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排序方式: 共有161条查询结果,搜索用时 15 毫秒
1.
R. S. Steneck C. B. Paris S. N. Arnold M. C. Ablan-Lagman A. C. Alcala M. J. Butler L. J. McCook G. R. Russ P. F. Sale 《Coral reefs (Online)》2009,28(2):367-378
As the science of connectivity evolves, so too must the management of coral reefs. It is now clear that the spatial scale
of disturbances to coral reef ecosystems is larger and the scale of larval connectivity is smaller than previously thought.
This poses a challenge to the current focus of coral reef management, which often centers on the establishment of no-take
reserves (NTRs) that in practice are often too small, scattered, or have low stakeholder compliance. Fished species are generally
larger and more abundant in protected reserves, where their reproductive potential is often greater, yet documented demographic
benefits of these reproductive gains outside reserves are modest at best. Small reproductive populations and limited dispersal
of larvae play a role, as does the diminished receptivity to settling larvae of degraded habitats that can limit recruitment
by more than 50%. For “demographic connectivity” to contribute to the resilience of coral reefs, it must function beyond the
box of no-take reserves. Specifically, it must improve nursery habitats on or near reefs and enhance the reproductive output
of ecologically important species throughout coral reef ecosystems. Special protection of ecologically important species (e.g.,
some herbivores in the Caribbean) and size-regulated fisheries that capitalize on the benefits of NTRs and maintain critical
ecological functions are examples of measures that coalesce marine reserve effects and improve the resilience of coral reef
ecosystems. Important too is the necessity of local involvement in the management process so that social costs and benefits
are properly assessed, compliance increased and success stories accrued. 相似文献
2.
Alane Ayana Vieira de Oliveira Couto Simon Hellemans Yves Roisin Martín Alejandro Montes Alexandre Vasconcellos 《Insect Conservation and Diversity》2020,13(4):351-359
- Connectivity loss during habitat fragmentation poses a serious threat to global biodiversity. The effects of this process depend on factors such as the dispersal ability and breeding systems of each species, the type of land use surrounding the habitat remnants and the position of fragments in the landscape.
- Termites are abundant in tropical ecosystems, and within this group, soil‐feeding species are the most sensitive to environmental degradation.
- We investigated whether the fragmentation of the Atlantic Forest that occurred approximately 110 years ago because of sugarcane plantations in Northeast Brazil affected the genetic diversity of a population of Embiratermes neotenicus (Termitidae: Syntermitinae) in 14 fragments separated by 3–104 m over an extent of 20 km.
- For 10 nests in each fragment, 10 individuals (n = 1400) were genotyped at five microsatellite loci. Our results show that the population exhibits weak genetic structure, with no relations between genetic variability and fragment features.
- This result may be explained by the extraordinarily long lifespan of individual colonies, given this species' peculiar breeding system, offering several opportunities for dispersal events and patch colonisation.
- Landscape features such as the arrangement of forest fragments and seasonal nature of the sugarcane matrix could enable this species to maximise dispersal success and avoid local extinction.
3.
计算42个辐射增敏剂的各阶分子连接性指数mXt及△mXt,并对其中38个非对称性化合物的分子连接性指数与其增敏活性进行定量构效关系(QuantitatireStructureActivityRelationship,QSAR)的研究,得到相关方程。并分析了影响增敏活性的1gP、ES及σ在一定程度上都可通过分子连接性指数表达出来。对这些增敏剂进行分子对称性的研究,发现对称性会降低分子的极性,进而降低其增敏活性。另外,还发现在这些增敏剂中存在亚类现象,并对各亚类的反应机理进行了探讨。 相似文献
4.
Christiane Trierweiler Ben J. Koks Rudi H. Drent Klaus-Michael Exo Jan Komdeur Cor Dijkstra Franz Bairlein 《Journal of Ornithology》2007,148(4):513-516
Autumn migration routes of two Dutch female Montagu’s Harriers (Circus pygargus) were documented for the first time using satellite telemetry. Both migrated to their African wintering area—one via the
Straits of Gibraltar through the Mediterranean and the other via Italy/Tunisia. The rate of travel was comparable to values
reported for larger raptor species. 相似文献
5.
The accumulation and seasonal impact of riverine discharge on coral reefs of the Meso-American Region (MAR) were estimated
using a numerical simulation of river runoff dispersion. River-reef connectivity, or source-sink dynamics of terrestrial runoff
was further assessed from more than 400 watersheds of the region onto discrete coral reef areas. Using land use for 2003 and
2004 in the MAR, this work builds upon a Regional Ocean Modeling System simulation of the MAR validated by ocean color satellite
data, and on the monthly river nutrient and sediment load and discharge provided by the World Resources Institute using the
N-SPECT model. Analysis of the variability of simulated runoff transport to the reefs showed that reefs of the Mesoamerican
Barrier Reef System (MBRS) were mostly impacted from June to September, following the peak time of river discharge. At that
time, the coastal and oceanic circulations contribute quickly to expel the runoff from the MBRS. High runoff concentration
waters leaving the eastern coast of Honduras during the months of October to December return to the southwestern MAR in March
as they are entrained in a cyclonic gyre. Coral reefs of the MAR are thus impacted twice, first from the coastal side with
runoff of local origin and later from the oceanic side with runoff from mixed origin. High probability of connectivity between
rivers and remote reefs is established as this study revealed that river runoff from the north shore of Honduras has a wide-spread
impact on most of the coral reefs of southern Belize, while watersheds on the Gulf of Honduras are mostly connected to coral
reefs in the northern shore of Honduras. Although the level of remote influence (or runoff concentration reaching the reef)
is lower than the local, the cumulative effect of numerous remote river-reef connections remains significant.
Communicated by Biology Editor Michael Lesser 相似文献
6.
Connectivity for large mammals across human-altered landscapes results from movement by individuals that can be described via nested spatial scales as linkages (or zones or areas) with compatible land use types, constrictions that repeatedly funnel movement (as corridors) or impede it (as barriers), and the specific paths (or routes) across completely anthropogenic features (such as highways). Mitigation to facilitate animal movement through such landscapes requires similar attention to spatial scale, particularly when they involve complex topography, diverse types of human land use, and transportation infrastructure. We modeled connectivity for Asian elephant (Elephas maximus) and gaur (Bos gaurus) in the Shencottah Gap, a multiple-use region separating two tiger reserves in the Western Ghats, India. Using 840 km of surveys for animal signs within a region of 621 km2, we modeled landscape linkages via resource selection functions integrated across two spatial resolutions, and then potential dispersal corridors within these linkages using circuit theoretical models. Within these corridors, we further identified potential small-scale movement paths across a busy transportation route via least-cost paths and evaluated their viability. Both elephants and gaur avoided human-dominated habitat, resulting in broken connectivity across the Shencottah Gap. Predicted corridor locations were sensitive to analysis resolution, and corridors derived from scale-integrated habitat models correlated best with habitat quality. Less than 1% of elephant and gaur detections occurred in habitat that was poorer in quality than the lowest-quality component of the movement path across the transportation route, suggesting that connectivity will require habitat improvement. Only 28% of dispersal corridor area and 5% of movement path length overlapped with the upper 50% quantile of the landscape linkage; thus, jointly modeling these three components enabled a more nuanced evaluation of connectivity than any of them in isolation. 相似文献
7.
Jelmer A. Elzinga Saskya van Nouhuys Dirk-Jan van Leeuwen Arjen Biere 《Basic and Applied Ecology》2007,8(1):75-88
Habitat fragmentation can disrupt communities of interacting species even if only some of the species are directly affected by fragmentation. For instance, if parasitoids disperse less well than their herbivorous hosts, habitat fragmentation may lead to higher herbivory in isolated plant patches due to the absence of the third trophic level. Community-level studies suggest that parasitoids tend to have limited dispersal abilities, on the order of tens of metres, much smaller than that of their hosts, while species-oriented studies document dispersal by parasitoids on the scale of kilometres. In this study the distribution patterns of three parasitoid species with different life histories and their moth host, Hadena bicruris, a specialist herbivore of Silene latifolia, were compared in a large-scale network of natural fragmented plant patches along the rivers Rhine and Waal in the Netherlands. We examined how patch size and isolation affect the presence of each species. Additionally, experimental plots were used to study the colonisation abilities of the species at different distances from source populations.In the natural plant patches the presence of the herbivore and two of the parasitoids, the gregarious specialist Microplitis tristis and the gregarious generalist Bracon variator were not affected by patch isolation at the scale of the study, while the solitary specialist Eurylabus tristis was. In contrast to the herbivore, the presence of all parasitoid species declined with plant patch size. The colonisation experiment confirmed that the herbivore and M. tristis are good dispersers, able to travel at least 2 km within a season. B. variator showed intermediate colonisation ability and E. tristis showed very limited colonisation ability at this spatial scale. Characteristics of parasitoid species that may contribute to differences in their dispersal abilities are discussed. 相似文献
8.
Alexandre Uezu Dennis Driesmans Beyer Jean Paul Metzger 《Biodiversity and Conservation》2008,17(8):1907-1922
In fragmented landscapes, agroforest woodlots can potentially act as stepping stones facilitating movement between forest
fragments. We assessed the influence of agroforest woodlots on bird distribution and diversity in the Atlantic forest region
(SE Brazil), and also tested which categories of species can use different types of connection elements, and whether this
use is influenced by the distance to large forest patches. We studied two fragmented landscapes, with and without stepping
stones linking large fragments, and one forested landscape. Using a point count, a bird survey was undertaken in the fragmented
landscapes in five different elements: large remnants (>400 ha), agroforest woodlots (0.4–1.1 ha), small patches (0.5–7 ha),
riparian corridor, and pasture areas (the main matrix). Generalist and open-area species were commonly observed in the agroforest
system or other connection elements, whereas only a few forest species were present in these connections. For the latter species,
the distance of woodlots to large patches was essential to determine their richness and abundance. Based on our results and
data from literature, we suggest that there is an optimal relationship between the permeability of the matrix and the efficiency
of stepping stones, which occurs at intermediate degrees of matrix resistance, and is species-dependent. Because the presence
of agroforest system favors a higher richness of generalist species, they appeared to be more advantageous for conservation
than the monoculture system; for this reason, they should be considered as a management alternative, particularly when the
matrix permeability requirement is met. 相似文献
9.
Roe deer is a protected species in Iran as its population and distribution in the country have considerably declined. Roe deer are threatened by several factors such as habitat fragmentation and road mortality, so studying their distribution and movement through the increasing habitat destruction and fragmentation is necessary. This will become increasingly important because climate change will transform the species’ future habitat and connectivity patterns. We evaluated the roe deer’s potential distribution range in northern Iran and, for the first time, developed connectivity models and designed corridors for the present and future to make better conservation plans. We collected 91 points indicating the presence of roe deer in the study region. After developing ensemble models using six species distribution algorithms, we defined high-ranked habitat cores using the concept of landscape suitability prioritization. From these, we designed connectivity and corridors in two time-frames with the help of least-cost paths and circuit theories to predict the potential movement throughout the study area. We estimated that the overall core habitats for roe deer in the present and future periods are, respectively, around 1200 km2 and 2600 km2, corresponding to 2 and 4 percent of the whole area. This suggests that the habitat core will expand in the future as a result of climate change. Similarly, the connectivity among the cores will strengthen. We also conclude that the temperature-driven and anthropogenic variables significantly affect the distribution of roe deer in northern Iran. It is necessary that conservationists and managers consider the designed corridors in the present study while planning conservation strategies. 相似文献
10.
Hepatocellular carcinoma (HCC) is a severe liver malignancy with few drug treatment options. In finding an effective treatment for HCC, screening drugs that are already FDA-approved will fast track the clinical trial and drug approval process. Connectivity Map (CMap), a large repository of chemical-induced gene expression profiles, provides the opportunity to analyze drug properties on the basis of gene expression. Support Vector Machines (SVM) were utilized to classify the effectiveness of drugs against HCC using gene expression profiles in CMap. The results of this classification will help us (1) identify genes that are chemically sensitive, and (2) predict the effectiveness of remaining chemicals in CMap in the treatment of HCC and provide a prioritized list of possible HCC drugs for biological verification. 相似文献