1,721,021 research outputs found
Thermal plasticity within and across generations and its relevance to contemporary evolution
No full text122 pg.Understanding and predicting how populations will react to changes in the environment is a long-standing goal in evolutionary ecology. It is also of considerable practical importance, as anthropogenic changes stress species worldwide. The relevance of phenotypic plasticity is becoming more apparent as species are forced to cope with rapid changes in the environment. This dissertation explores ways in which phenotypic plasticity will play a major role in determining the future of populations. In Chapters 1 and 2, I evaluate a modeling framework that could be used to predict plastic changes in key life history traits of ectotherms brought about by temperature. This work, based on the metabolic theory of ecology (MTE), assumes that biological rates scale exponentially with temperature. I first show the validity of the MTE for predicting lifespan gradients within species and then apply this temperature-life history relationship to predict changes in ectotherms resulting from global temperature increases over the next 50 years. In Chapter 3, I experimentally test the plastic response of sheepshead minnows, Cyprinodon variegatus, an estuarine fish common to the east coast, to combinations of temperature (24, 29, 34??C) and food availability (60, 80, or 100% of maximum consumption). The thermal response of juvenile growth rate was mediated by food availability, while the age at maturation was independently affected by temperature and food. Notably, and despite very different thermal and feeding regimes, the fish matured within a small size window. In Chapters 4 and 5, I explore transgenerational plasticity (TGP) as a means to cope with temperature changes. When the temperature experienced by the parents acts as a reliable indicator of thermal offspring environment, a parent can "pre-program" offspring traits appropriate for the predicted environment. This transfer of information from parent to offspring has been termed TGP, and is well studied in plants and invertebrates. In these chapters, I show that thermal TGP has a strong effect in larval growth of sheepshead minnows. I also explore how transgenerational and phenotypic plasticity interact to shape the size of fish throughout life, and provide evidence suggesting that the TGP effect lasts for at least 2 generations.Advisor(s): Munch, Stephan B.. Committee Member(s): Conover, David O.Futuyma, Douglas J.Lonsdale, Darcy J.Travis, Joseph ;Stony Brook University Libraries. SBU Graduate School in Department of Marine and Atmospheric Science. Charles Taber (Dean of Graduate School)
Semiparametric Bayesian modeling of density dependence
No full text110 pg.Density dependence is a foundation of population biology. Analysis of population data with parametric models has long provided estimates of the maximum reproductive rate and the form of density dependence. These in turn determine the limit of sustainable harvest and the population's stability, respectively. However, standard parametric analyses of population data generate incorrect inferences of density dependence in noisy and short series. Therefore, there is a clear need for improved statistical methods for inferring density dependence. In this thesis, I developed new semiparametric Bayesian (SB) methods for estimating reproductive rates and for identifying forms of density dependence. Using simulated data, I validated the superiority of the SB methods to parametric alternatives. Then, I conducted SB analyses of 285 fish populations' datasets to estimate reproductive rates and to identify the forms of density dependence. I compared the results of the SB analyses with those based on standard parametric analyses of the same datasets. The SB analysis indicated that the forms of density dependence in 3.4% of the datasets are Allee effects, whereas the parametric analysis indicated 1.5%, suggesting that Allee effects are more than twice as often as previously thought. However, both the SB and the parametric model (the linear model) generated essentially the same estimates of the reproductive rates, indicating that the linear model may be a reasonable approach to inferring the reproductive rates of fish populations.Advisor(s): Munch, Stephan B; Cerrato, Robert M. Committee Member(s): Ferson, Scott ; Ginzburg, Lev ; Sugihara, George.Stony Brook University Libraries. SBU Graduate School in Department of Marine and Atmospheric Science. Charles Taber (Dean of Graduate School)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Trade-offs between accuracy and interpretability in von Bertalanffy random-effects models of growth
No full textBetter understanding of variation in growth will always be an important problem in ecology. Individual variation in growth can arise from a variety of processes; for example, individuals within a population vary in their intrinsic metabolic rates and behavioral traits, which may influence their foraging dynamics and access to resources. However, when adopting a growth model, we face trade-offs between model complexity, biological interpretability of parameters, and goodness of fit. We explore how different formulations of the von Bertalanffy growth function (vBGF) with individual random effects and environmental predictors affect these trade-offs. In the vBGF, the growth of an organism results from a dynamic balance between anabolic and catabolic processes. We start from a formulation of the vBGF that models the anabolic coefficient (q) as a function of the catabolic coefficient (k), a coefficient related to the properties of the environment (γ) and a parameter that determines the relative importance of behavior and environment in determining growth (ψ). We treat the vBGF parameters as a function of individual random effects and environmental variables. We use simulations to show how different functional forms and individual or group variability in the growth function's parameters provide a very flexible description of growth trajectories. We then consider a case study of two fish populations of Salmo marmoratus and Salmo trutta to test the goodness of fit and predictive power of the models, along with the biological interpretability of vBGF's parameters when using different model formulations. The best models, according to AIC, included individual variability in both k and γ and cohort as predictor of growth trajectories, and are consistent with the hypothesis that habitat selection is more important than behavioral and metabolic traits in determining lifetime growth trajectories of the two fish species. Model predictions of individual growth trajectories were largely more accurate than predictions based on mean size-at-age of fish. Our method shares information across individuals, and thus, for both fish populations investigated, allows using a single measurement early in the life of individual fish or cohort to obtain accurate predictions of lifetime individual or cohort size-at-age
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