High Level Of Fragmentation Research Articles

Brooding crustaceans in a highly fragmented habitat: the genetic structure of Mediterranean marine cave‐dwelling mysid populations

Habitat fragmentation and climate change are two major threats on biodiversity. Fragmentation limits the number of patches and their decreased connectivity cannot always maintain populations at dynamic equilibrium. The natural extreme fragmentation of marine cave habitats represents an opportunity to understand how these processes interact. The hypothesis of a low gene flow among populations due to a high level of fragmentation was tested by analysing sequence variation in a fragment of the mitochondrial gene of the cytochrome oxidase subunit I in 170 individuals (23 localities across the NW Mediterranean) of two marine cave-dwelling mysids of the genus Hemimysis. The species Hemimysis margalefi recently replaced its congener Hemimysis speluncola, a species shift that could be related to the warming of the Mediterranean Sea and to differences in their thermal tolerances. There were too few H. speluncola samples to further discuss their genetic structuring, but for H. margalefi, the present study revealed high levels of genetic diversity and genetic structuring, as shown by the eight genetically distinct groups identified. The Croatian group might constitute a sibling species due to a strong divergence (15%). Nevertheless, these groups present reduced but orientated gene flow according to the general circulation in the Mediterranean, and fit a stepping-stone model. At local scale (Marseille area, France), gene flow among caves is dependent on unexpected local hydrodynamic barriers, that determine metapopulation sizes. Through the example of mysid species inhabiting marine caves, the present work confirms the strong influence of habitat disjunction (natural fragmentation) on population structure, and stresses the importance of coastal geomorphological features in inducing complex interactions between the circulation of water masses and the circulation of genes.

District Magnitude, Social Heterogeneity and Local Party System Fragmentation

Scholars analysing party system structures have generally followed two approaches. The ‘institutional’ approach emphasizes the role of electoral laws, while the ‘sociological’ approach highlights the effect of socioeconomic heterogeneity. Recently, evidence based on cross-country data indicated that a high level of fragmentation requires both a permissive electoral system and substantial socio-economic heterogeneity. As electoral rules have their main impact at the level of the constituency, using country-level data may not be ideal, however. Moreover, previous results appear to be driven by the inclusion of single-member district states. Both these caveats are addressed in this article. Based on a sample of Belgian municipal elections over the period 1982–2000, I show that the model incorporating an interaction between heterogeneity and district magnitude significantly outperforms specifications that disregard the interaction effect (a) at the constituency level and (b) in (mediumsize) multi-member districts.

Uncertainty analysis favours selection of spatially aggregated reserve networks

It has been widely argued that habitat fragmentation is bad for (meta)population persistence and that a high level of fragmentation is a similarly undesirable characteristic for a reserve network. However, modelling the effects of fragmentation for many species is very difficult due to high data demands and uncertainty concerning its effect on particular species. Hence, several reserve selection methods employ qualitative heuristics such as boundary length penalties that aggregate reserve network structures. This aggregation usually comes at a cost because low quality habitats will be included for the sake of increased connectivity. Here a biologically justified method for designing aggregated reserve networks based on a technique called distribution smoothing is investigated. As with the boundary length penalty, its use incurs an apparent biological cost. However, taking a step further, potential negative effects of fragmentation on individual species are evaluated using a decision-theoretic uncertainty analysis approach. This analysis shows that the aggregated reserve network (based on smoothed distributions) is likely to be biologically more valuable than a more fragmented one (based on habitat model predictions). The method is illustrated with a reserve design case study in the Hunter Valley of south-eastern Australia. The uncertainty analysis method, based on information-gap decision theory, provides a systematic framework for making robust decisions under severe uncertainty, making it particularly well adapted to reserve design problems.

Life history variation in cupuladriid bryozoans from either side of the Isthmus of Panama

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 280:145-161 (2004) - doi:10.3354/meps280145 Life history variation in cupuladriid bryozoans from either side of the Isthmus of Panama Aaron O¹Dea1,2,*, Amalia Herrera-Cubilla1, Helena Fortunato1, Jeremy B. C. Jackson1,2 1Center for Tropical Paleoecology and Archeology, Smithsonian Tropical Research Institute, Box 2072, Balboa, Ancon, Republic of Panama 2Geosciences Research Division, Scripps Institution of Oceanography University of California, San Diego La Jolla, California 92093-0244, USA *Email: odeaa@si.edu ABSTRACT: Cupuladriid bryozoans are able to produce new colonies both sexually through the production of larvae and asexually via fragmentation. The prevalence of asexual propagation and the physical and biological processes of fragmentation in cupuladriid species are currently little understood. In a large survey comprising collections of nearly 32000 cupuladriids from either side of the Isthmus of Panama, patterns of cupuladriid species richness, occurrence and abundance were measured together with levels of asexual propagation, fragmentation and regeneration. The Caribbean side is characterised by greater cupuladriid diversity and dominance of the genus Cupuladria over Discoporella while the eastern Pacific coast is characterised by lower cupuladriid diversity and complete dominance of Discoporella. Life history variation was not found to be constrained by phylogeny and no systematic differences were found in life history or morphologies between Cupuladria and Discoporella to explain the patterns in generic dominance across the isthmus. Nonetheless, striking differences occur in life history strategies across the isthmus. Eastern Pacific species tend to be large, flat and lightly calcified, resulting in high levels of fragmentation and hence asexual propagation. Conversely, Caribbean species produce a wider range of morphologies, including small, highly domed and highly calcified colonies that protect from fragmentation. By correlating colony morphologies with reproductive life histories within species, we show that morphologies, particularly colony strength and size, control levels of fragmentation and thus mode of propagation in cupuladriids. Life history strategies that promote asexual propagation are found to track levels of primary productivity both between oceans across the isthmus and between regions within oceans. KEY WORDS: Asexual · Sexual · Life history · Cupuladriid · Bryozoa · Reproduction · Panama Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 280. Online publication date: October 14, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Fragmentation and internal disturbance of native vegetation reserves in the Perth metropolitan area, Western Australia

Remnant vegetation in metropolitan areas tends to be highly fragmented and affected by disturbances from the urban environment. A rapid survey in 71 nature reserves in the metropolitan of Perth noted surrounding land uses, types of disturbances, rated the level of weeds, rubbish, formal and informal walking paths and fire influence, and estimated vegetation condition. These data were analysed against information on reserve area and shape, connectivity to other native vegetation, period of patch encapsulation, distance from the city centre and local population density to reveal patterns of fragmentation and disturbance in the metropolitan area. Smaller reserves occurred in the highly populated inner metropolitan area, and these reserves displayed high levels of fragmentation, higher levels of weed infestation and path density and low vegetation condition. Reserves were larger, with high levels of connectivity and with less weed cover and higher vegetation condition in the outer metropolitan area. The research highlighted that whilst reserve attributes are largely set in inner urban areas, planning is required in outer metropolitan areas to ensure patches remain well connected and of optimal size and shape. Inner metropolitan reserves should also be preserved and managed, as they are highly valuable for representing the vegetation types that once occurred there, and for providing natural areas for inner city residents.

Diagnostic analysis of conservation zones using remote sensing and GIS techniques in wet evergreen forests of the Western Ghats – An ecological hotspot, Tamil Nadu, India

This study highlights spatial characterization of evergreen forests of the Western Ghats – an ecological hotspot in Tamil Nadu, India – using remote sensing and GIS-based analysis in conjunction with ground-based phytosociological data. The evergreen forests of Tamil Nadu are distributed in four distinct hill ranges, Nilgiri, Anamalai, Palni and Tirunelveli, having different topographic, bioclimatic and disturbance levels. The evergreen forests in these four hill ranges are characterized for their uniqueness in terms of patch characteristics and phytosociology. A vegetation type map was prepared using IRS LISS III satellite data and was used to study the patch characteristics in terms of patch size, number, shape, porosity and landcover diversity (LD). The phytosociological characteristics, namely species richness, diversity, similarity and community assemblages, were studied using ground data collected from 95 sample points of 0.1 ha size. Patch size and number revealed distinct intactness and disturbance levels in these four hill ranges. Evergreen forests in the Tirunelveli hills comprising 216.09 km2 are distributed in 306 patches, and in the Palni hills, with 285 km2, forests are distributed in 1029 patches, indicating a high level of fragmentation. LD, indicating the spatial heterogeneity of landcover, was very high in the Nilgiri hills and low in the Tirunelveli hills. The spatial analysis helped to delineate homogenous large patches of evergreen forest, which can be adopted for appropriate conservation strategies. A total of 342 tree species belonging to 4490 stems were evaluated for phytosociology. Only 15–28% of similarity in terms of species distribution was found across the hill ranges. Conjunctive analysis of patch characteristics and species distribution showed high species richness in less fragmented evergreen forests and vice versa. The study identified the areas of prioritization in terms of ecorestoration and conservation based on patch and phytosociological characteristics.

Modelling disease spread in a novel host: rabies in the European badger Meles meles

Summary Although the red fox Vulpes vulpes is the main reservoir of rabies in Europe, badger Meles meles populations are known to be drastically affected. Models of badger population dynamics are combined with a fox/rabies model to examine the possibility of rabies spread in high‐density badger populations, such as those found in the United Kingdom (UK). Although some data exist on rabies epizootiology in the badger, there are no data on badger‐to‐badger contact rates (either healthy or diseased animals). As a starting point consensus expert opinion was used to devise contact probabilities, and the model was found to be insensitive to reasonable variation in these rates for the density of badgers at which these estimates were made. Density‐dependent (but not density‐independent) contact probabilities simulated short chains of infections that may occur in continental Europe at low badger densities, and simulated true epizootics at higher densities. Another possible reason for these short chains of infections in continental Europe is a very high level of fragmentation between social groups. Given the high level of territorial contiguity and possible contact rates found in some parts of the UK, the model suggests that rabies is capable of spreading within the UK badger population, and a provisional map showing the likelihood of an epizootic is presented.

Economic Fragmentation and FDI in China

China is one of the most popular investment destinations in the world. This paper argues that FDI inflows into China are in fact driven by some fundamental inefficiencies in the Chinese economy. Specifically, one of the inefficiencies has to do with a high level of fragmentation of both goods and asset markets. This fragmentation increases demand for FDI both because market fragmentation makes indigenous Chinese firms uncompetitive and because market fragmentation creates more investment opportunities for the mobile foreign capital. This paper is a chapter from a larger book-length research project, tentatively entitled, Selling China: The Institutional Foundation of Foreign Direct Investment During the Reform Era.

Processing of antibodies to the MHC class II antigen by B-cell lymphomas: release of Fab-like fragments into the medium

Lym-1, an anti-MHC class II Ab, displayed a unique processing pathway after binding to the surface of Raji B-lymphoma cells, in which Fab-like fragments were gradually released into the medium. The fragments had reduced interchain disulfide bonds. Fragmentation was markedly reduced by inhibitors of intracellular catabolism, namely ammonium chloride, chloroquine and leupeptin. The capacity of the process was high, and fragmentation of approximately 5×10 6 Ab molecules per cell per day was measured directly, in what can be considered to be a minimum estimate. Five other Abs to the MHC class II antigen were tested similarly on Raji and on three other B-cell lymphomas: none showed the same high level of fragmentation seen with Lym-1 binding to Raji, but significant fragmentation did occur with some of the Abs, particularly EDU-1 and L243. The level of fragmentation depended on the cell line as well as on the particular Ab. The other 5 Abs were all catabolized, to low molecular weight material, much more extensively than Lym-1. Part of the difference between Abs can probably be attributed to the fortuitous, preferential labeling of Lym-1 on the light chain, since the data suggest that the Fc fragment is fully degraded while the Fab-like fragment is released into the supernatant. This pathway of Ab processing is likely to be related to the physiology of the MHC class II antigen, which recycles into a mildly proteolytic intracellular compartment.

Enantioselective Ti(IV) Sulfoxidation Catalysts Bearing C3-Symmetric Trialkanolamine Ligands: Solution Speciation by 1H NMR and ESI-MS Analysis

Sulfoxidation catalysts generated from titanium(IV) isopropoxide and enantiopure trialkanolamine ligands promote the enantioselective oxidation of aryl alkyl sulfides to the corresponding sulfoxides even at low (1−2%) catalyst loadings. Electrospray ionization mass spectrometry (ESI-MS), in combination with conventional low-temperature NMR techniques, provides a powerful tool for understanding the unique nature of these catalysts. Tetradentate ligation of the titanium atom by the trialkanolamine ligand provides a highly robust titanatrane core which is retained even in hydroxylic solvents and/or under acidic conditions. In contrast, the remaining apical coordination site is shown to be substitutionally labile. Previously ill-defined species formed when the catalyst is generated in situ with a slight excess of trialkanolamine are shown to consist of discrete 2:1, 3:2, and 4:3 oligomers in which the excess trialkanolamine bridges multiple titanatrane units. In the presence of excess tert-butyl hydroperoxide, all of the precatalyst species are cleanly converted to a mononuclear titanium(IV) peroxo complex which serves as the active sulfoxidation catalyst. Ab initio molecular orbital calculations were used to probe the structure and position of protonation of the catalytic species. Other ionization techniques (fast ion bombardment or electron impact) proved less useful than ESI-MS due to high levels of fragmentation during the ionization process.

Continuous Script: "Immanent" Theory and Its Supplement

Continuous Script: “Immanent” Theory and Its Supplement Henry Sussman (bio) 1. The difference between the borderline of creativity and the borderline of psychological splitting, projective fantasies, exploitative behavior, apparent but superficial affability, and so on, is in many cases and under many conditions difficult to discern. But we can say this: the integration of the incommensurate tends to generate writing, as Derrida articulates it; whereas the existential traces of the borderline, in radical splitting, cold manipulativeness, and the like, void writing and its possibilities. As a marginal, interstitial medium, writing thrives at the frontiers between incommensurate thoughts, phenomena, and conditions. The splitting that has been a feature of subjectivity since the inception of the broader Modernity and that is accentuated in the borderline personality achieves a high level of fragmentation, whether as described as between “self-fragments” or as situated in the field of cognition. Radical splitting in effect quells the communication between fragments whose most comprehensive medium is writing. “Integration,” whether transpiring in psychoanalysis or creative work, is not a devolution to the point of banal homogeneity; it is, rather, the always fragile and tenuous communication between differends. 1 2. The middle ground between the (relatively) singular and mediated spheres is in fact a free-trade zone, a locus of negotiation, barter, exchange. In an age of depleted space and resources, it becomes increasingly crucial to define and elaborate this middle ground. At certain moments in history, e.g., the nineteenth century, the middle ground is equated with a difference-levelling mediocrity, and comes to be seen as a cultural and ethical travesty. 2 At other [End Page 63] moments, and I think here of Postmodernism, the middle ground in fact devours any other possible extremes, and there appears to be nothing outside. There is, in other words, the conservative attitude toward the middle ground, and the liberal one. It can be argued that a continuum consists only of a middle ground. The present essay can be read in one sense as an argument in defense of continua (as opposed to binary terms or their blanket rejection). Continua may not offer definitive results, but they provide for ranges of possibility and activity. The notions of “privacy” and “publicity” in language may be utter fictions, but the continuum between them may have a lot of light to shed on how people invoke language and behave. Continua do provide for extremes of thought and behavior; they just place those extremes in relation to the more “moderate” forms. Continua are the conceptual models that do the work of integration as it takes place in the psychoanalytical sphere. Much of the cultural work being done today, e.g., Judith Butler’s work on gender, inserts a spectrum-model where previously there had been a binary opposition, e.g., female-male. And work on postcolonial theory (and in the teaching of “World Civilizations”) places national and ethnic groupings in one vast arena in questioning earlier ideological constructs of differentiation. Continua do not by their very nature solve all problems located within their spheres. But their deployment is an implicit vote for integration, as opposed to pat ideology-based hierarchy, in the attempt to address and solve problems. 3. In a world of sublime overcrowding and tenuous supply, how human beings do as a species is integrally linked to how well they inhabit the middle ground. The interval between what has been known as “private” territory and the public sphere is, conceptually speaking, one of the continua whose exploration can be most fruitful. The self-sustaining, endlessly self-correcting discourse of postmodern literature (e.g., Beckett, the late Kafka and Joyce, Blanchot, Bernhard) and psychoanalysis (in different ways, Lacan, Kernberg) may in part be understood as an adaptation to the need of inhabiting the middle ground. Within this middle ground, we will need to learn to tolerate and understand each other, to integrate our own skewed tendencies and interests, even as the world has to accommodate more of us, with a corresponding diminution of individuated “private” space “around” us. 4. The Philosophy of Writing is the discursive space inhabited by the middle ground. The Philosophy of Writing is the interface linking the philosophical discourse that...

NISP vs. MNI in Quantification of Body-Part Representation

In an effort to understand the relative advantages and drawbacks of the minimum number of individuals (MNI) and number of identifiable specimens (NISP) for quantifying body-part representation in faunas from archaeological sites, we analyzed relations among NISP, MNI, fragmentation, and bulk density in the fauna from Ngamuriak, a Kenyan pastoral Neolithic site. Our findings suggest that MNI is at least as sensitive as NISP to effects of fragmentation. While MNI decreases with increasing fragmentation, NISP moves in two directions with fragmentation, increasing at low levels of fragmentation and decreasing at high levels of fragmentation. In addition, MNI appears more sensitive than NISP to the relative identifiability of different body parts. We believe MNI may be a less representative descriptor of relative element frequency than NISP in highly fragmented assemblages.