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81.
CHRIS METTAM MAURA E. CONNEELY SARAH J. WHITE† 《Biological journal of the Linnean Society. Linnean Society of London》1994,51(1-2):71-81
In the Severn Estuary and Bristol Channel, a multivariate analysis indicated eight groupings of macrobenthic fauna, each associated with a different physical habitat. Samples were faunistically impoverished, especially in sublittoral areas, but greater species richness was associated with reefs of Sabellaria alveolata , which extended well into the estuary. 相似文献
82.
Sex, diet and feeding method-related differences in body condition in the Oystercatcher Haematopus ostralegus 总被引:2,自引:0,他引:2
SARAH E.A. LE V. DIT DURELL JOHN D. GOSS-CUSTARD RICHARD W.G. CALDOW HEATH M. MALCOLM DANIEL OSBORN 《Ibis》2001,143(1):107-119
Measurements were made of Oystercatcher corpses to find the most reliable measure of body condition in live birds. Total body weight was as accurate as muscle thickness in assessing the weight of the pectoral muscles, a major store of protein reserves. Total body weight was also a good indicator of fat reserves. Wing‐length was the most reliable measure of body size. Body condition in live birds was measured as an individual's residual weight derived from a general linear model of (loge) body weight against age, month, (loge) wing‐length and time since capture. On the Exe estuary in autumn, there was no significant difference in body condition between same‐age Oystercatchers of different diets and feeding methods. In the winter months, however, body condition differed significantly between mussel feeders using different feeding methods, and between mussel feeders and birds that fed on worms and clams. Differences between diet/feeding methods were not the same for each age group. Birds with the highest mean body condition index in adults were mussel hammerers, in immatures mussel stabbers and in juveniles, worm/clam feeders. No significant difference in body condition was found between the sexes in any age group in autumn. In winter, when birds with the same diet/feeding method were considered, females were significantly heavier than males. However, when birds of all diets and feeding methods were combined, weight differences between the sexes were not apparent. We examine reasons why birds with certain diets and feeding methods may be heavier than others in winter, and why females are sometimes heavier than males. We conclude that, in most cases, it is due to differences between birds in their ability to achieve a common target weight. However, we conclude that adult females try to achieve a higher target weight than males, probably as a premigratory and prebreeding strategy. In the light of this, we consider the consequences for adult females, in terms of reproductive success and survival, of specializing in diets and feeding methods associated with lower body weights in winter. 相似文献
83.
RICHARD J. ALDRIDGE SARAH E. GABBOTT LUCY J. SIVETER JOHANNES N. THERON† 《Palaeontology》2006,49(4):857-871
Abstract: Bromalites from the Soom Shale are allocated to five main categories on the basis of shape, content and internal structure: those containing broken conodont elements; those containing brachiopod fragments; corrugated/spiral forms; coiled coprolites and wrinkled coprolites. It is impossible to allocate specific bromalites to the organisms that formed them, but the occurrence of crushed discinoid valves in several specimens demonstrates that an effective durophagous predator was present in the Soom Shale community. The presence of fragmented elements of conodonts in other specimens provides direct evidence of tiering within the predatory trophic level in the Soom Shale. Conodonts, other agnathan vertebrates, orthoconic cephalopods and eurypterids are all possible contenders for producing most of the bromalites recorded, but there may have been unrecorded large predators in the community. 相似文献
84.
Limiting similarity between invaders and dominant species in herbaceous plant communities? 总被引:3,自引:1,他引:2
SARAH M. EMERY 《Journal of Ecology》2007,95(5):1027-1035
85.
Flowers, Nectar and Insect Visits: Evaluating British Plant Species for Pollinator-friendly Gardens 总被引:1,自引:0,他引:1
Twenty-four plant species native or naturalized in Britain weregrown in the Cambridge University Botanic Garden, UK and evaluatedas potential resources for nectar-foraging bees, butterfliesand hoverflies. In ten plant species a series of measurementswere made, at regular intervals from dawn to dusk, of nectarsecretion rate and standing crop, and in all species insectvisits were monitored throughout daylight hours. The study revealeddifferences between plant species in the composition of theassemblage of insect visitors, and in the magnitude and temporaldistribution of the nectar reward. In some cases we found interestingcorrelations between temperature and secretion rates or patternsof insect visits. Species that received numerous insect visitsin our study are potentially valuable forage plants that mightbe planted by gardeners to support local pollinator populations.Deep flowers whose nectar is accessible to long-tongued bumblebees(Bombus hortorum, B. pascuorum) but not to honeybees may providelong-tongued pollinators with a resource refuge relatively freefrom honeybee competition. Features that make some of thoseplant species particularly interesting to observe in the gardeninclude robbing by short-tongued bumblebees inSaponaria,baseworkingby honeybees on closed flowers inMalva sylvestris, and apparentdisplacement of bumblebees by territorial behaviour of the solitarybeeAnthidium manicatumon species ofStachys.Copyright 1999 Annalsof Botany Company Wild flowers, gardens, nectar,Silene, Lychnis, Saponaria, Stachys, Malva, Dipsacus fullonum, Lythrum salicaria,pollinators, bumblebees,Bombus,honeybees,Apis,butterflies, Lepidoptera, hoverflies, Syrphidae,Anthidium manicatum, weeds. 相似文献
86.
SARAH L. BOULTER ROGER L. KITCHING BRADLEY G. HOWLETT KYLIE GOODALL 《Botanical journal of the Linnean Society. Linnean Society of London》2005,149(1):69-84
The pollination biology of Syzygium sayeri was documented using the special capabilities of the Australian Canopy Crane. Syzygium sayeri is a xenogamous species with poor self-compatibility, moderate levels of natural out-crossing, and the producer of copious amounts nectar throughout the day and night. Of a diverse fauna associated with, and visiting the flowers of S. sayeri , larger vertebrates (blossom bats and honeyeaters) account for approximately half its natural pollination rate, while the balance of pollination is attributable to a host of invertebrate visitors (wasps, flies, thrips, butterflies). Day and night pollinators contributed approximately equally to the successful pollination of S. sayeri ; although the number of individuals visiting flowers was greater during the day, further experimentation might reveal night visitors to be more effective pollinators. The co-occurrence of vertebrates and invertebrates, as well as day and night visitors, suggests that S. sayeri has a generalist pollination system, whereby the absence of a discrete set of faunae could be compensated for by the presence of other pollinators. What is not clear is the contribution of different pollinators to the population success (i.e. gene flow) of this species. Further study is needed to determine the contribution of each pollinator group to the flow of genetic material in populations of S. sayeri . © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 69–84. 相似文献
87.
SARAH JONES 《Bioethics》2010,24(7):358-364
The goal of this paper is both modest and ambitious. The modest goal is to show that intercountry adoption should be considered by ethicists and healthcare providers. The more ambitious goal is to introduce the many ethical issues that intercountry adoption raises. Intercountry adoption is an alternative to medical, assisted reproduction option such as in vitro fertilization (IVF), intracytoplasmic sperm injection, third party egg and sperm donation and surrogacy. Health care providers working with assisted reproduction are in a unique position to introduce their clients to intercountry adoption; however, providers should only do so if intercountry adoption is ethically equal or superior to the alternatives. This paper first presents a brief history of intercountry adoption. The second section compares intercountry adoption with medical alternatives. The third section examines the unique ethical challenges that are not shared by other medical alternatives. The final section concludes that it is simplistic for a healthcare provider to promote intercountry adoption unconditionally; however, in situation where intercountry adoption is practiced conscientiously it poses no greater ethical concern than several medical alternatives. This conclusion is preliminary and is intended as a start for further discussion. 相似文献
88.
SARAH COBURN MO SALMAN JACK RHYAN THOMAS KEEFE MATTHEW MCCOLLUM KEITH AUNE TERRY SPRAKER LOWELL MILLER 《The Journal of wildlife management》2010,74(3):532-538
ABSTRACT Stress hormones in Rocky Mountain bighorn sheep (Ovis canadensis canadensis), produced in response to environmental changes, road development, or high population density, may impact their immune systems to a threshold level that predisposes them to periodic, large-scale mortality. We compared the stress response to a novel environmental situation and repeated handling between bighorn sheep born and raised in captivity (CR) and bighorn sheep born in the wild (WC) and brought into captivity. We measured plasma epinephrine, norepinephrine, cortisol, and fecal glucocorticoid metabolites (FGM). Three weeks after each group's arrival we used a one-time drop-net event to elicit an acute stress response, and we collected blood samples from each sheep over 35 minutes, as well as one fecal sample. We collected blood and fecal samples from both groups on 7 other occasions over the subsequent 6 months. We also collected fecal samples from the pen at approximately 24-hour intervals for 3 days following every handling event to monitor the stress response to handling. We found that CR sheep had a stronger autonomic nervous system response than WC sheep, as measured by epinephrine and norepinephrine levels, but we found a very similar hypothalamic-pituitary–adrenal axis (HPA) response, measured by cortisol levels, to the acute stress event of a drop-net restraint. We also found that once the WC sheep had acclimated, as indicated by the return to the initial baseline FGM levels within 12 weeks, the CR and WC groups' HPA responses to sampling events were not significantly different from one another. Fecal samples can provide a noninvasive mechanism for managers to monitor baseline FGM for a given herd. Using long-term monitoring of FGM rather than values from a single point in time may allow managers to correlate these levels to outside influences on the herd and better understand the impacts of management changes, population density, or increased human developments on the health of the sheep population. 相似文献
89.
GABRIEL E. MACHOVSKY CAPUSKA SARAH L. DWYER MAURICE R. ALLEY KAREN A. STOCKIN DAVID RAUBENHEIMER 《Ibis》2011,153(3):631-635
Plunge‐diving is a highly successful strategy for dealing with the challenges confronting birds feeding on pelagic prey. We tested for evidence of fatal injuries due to collision between conspecifics in plunge‐diving Australasian Gannets Morus serrator and Cape Gannets Morus capensis, respectively, by performing post‐mortem examinations of carcasses recovered from New Zealand waters and analysing video footage of Cape Gannet foraging events from South Africa. We found evidence of accidental collisions between Gannets and also observed a case of attempted kleptoparasitism, in which a diving Cape Gannet targeted a previously captured fish in the beak of a conspecific. 相似文献
90.
Abstract Invasive exotic plants are a significant threat to areas of conservation value, with endangered ecological communities being especially vulnerable. We assessed the role of different anthropogenic disturbances in determining the success of exotic plants in the endangered Cumberland Plain Woodland community of western Sydney and examined the impact of these disturbances on soil characteristics that are likely to impact on vegetation, including total P, pH, water retention capacity, organic matter content and electrical conductivity. The disturbance types were: (i) land use incorporating clearing, agriculture and grazing by stock; (ii) creeks draining a developed catchment; and (iii) roads. Remnants that had been cleared and grazed had higher exotic and lower native species richness and cover than all other disturbance types. Areas that had been grazed but not cleared did not have more exotic species richness or cover than uncleared/ungrazed areas, thus retaining high conservation value. Areas within 2 m of a creek edge had higher exotic species richness and cover than areas further from the creek edge. Areas downslope of sealed roads had significantly higher exotic species richness and cover than areas below unsealed roads. No single soil attribute or combination of soil attributes was consistently able to account for variation in exotic species cover under the different disturbance types. Thus it appears that other factors such as site history and propagule pressure may be more important in determining exotic species success than soil characteristics alone, in this vegetation community. 相似文献