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11,506 results for “Dynamics”
Data from: Disturbance history mediates climate change effects on subtropical forest biomass and dynamics
The responses of forest communities to interacting anthropogenic disturbances like climate change and logging are poorly known. Subtropical forests have been heavily modified by humans and their response to climate change is poorly understood. We investigated the nine year-change observed in a mixed conifer-hardwood Atlantic forest mosaic that included both mature and selectively-logged forest patches in subtropical South America. We used demographic monitoring data within 10 1 ha plots that were subjected to distinct management histories (plots logged until 1955, until 1987, and unlogged) to test the hypothesis that climate change affected forest structure and dynamics differentially depending on past disturbances. We determined the functional group of all species based on life-history affinities as well as many functional traits like leaf size, specific leaf area, wood density, total height, stem slenderness, and seed size data for the 66 most abundant species. Analysis of climate data revealed that minimum temperatures and rainfall have been increasing in the last few decades of the 20th century. Floristic composition differed mainly with logging history categories, with only minor change over the nine annual census intervals. Aboveground biomass increased in all plots, but increases were higher in mature unlogged forests, which showed signs of forest growth associated with increased CO2, temperature, and rainfall/treefall gap disturbance at the same time. Logged forests showed arrested succession as indicated by reduced abundances of Pioneers and biomass-accumulators like Large Seeded Pioneers and Araucaria, as well as reduced functional diversity. Management actions aimed at creating regeneration opportunities for long-lived pioneers are needed to restore community functional diversity, and ecosystem services such as increased aboveground biomass accumulation. We conclude that the effects of climate drivers on the dynamics of Brazilian mixed Atlantic forests vary with land-use legacies, and can differ importantly from the ones prevalent in better known tropical forests.
Data from: Genetic monitoring and complex population dynamics: insights from a 12-year study of the Rio Grande silvery minnow
The endangered Rio Grande silvery minnow persists as a remnant population in a highly fragmented and regulated arid-land river system. The species is subject to dramatic fluctuations in density. Since 2003, the wild population has been supplemented by hatchery-reared fish. We report on a 12-year (1999 – 2010) monitoring study of genetic diversity and effective population size (Ne) of wild and hatchery stocks. Our goals were to evaluate how genetic metrics responded to changes in wild fish density and whether they corresponded to the number and levels of diversity of hatchery-reared repatriates. Genetic diversity and all measures of Ne in the wild population did not correlate with wild fish density until hatchery supplementation began in earnest. Estimates of variance and inbreeding effective size were not correlated. Our results suggest source-sink dynamics where captive stocks form a genetically diverse source and the wild population behaves as a sink. Nevertheless, overall genetic diversity of silvery minnow has been maintained over the last decade and we attribute this to a well designed and executed propagation management plan. When multiple factors like environmental fluctuation and hatchery supplementation act simultaneously on a population, interpretation of genetic monitoring data may be equally complex and require considerable ecological data.
Data from: Genet dynamics of a regenerating dwarf bamboo population across heterogeneous light environments in a temperate forest understorey
Despite the advantage of plant clonality in patchy environments, studies focusing on genet demography in relation to spatially heterogeneous environments remain scarce. Regeneration of bamboos in forest understoreys after synchronous die-off provides an opportunity for assessing how they come to proliferate across heterogeneous light environments. In a Japanese forest, we examined genet demography of a population of Sasa kurilensis over a 7-year period starting 10 years after die-off, shortly after which some genets began spreading horizontally by rhizomes. The aboveground biomass was estimated and genets were discriminated in 9-m2 plots placed under both canopy gaps and closed canopies. Overall, the results suggest that the survival and spread of more productive genets and the spatial expansion of genets into closed canopies underlie the proliferation of S. kurilensis. Compared to canopy gaps, the recovery rate of biomass was much slower under closed canopies for the first 10 years after the die-off, but became accelerated during the next seven years. Genet survival was greater for more productive genets (with greater initial number of culms), and the spaces occupied by genets that died were often colonized afterward by clonal growth of surviving genets. The number of genets decreased under canopy gaps due to greater mortality, but increased under closed canopies where greater number of genets colonized clonally from outside the plots than genets died. The colonizing genets were more productive (having larger culms) than those originally germinated within the plots, and the contribution of colonizing genets to the biomass was greater under closed canopies. Our study emphasizes the importance of investigating genet dynamics over relevant spatio-temporal scales to reveal processes underlying the success of clonal plants in heterogeneous habitats.
Data from: Spatio-temporal dynamics of density-dependent dispersal during a population colonisation
Predicting population colonisations requires understanding how spatio-temporal changes in density affect dispersal. Density can inform on fitness prospects, acting as a cue for either habitat quality, or competition over resources. However, when escaping competition, high local density should only increase emigration if lower-density patches are available elsewhere. Few empirical studies on dispersal have considered the effects of density at the local and landscape scale simultaneously. To explore this, we analyze 5 years of individual-based data from an experimental introduction of wild guppies Poecilia reticulata. Natal dispersal showed a decrease in local density dependence as density at the landscape level increased. Landscape density did not affect dispersal among adults, but local density-dependent dispersal switched from negative (conspecific attraction) to positive (conspecific avoidance), as the colonisation progressed. This study demonstrates that densities at various scales interact to determine dispersal, and suggests that dispersal trade-offs differ across life stages.
Data from: Biomechanical evaluation of peak reverse torque (PRT) in a dynamic compression plate-screw construct used in a goat tibia segmental defect model
Background Peak reverse torque (PRT) is a valid method to evaluate implants' secondary stability in the healing bone. The secondary stability is achieved by the implant over time and it has been positively correlated with the implants' osseointegration level. In other words, peak reverse torque is the force required to break the bone-implant interface. The purpose of this study was to compare the peak reverse torque for the self-tapping and non-self-tapping screws used in a dynamic compression plate–screw–bone construct after 60 days of loading when used to stabilize 2.5-cm defects in the tibia of goats. The second objective was to compare the peak removal torque of the screws placed in the different positions to evaluate the impact of construct biomechanics on implants osseointegration. Results In total, 176 non-self-tapping screws and 66 self-tapping screws were used to fix the 8-holes dynamic compression plates to the bones. The screws were placed in the tibiae from proximal (position sites 1,2, 3) to distal (position sites 4,5,6) and were removed 60 days post-implantation. The animals remained weight-bearing throughout the study period. The screws placed in the proximal diaphysis had significantly less peak reverse torque than screws placed in the distal diaphysis in both groups (p < 0.05). The peak reverse torque resistance was also significantly less for the non-self-tapping screws as compared with the self-tapping screws (p < 0.05). The intracortical fractures in the trans-cortex occurred significantly more frequently during the placement of non-self-tapping screws (p < 0.05) as compared with self-tapping screws (p < 0.05). Conclusions Based on these results, we concluded that self-tapping screws may be expected to maintain a more stable bone-implant interface during the first 60 days of loading as compared with non-self-tapping screws. This should be a consideration for orthopedic surgeons and scientists using bone plates to stabilize non-load sharing fractures when a stable plate-screw-bone interface is needed to ensure prolonged stability.
Data from: Assessing the effect of predator control on an endangered goose population subjected to predator-mediated food web dynamics
1. Assessing the effectiveness of conservation actions to halt population declines is challenging when confounded by other factors. We assessed whether culling of red fox, a predator currently increasing in the sub-Arctic, contributed to recent recovery of the critically endangered Fennoscandian population of Lesser White-fronted Goose Anser erythropus, while controlling for potentially confounding food web dynamics. 2. Using 19 years of data, 10 before and 9 after the implementation of annual red fox culling, we estimated the effect of this action on annual performance of the goose population. We corrected for the potentially confounding effects of cyclic rodent dynamics and semi-domestic reindeer carrion abundance, both of which are expected to trigger predator functional and numerical responses, as well as for annual variation in spring phenology. 3. Goose reproductive success fluctuated in synchrony with the rodent cycle and was negatively related to abundant carrion. When accounting for these aspects of food web dynamics, there was no evidence for an effect of red fox culling on reproductive success. There was, however, a tendency for fox culling to increase adult survival. 4. Our analysis suggests that goose performance in their breeding area is influenced by fluctuating offspring predation, mediated by mainly natural (rodents) and partly anthropogenic (semi-domestic reindeer) dynamic components of the food web. 5. Synthesis and applications. The effect of a decade-long red fox culling on goose reproductive success and survival is currently uncertain. This is despite the fact that predation drives reproductive success through changes in rodent and reindeer carrion abundance. New management actions may consist of regulation of reindeer herd sizes and/or removal of carcasses to reduce the subsidizing effect of reindeer carrion on mesopredators. Getting robust evidence regarding the impact of red fox culling on population recovery depends on continuing research to disentangle food web dynamics and efficiency of management actions.
Data from: Plant economic strategies of grassland species control soil carbon dynamics through rhizodeposition
1. The plant economics spectrum is increasingly recognized as a major determinant of plant species effects on terrestrial ecosystem functioning related to carbon cycling. However, the role of plant economic strategies in the effects of living root activity on soil organic carbon (SOC) dynamics through rhizodeposition remains unexplored, despite SOC being the largest terrestrial carbon pool. 2. Using a continuous 13C-labeling method allowing partitioning of plant and soil sources to carbon fluxes and pools, we studied here the linkages between plant economic strategies and SOC cycling processes in a 'common garden' greenhouse experiment. It includes a panel of 12 grassland species selected along a gradient of economic traits and belonging to three functionnal groups (C3 grasses, forbs and legumes). 3. All species induced an acceleration of native SOC mineralization but this rhizosphere priming effect (RPE) substantially differed across species and varied eleven-fold by the end of the experiment (from +26 to +295 % relative to unplanted soil). Interspecific variation in RPE was primarily linked to plant photosynthetic activity associated to species economic strategies of light and CO2 resource acquisition and processing. Fast-growing acquisitive species, such as legumes, featured large RPE, in relation with their high canopy photosynthesis coupled to high leaf photosynthetic capacity and large net primary productivity allocated aboveground. This large RPE was further associated with high root metabolic activity, rhizodeposition and soil microbial activity. In contrast, fine-root growth and economic traits related to soil resource foraging ability were poor predictors of RPE. 4. The formation of new root-derived SOC varied nine-fold across species and was similarly positively related to the net primary productivity allocated aboveground. Fast-growing acquisitive species with a high photosynthetic activity induced a disproportionately large RPE relative to SOC formation. 5. Synthesis. Overall, our study demonstrates that rhizodeposition is a major mechanism through which plant economic strategies of grassland species control soil carbon dynamics. Acquisitive versus conservative species were associated with high versus low rates of photosynthesis and rhizodeposition, in turn leading to fast versus slow SOC turnover. This emphasizes the importance of considering rhizosphere processes for understanding plant species effects on soil biogeochemistry.
Data from: Parental and hybrid Daphnia from the D. longispina complex: long-term dynamics in genetic structure and significance of overwintering modes
In recent decades, hybridization has become a focus of attention because of its role in evolutionary processes. However, little is known about changes in genetic structure within and between parental species and hybrids over time. Here, we studied processes of genetic change in parental species and hybrids from the Daphnia longispina complex (Crustacea, Cladocera) over a period of six years across ten habitats. These cyclical parthenogens respond to fluctuating environments by switching from asexual to sexual reproduction. Importantly, sexually produced diapausing eggs, which resist extreme conditions such as low temperatures and serve as dispersal stages, are produced to a lower extent by hybrids. Long-term microsatellite data revealed clear differences between hybrids and parental species. In hybrids, clonal diversity values were lower, whereas heterozygosity and linkage disequilibrium values were higher compared to parental species. Clonal diversity of hybrids responded to the strength of the winter, with cold winters resulting in few genotypes in the following spring. In time windows when only asexual hybrid females survive, priority effects will favour the establishment of the hybrid offspring before hatchlings from parental diapause eggs can enter the community. The constant high levels of heterozygosity maintained by clonal reproduction in hybrids might lead to their successful establishment over time, when they are able to escape competition from both parental species. Although we found evidence that hybrids diversity depends on fluctuating environments, a direct link between hybrid abundance and the strength of winter was missing. Because of reduced adaptability in clonally reproducing hybrids, multiple factors must contribute to promoting their long-term success in fluctuating environments.
Data from: Divergent plant–soil feedbacks could alter future elevation ranges and ecosystem dynamics
Plant–soil feedbacks (PSF) are important interactions that may influence range dynamics in a changing world. What remains largely unknown is the generality of plant–soil biotic interactions across populations and the potential role of specific soil biota, both of which are key for understanding how PSF might change future communities and ecosystems. We combined landscape-level field observations and experimental soil treatments to test whether a dominant tree alters soil environments to impact its own performance and range shifts towards higher elevations. We show: (1) soil conditioning by trees varies with elevation, (2) soil biota relate to PSF, (3) under simulated conditions, biotic PSF constrain range shifts at lower elevations but allow for expansions at higher elevations, and (4) differences in soil conditioning predict feedback outcomes in specific range-shift scenarios. These results suggest that variable plant–soil biotic interactions may influence the migration and fragmentation of tree species, and that models incorporating soil parameters will more accurately predict future species distributions.
Data from: Heterogeneity in plant-soil feedbacks and resident population dynamics affect mutual invasibility
1. Understanding the mechanisms governing coexistence is a central goal in ecology and has implications for conserving and restoring communities, yet the high diversity in many plant communities is difficult to explain. Theory suggests that plant-soil feedbacks (PSF) can lead to frequency-dependent coexistence by suppressing conspecifics more than heterospecifics, potentially helping to explain high-diversity plant communities. In addition, species-specific population dynamics, including the rate at which individuals are replaced in a population, or population turnover rate, may influence coexistence outcomes. 2. We have created a rigorous test of the coexistence predictions of theory by generating a soil heterogeneity experiment in the field and testing for mutual invasibility by establishing resident populations, then experimentally invading them. Experimental tests of mutual invasibility can demonstrate coexistence because, if species are able to invade one another's populations when at low density, they should exhibit long-term coexistence. We use pairs of congeners in this experiment that coexist at small spatial scales, sometimes within cm, at our field site. 3. We demonstrate that invader individuals established better in congener's soils than in conspecific soils, consistent with plant-soil feedback mediated coexistence. This effect was often mediated by competition with established resident plants. 4. Further, we show that soil heterogeneity interacted with the population turnover rate of the resident population to influence invasibility (P < 0.10), consistent with the theoretical prediction that a plant's population dynamics will interact with heterogeneity to influence coexistence. 5. Synthesis - Plant-soil feedbacks can in theory lead to frequency-dependent coexistence, and reciprocally negative feedback effects in greenhouse experiments are often consistent with this prediction. We provide the first field test of mutual invasibility structured by PSF, demonstrating that PSF can lead to coexistence when they create a patchy, or heterogeneous, soil environment. This work suggests that understanding the influence of PSF on diversity necessitates understanding the spatial scale at which soil heterogeneity emerges in the field. Thus high diversity might be maintained in plant communities by heterogeneity created by plants' influence on the soil, and this outcome depends strongly on population dynamics.
Data from: Seasonal dynamics and changing sea level as determinants of the community and trophic structure of oribatid mites in a salt marsh of the Wadden Sea
Global change processes affect seasonal dynamics of salt marshes and thereby their plant and animal communities. However, these changes have been little investigated for microarthropod communities. We studied the effect of seasonality and changes in sea level on oribatid mites in the natural salt marsh and on artificial islands in the back-barrier environment of the island Spiekeroog (Wadden Sea, Germany). Three zones of the artificial islands were filled with transplanted sods from the lower salt marsh zone and thereby exposed to three different inundation frequencies. We hypothesized that oribatid mite communities will differ along the natural salt marsh vegetation zones [upper salt marsh (USM), lower salt marsh (LSM), pioneer zone (PZ)], which are influenced by different tidal regimes. Accordingly, total oribatid mite densities declined from the USM and LSM to the PZ. Similarly, oribatid mite species compositions changed along the salt marsh transect and also responded to variations in inundation frequency in LSM on artificial islands with typical species of the USM, LSM and PZ being Multioppia neglecta (USM), Hermannia pulchella (LSM), Zachvatkinibates quadrivertex (LSM, PZ) and Ameronothrus schneideri (LSM, PZ). Oribatid mite density in the salt marsh and on the artificial islands was at a maximum in winter and spring; this was due in part to high density of juveniles, pointing to two reproductive periods. We hypothesized that oribatid mite trophic structure changes due to variations in abiotic (e.g., tidal dynamics, temperature) and biotic conditions (e.g., resource availability). Stable isotope (15N, 13C) and neutral lipid fatty acid analyses indicated that oribatid mite species have different diets with e.g., Z. quadrivertex feeding on macroalgae and fungi, A. schneideri feeding on microalgae and bacteria, and Scheloribates laevigatus and M. neglecta feeding on dead organic matter, bacteria and fungi. Overall, the results indicate that oribatid mite species in salt marshes are affected by changes in environmental factors such as inundation intensity, with the effects being most pronounced in species with narrow trophic niches and limited niche plasticity. The results also indicate that oribatid communities of the LSM respond little to short-term (one year) changes in inundation frequency.
Data from: Independent evolution of baleen whale gigantism linked to Plio-Pleistocene ocean dynamics
Vertebrates have evolved to gigantic sizes repeatedly over the past 250 Myr, reaching their extreme in today's baleen whales (Mysticeti). Hypotheses for the evolution of exceptionally large size in mysticetes range from niche partitioning to predator avoidance, but there has been no quantitative examination of body size evolutionary dynamics in this clade and it remains unclear when, why or how gigantism evolved. By fitting phylogenetic macroevolutionary models to a dataset consisting of living and extinct species, we show that mysticetes underwent a clade-wide shift in their mode of body size evolution during the Plio-Pleistocene. This transition, from Brownian motion-like dynamics to a trended random walk towards larger size, is temporally linked to the onset of seasonally intensified upwelling along coastal ecosystems. High prey densities resulting from wind-driven upwelling, rather than abundant resources alone, are the primary determinant of efficient foraging in extant mysticetes and Late Pliocene changes in ocean dynamics may have provided an ecological pathway to gigantism in multiple independent lineages.
Data from: Variation across river channels in demographic dynamics of a riparian herb with threatened status: management and conservation implications
PREMISE OF THE STUDY: Gesneria pauciflora is a rare-threatened plant growing in riparian forests. Periodic disturbances, expected in this habitat, could influence demographic dynamics on plant populations, yet their impact may not be the same across watershed. We hypothesize that differences in disturbances between the main-channel and tributaries may lead to spatial dissimilarities in population growth rate (λ), structure, and fecundity. METHODS: 1277 plants were tagged and monitored over a 1.5-years period. Every 6-months we measured plant size, survival and fecundity, in addition to appearance of seedlings. These variables were applied in Integral Projection Models to assess the population status of G. pauciflora. KEY RESULTS: Plants in the main-channel were smaller but were more likely to flower and fruit than those in the tributaries. Overall mortality was greater in the main-channel and more so during the rainy season. At both sites λ ranged from 0.9114-0.9865, and survival/growth of larger plants had a greater effect on lambda (> 0.90) regardless of site. CONCLUSIONS: Lambda values suggest that G. pauciflora is declining across the watershed. Higher mortality rates in the main channel (more-perturbed sites) might driving G. pauciflora to reproduced at smaller sizes, while the tributaries (less-perturbed sites) may benefit growth and lead to larger plant sizes. Extreme climatic events are expected to increase in the Caribbean and might decrease the population if left unmanaged. Management strategies that reduce the time plants require to reach larger sizes might be necessary to increase λ, and reintroduction of cuttings might be a possible solution.
Data from: Population dynamics of a northern-adapted mammal: disentangling the influence of predation and climate change
Community structure and interspecific interactions are particularly vulnerable to rapidly changing climatic regimes. Recent changes in both climate and vertebrate community assemblages have created a unique opportunity to examine the impacts of two dynamic forces on population regulation. We examined the effects of warming winter conditions and the reestablishment of a previously extirpated predator, the fisher (Martes pennanti), on regulatory mechanisms in a northern-adapted mammal, the porcupine (Erethizon dorsatum), along their southern range boundary. Using a long-term (17-year) capture–recapture data set, we (1) quantified the impacts of climate change and increased fisher predation on the survival of adult porcupines at their regional southern terminus, (2) assessed recruitment (via both adult fecundity and juvenile survival) of porcupines, and (3) modeled the relative importance of predation and winter conditions on the demography and population growth rate (λ). Severe winters and abundant predators interacted synergistically to reduce adult survivorship by as much as 44%, while expanding predator populations led to near reproductive failure among porcupines. Increasing predatory pressure, disruptions in this community module, and more frequent extreme winter weather events led to predicted extirpation within 50 years, whereas in the absence of predators, the population was viable. Our results provide a mechanistic understanding behind distributional shifts resulting from climate change and may be broadly relevant for predicting future distributional shifts in other northern-adapted mammalian species.
Data from: The escalatory Red Queen: population extinction and replacement following arms-race dynamics in poplar rust
Host-parasite systems provide convincing examples of Red Queen co-evolutionary dynamics. Yet, a key process underscored in Van Valen's theory – that arms-race dynamics can result in extinction – has never been documented. One reason for this may be that most sampling designs lack the breadth needed to illuminate the rapid pace of adaptation by pathogen populations. In this study we used a 25-years temporal sampling to decipher the demographic history of a plant pathogen: the poplar rust fungus, Melampsora larici-populina. A major adaptive event occurred in 1994 with the breakdown of R7 resistance carried by several poplar cultivars widely planted in Western Europe since 1982. The corresponding virulence rapidly spread in M. larici-populina populations, and nearly reached fixation in northern France, even on susceptible hosts. Using both temporal records of virulence profiles and temporal population genetic data, our analyses revealed that (i) R7 resistance breakdown resulted in the emergence of a unique and homogeneous genetic group, the so-called cultivated population, which predominated in northern France for about 20 years, (ii) selection for Vir7 individuals brought with it multiple other virulence types via hitchhiking, resulting in an overall increase in the population-wide number of virulence types and (iii) – above all – the emergence of the cultivated population superseded the initial population which predominated at the same place before R7 resistance breakdown. Our temporal analysis illustrates how antagonistic co-evolution can lead to population extinction and replacement, hence providing direct evidence for the escalation process which is at the core of Red Queen dynamics.
Data from: Control of signaling alignment during the dynamic courtship display of a jumping spider
During communication, alignment between signals and sensors can be critical. Signals are often best perceived from specific angles, and sensory systems can also exhibit strong directional biases. However, we know little about how animals establish and maintain such signaling alignment during communication. To investigate this, we characterized the spatial dynamics of visual courtship signaling in the jumping spider Habronattus pyrrithrix. The male performs forward-facing displays involving complex color and movement patterns, with distinct long- and short-range phases. The female views displays with 2 distinct eye types and can only perceive colors and fine patterns of male displays when they are presented in her frontal field of view. Whether and how courtship interactions produce such alignment between male display and female field of view is unknown. We recorded relative positions and orientations of both actors throughout courtship and established the role of each sex in maintaining signaling alignment. Males always oriented their displays toward the female. However, when females were free to move, male displays were consistently aligned with female principal eyes only during short-range courtship. When female position was fixed, signaling alignment consistently occurred during both phases, suggesting that female movement reduces communication efficacy. When female models were experimentally rotated to face away during courtship, males rarely repositioned themselves to re-align their display. However, males were more likely to present certain display elements after females turned to face them. Thus, although signaling alignment is a function of both sexes, males appear to rely on female behavior for effective communication.
Data from: Global gradients in vertebrate diversity predicted by historical area-productivity dynamics and contemporary environment
Broad-scale geographic gradients in species richness have now been extensively documented, but their historical underpinning is still not well understood. While the importance of productivity, temperature, and a scale-dependence of the determinants of diversity is broadly acknowledged, we here argue that limitation to a single analysis scale and data pseudoreplication have impeded an integrated evolutionary and ecological understanding of diversity gradients. We develop and apply a hierarchical analysis framework for global diversity gradients that incorporates an explicit accounting of past environmental variation and provides an appropriate measurement of richness. Due to environmental niche conservatism organisms generally reside in climatically defined bioregions, or "evolutionary arenas", characterized by in situ speciation and extinction. These bioregions differ in age and their total productivity and have varied over time in area and energy available for diversification. We show that, consistently across the four major terrestrial vertebrate groups, current-day species richness of the world's main 32 bioregions is best explained by a model that integrates area and productivity over geological time together with temperature. Adding finer-scale variation in energy availability as an ecological predictor of within-bioregional patterns of richness explains much of the remaining global variation in richness at the 110km grain. These results highlight the separate evolutionary and ecological effects of energy availability and provide a first conceptual and empirical integration of the key drivers of broad-scale richness gradients. Avoiding the pseudo-replication that impedes the evolutionary interpretation of non-hierarchical macroecological analyses, our findings integrate evolutionary and ecological mechanisms at their most relevant scales and offer a new synthesis regarding global diversity gradients.
Data from: Chronic nitrogen addition induces a cascade of plant community responses with both seasonal and progressive dynamics
Short-lived herbaceous plants provide a useful model to rapidly reveal how multiple generations of plants in natural plant communities of sensitive desert ecosystems will be affected by N deposition. We monitored dynamic responses of community structure, richness, evenness, density and biomass of herbaceous plants to experimental N addition (2:1 NH4+:NO3− added at 0, 0.5, 1, 3, 6 and 24 g N m− 2 a− 1) in three seasons in each of three years in the Gurbantunggut desert, a typical temperate desert of central Asia. We found clear rate-dependent and season-dependent effects of N deposition on each of these variables, in most cases becoming more obvious through time. N addition reduced plant richness, leading to a loss of about half of the species after three generations in the highest N application level. Evenness and density were relatively insensitive to all but the greatest levels of N addition for two generations, but negative effects emerged in the third generation. Biomass, both above and below ground, was non-linearly affected by N deposition. Low and intermediate levels of N deposition often increased biomass, whereas the highest level suppressed biomass. Stimulatory effects of intermediate N addition disappeared in the third generation. All of these responses are strongly interrelated in a cascade of changes. Notably, changes in biomass due to N deposition were mediated by declines in richness and evenness, and other changes in community structure, rather than solely being the direct outcome of release from limitation. The interrelationships between N deposition and the different plant community attributes change not only seasonally, but also progressively change through time. These temporal changes appear to be largely independent of interannual or seasonal climatic conditions.
Data from: Assessing the influence of temporal autocorrelations on the population dynamics of a disturbance specialist plant population in a random environment
Biological populations are strongly influenced by random variations in their environment, which are often autocorrelated in time. For disturbance specialist plant populations, the frequency and intensity of environmental stochasticity (via disturbances) can drive the qualitative nature of their population dynamics. In this article, we extended our earlier model to explore the effect of temporally autocorrelated disturbances on population persistence. In our earlier work, we only assumed disturbances were independent and identically distributed in time. We proved that the plant seed bank population converges in distribution, and we showed that the mean and variance in seed bank population size were both increasing functions of the autocorrelation coefficient for all parameter values considered, but the interplay between increasing population size and increasing variability caused interesting relationships between quasi-extinction probability and autocorrelation. For example, for populations with low seed survival, fecundity, and disturbance frequency, increasingly positive autocorrelated disturbances decreased quasi-extinction probability. Higher disturbance frequency coupled with low seed survival and fecundity caused a nonmontone relationship between autocorrelation and quasi-extinction, where increasingly positive autocorrelations eventually caused an increase in quasi-extinction probability. For higher seed survival, fecundity, and/or disturbance frequency, quasi-extinction probability was generally a monotonically increasing function of the autocorrelation coefficient.
Data from: Temporal genetic analysis of the endangered tidewater goby: metapopulation dynamics or drift in isolation?
Extinction and colonization dynamics are critical to understanding the evolution and conservation of metapopulations. However, traditional field studies of extinction–colonization are potentially fraught with detection bias and have rarely been validated. Here, we provide a comparison of molecular and field-based approaches for assessment of the extinction–colonization dynamics of tidewater goby (Eucyclogobius newberryi) in northern California. Our analysis of temporal genetic variation across 14 northern California tidewater goby populations failed to recover genetic change expected with extinction–colonization cycles. Similarly, analysis of site occupancy data from field studies (94 sites) indicated that extinction and colonization are very infrequent for our study populations. Comparison of the approaches indicated field data were subject to imperfect detection, and falsely implied extinction–colonization cycles in several instances. For northern California populations of tidewater goby, we interpret the strong genetic differentiation between populations and high degree of within-site temporal stability as consistent with a model of drift in the absence of migration, at least over the past 20–30 years. Our findings show that tidewater goby exhibit different population structures across their geographic range (extinction–colonization dynamics in the south vs. drift in isolation in the north). For northern populations, natural dispersal is too infrequent to be considered a viable approach for recolonizing extirpated populations, suggesting that species recovery will likely depend on artificial translocation in this region. More broadly, this work illustrates that temporal genetic analysis can be used in combination with field data to strengthen inference of extinction–colonization dynamics or as a stand-alone tool when field data are lacking.
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.