Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

The importance of large breeding individuals for maintaining the health of marine fish and invertebrate populations has long been recognized. Unfortunately, decades of human harvesting that preferentially remove larger individuals have led to drastic reductions in body sizes of many of these species. Such size-selective harvesting is particularly worrisome for sequentially hermaphroditic species where the larger size classes are composed primarily of one sex. Whether these species can maintain stable sex ratios under sustained harvesting pressure depends on the level of plasticity of their life-history traits. Here, we show that populations of a marine limpet (Lottia gigantea) can adjust a fundamental aspect of their life history (the timing of sex change) when subjected to size-selective harvesting. As predicted by theoretical models, individuals from harvested populations change sex at smaller sizes and grow at slower rates compared to individuals from protected populations. In addition, the relative size at which the change from male to female occurs remains constant (?0.75; size at sex change/maximum size) across populations, regardless of harvesting pressure. Our results show that population-level demographic and life-history data, in conjunction with existing theory, can be sufficient to predict the responses of sequential hermaphrodites to harvesting pressure. Furthermore, they suggest such species can potentially adapt to size-selective harvesting

Phenomenological Ontology: Turning to Practice

Ontology is often reduced to epistemology, that is, to yet another conceptual category for discussion. We do this because historically we are comfortable with the mental and are habituated to reducing everything to mental representation. But ontology is not rational discussion of ‘what is’; it is, rather, the cultivation of contact with ‘what is.’ And that means practice. We shy away from practice as though it is some native witchcraft, and prefer instead to think about it. The present paper proposes that instead of merely thinking about ontology, we practice toward its realization. I call this phenomenological ontology. Ontological practice is not native voodoo-ism, nor New-Ageism, but has been part of every culture, historically submerged due to the dominance of epistemology and Kantianism. We need to get out of amnesia and rediscover ontological practice. Hence, this can also be called the practice of anamnesis, which forms a part of the discussion here. The essay outlines a 3-part ontological practice that, at the broadest level, can be derived from most source events of cultures—these are a) affective transfer, or a serious effort to connect thought and affect; b) resisting subjectification through objects; and c) recuperation of cultural memory

Gradientes de Intesidade: o espaço háptico deleuziano e os três "erres" do currículo

Seguindo Deleuze, faço uma tentativa para ir além da noção, própria do senso comum, que concebe o espaço, nas relações educacionais, como homogêneo e mero ambiente. Proponho uma espécie de "diferenciação espacial" que nos permita considerar seriamente o espaço como uma categoria ontológica produtiva, como um acontecimento, e não como um a priori, como um pano de fundo. Argumento que o próprio caráter do espaço é afetado pelo que ocorre nos processos de ensino e na aprendizagem e que, inversamente, esses processos são afetados pelo espaço. Da mesma forma que a presença (ou a ausência) da matéria determina a intensidade da curvatura gravitacional no espaço astronômico, o qual, por sua vez, afeta as relações entre a matéria, assim também características espaciais diversas podem ser associadas com diferentes práticas curriculares e, inversamente, diferentes práticas curriculares podem afetar diferentemente o espaço curricular

Art, politics, perception

Art instructors are used to the question, sometimes benign, sometimes inquisitive, sometimes disparaging, sometimes hostile, from myriad sources including parents, teachers, administrators, and certainly students, “What is the point of learning art?” This question of course rides on the shoulder of many other unstated underlying questions such as “Is not art a luxury or a middle class pursuit?” “Can we not leave art to those genuinely interested or talented in art?” “How is art practically useful?” “Is not art redundant in the age of digitalized production and reproduction?” And so on

Fossils, phylogenies, and the challenge of preserving evolutionary history in the face of anthropogenic extinctions

10.1073/pnas.1409886112Proceedings of the National Academy of Sciences of the United States of America112164909-491

Differential Extinction and the Contrasting Structure of Polar Marine Faunas

Background: The low taxonomic diversity of polar marine faunas today reflects both the failure of clades to colonize or diversify in high latitudes and regional extinctions of once-present clades. However, simple models of polar evolution are made difficult by the strikingly different faunal compositions and community structures of the two poles.Methodology/Principal Findings: A comparison of early Cenozoic Arctic and Antarctic bivalve faunas with modern ones, within the framework of a molecular phylogeny, shows that while Arctic losses were randomly distributed across the tree, Antarctic losses were significantly concentrated in more derived families, resulting in communities dominated by basal lineages. Potential mechanisms for the phylogenetic structure to Antarctic extinctions include continental isolation, changes in primary productivity leading to turnover of both predators and prey, and the effect of glaciation on shelf habitats.Conclusions/Significance: These results show that phylogenetic consequences of past extinctions can vary substantially among regions and thus shape regional faunal structures, even when due to similar drivers, here global cooling, and provide the first phylogenetic support for the “retrograde” hypothesis of Antarctic faunal evolution.</p

A molecular phylogenetic analysis of strombid gastropod morphological diversity

The shells of strombid gastropods show a wide variety of forms, ranging from small and fusiform to large and elaborately ornamented with a strongly flared outer lip. Here, we present the first species-level molecular phylogeny for strombids and use the resulting phylogenetic framework to explore relationships between species richness and morphological diversity. We use portions of one nuclear (325 bp of histone H3) and one mitochondrial (640 bp of cytochrome oxidase I, COI) gene to infer relationships within the two most species-rich genera in the Strombidae: Strombus and Lambis. We include 32 species of Strombus, representing 10 of 11 extant subgenera, and 3 of the 9 species of Lambis, representing 2 of 3 extant subgenera. Maximum likelihood and Bayesian analyses of COI and of H3 and COI combined suggest Lambis is nested within a paraphyletic Strombus. Eastern Pacific and western Atlantic species of Strombus form a relatively recent monophyletic radiation within an older, paraphyletic Indo-West Pacific grade. Morphological diversity of subclades scales positively with species richness but does not show evidence of strong phylogenetic constraints. © 2006 Elsevier Inc. All rights reserved

Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

The importance of large breeding individuals for maintaining the health of marine fish and invertebrate populations has long been recognized. Unfortunately, decades of human harvesting that preferentially remove larger individuals have led to drastic reductions in body sizes of many of these species. Such size-selective harvesting is particularly worrisome for sequentially hermaphroditic species where the larger size classes are composed primarily of one sex. Whether these species can maintain stable sex ratios under sustained harvesting pressure depends on the level of plasticity of their life-history traits. Here, we show that populations of a marine limpet (Lottia gigantea) can adjust a fundamental aspect of their life history (the timing of sex change) when subjected to size-selective harvesting. As predicted by theoretical models, individuals from harvested populations change sex at smaller sizes and grow at slower rates compared to individuals from protected populations. In addition, the relative size at which the change from male to female occurs remains constant (similar to 0.75; size at sex change/maximum size) across populations, regardless of harvesting pressure. Our results show that population-level demographic and life-history data, in conjunction with existing theory, can be sufficient to predict the responses of sequential hermaphrodites to harvesting pressure. Furthermore, they suggest such species can potentially adapt to size-selective harvesting.This is the publisher’s final pdf. The published article is copyrighted by University of Chicago and can be found at: http://www.press.uchicago.edu/journals.html.Keywords: Age, Sex change, Animals, Population structure, Growth, Body size, Fish, Southern California, Owl limpet, Lottia gigantea

Which simple types have a unique inhabitant?

International audienceWe study the question of whether a given type has a unique inhabitant modulo program equivalence. In the setting of simply-typed lambda-calculus with sums, equipped with the strong βη-equivalence, we show that uniqueness is decidable. We present a saturating focused logic that introduces irreducible cuts on positive types "as soon as possible". Backward search in this logic gives an effective algorithm that returns either zero, one or two distinct inhabitants for any given type. Preliminary application studies show that such a feature can be useful in strongly-typed programs, inferring the code of highly-polymorphic library functions, or "glue code" inside more complex terms