1,457 research outputs found

    Studies in the population dynamics of some Teesdale plants

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    The study was essentially a demographic one. Few studies of this kind have been carried out on rare plant populations. Permanent quadrats (selected subjectively for the presence of some Teesdale plants, including Gentlana verna and Polygala amarelle) were established on Widdybank and Cronkley Fells in the Northern Pennines. The quadrats were all established on the grazed or eroding areas of sugar limestone grassland. For each quadrat the grid positions of all the individuals of the species being recorded were plotted on a chart. The fate of the initially recorded mixed-age population and that of all subsequent additions was noted at each visit. Larger permanently marked sample sites, usually adjacent to a permanent quadrat, were recorded once a year for the number of flowering and non-flowering individuals. Individuals which flowered were then recorded for the number of flowers, fruits and seeds they produced. From these data the population flux, mortality, survival and age-distribution of the individuals in the quadrats were obtained. The relative importance of sexual reproduction was ascertained by closely following the appearance of seedlings and vegetative shoots in each of the quadrats where a species produced both

    An Improved Holding Chamber for the Measurement of Oxygen Consumption in Mice

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    An apparatus is described which has been useful in classroom demonstrations and for research in metabolic studies of mice. The unique feature of this modification of basic metabolators is a standard taper ground glass joint

    The Evolution of Sociality and the Polyvagal Theory

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    The polyvagal theory (PT), offered by Porges (2021), proposes that the autonomic nervous system (ANS) was repurposed in mammals, via a second vagal nerve, to suppress defensive strategies and support the expression of sociality. Three critical assumptions of this theory are that (1) the transition of the ANS was associated with the evolution of social mammals from asocial reptiles; (2) the transition enabled mammals, unlike their reptilian ancestors, to derive a biological benefit from social interactions; and (3) the transition forces a less parsimonious explanation (convergence) for the evolution of social behavior in birds and mammals, since birds evolved from a reptilian lineage. Two recently published reviews, however, provided compelling evidence that the social asocial dichotomy is overly simplistic, neglects the diversity of vertebrate social systems, impedes our understanding of the evolution of social behavior, and perpetuates the erroneous belief that one group, non-avian reptiles, is incapable of complex social behavior. In the worst case, if PT depends upon a transition from asocial reptiles to social mammals, then the ability of PT to explain the evolution of the mammalian ANS is highly questionable. A great number of social behaviors occur in both reptiles and mammals. In the best case, PT has misused the terms social and asocial. Even here, however, the theory would still need to identify a particular suite of behaviors found in mammals and not reptiles that could be associated with, or explain, the transition of the ANS, and then replace the asocial and social labels with more specific descriptors.Comment: 15 pages, 1 figur

    Riccarton Bush and the natural and social realities of native trees in Christchurch, New Zealand

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    Urbanization has destroyed and fragmented previously large areas of natural habitat. Small remnants that still exist in numerous cities will be unable to sustain many viable wild plant populations if they do not expand into the surrounding urban matrix. Residential gardens surrounding such remnants, and which form a significant component of urban green space in many cities, could play a role in redressing this problem. Riccarton Bush, a 7.8 hectare forest remnant, and its surrounding suburban residential area, in Christchurch, New Zealand, is a good example. Over 125 years the reported number of native vascular plants in the bush has declined by a third. My study was an attempt to understand: 1) the ecological, social and cultural factors influencing the dispersal and regeneration of 12 native bird-dispersed woody species from Riccarton Bush, into surrounding residential properties; and 2) the potential role residential properties could play in the future of the bush. To examine these diverse factors I adopted an interdisciplinary research approach combining methodologies, concepts and theories from ecology and the social sciences. In a broader context my work was an attempt to demonstrate how urban ecology can further develop and strengthen by adopting and integrating new methodologies, theories and concepts. The ecological component involved recording individuals of the study species found on 90 randomly selected properties within a 1.4 km radius of the bush. Soil samples were also collected from 31 of those properties and placed in a glasshouse and the study species that germinated were recorded. Results showed some species, particularly kahikatea (Dacrycarpus dacrydioides), the most abundant species in the bush, are being dispersed and establishing on properties predominantly within 250 m of the forest margin. These juveniles are not reaching maturity as most gardeners tend to remove all non-planted woody species. Qualitative interviews with 16 residents and a quantitative survey of the residents of 85 of the properties provided insights into the social context which these natural processes were operating. Using notions of place and performance I argue that gardens are continuously created and recreated by humans and non-humans. Residents attempt to create and maintain a garden that fulfils their individual and familial needs and desires (e.g., aesthetics, leisure and privacy), and public responsibilities such as ensuring they have a ‘neat’ and ‘tidy’ garden. This involves selecting plants for colour, shape and the care they require, and encouraging certain performances (e.g., flowering) while controlling other undesirable plants and performances (e.g. growth, spread and shading). While people make connections between native plants, belonging and identity; the ‘scientific’ demarcation between native and exotic species often becomes obscured as the garden is co-created by people and plants. Some plants become more significant than others but usually this is attributable to their performances rather than whether they are native or exotic. Residential gardens have the potential to play a major role in the conservation of species restricted to urban remnants. My research suggests that although the potential exists for woody species restricted to Riccarton Bush to naturally regenerate in nearby gardens, this will not happen without human intervention. Plants will need to be eco-sourced and propagated to avoid detrimental impacts on the genetic health of remnant populations, and then actively planted in gardens. The success of such planting initiatives will be increased by providing residents with information about the plants that are suitable for their performative needs and desires (e.g., the size, colour, and maintenance requirements of plants) and, most importantly, control over the location of plantings. In concluding, I argue that by adopting new concepts, theories and methodologies, the productivity, creativity and relevance of urban ecology can be significantly enhanced

    DISTRIBUTION AND STATUS OF THE SUWANNEE COOTER, PSEUDEMYS CONCINNA SUWANNIENSIS, IN THE ALAFIA RIVER (HILLSBOROUGH COUNTY, FLORIDA, USA)

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    The Suwannee Cooter, Pseudemys concinna suwanniensis, is a geographically limited turtle of conservation concern that inhabits Florida rivers draining into the northeastern Gulf of Mexico. Threats impacting its conservation status include take for human consumption, predation of turtles and nests, loss or degradation of nesting and basking habitat, water quality degradation, and boat strikes. Our surveys revealed that the Alafia River, which drains into Hillsborough Bay (northeastern Tampa Bay), is likely the stronghold of the southern distribution of P. c. suwanniensis. Multiple survey methods during 2015-2020 revealed that a substantial population of Suwannee Cooters inhabits much of this blackwater river system, including the main channel and at least one of its two primary tributaries. GIS analysis showed that more than half of the shoreline within the occupied extent is currently protected by conservation lands, although additional protection of private lands and improved habitat management protocols are needed to assure the population’s conservation

    Waveguide Splitter For Lower Hybrid Current Drive

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