1,720,995 research outputs found
Evolutionary History, Extinction, and Environmental Variability Shape the Tropical and Subtropical Diversity Disparity of Terrestrial Mammals
No full textEMBARGO NOTE: This item is embargoed until 2026-08-01Tropical and subtropical moist forests are home to over half of all extant vertebrate species worldwide, yet they face increasing anthropogenic pressures that are degrading multiple facets of their diversity. High tropical species diversity has been hypothesized to have resulted from an evolutionary history of high species diversification in stable environments relative to temperate regions. However, recent studies have found that varying degrees of environmental variability and historical extinction of large-bodied vertebrates likely lead to the uneven distribution of species richness and body sizes among tropical regions (i.e., tropical diversity disparity) on different continents. However, little is known about how evolutionary history, historical extinction, and environmental variability have shaped the geographic differences among tropical regions in other facets of their diversity. This limited knowledge not only hinders our ability to unravel fundamental questions about drivers of biodiversity distributions but also to assess biodiversity changes that have implications for conservation given ongoing anthropogenetic pressure and environmental change.
Hence, to address this research gap, I tested the relative effects of evolutionary and macroecological drivers on 1) community structure, 2) predator-prey interactions, and 3) functional diversity of vertebrate assemblages in tropical and subtropical moist forests globally. I focused on mammals because this well-studied vertebrate class has species-level functional trait data, a well-resolved phylogeny, and community composition data available from both in-situ observations and the reconstructed ranges of extinct species.
First, using in-situ observations from 15 protected tropical forests worldwide, I found that the coupled phylogenetic and functional community structure of ground-dwelling mammals has been shaped by slow niche evolution, and phylogenetic clustering tendencies were predicted by colonization time. Second, I found geographic differences in the dietary breadth of carnivoran predators among 380 large mammal communities in the Neotropical, Afrotropical, and Indomalayan realms, for which speciation rates and present temperature seasonality supported dietary niche generalization while historical extinction led to dietary niche specialization. Thirdly, I found geographic differences in the vulnerability to functional diversity loss of tropical and subtropical moist forest mammals from historical and predicted future extinctions. Functional vulnerability to loss increased in mammal assemblages with slower niche evolution but decreased under greater present environmental variability. By integrating evolutionary and macroecological approaches, this dissertation has unraveled the essential roles of evolutionary history, extinction, and present environmental variability in shaping multiple facets of the diversity of extant forest mammals in the global tropics and subtropics
The Functional Side of Diversity: Effects of Environmental Conditions and Human Disturbance on Tropical Forest Mammal Communities
No full textBiodiversity provides many benefits to humans, but human activity is rapidly driving the loss of biodiversity, particularly in the tropics. Relevant species characteristics such as body size and diet, known as traits, provide insight into the biological roles of diverse species in an ecosystem. Little is known about the trait diversity of large mammals in tropical rainforests because of the reclusive nature of these species but increasing our knowledge can provide important information about critical ecosystem functions performed by mammals. In addition, many tropical mammals are currently endangered, threatening the persistence of their ecological functions. To address this pressing issue in this dissertation, I investigate how environmental and anthropogenic conditions affect mammal trait diversity in tropical rainforests around the world. This work overcomes prior data limitations by using data from the largest tropical forest remote camera monitoring network in the world. I assess the ecological drivers of trait diversity at an unprecedented scope and scale by coupling these data with cutting-edge remote sensing techniques.
First, I found that mammal trait diversity remained constant over the course of a decade within a Costa Rican national park surrounded by a human dominated landscape, potentially due to high functional redundancy among this mammal community. Second, in a global comparison of 15 tropical forest national parks, I found that trait diversity was higher in parks where the amount of healthy plant growth was higher, while human-induced extinctions reduced trait diversity and therefore degraded ecosystem functions. Third, I investigated how microhabitat characteristics affected species trait diversity in a national park in Tanzania and revealed that higher forest floor habitat surface area was associated with increased mammal trait diversity, and that carnivorous and social species showed preference for higher habitat surface area. Finally, in a global analysis of species spatial overlap, I identified that species with similar traits were more likely to co-occur in the presence of high human density, suggesting that human presence is altering the spatial distribution of ecosystem functions in protected areas, potentially leading to changes in species interactions and increased extinction risk. Together, this dissertation reveals the importance of functional traits for understanding environmental and anthropogenic effects on biodiversity and identify factors that structure the critical ecological roles of mammals in tropical rain forests
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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