1,720,986 research outputs found
Severe limitations of the FEve metric of functional evenness and some alternative metrics
No full textAbstract The metric of functional evenness FEve is an example of how approaches to conceptualizing and measuring functional variability may go astray. This index has several critical conceptual and practical drawbacks: Different values of the FEve index for the same community can be obtained if the species have unequal species abundances; this result is highly likely if most of the traits are categorical. Very minor differences in even one pairwise distance can result in very different values of FEve. FEve uses only a fraction of the information contained in the matrix of species distances. Counterintuitively, this can cause very similar FEve scores for communities with substantially different patterns of species dispersal in trait space. FEve is a valid metric only if all species have exactly the same abundances. However, the meaning of FEve in such an instance is unclear as the purpose of the metric is to measure the variability of abundances in trait space. We recommend not using the FEve metric in studies of functional variability. Given the wide usage of FEve index over the last decade, the validity of the conclusions based on those estimates is in question. Instead, we suggest three alternative metrics that combine variability in species distances in trait space with abundance in various ways. More broadly, we recommend that researchers think about which community properties (e.g., trait distances of a focus species to the nearest neighbor or all other species, variability of pairwise interactions between species) they want to measure and pick from among the appropriate metrics
Ecosystem Function, Principles of
No full textDuring the last few decades, scientists have extensively researched the relationship between biodiversity, ecosystem functions, and ecosystem services. Biodiversity is undergoing an unprecedented decline in human history, while ecosystem functions and services are deteriorating on a global scale. Ecosystems are composed of communities of organisms that interact with one another and the abiotic environment. The interactions of organisms and their environment are represented in processes (e.g., photosynthesis, cycling of nutrients) that are called ecosystem functions (e.g., primary productivity) and represent the capacity of ecosystems to provide ecosystem services. An understanding of how biodiversity and ecosystem functioning are related is necessary for determining how to sustain ecosystem services and therefore future generations. This chapter synthesizes key concepts from relevant scientific publications concerning ecosystem functions and their relationship to biodiversity and ecosystem services.Fil: Barral, María Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible - Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; Argentina. Universidad FASTA. Facultad de Ingeniería; ArgentinaFil: Sirimarco, Marina Ximena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible - Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; Argentina. Universidad FASTA. Facultad de Ingeniería; ArgentinaFil: Ross, Virginia. Dartmouth College; Estados UnidosFil: Wall, Diana. State University of Colorado - Fort Collins; Estados Unido
Threatened species: classification systems and their applications
No full textThreatened species are those species most at risk of becoming extinct in the near future. Multiple systems have been created to classify species according to their extinction risk at national, regional and global levels. The resulting threatened species assessments can provide valuable insight into current biodiversity status and trends. Threatened species lists have become important tools for conservation and are widely influential in informing national and international conservation policies and priority-setting strategies, conservation planning and resource allocation, directing scientific research and generating public awareness of the mounting biodiversity crisis and its impact on human well-being
Antarctic ecosystems
No full textTerrestrial environments of Antarctica include some of the most extreme on Earth, challenging the very existence of life itself. This article outlines briefly the geological and biological history of the continent, leading on to the conditions currently experienced, before describing its terrestrial biogeography and biota. Major determinants of terrestrial biodiversity and ecosystem function are discussed and consideration given to natural and human-induced processes of ecosystem development and change
<i>In Situ, Ex Situ</i> Conservation
No full textIn situ and ex situ conservation focuses on the maintenance of species diversity within or away from their natural habitats, respectively. This article outlines why conservation is needed, the major threats to species, and how diversity is maintained at the ecosystem, species, and genetic levels. A model for biodiversity conservation is presented which includes: selection of target taxa for conservation, gene pool concepts, ecogeographic surveys, field surveying, clarification of conservation objectives, the two basic conservation strategies (in situ and ex situ) and the range of conservation techniques, and ways that conservation is often linked to some form of utilization.</p
Old and new challenges in using species diversity for assessing biodiversity
No full textAlthough the maintenance of diversity of living systems is critical for ecosystem functioning, the accelerating pace of global change is threatening its preservation. Standardized methods for biodiversity assessment and monitoring are needed. Species diversity is one of the most widely adopted metrics for assessing patterns and processes of biodiversity, at both ecological and biogeographic scales. However, those perspectives differ because of the types of data that can be feasibly collected, resulting in differences in the questions that can be addressed. Despite a theoretical consensus on diversity metrics, standardized methods for its measurement are lacking, especially at the scales needed to monitor biodiversity for conservation and management purposes. We review the conceptual framework for species diversity, examine common metrics, and explore their use for biodiversity conservation and management. Key differences in diversity measures at ecological and biogeographic scales are the completeness of species lists and the ability to include information on species abundances. We analyse the major pitfalls and problems with quantitative measurement of species diversity, look at the use of weighting measures by phylogenetic distance, discuss potential solutions and propose a research agenda to solve the major existing problems
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
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