Biological diversity would apparently seem the most intuitive and easily studied of all the ecological concepts. However, in practice biodiversity has suffered from great number of definitions that vary with the specific needs of the different researchers, thus making it extremely confusing as an ecological concept. In this paper, I shortly review the concept of biodiversity showing that there exists a substantial ambiguity among ecologists as far as biodiversity conceptualization and evaluation is concerned. I conclude that, due to this major (...) disagreement on its very nature, biodiversity may be defined simply as a set of multivariate summary statistics for quantifying different characteristics of community structure. (shrink)

A desirable property of a diversity index is strict concavity. This implies that the pooled diversity of a given community sample is greater than or equal to but not less than the weighted mean of the diversity values of the constituting plots. For a strict concave diversity index, such as species richness S, Shannon''s entropy H or Simpson''s index 1-D, the pooled diversity of a given community sample can be partitioned into two non-negative, additive components: average within-plot diversity and between-plot (...) diversity. As a result, species diversity can be summarized at various scales measuring all diversity components in the same units. Conversely, violation of strict concavity would imply the non-interpretable result of a negative diversity among community plots. In this paper, I apply this additive partition model generally adopted for traditional diversity measures to Aczél and Daróczy''s generalized entropy of type . In this way, a parametric measure of -diversity is derived as the ratio between the pooled sample diversity and the average within-plot diversity that represents the parametric analogue of Whittaker''s -diversity for data on species relative abundances. (shrink)

Community diversity has been studied extensively in relation to its effects on ecosystem functioning. Testing the consequences of diversity on ecosystem processes will require measures to be available based on a rigorous conceptualization of their very meaning. In the last decades, literally dozens of measures of diversity have been proposed. However, rather than using unrelated metrics, we need to identify their separate components so that possible links between them and ecosystem functioning can be examined using an agreed-upon language. In this (...) paper, first, a short overview on new and old measures of community diversity is presented. Next, I propose a general framework in which most of the existing measures of diversity are sorted into four interrelated semantic classes: richness, abundance-weighted diversity, evenness and divergence. In this view, this paper constitutes an attempt to organize the very large number of existing diversity measures avoiding ambiguities in the meaning of the different facets of community diversity. (shrink)

Traditional diversity measures such as the Shannon entropy are generally computed from the species' relative abundance vector of a given community to the exclusion of species' absolute abundances. In this paper, I first mention some examples where the total information content associated with a given community may be more adequate than Shannon's average information content for a better understanding of ecosystem functioning. Next, I propose a parametric measure of statistical information that contains both Shannon's entropy and total information content as (...) special cases of this more general function. (shrink)

This reply paper includes two brief remarks in rejoinder to the commentary papers of Myers and Patil, Podani, and Sarkar. The first observation concerns the fundamental nature of ecological diversity measures, while the second one specifically addresses some interesting mathematical connections between α- and β-diversity.

Why do we remember the past and not the future? What does it mean for time to "flow"? Do we exist in time or does time exist in us? In lyric, accessible prose, Carlo Rovelli invites us to consider questions about the nature of time that continue to puzzle physicists and philosophers alike. For most readers this is unfamiliar terrain. We all experience time, but the more scientists learn about it, the more mysterious it remains. We think of it (...) as uniform and universal, moving steadily from past to future, measured by clocks. Rovelli tears down these assumptions one by one, revealing a strange universe where at the most fundamental level time disappears. He explains how the theory of quantum gravity attempts to understand and give meaning to the resulting extreme landscape of this timeless world. Weaving together ideas from philosophy, science and literature, he suggests that our perception of the flow of time depends on our perspective, better understood starting from the structure of our brain and emotions than from the physical universe. (shrink)

Introduction: Mexican Philosophy: What Is It and Why It Matters -- Relajo -- Nepantla -- Zozobra -- Corazonada -- Tik -- Figure of the World -- Mexistentialism.

I am a theoretical physicist, and, following Aristotles' injunction (Aristotle, Physics III, 202b 34), I do consider it my responsibility to discuss the problem of the notion of infinity in the world--in particular, to "inquire whether there is such a thing or not." I will do so here by illustrating some aspects of the notion of infinity in the natural sciences.

"¿Cómo salimos del silencio? Este y otros interrogantes fluyen como una constante en esta minuciosa investigación, que ofrece un enfoque panorámico sobre el estudio de las lenguas. En palabras de Carlos Fuentes, el encanto de esta obra está en que aborda cosas que creíamos saber sobre las lenguas y descubre lo que no sabíamos sobre lo que creíamos saber" -- Prové de l'editor.

Based on existing moral philosophy, Carlo Prisco introduces Eusebism as a way to develop new perspectives on being and relating by offering practical tools to approach everyday life and transfer good thought into action.

All human civilizations have thought that the world was made of sky above and the Earth below. All except one. For the Greeks, the Earth was a rock floating in space, and under the earth there was no ground, no turtles, nor the gigantic columns of which the Bible speaks. How did the Greeks understand that the Earth is suspended in nothingness? Who understood this and how? It is this unique "scientific revolution" of Anaximander of which the author speaks, which (...) Karl Popper called "one of the most daring ideas, revolutionary and portentous in the entire history of human thought" The concern is with the conflict that was opened, still burning, with the nature of scientific thought, its critical and rebellious character, the force with which it subverts the order of things and our image of the world of scientific knowledge, and the highly effective "error" at the same time --as we teach physics in the twentieth century. Speaking of Anaximander, the author invites us to reflect on what his ideas mean to the scientific revolution opened by Einstein. (shrink)

The degree to which abundances are divided equitably among community species or evenness is a basic property of any biological community. Several evenness indices have been proposed to summarize community structure. However, despite their potential applicability in ecological research, none seems to be generally preferred. In this paper we show that, unlike other evenness indices without any clear information-theoretical meaning, Hill's parametric diversity measure E ,0 has an immediate relation to Rényi's generalized information. Therefore, E ,0 might be adequate for (...) summarizing community structure within the context of a general theoretical framework of diversity analysis based on information theory. (shrink)

Traditional diversity indices are computed from the abundances of species present and are insensitive to taxonomic differences between species. However, a community in which most species belong to the same genus is intuitively less diverse than another community with a similar number of species distributed more evenly between genera. In this paper, we propose an information-theoretical measure of taxonomic diversity that reflects both the abundances and taxonomic distinctness of the species. Unlike previous measures of taxonomic diversity, such as Rao's quadratic (...) entropy, in this new measure the analyzed taxonomic properties are associated with the single species instead of species pairs. (shrink)

The degree to which abundances are evenly divided among the species of a given community is a basic property of any biological community. Several evenness indices have thus far been proposed in ecological literature. However, despite their vast potential applicability in ecological research, none seems to be generally preferred. In this paper, I first summarize the basic requirements that evenness measures should meet to adequately behave in ecological studies. Then, I discuss the major drawbacks of these requirements and propose an (...) alternative family of measures that are based on the notion of specificity used in fuzzy set theory for measuring the uncertainty associated with a fuzzy set. (shrink)

This book recovers Dionysus and Apollo as the twin conceptual personae of life's dual rhythm in an attempt to redesign contemporary theory through the reciprocal affirmation of event and form, earth and world, dance and philosophy.

La literatura nacida en ámbito monástico o asociada al mismo, ofrece aspectos ponderables sobre la antropología teológica. Señalaremos algunos conceptos al respecto, sobre todo a partir de la memoria y la construcción de la propia identidad. El Himno de la Perla se caracteriza por haber sido objeto de disímiles interpretaciones, siendo considerado desde un texto iranio a una composición gnóstica. Presentaremos una lectura narrativa, tomando como categorías de aproximación el recuerdo y el olvido, a partir de las cuales plantearemos un (...) posible vínculo entre el Himno de la Perla y el Pseudo-Macario. Quispel, ya en 1967, estableció un parentesco de Teología (Verwandschaft der Teologie), destacando que también se encuentran paralelismos de forma. Tomando en cuenta este notable aporte, procuraremos indagar en la literatura pseudo-macariana acerca de tales parentescos con el Himno de la Perla y la literatura sobre el apóstol Tomás. (shrink)

Multi-Task Learning tries to improve the learning process of different tasks by solving them simultaneously. A popular Multi-Task Learning formulation for SVM is to combine common and task-specific parts. Other approaches rely on using a Graph Laplacian regularizer. Here we propose a combination of these two approaches that can be applied to L1, L2 and LS-SVMs. We also propose an algorithm to iteratively learn the graph adjacency matrix used in the Laplacian regularization. We test our proposal with synthetic and real (...) problems, both in regression and classification settings. When the task structure is present, we show that our model is able to detect it, which leads to better results, and we also show it to be competitive even when this structure is not present. (shrink)

An enduring concern for educational policy in many affluent countries is the endemic nature of educational inequalities that are predominately located in poor urban contexts. Given the inabilities of school reform per se to deal with these inequalities, the paper focuses on issues of scarcity and spatial processes that are implicated in the formation of young people's educational identities - identities that then mediate the conversion of educational resources into educational attainments or achievements.