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401.
Frugivorous migrants may select fruit-rich habitats en route to attain high food rewards, yet their stopover behavior may also be shaped by other considerations, such as predation risk. During 1996–2001 we investigated autumn stopover habitat use of three Sylvia warblers (sylviids; S. hortensis, S. atricapilla and S. curruca) and three Turdidae chats (turdids; Cercotrichas galactotes, Oenanthe hispanica and Phoenicurus phoenicurus) in planted groves of the fruiting tree Pistacia atlantica in Lahav Forest, Israel, which is located at the edge of a desert. We used fecal analysis, a constant-effort trapping scheme and field observations to estimate the extent of frugivory, and bird habitat and microhabitat selection with regard to natural fruit and foliage densities. We also measured bird microhabitat selection in a set of fruit-manipulated trees. We trapped a total of 2,357 birds during the course of the study. Although sylviids exhibited higher frugivory level than turdids, both species groups exhibited a similar significantly positive correlation between bird and fruit densities at the habitat scale. However, at the microhabitat scale, sylviids selected densely foliated trees, whilst turdids were randomly distributed among trees. Our findings suggest that both species groups selected fruit-rich stopover habitats to take advantage of the high food availability before the demanding migration journey. No other mechanism except predation avoidance can explain the sylviids microhabitat selection; the migrants used foliage cover to reduce bird detectability by raptors. We conclude that en route passerines may use staging habitats in a sophisticated manner, by adopting scale-related behavior with regard to the availability of food and refuge cover. 相似文献
402.
Genetic variation in honeybee, Apis mellifera, populations can be considerably influenced by breeding and commercial introductions, especially in areas with abundant beekeeping. However, in southern Africa apiculture is based on the capture of wild swarms, and queen rearing is virtually absent. Moreover, the introduction of European subspecies constantly failed in the Cape region. We therefore hypothesize a low human impact on genetic variation in populations of Cape honeybees, Apis mellifera capensis. A novel solution to studying genetic variation in honeybee populations based on thelytokous worker reproduction is applied to test this hypothesis. Environmental effects on metrical morphological characters of the phenotype are separated to obtain a genetic residual component. The genetic residuals are then re-calculated as coefficients of genetic variation. Characters measured included hair length on the abdomen, width and length of wax plate, and three wing angles. The data show for the first time that genetic variation in Cape honeybee populations is independent of beekeeping density and probably reflects naturally occurring processes such as gene flow due to topographic and climatic variation on a microscale. 相似文献
403.
The burrowing activity of the invasive red-swamp crayfish, Procambarus clarkii, was studied along a 25-m-long transect in an irrigation ditch system in Italy. Our objective was to understand the factors inducing this species intense digging, which can result in bank collapse and consequently in severe damage to both agricultural fields and natural ecosystems. Burrow morphology and position, together with their occupancy by crayfish and digging, were recorded once every 6 h for 10 consecutive days. The majority of burrows were simple, although a few had a chimney and were constructed at a farther distance from the water surface than simple burrows. Burrow occupancy and digging, together with their plugged/unplugged status, were constant throughout a 24-h cycle and were not related to any abiotic parameter of the habitat. Crayfish occupied and dug a burrow for a relatively short time (6 h on average). Once abandoned, old burrows were rarely reoccupied and often collapsed, while crayfish excavated new ones. As a result, the overall number of burrows increased. This massive use of banks by P. clarkii seems to be related to soil composition and humidity, which favour crayfish digging but also cause the easy collapse of burrows. 相似文献
404.
We reconstructed the flora of a European region at a historical point in time from historical topographical maps that contain rather precise information about the condition and composition of habitats. The ecological information obtained from these maps can be enriched through the potential of broadly diversified archival information. This study is confined to grassland communities. Considerations in terms of phytosociology make historical lists of plant species a good starting point for the reconstruction of grassland communities. The combination of historical and scientific methods proves suitable for reconstructing specific historical environmental conditions. Taking into account the frequency of relevant historical sources in European archives as well as in archives abroad, this approach claims for far-reaching application to ecosystem restoration matters, especially if ecological information from natural sources is missing. 相似文献
405.
Little is known about seasonal changes in burrowing activity and burrow architecture in subterranean African mole-rats (Bathyergidae, Rodentia). The solitary genus Heliophobius is the least known genus of this family. We examined burrow systems of the silvery mole-rat ( Heliophobius argenteocinereus) in Malawi in two periods of the dry season. Burrow pattern was influenced by the time of the year, becoming more reticulated at the peak of the dry season when soil was dry and hard. Overall digging activity did not cease during the dry season; yet burrowing strategy changed and the soil was deposited in tunnels rather than transported to mounds. The length of burrow systems was correlated with the body mass of the respective occupants. In spite of their solitary habits – and contrary to the prediction of the aridity food-distribution hypothesis – silvery mole-rats are able to occupy poor habitats with low food supply. 相似文献
406.
Arsenic, a carcinogenic trace element, threatens not only the health of millions of humans and other living organisms, but also global sustainability. We present here, for the first time, the global industrial-age cumulative anthropogenic arsenic production and its potential accumulation and risks in the environment. In 2000, the world cumulative industrial-age anthropogenic arsenic production was 4.53 million tonnes. The world-wide coal and petroleum industries accounted for 46% of global annual gross arsenic production, and their overall contribution to industrial-age gross arsenic production was 27% in 2000. Global industrial-age anthropogenic As sources (as As cumulative production) follow the order: As mining production >As generated from coal >As generated from petroleum. The potential industrial-age anthropogenic arsenic input in world arable surface in 2000 was 2.18 mg arsenic kg–1, which is 1.2 times that in the lithosphere. The development of substitute materials for arsenic applications in the agricultural and forestry industries and controls of arsenic emissions from the coal industry may be possible strategies to significantly decrease arsenic pollution sources and dissipation rates into the environment. 相似文献
407.
In the species-specific and obligate mutualism between the fig (Ficus carica) and its pollinator (the fig wasps Blastophaga psenes), a third participant, the ant Crematogaster scutellaris, is a predator of the wasps. Here, we ask how ant workers can rapidly localise such prey, whose availability is limited in time and space. Using a Y-tube olfactometer, we tested ant response to odours emitted by different types of figs (receptive female, ripe female or male figs) and by fig wasps (pollinators or non-pollinators). We demonstrate that ants were significantly attracted only to odours emitted by pollinators, either alone or associated with odours of male figs (releasing wasps). Detection of prey odour by ants is an important trait that can explain their observed high rate of predation on pollinators, and could have important implications on the stability of the fig/fig wasp mutualism. 相似文献
408.
Laurent P Dooms C Braekman JC Daloze D Habib-Jiwan JL Rozenberg R Termonia A Pasteels JM 《Die Naturwissenschaften》2003,90(11):524-527
Several species of Doryphorina leaf beetles from Central- and South America produce oleanane triterpene glycosides in their defensive glands. The presence of pentacyclic triterpenes in insects is intriguing since they lack the key enzymes necessary to synthesize these compounds. Since -amyrin is a common constituent of leaf waxes, we hypothesized that these leaf beetles use this compound as a precursor to their oleanane glycosides. To test this hypothesis we first confirmed the presence of -amyrin in Ipomoea batatas, the food plant of Platyphora kollari. Next, adults of P. kollari were fed for 10 days with I. batatas leaf disks painted with a solution of [2,2,3-2H3]-amyrin ([2,2,3-2H3]-1). The secretion from their defensive glands was collected and analyzed by HPLC-ESIMS. The results demonstrated that the secretion of beetles fed with an amount of [2,2,3-2H3]-amyrin corresponding to the quantity of unlabeled (natural) -amyrin present in the leaf disks contained on average 5.1% of [2,2,3-2H3]-3-O--d-glucopyranosyl-(1-->4)--d-glucuronopyranosyl-hederagenin ([2,2,3-2H3]-2), whereas the secretions of beetles fed with 10 times this amount of [2,2,3-2H3]-amyrin contained on average 23.9% of [2,2,3-2H3]-2. In both series of experiments, the percentage of labeled versus unlabeled triterpene glycoside in the secretion was positively correlated with the amount of deuterated -amyrin ingested. These results demonstrate for the first time that some leaf beetles are able to metabolize a widespread triterpenic constituent of leaf wax into more complex glycosides that are stored in their defensive glands. 相似文献
409.
Adaptation Options Strategies for Hazards and Vulnerability Mitigation: An International Perspective
C.?Emdad?HaqueEmail author Ian?Burton 《Mitigation and Adaptation Strategies for Global Change》2005,10(3):335-353
The broad objective of this special issue of Mitigation and Adaptation Strategies for Global Change is to address some of the gaps in our knowledge and understanding of the policies, programs, and measures that might be applied
to natural hazards and their impacts in an era of climate change. Given the global impacts of climate change and world-wide
pattern of increasing losses from natural hazards we necessarily adopt an international perspective. The specific goals of
the special issue are to: (a) encompass experiential aspects, emphasizing current practice of mitigation and its associated
measures, and their results; and (b) explore primary or root causes of alarming shifts in human and economic costs of environmental
extremes. Special emphasis is placed on how human activities are playing a key role in enhancing vulnerability to NTEE (nature-triggered
environmental extremes), quite independently from the anthropogenic causes of climate change. The goals are also (c) to examine
costs, risks, and benefits (of all kinds including social, political, ecological) of mitigation, and adjustment and adaptation
measures; and (d) analyze policy implications of alternative measures. These components are expected to make significant contributions
to policy considerations – formulation, implementation and evaluation. There is much uncertainty about the rate of climate
change; however, the fact of increase of the atmospheric temperature in the last century is no longer a subject of scientific
or policy debate. Due to such changes in the geophysical parameters, certain types of nature-triggered environmental extreme
events are likely to continue to increase. How global warming will affect regional climates and pertinent variables is not
well known, limiting our ability to predict consequential effects. This factor poses serious constraints against any straightforward
policy decisions. Research findings of the work of this volume reaffirm that human dimensions, specifically our awareness
and decision-making behavior, are powerful explanatory factors of increasing disaster losses. Disaster mitigation through
addressing human, social, and physical vulnerability is one of the best means for contributing to ‘climate change adaptation
plans’, and sustainable development goals. Recent lessons from various countries have depicted that the formulation of mitigation
strategies cannot be exclusively top-down as it requires social, political, and cultural acceptance and sense of ownership.
An interactive, participatory process, involving local communities, produces best expected outcomes concerning mitigation,
preparedness, and recovery. An emerging consensus is that there is a need to move towards the ‘mission’ of the International
Strategy for Disaster Reduction which aims at building disaster resilient communities by promoting increased awareness of
the importance of disaster reduction as an integral component of sustainable development, with the goal of reducing human,
social, economic and environmental losses due to natural hazards and related technological and environmental disasters. Sharing
of best practices and lessons globally is certain to produce more efficiency and understanding in policy and decision making. 相似文献
410.
The effect of queen pheromones on worker honey bee ovary development 总被引:11,自引:4,他引:11
We report results that address a long-standing controversy in honey bee biology, the identity of the queen-produced compounds that inhibit worker honey bee ovary development. As the honey bee is the only organism for which identities have been proposed for any pheromone that regulates reproduction, the resolution of its identity is of broad significance. We examined the effects of synthetic honey bee queen mandibular pheromone (QMP), four newly identified queen retinue pheromone components, and whole-queen extracts on the ovary development of caged worker bees. The newly identified compounds did not inhibit worker ovary development alone, nor did they improve the efficacy of QMP when applied in combination. QMP was as effective as queen extracts at ovary regulation. Caged workers in the QMP and queen extract treatments had better developed ovaries than did workers remaining in queenright colonies. We conclude that QMP is responsible for the ovary-regulating pheromonal capability of queens from European-derived Apis mellifera subspecies. 相似文献