896 resultados para Fauna silvestre
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Mode of access: Internet.
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Vita.
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Senior thesis written for Oceanography 445
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Gnathostome vertebrate remains from fine-grained sandstones of the Silverband Formation in the Grampians, Victoria include dissociated fin spines, scales and teeth. These elements arc assigned herein to the acanthodians Sinacanthus? micracanthus (fin spines) and Radioporacanthodes sp. cf. R. qujingensis (scales and tooth whorls). This fauna indicates a Late Silurian (?late Ludlow) age for the vertebrate-beating Stratum. Under current systematic groupings, the two gnathostome taxa from the Silverband Formation belong to two different families, the Sinacanthidae and the Poracanthodidae. However. the preserved association could indicate that the three element types derived from the same biological species. The possibility that the Sinacanthidae is a sister group to the Climatiidae and the Poracanthodidae is raised by this scenario. The Sinacanthidae is tentatively reassigned to the Acanthodii, as it is considered to lack diagnostic chondrichthyan characters.
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Spiders are among the most abundant predators recorded in grain crops in Australia. They are voracious predators, and combined with their high abundance, may play an important role in the reduction of pest populations. The significance of spider assemblages as biological control agents of key pests such as Helicoverpa spp. in Australian agroecosystems is largely unknown. A thorough inventory was made of the spider fauna inhabiting unsprayed soybean fields at Gatton, south-east Queensland. One-hundred-and-two morphospecies from 28 families were collected using vacuum sampling and pitfall traps across two summer seasons (2000-01, 2001-02). No-choice feeding tests in the laboratory, using eggs and larvae of Helicoverpa armigera (Hubner) as prey, were used to ascertain the predatory potential of each spider group. The field-collected spider assemblage ate on average 2.4 (+/-0.7 standard error) to 5.0 (+/-0.8) eggs per 24 h per spider (10-25% of those available), depending on level of starvation. Clubionidae were the only spiders to readily consume eggs in the laboratory (mean of 18.4 +/- 1.5 eggs per starved spider and 8.2 +/- 3.9 per non-starved spider after 24 h). Starved spiders consumed 9.4 (+/- 0.1) first-instar larvae per 24 h per spider (90% of those available). This information was combined with field observations and literature from Australian and overseas studies to assess the potential of spider groups as predators of Helicoverpa spp. Lycosidae, Clubionidae, Oxyopidae, Salticidae and Thomisidae have the capacity to contribute to control of Helicoverpa spp.
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A recent preliminary survey revealed that 12 species of unstalked crinoids occur on a gentle sandy slope (12-18 m depth) at Lizard Island, Great Barrier Reef, Australia; five of which are also found on coral reefs. The other seven appear to constitute a unique assemblage restricted to unconsolidated substrates, where most cling to algae or hide beneath rubble or sponges. Members of this assemblage exhibit all of the basic feeding postures found among reef-dwelling species. However, Comatula rotalaria, which lacks anchoring cirri and bears uniquely differentiated short and long arms, exhibits a posture different from other living crinoids. Quantitative transects reveal apparent depth-related differences in species composition: C. rotalaria dominated the 12 transects in 12-13 m (84% of 82 specimens), while Comatella nigra, Comatula cf. purpurea, Amphimetra cf. tessellata and Zygometra microdiscus accounted for 96% of 54 specimens observed along 12 transects in 16-17 m.
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Cities have a major impact on Australian landscapes, especially in coastal regions, to the detriment of native biodiversity. Areas suitable for urban development often coincide with those areas that support high levels of species diversity and endemism. However, there is a paucity of reliable information available to guide urban conservation planning and management, especially regarding the trade-off between investing in protecting and restoring habitat at the landscape level, and investing in programmes to maintain the condition of remnant vegetation at the local (site) level. We review the literature on Australian urban ecology, focusing on urban terrestrial and aquatic vertebrate and invertebrate fauna. We identify four main factors limiting our knowledge of urban fauna: (i) a lack of studies focusing at multiple ecological levels; (ii) a lack of multispecies studies; (iii) an almost total absence of long-term (temporal) studies; and (iv) a need for stronger integration of research outcomes into urban conservation planning and management. We present a set of key principles for the development of a spatially explicit, long-term approach to urban fauna research. This requires an understanding of the importance of local-level habitat quality and condition relative to the composition, configuration and connectivity of habitats within the larger urban landscape. These principles will ultimately strengthen urban fauna management and conservation planning by enabling us to prioritize and allocate limited financial resources to maximize the conservation return.
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It has been suggested that timber plantations could play an important role in the conservation of biodiversity in cleared rainforest landscapes, not only because of their potential to cost-effectively reforest large areas of land, but also because they may provide habitat for rainforest plants and animals. However, this last claim is largely untested. In this study, we surveyed the occurrence of a range of animal taxa in monoculture and mixed species timber plantations and restoration plantings in tropical and subtropical Australia. We used the richness of ‘rainforest-dependent’ taxa (i.e., birds, lizards and mites associated with rainforest habitats) in reforested sites as our measure of their ‘biodiversity value’. We also examined whether the biodiversity value of reforested sites was correlated with habitat attributes, including plant species richness and vegetation structure and, further, whether biodiversity value was affected by the proximity of reforested sites to intact rainforest.
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A major goal of the Comprehensive Everglades Restoration Plan (CERP) is to recover historical (pre-drainage) wading bird rookeries and reverse marked decreases in wading bird nesting success in Everglades National Park. To assess efforts to restore wading birds, a trophic hypothesis was developed that proposes seasonal concentrations of small-fish and crustaceans (i.e., wading bird prey) were a key factor to historical wading bird success. Drainage of the Everglades has diminished these seasonal concentrations, leading to a decline in wading bird nesting and displacing them from their historical nesting locations. The trophic hypothesis predicts that restoring historical hydrological patterns to pre-drainage conditions will recover the timing and location of seasonally concentrated prey, ultimately restoring wading bird nesting and foraging to the southern Everglades. We identified a set of indicators using small-fish and crustaceans that can be predicted from hydrological targets and used to assess management success in regaining suitable wading bird foraging habitat. Small-fish and crustaceans are key components of the Everglades food web and are sensitive to hydrological management, track hydrological history with little time lag, and can be studied at the landscape scale. The seasonal hydrological variation of the Everglades that creates prey concentrations presents a challenge to interpreting monitoring data. To account for the variable hydrology of the Everglades in our assessment, we developed dynamic hydrological targets that respond to changes in prevailing regional rainfall. We also derived statistical relationships between density and hydrological drivers for species representing four different life-history responses to drought. Finally, we use these statistical relationships and hydrological targets to set restoration targets for prey density. We also describe a report-card methodology to communicate the results of model-based assessments for communication to a broad audience.
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Estuarine productivity is highly dependent on the freshwater sources of the estuary. In Florida Bay, Taylor Slough was historically the main source of fresh water. Beginning in about 1960, and culminating with the completion of the South Dade Conveyance System in 1984, water management practice began to change the quantity and distribution of flow from Taylor Slough into Northeastern Florida Bay. These practices altered salinity and hydrologic parameters that had measurable negative impacts on vertebrate fauna and their habitats. Here, I review those impacts from published and unpublished literature and anecdotal observations. Almost all vertebrates covered in this review have shown some form of population decline since 1984; most of the studies implicate declines in food resources as the main stressor on their populations. My conclusion is that the diversion of fresh water resulted in an ecological cascade starting with hydrologic stresses on primary then secondary producers culminating in population declines at the top of the food web.
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Rodents are often involved at several stages of trophic dynamics. Consequently they often play crucial roles in the structure and function of many complex ecological systems. This study sought to address the lack of baseline data concerning rodents in tropical areas, and south Florida in particular. Live trapping took place in the four major habitat types of the Long Pine Key area of Everglades National Park over the course of one year. I compared population structures and abundance of murid rodents in the four habitat types, and tested multiple weather variables for their effectiveness as predictors of rodent abundance. I found the Long Pine Key area to be depauperate in terms of species diversity. Each of the four species of rodent encountered favored a particular habitat type. The density of the understory vegetation and the avoidance of avian predators in particular appear to be the most important factors in the distribution and abundance of rodents in the Long Pine Key area of Everglades National Park.