959 resultados para bivalve fauna


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Results of fauna and vegetation surveys conducted around Portland Aluminium smelter between 1979 and 2004 found small mammal abundance and diversity had declined and changes in vegetation communities were related to changes in fire patterns, vegetation fragmentation and weed invasion. Small mammal numbers were greater in nearby National Parks.

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Progression of disease caused by the plant pathogen Phytophthora cinnamomi was correlated to rainfall events and resulted in a loss of plant species diversity in heathland vegetation at Anglesea, Victoria. Lower captures of small mammals were recorded in diseased areas. Management of disease using the chemical phosphite was also evaluated.

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The paper considers the biogeography and palaeogeographic implications of the Permian marine bivalve faunas of Northeast Asia, with a focus on the dynamic relationships between biotic similarities and palaeogeographic distance through an interval of ca. 50 million years. A stage-by-stage time series analysis of the biotic similarities between two previously recognized biochores in Northeast Asia, the Kolyma–Omolon and Verkhoyan–Okhotsk provinces, has been carried out using both the Jaccard and Dice similarity indices based on the spatio-temporal distributions of 355 Permian marine bivalve species in Northeast Asia. The outcome of this analysis, combined with other empirical data and previously published tectonic, sedimentological and palaeontological information, suggests that (1) the bivalve faunas from these two provinces were distinctive from one another as two separate biochores throughout all but the earliest (Asselian) Permian stages and (2) the biotic similarities between the Verkhoyan–Okhotsk and Kolyma–Omolon provinces remained consistently low since Sakmarian, all falling well below the minimum threshold of the Jaccard index of 0.42 required for distinguishing marine biotic provinces. We interpret these below-threshold Jaccard biotic similarities as an indication of significant palaeogeographic separation between the Verkhoyan-Okhotsk and Kolyma–Omolon provinces, which is in turn considered to indicate rifting and seafloor spreading of the Omolon microcontinent and associated terranes and island arcs away from the North Asian craton, at least from the Sakmarian to the beginning of the Late Permian.
Palaeo-distance separation appears to be the primary and most significant biogeographic determinant in accounting for the differences in the spatial distribution of most Permian bivalve species in Northeast Asia. Several other variables also appear to have played a significant role, including regional climate conditions, ocean currents and merged island chains as geographic barriers. In particular, the relatively high biotic similarity between the Verkhoyan–Okhotsk and Kolyma–Omolon provinces during the Late Wuchiapingian and Changhsingian may have been related to the shallowing of the deep-water basins (Oimyakon, Ayan-Yuryakh, Balygychan and Sugoi basins) that had previously separated the two provinces and the flooding (submergence) of the Okhotsk–Taigonos volcanic arc system, thus allowing the invasion of lower latitude warm-water Palaeotethyan and even Gondwanan species into Northeast Asia.

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Despite Australia having a high diversity of freshwater crayfish species, the ecology of many of these species remains poorly known, particularly burrowing crayfish of the genus Engaeus. Biological information on colour, behaviour, burrow structure, associated burrow fauna and habitat of the East Gippsland Burrowing Crayfish Engaeus orientalis obtained during incidental observations in 2007 and 2008 is provided. The burrow structure took the form of radiating runways under a rock slab, while the burrow location was in a semi-disturbed site away from water. Both are atypical for this species.

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This article provides a context to, attempts an explanation for, and proposes a response to the recent demonstration of rapid and severe decline of the native mammal fauna of Kakadu National Park. This decline is consistent with, but might be more accentuated than, declines reported elsewhere in northern Australia; however, such a comparison is constrained by the sparse information base across this region. Disconcertingly, the decline has similarities with the earlier phase of mammal extinctions that occurred elsewhere in Australia. We considered four proximate factors (individually or interactively) that might be driving the observed decline: habitat change, predation (by feral cats), poisoning (by invading cane toads), and novel disease. No single factor readily explains the current decline. The current rapid decline of mammals in Kakadu National Park and northern Australia suggests that the fate of biodiversity globally might be even bleaker than evident in recent reviews, and that the establishment of conservation reserves alone is insufficient to maintain biodiversity. This latter conclusion is not new; but the results reported here further stress the need to manage reserves far more intensively, purposefully, and effectively, and to audit regularly their biodiversity conservation performance.

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Numerous Permian limestone blocks exposed along the Yarlung-Zangbo Suture Zone have been named Tibetan facies exotic limestone blocks or Chitichun-type Permian deposits.The Gyanyima limestone block,one of those limestone blocks,is located in Burang County,southwestern Tibet.Fusulines are abundant in the Gyanyima limestone block especially for Middle Permian Xilanta Formation.The fusuline fauna comprises 10 genera,respectively Neoschwagerina, Yangchienia, Armenina, Verbeekina, Paraverbeekina, Kahlerina, Lantschichites, Codonofusiella,Chusenella, Nankinella.This fauna indicates a Midian age(Late Guadalupian or Lengwuan age of South China) in terms of the coexistence of Kahlerina, Lantschichites, Codonofusiella and Neoschwagerina.

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A fusuline fauna consisting of 9 species of 4 genera from the Xiala Formation of the Mujiucuo section, Xainza County, Tibet, China is described. The fusuline fauna is dominated by Nankinella and Chusenella and indicates a Midian (Late Guadalupian) age. The earliest record of fusuline fauna during the Midian in the Lhasa Block suggests that the block rifted later than the Qiangtang Block to the north and the Baoshan and Tengchong blocks to the east, all of which yield much earlier fusuline faunas of Yakhtashian (Artinskian) age, but had drifted away from Gondwana to a relatively warm temperate zone in the Late Guadalupian (Middle Permian).