhibiting a drop in speciation rates rather than an increase in extinction. Our study reveals eurypterids show depressed speciation rates throughout the Devonian but no abnormal peaks in extinction. Loss of morphospace occupation is random across all Paleozoic extinction events; however, differential origination during the Devonian results in a migration and subsequent stagnation of occupied morphospace. This shift appears linked to an ecological transition from euryhaline taxa to freshwater species with low morphological diversity alongside a decrease in endemism. These results demonstrate the importance of the Devonian biotic crisis in reshaping Paleozoic ecosystems.

Data from: Plant interactions as biotic drivers of plasticity in leaf litter traits and decomposability of Quercus petraea

The importance of plant litter traits and decomposability for nutrient cycling processes and plant community dynamics through plant-litter-soil feedbacks has been largely emphasized. However, the role of biotic interactions as drivers of intraspecific variability in litter traits remains surprisingly little studied. In this study, we used a large-scale, multi-site network of long-term tree removal experiments manipulating the abundance of a foundation tree species, i.e. Quercus petraea, to assess how plant interactions control intraspecific variation in oak leaf litter traits and decomposability. We studied 19 plots across eight experimental sites covering a large gradient of oak abundance, stand age and local abiotic context. Oak leaf litter quality strongly declined with tree removal in early forest successional stage. Litter became poorer in nutrients such as N and Mg and richer in secondary metabolites such as lignin and condensed tannins. This in turn slowed its decomposition. Importantly, litter N loss switched from N release to N immobilization. Variance partitioning indicated that oak abundance explained as much variation in oak leaf litter traits as oak age and twice as much as soil inherent fertility. Confirmatory path analysis revealed that the decline of oak leaf litter quality induced by tree removal was most likely driven by a shift in understory plant species composition. Plasticity of oak leaf litter traits to the shortage of nutrient supply related to the development of understory plants competitors with higher nutrient capture and retention ability could potentially explain this response pattern. Our data also give consistent but weaker support that the decline of oak leaf litter quality could be driven by alleviated competition for light among canopy trees and subsequent enhanced crown exposure to light. Overall, our study provides evidence that biotic factors such as plant interactions are major drivers of plasticity in leaf litter traits and decomposability. This finding contributes to the emerging view that phenotypic plasticity is fundamentally related to biotic interactions for sessile organisms, especially for long-lived and large plant species such as trees. Taking this source of functional diversity into account could help us to better understand plant community dynamics and ecological processes in terrestrial ecosystems.