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11,506 results for “Dynamics”
Spatiotemporal population dynamics of the Caddo Madtom (Noturus taylori), a narrow-range endemic of the Ouachita Highlands
<p>The Caddo Madtom, Noturus taylori, is endemic to three river drainages of the Ouachita Highlands in the southeastern United States. Conservation concern for N. taylori has been heightened by recent studies based on analyses of allozyme data suggesting population decline and a possible extirpation event, which lead to N. taylori petitioned for listing under the Endangered Species Act in 2011. The objective of this study was to determine if contemporary factors, historic processes, or a combination of both, using microsatellite DNA loci and mitochondrial (mt) DNA, have influenced patterns of genetic structuring for N. taylori to better inform conservation management strategies. Phylogeographic and Bayesian cluster analyses suggest that genetic structuring between Caddo and Ouachita river drainages was shaped by historical processes prior to construction of reservoir dams that dissect the drainages. We found no evidence that reservoir dams influenced contemporary patterns of genetic structure, thus it is likely that larger river courses, and life-history characteristics conducive to headwater habitats, play important roles in limiting gene flow between drainages, and to some extent within drainages. Genetic diversity of N. taylori was relatively high compared to other endangered madtom species; however, compared to the Ouachita River population, genetic diversity was significantly lower for the Caddo River population. Collectively, these results suggest that N. taylori populations are not heavily impaired, and the genetic variation and structuring is most attributable to historic processes. However, the endemic status and narrowly fragmented distribution still renders N. taylori populations vulnerable to extirpation or extinction by stochastic events.</p>
Metapopulation dynamics and foraging plasticity in a highly vagile seabird, the southern rockhopper penguin
<p>Population connectivity is driven by individual dispersal potential and modulated by natal philopatry. In seabirds, high vagility facilitates dispersal yet philopatry is also common, with foraging area overlap often correlated with population connectivity. We assess the interplay between these processes by studying past and current connectivity and foraging niche overlap among southern rockhopper penguin colonies of the coast of southern South America using genomic and stable isotope analyses. We found two distinct genetic clusters and detected low admixture between northern and southern colonies. Stable isotope analysis indicated niche variability between colonies, with Malvinas/Falklands colonies encompassing the species entire isotopic foraging niche, while the remaining colonies had smaller, nonoverlapping niches. A recently founded colony in continental Patagonia differed in isotopic niche width and position with Malvinas/Falklands colonies, its genetically identified founder population, suggesting the exploitation of novel foraging areas and/or prey items. Additionally, dispersing individuals found dead across the Patagonian shore in an unusual mortality event were also assigned to the northern cluster, suggesting northern individuals reach southern localities, but do not breed in these colonies. Facilitated by variability in foraging strategies, and especially during unfavorable conditions, the number of dispersing individuals may increase and enhance the probability of founding new colonies. Metapopulation demographic dynamics in seabirds should account for interannual variability in dispersal behavior and pay special attention to extreme climatic events, classically related to negative effects on population trends.</p>
Data from: Spatio-temporal dynamics of impulse responses to figure motion in optic flow neurons
White noise techniques have been used widely to investigate sensory systems in both vertebrates and invertebrates. White noise stimuli are powerful in their ability to rapidly generate data that help the experimenter decipher the spatio-temporal dynamics of neural and behavioral responses. One type of white noise stimuli, maximal length shift register sequences (m-sequences), have recently become particularly popular for extracting response kernels in insect motion vision. We here use such m-sequences to extract the impulse responses to figure motion in hoverfly lobula plate tangential cells (LPTCs). Figure motion is behaviorally important and many visually guided animals orient towards salient features in the surround. We show that LPTCs respond robustly to figure motion in the receptive field. The impulse response is scaled down in amplitude when the figure size is reduced, but its time course remains unaltered. However, a low contrast stimulus generates a slower response with a significantly longer time-to-peak and half-width. Impulse responses in females have a slower time-to-peak than males, but are otherwise similar. Finally we show that the shapes of the impulse response to a figure and a widefield stimulus are very similar, suggesting that the figure response could be coded by the same input as the widefield response.
Data from: Long-term population dynamics of dreissenid mussels (Dreissena polymorpha and D. rostriformis): a cross-system analysis
Dreissenid mussels (including the zebra mussel Dreissena polymorpha and the quagga mussel D. rostriformis) are among the world's most notorious invasive species, with large and widespread ecological and economic effects. However, their long‐term population dynamics are poorly known, even though these dynamics are critical to determining impacts and effective management. We gathered and analyzed 67 long‐term (>10 yr) data sets on dreissenid populations from lakes and rivers across Europe and North America. We addressed five questions: (1) How do Dreissena populations change through time? (2) Specifically, do Dreissena populations decline substantially after an initial outbreak phase? (3) Do different measures of population performance (biomass or density of settled animals, veliger density, recruitment of young) follow the same patterns through time? (4) How do the numbers or biomass of zebra mussels or of both species combined change after the quagga mussel arrives? (5) How does body size change over time? We also considered whether current data on long‐term dynamics of Dreissena populations are adequate for science and management. Individual Dreissena populations showed a wide range of temporal dynamics, but we could detect only two general patterns that applied across many populations: (1) Populations of both species increased rapidly in the first 1–2 yr after appearance, and (2) quagga mussels appeared later than zebra mussels and usually quickly caused large declines in zebra mussel populations. We found little evidence that combined Dreissena populations declined over the long term. Different measures of population performance were not congruent; the temporal dynamics of one life stage or population attribute cannot generally be accurately inferred from the dynamics of another. We found no consistent patterns in the long‐term dynamics of body size. The long‐term dynamics of Dreissena populations probably are driven by the ecological characteristics (e.g., predation, nutrient inputs, water temperature) and their temporal changes at individual sites rather than following a generalized time course that applies across many sites. Existing long‐term data sets on dreissenid populations, although clearly valuable, are inadequate to meet research and management needs. Data sets could be improved by standardizing sampling designs and methods, routinely collecting more variables, and increasing support.
Drivers of longitudinal telomere dynamics in the long-lived bat species, Myotis myotis
<p>Age related telomere shortening is considered a hallmark of the ageing process. <a name="_Hlk10395680">However, a recent cross-sectional ageing study of relative telomere length (rTL) in bats failed to detect a relationship between rTL and age in the long-lived genus <i>Myotis</i> (<i>M. myotis</i> and <i>M. bechsteinii</i>), suggesting some other factors are responsible for driving telomere dynamics in these species</a>. Here, we test if longitudinal rTL data show signatures of age-associated telomere attrition in <i>M. myotis</i> and differentiate which intrinsic or extrinsic factors are likely to drive telomere length dynamics.<a name="_Hlk30419416"> </a><a name="_Hlk26682824"></a><a name="_Hlk14445670">Using qPCR, rTL was measured in 504 samples from a marked population, from Brittany, France</a>, captured between 2013 and 2016. These represent 174 individuals with an age range of 0 to 7+ years. We find no significant relationship between rTL and age (<i>p</i> = 0.762), but demonstrate that within-individual rTL is highly variable from year to year. To investigate the heritability of rTL, a population pedigree (n=1744) was constructed from genotype data generated from a 16 microsatellite multiplex, designed from an initial, low coverage, Illumina genome for <i>M. myotis</i>. Heritability was estimated in a Bayesian, mixed model framework, and showed that little of the observed variance in rTL <a name="_Hlk513597000">is heritable (<i>h<sup>2</sup>= </i>0.06 – 0.01)</a>. Rather, correlations of first differences, correlating yearly changes in telomere length and weather variables, demonstrate that, during the spring transition, average temperature, minimum temperature, rainfall and windspeed correlate with changes in longitudinal telomere dynamics. <a name="_Hlk10396857">As such, rTL may represent a useful biomarker to quantify the physiological impact of various environmental stressors in bats.</a></p>
Data from: No release for the wicked: enemy release is dynamic and not associated with invasiveness
The enemy release hypothesis predicts that invasive species will receive less damage from enemies, compared to co-occurring native and noninvasive exotic species in their introduced range. However, release operating early in invasion could be lost over time and with increased range size as introduced species acquire new enemies. We used three years of data, from 61 plant species planted into common gardens, to determine whether (1) invasive, noninvasive exotic, and native species experience differential damage from insect herbivores and mammalian browsers, and (2) enemy release is lost with increased residence time and geographic spread in the introduced range. We find no evidence suggesting enemy release is a general mechanism contributing to invasiveness in this region. Invasive species received the most insect herbivory, and damage increased with longer residence times and larger range sizes at three spatial scales. Our results show that invasive and exotic species fail to escape enemies, particularly over longer temporal and larger spatial scales.
Extinction dynamics under extreme conservation threat: The flora of St. Helena
<p><span><span><span><span><span><span><span><span><span><span><span>The flora of the island of St Helena provides an amplified system for the study of extinction by reason of the island's high endemism, small size, vulnerable biota, length of time of severe disturbance (since 1502) and severity of threats. Endemic plants have been eliminated from 96.5% of St Helena by habitat loss. There are eight recorded extinctions in the vascular flora since 1771 giving an extinction rate of 581 extinctions per million species per year (E/MSY). This is considerably higher than background extinction rates, variously estimated at 1 or 0.1 E/MSY. We have no information for plant extinctions prior to 1771 but applying the same extinction rate to the period 1502 to 1771 suggests that there may be around ten unrecorded historical extinctions. We use census data and population decline estimates to project likely extinction forward in time. The projected overall extinction rate for the next 200 years is somewhat higher at 625 E/MSY. However, our data predict an extinction crunch in the next 50 years with 4 species out of the remaining 48 likely to become extinct during this period. It is interesting that during a period when the native plant areas dropped to 3.5% of the original, the extinction rate appears to have remained shallowly linear with under 30% of the endemic flora becoming extinct.</span></span></span></span></span></span></span></span></span></span></span></p>
Data from: Age-related sex differences in body condition and telomere dynamics of red-sided garter snakes
Life-history strategies vary dramatically between the sexes, which may drive divergence in sex-specific senescence and mortality rates. Telomeres are tandem nucleotide repeats that protect the ends of chromosomes from erosion during cell division. Telomeres have been implicated in senescence and mortality because they tend to shorten with stress, growth and age. We investigated age-specific telomere length in female and male red-sided garter snakes, Thamnophis sirtalis parietalis. We hypothesized that age-specific telomere length would differ between males and females given their divergent reproductive strategies. Male garter snakes emerge from hibernation with high levels of corticosterone, which facilitates energy mobilization to fuel mate-searching, courtship and mating behaviours during a two to four week aphagous breeding period at the den site. Conversely, females remain at the dens for only about 4 days and seem to invest more energy in growth and cellular maintenance, as they usually reproduce biennially. As male investment in reproduction involves a yearly bout of physiologically stressful activities, while females prioritize self-maintenance, we predicted male snakes would experience more age-specific telomere loss than females. We investigated this prediction using skeletochronology to determine the ages of individuals and qPCR to determine telomere length in a cross-sectional study. For both sexes, telomere length was positively related to body condition. Telomere length decreased with age in male garter snakes, but remained stable in female snakes. There was no correlation between telomere length and growth in either sex, suggesting that our results are a consequence of divergent selection on life histories of males and females. Different selection on the sexes may be the physiological consequence of the sexual dimorphism and mating system dynamics displayed by this species.
Data from: Monarch butterflies use an environmentally sensitive, internal timer to control overwintering dynamics
The monarch butterfly (Danaus plexippus) complements its iconic migration with diapause, a hormonally controlled developmental program that contributes to winter survival at overwintering sites. Although timing is a critical adaptive feature of diapause, how environmental cues are integrated with genetically-determined physiological mechanisms to time diapause development, particularly termination, is not well understood. In a design that subjected western North American monarchs to different environmental chamber conditions over time, we modularized constituent components of an environmentally-controlled, internal diapause termination timer. Using comparative transcriptomics, we identified molecular controllers of these specific diapause termination components. Calcium signaling mediated environmental sensitivity of the diapause timer, and we speculate that it is a key integrator of environmental condition (cold temperature) with downstream hormonal control of diapause. Juvenile hormone (JH) signaling changed spontaneously in diapause-inducing conditions, capacitating response to future environmental condition. Although JH is a major target of the internal timer, it is not itself the timer. Epigenetic mechanisms are implicated to be the proximate timing mechanism. Ecdysteroid, JH, and insulin/insulin-like peptide (IIS) signaling are major targets of the diapause program used to control response to permissive environmental conditions. Understanding the environmental and physiological mechanisms of diapause termination sheds light on fundamental properties of biological timing, and also helps inform expectations for how monarch populations may respond to future climate change.
Data from: Distinguishing distribution dynamics from temporary emigration using dynamic occupancy models
1. Dynamic occupancy models are popular for estimating dynamic distribution rates (colonization and extinction) from repeated presence/absence surveys of unmarked animals. This approach assumes closure among repeated samples within primary periods, allowing estimation of dynamic rates between these periods. However, the impact of temporary emigration (reversible changes in sampling availability) on dynamic rate estimates, has not been tested. 2. Using simulated data, we investigated the degree to which temporary emigration could mislead researchers interested in quantifying dynamics. We then compared results from three avian point count datasets to evaluate the likelihood that temporary emigration confounds estimates of dynamics for 19 species under a popular sampling protocol. 3. Simulated experiments indicated that when secondary periods were open to temporary emigration, presence of dynamics was correctly identified ≥ 95.1% of the time, and dynamic rate estimates were accurate. However, dynamic rate estimates were biased when secondary periods were closed to temporary emigration. In empirical datasets, dynamic occupancy models had greater support than closed models for all species when secondary sampling periods occurred in immediate succession (i.e., 3 samples within 10 minutes); however, our results suggest that this is because these estimates were heavily influenced by temporary emigration. When counts within a primary period were separated by 24-48 hours, we found evidence of dynamics for less than half of these species. We recommend an alternative sampling approach that allows accurate estimation of dynamic rates when temporary emigration is of no interest, and introduce a novel model for estimating both processes simultaneously in rare cases where they are both of biological interest. 4. Concern for violating the occupancy modeling closure assumption has led to widespread recommendations that samples within primary periods be conducted extremely close in time. However, this may not be the best approach when interest is in quantifying dynamic rates. While dynamic occupancy models provide estimates of 'colonization' and 'extinction,' these values do not inherently represent dynamics unless temporary emigration has been explicitly modeled, or accounted for with sampling design. Naiveté to this fact can result in incorrect conclusions about biological processes.
Exploring dynamical phase transitions with a Cavity-QED platform
<p>Atom-light interactions in optical cavities provide a platform for investigating many-body quantum physics in controlled environments. In particular, they have been proposed for the realization of collective quantum spin models with tunable long-range interactions. Besides the investigation of the rich steady-state phases that can arise due to the interplay between atom-light interactions and dissipation from the cavity, one opportunity offered by these systems is the study of out-of-equilibrium dynamical phases of matter precluded from existence at equilibrium . Moreover, these phases can display intriguing universal behaviors akin to standard equilibrium phase transitions. Here, we report the observation of distinct dynamical phases of matter in a nearly unitary implementation of the collective XY spin model with transverse and longitudinal fields simulated via an ensemble of ∼10<sup>6</sup> <sup>88</sup>Sr atoms. The unique properties of our cavity-QED platform allow us to probe thedependence of the associated dynamical phase transitions on parameter space, system size and initial state. In the spirit of quantum simulation our observations can be linked to similar dynamical phases featured in a range of related scystems, including the Josephson effect in superfluid helium , coupled atomic and solid-state polariton condensates, with complementary types of control including the magnitude and sign of Hamiltonian parameters. Moreover, our system offers potential for the generation of metrologically useful entangled states in optical transitions, which can enable real metrological gains via quantum enhancement in state-of-the-art atomic clocks.</p>
Data from: Effects of soil type and light on height growth, biomass partitioning, and nitrogen dynamics on 22 species of tropical dry forest tree seedlings: comparisons between legumes and nonlegumes
PREMISE OF THE STUDY: The seedling stage is particularly vulnerable to resource limitation, with potential consequences for community composition. We investigated how light and soil variation affected early growth, biomass partitioning, morphology, and physiology of 22 tree species common in tropical dry forest, including eight legumes. Our hypothesis was that legume seedlings are better at taking advantage of increased resource availability, which contributes to their successful regeneration in tropical dry forests. METHODS: We grew seedlings in a full-factorial design under two light levels in two soil types that differed in nutrient concentrations and soil moisture. We measured height biweekly and, at final harvest, biomass partitioning, internode segments, leaf carbon, nitrogen, δ 13 C, and δ 15 N. KEY RESULTS: Legumes initially grew taller and maintained that height advantage over time under all experimental conditions. Legumes also had the highest final total biomass and water-use efficiency in the high-light and high-resource soil. For nitrogen-fixing legumes, the amount of nitrogen derived from fixation was highest in the richer soil. Although seed mass tended to be larger in legumes, seed size alone did not account for all the differences between legumes and nonlegumes. Both belowground and aboveground resources were limiting to early seedling growth and function. CONCLUSIONS: Legumes may have a different regeneration niche, in that they germinate rapidly and grow taller than other species immediately after germination, maximizing their performance when light and belowground resources are readily available, and potentially permitting them to take advantage of high light, nutrient, and water availability at the beginning of the wet season.
Learning from dynamic traits: Seasonal shifts yield insights into ecophysiological tradeoffs across scales from macroevolutionary to intra-individual
<p><strong>Premise of the Research.</strong> Phylogenetic comparative methods provide a powerful approach for exploring the macroevolution of plant functional traits. Such approaches can uncover trait-trait correlations through evolutionary time, as well as provide evidence of the role of traits in adaptation across environmental gradients. For continuous traits, most phylogenetic comparative approaches to date employ a single trait value per species, often a mean of sampled individuals, or alternatively incorporate intraspecific variation as a distribution around such a mean. It has been known for quite some time that many of the most physiologically and ecologically important plant traits are actually highly plastic, changing dynamically across a growing season, with whole-plant development, or in response to environmental conditions. Here we demonstrate one possible approach to assessing the evolution of such dynamic traits, the use of function-valued phylogenetic comparative methods.<br> <strong>Methodology.</strong> Leaf traits were sampled across 25 taxa in the genus <em>Cornus</em> at six time points throughout the growing season in a common garden context, followed by contrasting sets of alternative analyses to demonstrate the consequences of researcher decisions on study conclusions.<br> <strong>Pivotal Results. </strong>The vast majority of assessed traits exhibit substantial seasonal shifts. These shifts cause traditional macroevolutionary correlations assessed at different sampling dates to yield conflicting results. Function-valued approaches indicate that seasonal shifts in many traits are evolutionarily correlated, with implications for the origin of trait-trait tradeoffs. Seasonal trait plasticity is also evolutionarily correlated with native habitat environmental gradients across <em>Cornus</em>.<br> <strong>Conclusions.</strong> Because a very large number of plant functional traits are not fixed, but vary dynamically over time or with environmental conditions, stronger insights into the evolution of plant functional traits can emerge when this dynamism is explicitly incorporated into phylogenetic comparative approaches. We encourage the adoption of such approaches, as well as the development of better tools for doing so.</p>
Evolutionary dynamics of structural variation at a key locus for color pattern diversification in cichlid fishes
<p>Color patterns in African cichlid fishes vary spectacularly. Although phylogenetic analysis showed already 30 years ago that many color patterns evolved repeatedly in these adaptive radiations, only recently have we begun to understand the genomic basis of color variation. Horizontal stripe patterns evolved and were lost several times independently across the adaptive radiations of Lake Victoria, Malawi, and Tanganyika and regulatory evolution of agouti-related peptide 2 (agrp2/asip2b) has been linked to this phenotypically labile trait. Here, we asked whether the agrp2 locus exhibits particular characteristics that facilitate divergence in color patterns. Based on comparative genomic analyses, we discovered several recent duplications, insertions, and deletions. Interestingly, one of these events resulted in a tandem duplication of the last exon of agrp2. The duplication likely precedes the East African radiations that started 8–12 Ma, is not fixed within any of the radiations, and is found to vary even within some species. Moreover, we also observed variation in copy number (two to five copies) and secondary loss of the duplication, illustrating a surprising dynamic at this locus that possibly promoted functional divergence of agrp2. Our work suggests that such instances of exon duplications are a neglected mechanism potentially involved in the repeated evolution and diversification that deserves more attention.</p>
Data from: Context-dependent defences in turtle ants: resource defensibility and threat level induce dynamic shifts in soldier deployment
1. Induced defences involve the dynamic deployment of limited and specialized defensive resources across multiple locations, to maximize organismal defensive function and fitness. They have been studied intensively in plants and solitary animals, but the induced defences of complex animal societies are poorly understood by comparison, despite the coordinated defensive actions of these taxa. 2. Here, we ask whether the level of environmental danger induces shifts in the deployment of limited and morphologically specialized soldiers across multiple nests in colonies of the turtle ant Cephalotes rohweri. Specifically, we test whether less defensible nests induce greater soldier deployment, and whether elevated enemy threat induced further increases in deployment, or reduced deployment consistent with a risk-limiting strategy. 3. We used colony-collection data to provide natural ecological context to our experiments, a field experiment to address how nest-entrance defensibility and soldier number impact defensive performance, and laboratory experiments to test whether differences in nest defensibility and threat level induce dynamic shifts in soldier deployment to new nests. 4. Less defensible nests were lost rapidly in our field experiment, irrespective of soldier number, but soldier deployment significantly increased survivorship of more defensible nests. Concordantly, less defensible nests induced the deployment of more soldiers per nest under low threat in laboratory experiments. Nevertheless, high-threat conditions revealed a risk-limiting soldier deployment strategy: with more danger, the number of soldiers per nest was significantly reduced in less defensible nests, as was the overall number of new soldier-defended nests. Total deployment to new nests was also consistently lower under high threat, dropping from 40% to 30% across colonies. 5. Induced soldier-based defences in turtle ants are therefore context-dependent, and dynamically scaled back at multiple levels when the environment is more dangerous. This dynamic, risk-limiting strategy is in strong contrast to stable patterns of soldier production in ants, and to typical task-allocation dynamics in members of the worker caste. Moreover, these findings establish that the evolution of specialized defensive agents can be coupled with sophisticated and inducible deployment strategies in complex social taxa, as we see for organisms at other levels of biological complexity.
Data from: Variation in population structure and dynamics of montane forest tree species in Ethiopia guide priorities for conservation and research
The greatest extent of Afromontane environments in the world is found in Ethiopia. These areas support exceptional biodiversity, but forest cover and ecological integrity have declined sharply in recent decades. Conservation and management efforts are hampered in part by an inadequate understanding of the basic ecology of major tree species. We investigated population structure and inferred population dynamics from size frequency distributions of 22 forest tree species encountered in montane forests of Ethiopia. We collected new empirical data from four sites in the Bale Mountains, where some of the country's most extensive and least disturbed forests remain, and conducted a systematic review and analysis of all such studies that reported population structure for one or more of these species in Ethiopia. Thirteen widespread montane tree species showed a reverse-J size distribution, indicating a relatively stable population structure. Six other species had size-frequency distributions that indicate episodic recruitment and/or removal of certain size classes. Specific causes of these patterns are uncertain: they may involve timber harvesting, herbivory, fire, or natural disturbances, but patterns were inconsistent and locality dependent. For three other tree species, existing data are inadequate for any interpretation of population structure and dynamics. A species of particular conservation concern that emerged from this analysis was Hagenia abyssinica, which was found in all areas to consist only of larger individuals with no recent recruitment. For management and conservation purposes, the species in most urgent need of new research are those with inadequate or inconsistent data, and H. abyssinica..
Data from: Age-structure and transient dynamics in epidemiological systems
Mathematical models of childhood diseases date back to the early twentieth century. In several cases, models that make the simplifying assumption of homogeneous time-dependent transmission rates give good agreement with data in the absence of secular trends in population demography or transmission. The prime example is afforded by the dynamics of measles in industrialized countries in the pre-vaccine era. Accurate description of the transient dynamics following the introduction of routine vaccination has proved more challenging, however. This is true even in the case of measles which has a well-understood natural history and an effective vaccine that confers long-lasting protection against infection. Here, to shed light on the causes of this problem, we demonstrate that, while the dynamics of homogeneous and age-structured models can be qualitatively similar in the absence of vaccination, they diverge subsequent to vaccine roll-out. In particular, we show that immunization induces changes in transmission rates, which in turn reshapes the age distribution of infection prevalence, which effectively modulates the amplitude of seasonality in such systems. To examine this phenomenon empirically, we fit transmission models to measles notification data from London that span the introduction of the vaccine. We find that a simple age-structured model provides a much better fit to the data than does a homogeneous model, especially in the transition period from the pre-vaccine to the vaccine era. Thus, we propose that age structure and heterogeneities in contact rates are critical features needed to accurately capture transient dynamics in the presence of secular trends.
An improved understanding of ungulate population dynamics using count data: insights from western Montana
<p class="FirstParagraph">Understanding the dynamics of ungulate populations is critical given their ecological and economic importance. In particular, the ability to evaluate the evidence for potential drivers of variation in population trajectories is important for informed management. However, the use of age ratio data (e.g., juveniles:adult females) as an index of variation in population dynamics is hindered by a lack of statistical power and difficult interpretation. Here, we show that the use of a population model based on count, classification and harvest data can dramatically improve the understanding of ungulate population dynamics by: 1) providing estimates of vital rates (e.g., per capita recruitment and population growth) that are easier to interpret and more useful to managers than age ratios and 2) increasing the power to assess potential sources of variation in key vital rates. We used a time series of elk (<i>Cervus canadensis</i>) spring count and classification data (2004 to 2016) and fall harvest data from hunting districts in western Montana to construct a population model to estimate vital rates and assess evidence for an association between a series of environmental covariates and indices of predator abundance on per capita recruitment rates of elk calves. Our results suggest that per capita recruitment rates were negatively associated with cold and wet springs, and severe winters, and positively associated with summer precipitation. In contrast, an analysis of the raw age ratio data failed to detect these relationships. Our approach based on a population model provided estimates of the region-wide mean per capita recruitment rate (mean = 0.25, 90% CI = 0.21, 0.29), temporal variation in hunting-district-specific recruitment rates (minimum = 0.09; 90% CI = [0.07, 0.11], maximum = 0.43; 90% CI = [0.38, 0.48]), and annual population growth rates (minimum = 0.83; 90% CI = [0.78, 0.87], maximum = 1.20; 90% CI = [1.11, 1.29]). We recommend using routinely collected population count and classification data and a population modeling approach rather than interpreting estimated age ratios as a substantial improvement in understanding population dynamics.</p>
Dynamic inferential NOx emission prediction model with delay estimation for SCR de-NOx process in coal-fired power plants
<p><span><span>The selective catalytic reduction (SCR) de</span><span>-</span><span>NO<sub>x</sub> </span><span>process in coal-fired power plants not only displays nonlinearity, large inertia, and time variation but also a lag in NO<sub>x</sub> analysis; </span><span>hence,</span><span> it is difficult to obtain an accurate model </span><span>that </span><span>can be used to control NH<sub>3</sub> injection </span><span>during changes in the </span><span>operating state. </span><span>In this work,</span><span> a novel dynamic inferential model with delay estimation was proposed for NO<sub>x</sub> emission prediction. First, k-nearest neighbour mutual information (knnMI) was used to estimate the time-delay of the descriptor variables, followed by reconstruction of the phase space of the model data. Second, multi-scale wavelet kernel partial least square (mwKPLS) was</span><span> used</span><span> to improve the prediction ability, </span><span>and this was followed by verification using </span><span>benchmark dataset experiments. Finally, the delay-time difference (DTD) method and feedback correction strategy </span><span>were </span><span>proposed to deal with the time variation of the SCR de</span><span>-</span><span>NO<sub>x</sub> process.</span> <span>Through the analysis of the </span><span>experimental field data </span><span>in the</span> <span>steady state, </span><span>the variable</span><span> state and </span><span>the </span>NO<sub>x</sub> analyser blowback process<span>, the results proved that</span><span> this dynamic model has </span><span>high prediction accuracy</span><span> during</span><span> state changes and can </span><span>realize</span><span> advance prediction of the NO<sub>x</sub> emission. </span></span></p>
Over 80 years without major disturbance, late successional Białowieża woodlands exhibit complex dynamism, with coherent compositional shifts towards true old‐growth conditions
<p>1. Controversies about successional dynamics of woodland communities have a long history, dating back to the classical debates between Clements and Gleason and continuing into the present. These debates have largely concerned the predictability or convergence of forest developmental trends as well as the relative importance of different mechanisms and forces driving forest succession. However, opportunities for rigorous testing of competing hypotheses are limited, mainly because plot-based studies of forest vegetation spanning more than a decade are scarce and even fewer concern late-successional stands.</p> <p>2. We exploit a unique long-term data set from mesic temperate forests of eastern Poland, spanning ca. 80 years (1936-2012) in strictly protected, late-successional woodlands assigned to seven different 'structural types'. We use non-metric multidimensional scaling to assess stability of species composition over the study period. We examine predictability of composition and change trajectories over time using Mantel statistics, and we examine changes in distributions of dissimilarity indices to assess convergence or divergence at the examined time and spatial scales.</p> <p>3. Tree communities in Białowieża Forest have changed substantially over the last eight decades. Several species (aspen, birch, pine, oak, ash, maple and spruce) exhibited large decreases in density, while few other species (especially hornbeam and lime) have increased in importance across a wide range of initial compositional types. Forest types recognized in earlier periods have become much less distinguishable. Metrics do not yet show clear successional convergence, mainly due to a) declines in the previously broadly distributed spruce and b) persistence of large individuals of intermediate, long-lived species (even though these species lack significant regeneration).</p> <p>4. Synthesis. Late-successional woodland communities of Białowieża Forest are clearly dynamic and do not show quasi-equilibrial properties often assumed of old-growth forests. Forest types previously recognized as distinct have become progressively less differentiated. Plausible explanations invoke alteration in competitive relationships due to complex changes in environment, including climate, N deposition, natural and human disturbance, and ungulate herbivory over 70 years. Hornbeam and lime have been favored over spruce, pine, oak and birch, although the resulting successional convergence is far from complete at this time. In the absence of major disturbance, we expect future decades to show continued and successional homogenization.</p>
ScienceDex guides
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These curated guides explain access requirements, typical timelines, costs, and reuse considerations for widely used research datasets.
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.