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 953 毫秒
1.
An ecogeographical analysis of the V. narbonensis complex and V. bithynica was conducted using herbarium specimens and genebank accessions. 956 specimens were included in the study from 26 herbaria, with geographical and ecological data recorded for each specimen. A distribution map of each taxa was produced, and the geographical and ecological preferences of each taxa were analysed and discussed. The taxa with the widest distribution were found to be V. narbonensis, V. bithynica and V. johannis, and the rarest taxa were V. galilaea var. galilaea and V. narbonensis var. aegyptiaca. The complex includes three endemic species; V. hyaeniscyamus, V. kalakhensis and V. eristalioides. The complex as a whole, was most frequently collected from grasslands, as a weed in cultivated fields and in wasteland. It showed a strong preference for calcareous soils. It was found that the quality of the passport data varied widely, but that in general the specimens from more recent collections included more detailed passport data. Herbarium specimens are invaluable in ecogeographic studies as the information obtained can be used as a guide for future collecting missions and in determining areas of importance when collecting material for conservation. Finally as the whole plant is available, the identification of each specimen can be checked.  相似文献   

2.
On the bases of analysis of the collecting sites of 1160 herbarium specimens and 1640 genebank accessions of wild Avena L. species from the world collection of the Vavilov Institute of Plant Genetic Resources maps of areas of the species were produced data base. A comparison of the climate conditions of the Mediterranean, Southwestern Asiatic and Abyssinian centers of diversity with those of the oat species distribution areas shows that all oat species mostly prefer the moderately hot, semi-arid and dry climate. An analysis of the range of soils in the areas of wild oat species distribution has shown that the collected accessions, preferred different types of soil. When considering the soil diversity within the areas of natural distribution of wild oat species, it could be established that the majority of diploid and tetraploid taxa prefer to grow on mountain or plain cinnamon soils; the hexaploid taxa favorites were the mountain forest brown or red-brown soils, as well as subtropical desert soils. An analysis of the database of geographic distribution on wild oat species showed a full picture of oat species diversity, and a basis to make plans concerning further collecting activities or a basis for selecting potential sources of novel genes that can improve some valuable traits and characters to use them for practical purposes.  相似文献   

3.
Distribution, conservation status, trends, actions and ethnobotanical notes of segetal species growing in South Italy are presented and discussed. For the most threatened segetal species details and suggestions for their conservation are reported. Research work was made directly in the field for collecting samples and in the laboratory for checking several herbarium samples. To the best of our knowledges, a summary table of all species occurring in the field, of the investigated environments, and their ecological focus areas, is provided for the first time.  相似文献   

4.
Fish communities in four lakes sampled over several years were compared against a reference data set of forty-nine lakes in south-central Ontario. Two of the temporal-comparison lakes (Crosson and Grindstone) exhibit significant changes in their fish communities relative to the reference set. This was due to the extirpation of various fish species (white sucker Catostomus commersoni, lake trout Salvelinus namaycush, and blacknose shiner Notropis heterolepis) during the intervening years. A control lake in the temporal comparison (Poorhouse) showed little change in species composition over time and no loss of species. The fourth temporal lake, Plastic Lake, also showed little change likely as a consequence of the previously documented extinctions in this lake. White suckers within Crosson Lake have demonstrated intermittent recruitment and a 89% reduction in population abundance due to acid-induced reproductive constraints in their spawning stream. Similar conditions contributed to the loss of sucker populations and additional species in Grindstone and Plastic Lakes also. Various species in many of the lakes represent metapopulations. Given the barriers imposed by outflow drainage conditions, these accelerated rates of local extinctions have not been balanced by colonizations from other lakes within the watershed. As a consequence the underlying fish communities have been changed and will remain so without active rehabilitation.  相似文献   

5.
6.
The distribution, ecology and conservation status of the majority of plant species are poorly known. One of the challenges ahead is to address this knowledge gap and give more emphasis to this important group of species that represents a critical component of earth’s biodiversity. Full conservation assessments require expert knowledge of the group concerned, but for the majority of plant species, especially those from the tropics, the best source of knowledge is specimens housed within herbaria. Digitisation projects are underway to render information from this important global biodiversity resource more accessible; the next step is to assemble and utilise these data to make better informed conservation decisions. One crucial question is: how many herbarium specimens are needed to detect threatened species? Such information would inform and help to prioritise digitisation efforts. Using 11,461 herbarium records we assessed species geographic range to determine a preliminary conservation status of 661 endemic species of Leguminosae and Orchidaceae from Madagascar, following the IUCN criteria. By capturing 15 georeferenced specimens per species we produced range estimates for use in conservation assessments consistent with estimates based on all known specimens, for more than 95% of species. None of the threatened species were misclassified as not threatened, and less than 3% of species would receive conservation support as a result of being falsely identified as threatened. This approach can therefore help progress towards the Global Strategy for Plant Conservation target of a conservation assessment for each plant species, while reducing digitisation effort by up to half.  相似文献   

7.
Conservation planning is sensitive to a number of scale-related issues, such as the spatial extent of the planning area, or the size of units of planning. An extensive literature has reported a decline in efficiency of conservation outputs when planning at small spatial scales or when using large planning units. However, other key issues remain, such as the grain size used to represent the spatial distribution of conservation features. Here, we evaluate the effect of grain size of species distribution data versus size of planning units on a set of performance measures describing efficiency (ratio of area where species are represented/total area needed), rate of commission errors (species erroneously expected to occur), representativeness (proportion of species achieving the target) and a novel measure of overall conservation uncertainty (integrating commission errors and uncertainty in the actual locations where species occur). We compared priority areas for the conservation of freshwater fish in the Daly River basin (northern Australia). Our study demonstrates that the effect of grain size of species distribution data was more important than planning unit size on conservation planning performance, with an increase in commission errors up to 80% and conservation uncertainty over 90% when coarse data were used. This was more pronounced for rare than common species, where the mismatch between coarse representations of biodiversity patterns and the smaller areas of actual occupancy of species was more evident. Special attention should be paid to the high risk of misallocation of limited budgets when planning in heterogeneous or disturbed environments, where biodiversity is patchily distributed, or when planning for conservation of rare species.  相似文献   

8.
Floristic survey data from spring wetlands in the Great Artesian Basin of Australia were assessed to generate a ranked list of significant flora values. A system was designed to score endemic species and remote populations of plants, using an extensive herbarium database to set the spring flora in context. The sum of these indices for individual wetland complexes yielded a ranked score. The high priority wetland complexes (scoring five or greater) adequately represent their floristic composition, capture all endemic plant species and 76% of the flora. Although data are limited, many of the high value spring wetlands have endemic fauna of which the snails have been most thoroughly surveyed. The procedure provides direction for an efficient conservation program that if implemented should provide security against a range of threatening processes.  相似文献   

9.
We assessed national scale changes in the forage plants of bumblebees in Britain, as a means of providing quantitative evidence for the likely principal cause of declines in bumblebee species. We quantified the relative value of native and long-established plant species as forage (nectar and pollen) resources for bumblebees by collating visitation data from 14 field sites across Britain. Twentieth Century changes in range and frequency of these forage plants were assessed using data from the New Atlas of the British and Irish Flora (1930-1969 to 1987-1999) and the Countryside Surveys of Britain (1978-1998). Forage plants declined in both large-scale range and local-scale frequency between the two survey periods. These changes were of greater magnitude than changes in other native plant species, reflecting serious reductions in quality of foraging habitats for bees as well as a general decline in insect-pollinated plants. Seventy-six percent of forage plants declined in frequency within 1-km squares, including those (e.g. Trifolium pratense) of particular value for threatened bumblebee species. We consider how our findings relate to other recorded changes in the British flora, how they may help to explain declines in bumblebees and how they could contribute to a conservation strategy.  相似文献   

10.
National and International Red Lists and Legal Acts specify species with conservation needs, mainly on the basis of personal experiences. For effective conservation we need scientifically justified prioritization and grouping of these species. We propose a new combined approach where species are grouped according to the similar activities needed for their conservation. We used the national list of vascular plant species with conservation need for Estonia (301 species), and linked these species to eight qualitative conservation characteristics, four reflecting natural causes of rarity (restricted global distribution; restricted local distribution within a country; always small populations; very rare habitat type), and four connected with nature management (species needing the management of semi-natural grasslands; species needing local disturbances like forest fires; species needing traditional extensive agriculture; species which may be threatened by collecting). Only one positive association occurred among the characteristics - between restricted local distribution and small size of populations. Thus, natural causes of rarity and management aspects are not overlapping, and both should be used in conservation activities. Species grouping by different conservation characteristics allows one to focus on species groups with similar conservation needs instead of individual species. Prioritization of species with conservation needs can be based on the number of conservation characteristics that are associated with a particular species. Our prioritization did not correlate with the categories of the national Red Data Book, but a positive association was found with legal protection categories. The legislation, however, covers only the natural causes of rarity. We propose a new combined approach for plant species’ conservation planning that starts by considering human induced rarity and progresses through to natural rarity causes.  相似文献   

11.
Quantifying species turnover is an important aspect of biodiversity monitoring. Turnover measures are usually based on species presence/absence data, reflecting the rate at which species are replaced. However, measures that reflect the rate at which individuals of a species are replaced by individuals of another species are far more sensitive to change. In this paper, we propose families of turnover measures that reflect changes in species proportions. We study the properties of our measures, and use simulation to assess their success in detecting turnover. Using data on the British farmland bird community from the breeding bird survey, we evaluate our measures to quantify temporal turnover and how it varies across the British mainland.  相似文献   

12.
Information on plant adaptation can be very useful in agrobiodiversity studies. Ecogeographical land characterization (ELC) maps constitute a new tool in this direction with great potential. To assess the usefulness of this approach, an ELC map of Spain was created through multivariate methods. Its performance to characterize plant habitat preferences was compared with existing ecological regions and land cover maps. Collecting sites and seed weight from eight plant species were used to test the ELC map. Categories from each map were assigned to accessions using collecting sites. Chi-square tests were applied to test if category frequency distributions for each species followed a distribution proportional to the relative frequency of categories in each map. The tests found significant differences in the eight species studied. Thus, Bonferroni confidence intervals (BCI) classified categories from maps in preferred, neutral or avoided habitats. Seed weight was used as a proxy for plant adaptation. Comparison between observed and expected ranking of BCI and quartile classes in terms of seed weight means, and GLM and post-hoc tests carried out to test the effect of these classes upon seed weight showed consistently better results for the ELC map. Species results and applications of ecogeographic maps in plant genetic resources conservation are discussed.  相似文献   

13.
Species monitoring is one key approach to assess human impact on nature. Four main approaches have been applied in bird monitoring: comparing distribution atlases from different times, repeated monitoring programmes, checklist programmes, and species-specific surveys. We evaluate the potential of another type of data for monitoring: presence-only data on species sightings reported voluntarily by the public to open-access internet platforms, here the Species Gateway (SG) in Sweden. We regressed data on the 242 bird species observed 2001–2009 in the Swedish Bird Survey (SBS) against the corresponding SG data. We also investigated the relationship for groups of species utilizing different habitats and displaying a significant inter-annual variation, a coefficient of variation >0.3 according to the SBS. We found support for a positive relationship in inter-annual variation in population level between the two datasets. However, the species subsets displayed variation from positive to negative correlations. Restricting the analysis to species with high inter-annual variation increased the positive correlation between the data sets. The reason for the mismatch between the two datasets may be explained by temporal changes in the willingness to report certain common species to the SG. Another reason may be an imbalance in the coverage of common versus uncommon species among the two datasets. The use of voluntary citizen-based data requires great care and good knowledge of the limitation of the data. If these requirements are fulfilled, we suggest that they may be a complement to standardised programmes, especially for assessing uncommon species of conservation concern.  相似文献   

14.
为准确表征祁连山国家公园产水量时空差异性,探究产水量影响因素和驱动机制。基于降水量、参考作物蒸散量、土壤深度、根系深度和土地利用类型等参数,利用InVEST模型可视化祁连山国家公园1990—2018年产水量时空格局,使用地理探测器并结合情景模拟方法,评估和量化气候、土地利用、植被、地形等因子对祁连山国家公园产水量空间异质性和产水量变化的影响。结果表明:(1)1990—2018年研究区产水量以0.56×108 m3/a的速度显著增加,在空间上呈自西向东递增趋势;(2)耕地和林地产水深度最大,未利用土地和草地是研究区产水量的主要贡献者,且产水深度高值区位于3 200~4 600 m高海拔处;(3)降水量是产水量空间异质性的第一驱动因素,与实际蒸散量以及土地利用类型的交互作用占主导地位;(4)1990—2018年,气候变化是产水量变化的主要驱动因子,对总产水量影响为正向作用,其次为土地利用变化,主要影响产水量变化的空间分布,对总产水量影响不大。研究成果可进一步为祁连山国家公园水资源管理和可持续发展提供基础理论依据。  相似文献   

15.
88 herbarium specimens of the genus Lolium were scored for 22 characters, comprising 7 vegetative, 8 inflorescence and 7 seed characters. The aim was to review the species relationship and to produce a lateral key to the genus. The data were analysed using principal components analysis, discriminant function analysis and cluster analysis. All analyses separated L. perenne, L. multiflorum and L. temulentum from each other. The 2 varieties of L. rigidum showed varying degrees of separation from each other and from L. multiflorum. Their distinction as a species and as 2 varieties is discussed. L. perenne and L. rigidum were shown to contain the greatest similarity between species and L. temulentum was found to be the most distinct. A lateral key is proposed that separates the species on the basis of 11 morphological characters that are easily scored in the field.  相似文献   

16.
基于土壤系统分类的河南省土壤有机质时空变异研究   总被引:2,自引:0,他引:2  
利用1982年河南省第二次土壤普查数据和2009年采样数据,采用传统统计学、地统计学和地理信息系统(GIS)的方法,在土壤系统分类的基础上,对产粮大省河南省土类土壤有机质(SOM)含量时空变异特征进行了分析研究,揭示了不同土类SOM时空变异规律,并分析讨论了影响其时空变异的主要原因,对河南省不同土壤类型的合理施肥与养分调控具有指导和借鉴意义。结果表明:从1982年到2009年,河南省SOM含量均值由12.21g kg-1增加至16.02 g kg-1,增加了31.70%,变异系数分别为67.90%和35.52%。两个时期SOM变异函数均符合球状模型,块金效应值由56.10%变为60.18%,变程由569.05km变为547.22km,SOM含量空间自相关性变弱,自相关距离减小。河南省SOM自西向东逐渐增加,平原地区增加较多,而河南省南部、偏北部和西部山区地区有所减少;系统分类中的底锈干润雏形土、淡色潮湿雏形土、灌淤旱耕人为土、干润冲积新成土、干润砂质新成土、简育湿润变性土、简育湿润雏形土SOM平均含量从1982年到2009年有较大的提高,分别提高了5.76g kg-1、5.61g kg-1、5.56g kg-1、5.47g kg-1、5.42g kg-1、4.99g kg-1、3.05g kg-1,而湿润正常新成土和干润正常新成土SOM含量有所降低,分别降低了2.47g kg-1和1.90g kg-1。因成土母质、气候条件、土壤质地、土地利用方式和人为活动的影响使得河南省不同土类的SOM出现时间和空间上的差异。SOM含量增加的土类主要分布在平原耕地地区,秸秆还田以及有机肥的施入,使该区域SOM含量有较大程度的提高。  相似文献   

17.
Large mammals face high risks of anthropogenic extinction owing to their larger body mass and associated life history traits. Recent worldwide mammal declines have highlighted the conservation importance of effective assessments of trends in distribution and abundance of species. Yet reliable data depicting the nature and extent of changes in population parameters is sparse, primarily due to logistical problems in covering large areas and difficulties in obtaining reliable information at large spatial scales, particularly over time. We used key informant surveys to generate detection histories for 18 species of large mammals (body mass > 2 kg) at two points in time (present and 30 years ago) in the Southern subregion of the Western Ghats global biodiversity hotspot. Multiple-season occupancy models were used to assess temporal trends in occupancy, detectability and vital rates of extinction and colonization for each species. Our results show significant declines in distribution for large carnivores, the Asian elephant and endemic ungulates and primates. There is a significant decline in detectability for 16 species, which suggests a decline in their abundance. These patterns of change in distribution and abundance repeat in our assessments of spatial variation in occupancy dynamics between the three contiguous forest complexes and two human-dominated landscapes into which the southern Western Ghats has been fragmented. Extinction rates are highest in the human-dominated landscapes. Declines in abundance for several species suggest the presence of extinction debts, which may soon be repaid with imminent range contractions and subsequent species extinctions unless immediate remedial conservation measures are taken. Detection/non-detection surveys of key informants used in an occupancy modeling framework provide potential for rapid conservation status assessments of multiple species across large spatial scales over time.  相似文献   

18.
A priority list of 323 plant species was created through a consultative process for ex situ conservation in the recently inaugurated Israel Plant Gene Bank (IGB). The IGB is set up to preserve plant genetic resources and the endangered genetic variability of the Israeli flora. Upon its inauguration, we consulted with the country’s leading plant breeders and botanists in an attempt to create a list of the most important plant species to be included in the initial collections. The list includes crop wild relatives (CWRs), selected according to their contribution to humans: edible plants (grains, vegetables, oil); forage plants; species with potential industrial and biotechnological applications (e.g. spices, medicinal plants, aromatic plants, fibers, dyes), and species with horticultural and forestry potential. We further ranked the species on the basis of assessed values for each of seven characteristics: distribution range in the country; abundance; rarity of the growing habitats; endemism; red number index—representing imminent threat of extinction; availability of samples in Israeli collections, and genetic relationship to cultivated crops. The sum of the assessed values for these seven characteristics was used to group the species on the list into four main prioritized-collection schemes. Statistical analysis indicated that all attributes had similar influence on the collecting prioritization scheme. In general, rare species with low abundance in their growing habitats were ranked in the highest priority group, while highly distributed species were sorted together into a lower priority group. The prioritization scheme will be used to optimize the collection in the IGB with the aim of establishing its collecting activities.  相似文献   

19.
Predicting relative extinction risks of animals has become a major challenge in conservation biology. Identifying life-history and ecological traits related to the decline of species helps understand what causes population decreases and sets priorities for conservation action. Here, we use Dutch breeding bird data to correlate species characteristics with national population changes. We modelled population changes between 1990 and 2005 of all 170 breeding bird species using 25 life-history, ecological and behavioural traits as explanatory variables. We used multiple regression and multi-model inference to account for intercorrelated variables, to assess the relative importance of traits that best explain interspecific differences in population trend, and to identify the environmental changes most likely responsible. We found that more breeding birds have increased than decreased in number. The most parsimonious models suggest that ground-nesting and late arrival at the breeding grounds in migratory birds are most strongly correlated with decline. Increasing populations are mainly found among herbivores, sedentary and short-distance migrants, herb- and shrub-nesting birds and large species with a small European range. Declines in ground-nesting and late arriving migrant birds suggest that agricultural intensification, eutrophication and climate change are most likely responsible for changes in Dutch breeding bird diversity. We illustrate that management strategies should primarily focus on the traits and causes responsible for the population changes, in order to be effective and sustainable.  相似文献   

20.
Long term data to estimate population trends among species are generally lacking. However, Natural History Collections (NHCs) can provide such information, but may suffer from biases due to varying sampling effort. To analyze population trends and range-abundance dynamics of Swedish longhorn beetles (Coleoptera: Cerambycidae), we used collections of 108 species stretching over 100 years. We controlled for varying sampling effort by using the total number of database records as a reference for non-red-listed species. Because the general frequency of red-listed species increased over time, a separate estimate of sampling effort was used for that group. We observed large interspecific variation in population changes, from declines of 60% to several hundred percent increases. Most species showed stable or increasing ranges, whereas few seemed to decline in range. Among increasing species, rare species seemed to expand their range more than common species did, but this pattern was not observed in declining species. Historically, rare species did not seem to be at larger risk of local extinction, and population declines were mostly due to lower population density and not loss of sub-populations. We also evaluated the species’ declines under IUCN red-list criterion A, and four currently not red-listed species meet the suggested threshold for Near Threatened (NT). The results also suggested that species’ declines may be overlooked if estimated only from changes in species range.  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