首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Broad‐scale movements of migrant songbirds during the post‐fledging period are hypothesized to aid in the development of navigational abilities, to allow individuals to prospect for future breeding territories (combined as regional exploration), or as representing the commencement of migration. Using an automated radio telemetry array, we compared broad‐scale post‐fledging movements of hatch‐year individuals from two closely related species: blackpoll warblers Setophaga striata and myrtle warblers Setophaga coronata coronata. These two species have contrasting migratory strategies (long‐distance vs short‐distance), and we studied populations from two different islands in Nova Scotia that have different geographical landscape features. Locally‐hatched individuals affixed with VHF radios in August were tracked throughout the Gulf of Maine region for up to 2.5 months after tagging. Departure date and direction, daily probability of initiating a flight, daily displacement, total displacement and net displacement were assessed to see if there was support for the commencement of migration or regional exploration hypotheses. We observed differences between both species and islands. Compared to blackpolls, myrtles departed later, had more variable timings and directions of departure, made fewer regional‐scale flights, were more directional in their movements, and had higher net displacement. Total displacement and daily flight distances were similar between species. Variability of departure behaviour of myrtles was observed on the island farther from the mainland and both species made longer flights from that island. These results are consistent with the hypothesis that hatch‐year blackpoll movements are a form of regional exploration and hatch‐year myrtle movements represent the initial stages of migration. Species differences may be related to migratory strategy (long‐distance vs short‐distance), where the need to acquire information during post‐fledging for navigational purposes is higher for blackpolls than myrtles. Island differences suggest that habitat quality and ecological barriers influence broad‐scale movements, and myrtles are more facultative in their behaviour than blackpolls.  相似文献   

2.
Recent studies have suggested that the long distance movements of some terrestrial mammals are not migratory, but rather nomadic. Moreover, the spatial heterogeneity and temporal predictability of resources were proposed as factors contributing to alternative movement strategies, such as sedentarism (i.e., range residency), migration, and nomadism. Here, we propose that, at the individual level, a dependence on spatial memory is another important parameter for distinguishing among population-level patterns of spatial distribution. For instance, migratory animals would have a long memory of the areas they prefer to revisit, whereas nomadic animals would remember recently visited areas as places to avoid as they search for resources. We develop a computational model in which individuals’ movement decisions are based on the animals’ spatial memory of previously visited areas. Through this approach, we delineate how the interplay between landscape persistence and spatial memory leads to sedentarism, migration, and nomadism.  相似文献   

3.
The most common framework under which ungulate migration is studied predicts that it is driven by spatio–temporal variation in plant phenology, yet other hypotheses may explain differences within and between species. To disentangle more complex patterns than those based on single species/ single populations, we quantified migration variability using two sympatric ungulate species differing in their foraging strategy, mating system and physiological constraints due to body size. We related observed variation to a set of hypotheses. We used GPS‐collar data from 537 individuals in 10 roe Capreolus capreolus and 12 red deer Cervus elaphus populations spanning environmental gradients across Europe to assess variation in migration propensity, distance and timing. Using time‐to‐event models, we explored how the probability of migration varied in relation to sex, landscape (e.g. topography, forest cover) and temporally‐varying environmental factors (e.g. plant green‐up, snow cover). Migration propensity varied across study areas. Red deer were, on average, three times more migratory than roe deer (56% versus 18%). This relationship was mainly driven by red deer males which were twice as migratory as females (82% versus 38%). The probability of roe deer migration was similar between sexes. Roe deer (both sexes) migrated earliest in spring. While territorial male roe deer migrated last in autumn, male and female red deer migrated around the same time in autumn, likely due to their polygynous mating system. Plant productivity determined the onset of spring migration in both species, but if plant productivity on winter ranges was sufficiently high, roe deer were less likely to leave. In autumn, migration coincided with reduced plant productivity for both species. This relationship was stronger for red deer. Our results confirm that ungulate migration is influenced by plant phenology, but in a novel way, that these effects appear to be modulated by species‐specific traits, especially mating strategies.  相似文献   

4.
Understanding animal movements across heterogeneous landscapes is of great interest because it helps explain the dynamic processes influencing the distribution of individuals in space. Research on how animals move relative to short‐range environmental characteristics are scarce. Our objective was to determine the variables influencing movement of a large ungulate, the moose Alces alces, ranging across a boreal landscape, and to link movement behaviour with limiting factors at a fine scale. We assessed 7 candidate models composed of vegetation, solar energy, and topography variables using step selection functions (SSF) for male and female moose across daily and annual periods. We selected and weighted models using the Bayesian Information Criterion. Variables influencing small‐scale movements of moose differed among periods and between sexes, likely in response to corresponding changes in the importance of limiting factors. Best models often combined many types of variables, although simpler models composed of only vegetation or topography variables explained male's movements during rut and early winter. Moose steps were observed in good feeding stands from summer to early winter for females and from spring to early winter for males, supporting other studies of moose habitat selection. From summer to early winter, females alternatively selected and avoided cover stands during day and night, respectively. Solar energy reaching the ground was important, particularly during late winter and spring, likely due to its effect on snow cover, air temperature, or plant phenology. Moose generally moved in gentle slopes and variable elevation, which may have increased their chances of finding high quality forage, or improved their search of suitable calving sites or mates. Our study revealed the great complexity and dynamic aspects of animal movements in a heterogeneous landscape. Analysis of animal movement provides complementary information to more static habitat selection analyses and helps understanding the spatial variations in the distribution of individuals through time.  相似文献   

5.
Animal movement is a fundamental process shaping ecosystems at multiple levels, from the fate of individuals to global patterns of biodiversity. The spatio‐temporal dynamic of food resources is a major driver of animal movement and generates patterns ranging from range residency to migration and nomadism. Arctic tundra predators face a strongly fluctuating environment marked by cyclic microtine populations, high seasonality, and the potential availability of sea ice, which gives access to marine resources in winter. This type of relatively poor and highly variable environment can promote long‐distance movements and resource tracking in mobile species. Here, we investigated the winter movements of the arctic fox, a major tundra predator often described as a seasonal migrant or nomad. We used six years of Argos satellite telemetry data collected on 66 adults from Bylot Island (Nunavut, Canada) tracked during the sea ice period. We hypothesized that long‐distance movements would be influenced by spatio‐temporal changes in resource availability and individual characteristics. Despite strong annual and seasonal changes in resource abundance and distribution, we found that a majority of individuals remained resident, especially those located in an area characterized by highly predictable pulse resources (goose nesting colony) and abundant cached food items (eggs). Foxes compensated terrestrial food shortage by commuting to the sea ice rather than using long‐distance tracking or moving completely onto the sea ice for winter. Individual characteristics also influenced movement patterns: age positively influenced the propensity to engage in nomadism, suggesting older foxes may be driven out of their territories. Our results show how these mammalian predators can adjust their movement patterns to favor range residency despite strong spatio‐temporal fluctuations in food resources. Understanding the movement responses of predators to prey dynamics helps identifying the scales at which they work, which is a critical aspect of the functioning and connectivity among meta‐ecosystems.  相似文献   

6.
Long‐distance seed dispersal influences many critical ecological processes by improving chances of gene flow and maintaining genetic diversity among plant populations. Accordingly, large‐scale movements by frugivores may have important conservation implications as they provide an opportunity for long‐distance seed dispersal. We studied movement patterns, resource tracking, and potential long‐distance seed dispersal by two species of Ceratogymna hornbills, the black‐casqued hornbill C. atrata, and the white‐thighed hornbill C. cylindricus, in lowland tropical forests of Cameroon. We determined fruiting phenology of 24 tree species important in hornbill diet at monthly intervals and compared these patterns to monthly hornbill census data. After capture and radio‐tagging of 16 hornbills, we used radio telemetry by vehicle and fixed wing aircraft to determine the extent of long‐distance movements. Hornbills exhibited up to 20‐fold changes in numbers in response to fruit availability in our 25 km2 study area. Also, hornbills made large‐scale movements up to 290 km, which are larger than any movement previously reported for large avian frugivores. Together, these observations provide direct evidence that hornbills are not resident and that hornbills track available fruit resources. Our results suggest that Ceratogymna hornbills embark on long‐distance movements, potentially dispersing seeds and contributing to rain forest regeneration and diversity.  相似文献   

7.
The annual migration cycle of waterbirds often involves several distinct movement stages, for example within‐winter movements or the moult migration during summer, which require a high degree of individual flexibility in migration direction. Here, we investigate whether such flexibility is a common characteristic of waterbird migration by analysing movement behaviour of a dabbling duck, the gadwall Anas strepera, during the little studied, intermediate autumn period. The tracking of individuals via satellite transmitters (n = 7) as well as the ring re‐encounter analysis of three European gadwall populations (Germany, England, Russia) revealed that autumn movements were multidirectional. Furthermore, the comparison with winter re‐encounters suggested that autumn movements were partly independent of the movements towards subsequently used south to southwestern wintering areas. Some individuals even travelled long distances north‐ or eastwards. Accordingly, some autumn locations were characterized by a harsh climate, thus serving as temporary staging sites but necessitating further movements when wetlands freeze during winter. The occurrence of such detours or reversals of migration was confirmed by the transmitter data. Inter‐individual variability in distance and direction of autumn movements was found for both sexes and age‐classes indicating that gadwalls, in general, followed flexible movement strategies. Based on the extent of multidirectional autumn movements, we hypothesize important benefits of such flights and suggest that the analysis of year‐round movement patterns of individual animals during their distinct life‐history stages is essential to understand how they can successfully reproduce and survive.  相似文献   

8.

Aim

To quantify changes in vegetation productivity over the past three decades across five barren ground caribou (Rangifer tarandus groenlandicus) herd ranges and assess how these changes are influencing caribou movement rates.

Location

Northwest Territories and Nunavut, Canada.

Methods

As an indicator of vegetation productivity, the enhanced vegetation index (EVI) was calculated on newly developed cloud‐free, gap‐free, Landsat surface reflectance image composites representing 1984–2012. Changes in EVI were assessed on a pixel basis using Theil‐Sen's nonparametric regression and compared across herd ranges and land cover types using generalized least squares regression. Animal movement velocity was calculated from caribou telemetry data and generalized additive mixed models were used to link movement rates with vegetation productivity during the post‐calving phase of the year (July and August).

Results

Vegetation productivity increased across the five caribou herd ranges examined. The largest productivity increase occurred over the ranges of the most western herds, with the largest observed changes in grassland or shrub habitats. Caribou tended to move more slowly through tundra habitats with elevated levels of productivity to a point, while grasslands movement rates decreased linearly with increasing productivity. Movement velocities peaked at intermediate productivity levels in shrub habitats.

Main conclusions

Over the three decades of collected data, barren ground caribou habitats have become more productive, which is consistent with other studies that have documented increases in Arctic vegetation productivity. The more western herds, whose ranges are also closest to the Arctic Ocean, experienced the largest increases in productivity. Finally, we demonstrate that barren ground caribou movement patterns will likely change as a result of changing vegetation productivity in complex manners depending on herd, habitat type and the magnitude of change in vegetation productivity.  相似文献   

9.
Distribution models are increasingly being used to understand how landscape and climatic changes are affecting the processes driving spatial and temporal distributions of plants and animals. However, many modeling efforts ignore the dynamic processes that drive distributional patterns at different scales, which may result in misleading inference about the factors influencing species distributions. Current occupancy models allow estimation of occupancy at different scales and, separately, estimation of immigration and emigration. However, joint estimation of local extinction, colonization, and occupancy within a multi‐scale model is currently unpublished. We extended multi‐scale models to account for the dynamic processes governing species distributions, while concurrently modeling local‐scale availability. We fit the model to data for lark buntings and chestnut‐collared longspurs in the Great Plains, USA, collected under the Integrated Monitoring in Bird Conservation Regions program. We investigate how the amount of grassland and shrubland and annual vegetation conditions affect bird occupancy dynamics and local vegetation structure affects fine‐scale occupancy. Buntings were prevalent and longspurs rare in our study area, but both species were locally prevalent when present. Buntings colonized sites with preferred habitat configurations, longspurs colonized a wider range of landscape conditions, and site persistence of both was higher at sites with greener vegetation. Turnover rates were high for both species, quantifying the nomadic behavior of the species. Our model allows researchers to jointly investigate temporal dynamics of species distributions and hierarchical habitat use. Our results indicate that grassland birds respond to different covariates at landscape and local scales suggesting different conservation goals at each scale. High turnover rates of these species highlight the need to account for the dynamics of nomadic species, and our model can help inform how to coordinate management efforts to provide appropriate habitat configurations at the landscape scale and provide habitat targets for local managers.  相似文献   

10.
Gene flow in animals is limited or facilitated by different features within the landscape matrix they inhabit. The landscape representation in landscape genetics (LG) is traditionally modeled as resistance surfaces (RS), where novel optimization approaches are needed for assigning resistance values that adequately avoid subjectivity. Also, desert ecosystems and mammals are scarcely represented in LG studies. We addressed these issues by evaluating, at a microgeographic scale, the effect of landscape features on functional connectivity of the desert‐dwelling Dipodomys merriami. We characterized genetic diversity and structure with microsatellites loci, estimated home ranges and movement of individuals using telemetry—one of the first with rodents, generated a set of individual and composite environmental surfaces based on hypotheses of variables influencing movement, and assessed how these variables relate to individual‐based gene flow. Genetic diversity and structure results evidenced a family‐induced pattern driven by first‐order‐related individuals, notably determining landscape genetic inferences. The vegetation cover and soil resistance optimized surface (NDVI) were the best‐supported model and a significant predictor of individual genetic distance, followed by humidity and NDVI+humidity. Based on an accurate definition of thematic resolution, we also showed that vegetation is better represented as continuously (vs. categorically) distributed. Hence, with a nonsubjective optimization framework for RS and telemetry, we were able to describe that vegetation cover, soil texture, and climatic variables influence D. merriami's functional connectivity at a microgeographic scale, patterns we could further explain based on the home range, habitat use, and activity observed between sexes. We describe the relationship between environmental features and some aspects of D. merriami‘s behavior and physiology.  相似文献   

11.
The importance of landscape connectivity in determining biodiversity outcomes under environmental change has led to indices of connectivity becoming amongst the most widely used measures in conservation. Thus, it is vital that our understanding of connectivity and our use of indices describing it are reliable. Dispersal is the key ecological process involved in determining connectivity, and there is increasing evidence of substantial within‐population variability in dispersal behaviours. Here, we incorporate this inter‐individual variability into two approaches for estimating connectivity, least cost path analysis and stochastic movement simulation. Illustrative results demonstrate that including dispersal variability can yield substantially different estimates of connectivity. While connectivity is typically similar between nearby patches, the frequency of movements between patches further apart is often substantially increased when inter‐individual variability is included. Given the disproportionate role that unusual long‐distance dispersal events play in spatial dynamics, connectivity indices should seek to incorporate variability in dispersal behaviour.  相似文献   

12.
Migration strategies differ greatly among and within avian populations. The associated trade‐offs and fitness consequences of diverse strategies and how they persist are pertinent questions in migration research. Migration is a costly endeavour, presumably compensated for by better survival conditions in the non‐breeding area. One way to assess the cost of alternative strategies is to investigate the investment in movement across the entire annual cycle, an assessment made increasingly feasible with improvements in tracking technology. Our study focuses on lesser black‐backed gulls, generalist seabirds that exploit a broad range of resources, exhibit diverse migration strategies and have potentially altered migration strategies in response to human activities and climate change. We used GPS tracking to quantify lesser black‐backed gulls’ movement throughout their annual cycle and compare trade‐offs among four migration strategies. The annual cumulative distance travelled by long distance migrants wintering in west Africa, over 4000 km from their breeding colony, did not differ significantly from individuals of the same breeding colony wintering only a few hundred kilometres away in Great Britain. Short distance migrants returned to the colony first, and long distance migrants returned last. Sex and wing length were not correlated with maximum range, cumulative distance travelled or timing. Individuals spent only a small proportion of their time in flight and spent on average 17% of their time at sea throughout an annual cycle, suggesting a reliance on inland resources for many individuals. Analysing movement throughout the annual cycle can change our perspective and understanding of consequences of different migration strategies. Our study shows that a range of migration strategies coexists and we propose that the long term costs and benefits of these strategies balance out. Diversity in migration strategies may contribute to the resilience of this species in the face of ongoing anthropogenic impact on the environment.  相似文献   

13.
Despite many bird species migrating regularly within the African continent, in response to rainfall and breeding opportunities, documented evidence of the spatiotemporal patterns of such movements is scarce. We use satellite telemetry to document the year round movement of an intra‐African migrant breeding in the savannah zone of sub‐Saharan Africa, the African cuckoo. After breeding in central Nigeria, the birds migrated to more forested sites in the Adamawa region of Cameroon (n = 2) and western Central African Republic (n = 1). Departure from the breeding ground coincided with deteriorating environmental conditions whereas arrival at the non‐breeding sites matched period of increasing vegetation greenness. Migratory movements generally occurred during dark hours. In total, an average distance of 748 km in 66 d was covered during the post‐breeding migration and 744 km in 27 d during return journey with considerable individual variation and with more stopover sites used during post‐breeding migration. The diversity of migration routes followed suggests a relatively variable or flexible initial migration strategy, high individual route consistency as well as high fidelity for non‐breeding grounds.  相似文献   

14.
Estimating migration parameters of individuals and populations is vital for their conservation and management. Studies on animal movements and migration often depend upon location data from tracked animals and it is important that such data are appropriately analyzed for reliable estimates of migration and effective management of moving animals. The Net Squared Displacement (NSD) approach for modelling animal movement is being increasingly used as it can objectively quantify migration characteristics and separate different types of movements from migration. However, the ability of NSD to properly classify the movement patterns of individuals has been criticized and issues related to study design arise with respect to starting locations of the data/animals, data sampling regime and extent of movement of species. We address the issues raised over NSD using tracking data from 319 moose (Alces alces) in Sweden. Moose is an ideal species to test this approach, as it can be sedentary, nomadic, dispersing or migratory and individuals vary in their extent, timing and duration of migration. We propose a two-step process of using the NSD approach by first classifying movement modes using mean squared displacement (MSD) instead of NSD and then estimating the extent, duration and timing of migration using NSD. We show that the NSD approach is robust to the choice of starting dates except when the start date occurs during the migratory phase. We also show that the starting location of the animal has a marginal influence on the correct quantification of migration characteristics. The number of locations per day (1–48) did not significantly affect the performance of non-linear mixed effects models, which correctly distinguished migration from other movement types, however, high-resolution data had a significant negative influence on estimates for the timing of migrations. The extent of movement, however, had an effect on the classification of movements, and individuals undertaking short- distance migrations can be misclassified as other movements such as sedentary or nomadic. Our study raises important considerations for designing, analysing and interpreting movement ecology studies, and how these should be determined by the biology of the species and the ecological and conservation questions in focus.  相似文献   

15.
Processes responsible for shaping community patterns act at specific spatial scales. In this study, we aimed at disentangling the effects of climate, soil and space as drivers of variation in a coastal grassland plant community. We were specifically interested in evaluating the relative influence of those processes at broad and fine spatial scales as well as when considering species groups with good and poor long‐distance dispersal capacity. We sampled grassland vegetation at 16 sites distributed along a latitudinal gradient of more than 500 km in subtropical southern Brazil and used variation partitioning procedures to ascertain the relative influence of climatic, edaphic and spatial processes on variation in species composition at different spatial scales, considering the entire community and subsets with only species from the Asteraceae family (good long‐distance dispersal) and Poaceae (poor long‐distance dispersal). Climatic filters were the most responsible for shaping grassland community composition at the broad scale, while edaphic filters showed higher importance at the fine scale. When not considering the influence of spatial scale, we observed higher influence of climate structured in space. Composition patterns of species with poor long‐distance dispersal (Poaceae) were more closely related to spatial variables than those of species with effective dispersal (Asteraceae). Our results stressed the importance of addressing different spatial scales to rightly ascertain the magnitude that different drivers exert on plant community assembly. Dividing the community into groups with different dispersal abilities proved useful for a more detailed understanding of the community assembly processes.  相似文献   

16.
Aim Woody plants affect vegetation–environment interactions by modifying microclimate, soil moisture dynamics and carbon cycling. In examining broad‐scale patterns in terrestrial vegetation dynamics, explicit consideration of variation in the amount of woody plant cover could provide additional explanatory power that might not be available when only considering landscape‐scale climate patterns or specific vegetation assemblages. Here we evaluate the interactive influence of woody plant cover on remotely sensed vegetation dynamics across a climatic gradient along a sky island. Location The Santa Rita Mountains, Arizona, USA. Methods Using a satellite‐measured normalized difference vegetation index (NDVI) from 2000 to 2008, we conducted time‐series and regression analyses to explain the variation in functional attributes of vegetation (productivity, seasonality and phenology) related to: (1) vegetation community, (2) elevation as a proxy for climate, and (3) woody plant cover, given the effects of the other environmental variables, as an additional ecological dimension that reflects potential vegetation–environment feedbacks at the local scale. Results NDVI metrics were well explained by interactions among elevation, vegetation community and woody plant cover. After accounting for elevation and vegetation community, woody plant cover explained up to 67% of variation in NDVI metrics and, notably, clarified elevation‐ and community‐specific patterns of vegetation dynamics across the gradient. Main conclusions In addition to the environmental factors usually considered – climate, reflecting resources and constraints, and vegetation community, reflecting species composition and relative dominance – woody plant cover, a broad‐scale proxy of many vegetation–environment interactions, represents an ecological dimension that provides additional process‐related understanding of landscape‐scale patterns of vegetation function.  相似文献   

17.
18.
Other than during periods of migration, animal movement tends to be poorly described, despite the potential importance of such movements, which may prove crucial for surviving periods of bad weather and low food availability. We analysed within‐winter (December–February) movements of Mallard using the EURING Data Bank. Most movements were directed towards the south or southwest during all three winter months. Distances covered increased with winter harshness and generally decreased from 1952 to 2004. Mallards appear to move less than other duck species during winter. Long‐distance movements of Mallards seem to be related to cold weather, birds only moving long distances in large numbers during the very coldest winters. Movements are not restricted during midwinter, but occur throughout the winter. The decreasing within‐winter movement over time (1952–2004) could be explained by decreasing reporting probabilities and/or warmer winters in recent decades. However, the first is only true if the decrease in reporting probability increases with distance moved, for which we found no indication in our study. Therefore, we suggest that the pattern found is evidence of long‐term winter warming reducing the distance of within‐winter movements in this species.  相似文献   

19.
Aim Vegetation exhibiting landscape‐scale regular spatial patterns has been reported for arid and semi‐arid areas world‐wide. Recent theories state that such structures are bound to low‐productivity environments and result from a self‐organization process. Our objective was to test this relationship between periodic pattern occurrence and environmental factors at a global scale and to parametrize a predictive distribution model. Location Arid and semi‐arid areas world‐wide. Methods We trained an empirical predictive model (Maxent) for the occurrence of periodic vegetation patterns, based on environmental predictors and known occurrences verified on Landsat satellite images. Results This model allowed us to discover previously unreported pattern locations, and to report the first ever examples of spotted patterns in natural systems. Relationships to the main environmental drivers are discussed. Main conclusions These results confirm that periodic patterned vegetations are ubiquitous at the interface between arid and semi‐arid regions. Self‐organized patterning appears therefore to be a biome‐scale response to environmental conditions, including soil and topography. The set of correlations between vegetation patterns and their environmental conditions presented in this study will need to be reproduced in future modelling attempts.  相似文献   

20.
The movement ability of species in fragmented landscapes must be considered if habitat restoration strategies are to allow maximum benefit in terms of increased or healthier wildlife populations. We studied movements of a range of bird species between woodland patches within a high‐altitude Polylepis/matrix landscape in the Cordillera Vilcanota, Peru. Movement rates between Polylepis patches differed across guilds, with arboreal omnivores, arboreal sally‐strikers and nectarivores displaying the highest movement rates, and understorey guilds and arboreal sally‐gleaners the lowest movement rates. Birds tend to avoid flights to more distant neighboring patches, especially when moving from patches which were themselves isolated. The decline in bird flight frequencies with increasing patch isolation followed broken‐stick models most closely, and while we suggest that there is evidence for a decline in between‐patch movements over distances of 30–210 m, there was great variability in movement rates across individual patches. This variability is presumably a result of complex interactions between patch size, quality and configuration, and flight movement patterns of individual bird species. Our study does, however, highlight the contribution small woodland patches make toward fragmented Polylepis ecosystem functioning, and we suggest that, where financial resources permit, small patch restoration would be an important compliment to the restoration of larger woodland patches. Most important is that replanting takes place within 200 m or so of existing larger patches. This will be especially beneficial in allowing more frequent use of woodland elements within the landscape and in improving the total area of woodland patches that are functionally connected.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号