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 437 毫秒
1.
The Baja California Peninsula is home to 85 species of cacti, of which 54 are endemic, highlighting its importance as a cactus diverse region within Mexico. Many species are under threat due to collection pressure and habitat loss, but ensuring maximal protection of cacti species requires a better understanding of diversity patterns. We assessed species richness, endemism, and phylogenetic and morphological diversity using herbarium records and a molecular phylogeny for 82 species of cacti found in the peninsula. The four diversity measures were estimated for the existing nature reserve network and for 314 hexagrids of 726 km2. Using the hexagrid data, we surveyed our results for areas that best complement the current protected cacti diversity in the Baja California Peninsula. Currently, the natural reserve network in Baja shelters an important amount of the cacti diversity (74% of the species, 85.9% of the phylogenetic diversity, 76% of endemics and all the growth forms). While species richness produced several solutions to complement the diversity protected, by identifying priority species (endemic species with high contribution to overall PD) one best solution is reported. Three areas (San Matías, Magdalena and Margarita Islands and El Triunfo), selected using species richness, PD and endemism, best complement the diversity currently protected, increasing species richness to 89%, PD to 94% and endemism to 89%, and should be considered in future conservation plans. Two of these areas could be included within nature reserves already established.  相似文献   

2.
One of the most serious environmental problems is the current acceleration in the rate of species extinction associated with human activities, which is occurring particularly rapidly in freshwaters. Here we examine whether endemic water beetles are effectively protected by existing conservation measures in the Iberian Peninsula and the Balearic Islands, a region of high diversity and intense human pressure. We used an exhaustive database for aquatic beetles in the region to address such issues. Firstly, we identify the most threatened endemic taxa using a categorization system to rank species according to their conservation priority or vulnerability. Of the 120 endemic species of water beetles used in the analysis, only two (Ochthebius ferroi and Ochthebius javieri) were identified as being extremely vulnerable, 71 were highly vulnerable and 46 moderately vulnerable, with only a single species identified as having low vulnerability status. Since no Iberian species of aquatic Coleoptera has legal protection, the only conservation measure available for these species is the extent to which they occur in protected areas. Here we identify distributional hotspots for threatened endemic species, and evaluate the extent to which these are already included in the Natura 2000 network in Spain and Portugal. Despite a high degree of concordance between hotspots and Natura 2000 sites, the distribution of four species falls completely outside the network. The analysis also reveals that Natura 2000 fails to protect saline water bodies, despite their high conservation interest and narrow global distribution. The picture revealed here with water beetles is likely to be similar for others groups of freshwater macroinvertebrates, since Coleoptera are known to be good surrogates of aquatic biodiversity in the region. Finally, the degree of protection provided via Natura 2000, and the utility of red lists are discussed.  相似文献   

3.
The Peninsula of Baja California, Mexico has long been recognized as a hotspot for plant richness and endemism. However, its extraordinary diversity is not adequately protected by the existing protected areas. We analyzed the distribution of the endemic vascular flora of the peninsula, and its presence or absence in protected areas. We also identified regions with greater numbers of endemic species not currently under protected status. The families Asteraceae, Cactaceae, and Fabaceae alone contain 40% of the endemic species. All the peninsular species within the Begoniaceae, Thymeliaceae, Araliaceae and Hippocastanaceae are endemic. Of the total number of endemic taxa in the region, 76.4% are present within protected areas. The endemic genera Adenothamnus, Carterothamnus, Faxonia, and Ornithostaphylos are entirely absent from protected areas. Of the 567 endemics found in protected areas 75 represent varieties or subspecies Of the 175 not found in protected areas 21 are varieties or subspecies. A gap analysis identified that the areas with the highest number of unprotected endemic species are in the Mediterranean-type ecosystems of the north-west part of the peninsula and in the deciduous dry tropical communities of the cape region at the southernmost tip of Baja California. Our findings suggest that it is necessary to create several protected areas along the peninsula for the successful conservation of rare and endemic taxa These new areas should encompass a latitudinal gradient of biogeographical units (including Mediterranean communities and montane habitats of the Sierras) along the peninsula.  相似文献   

4.
The collembological composition of samples from the Central and Western Pyrenees (Northern Spain) was studied. Soils from two biotopes (pine forest and Rhododendron shrub) were studied in Nuria and Vallibierna, using different diversity indices and multivariate analyses. Ten species were found that were endemic to the Iberian Peninsula. Three of these are exclusive to the Pyrenees: Ceratophysella elegans, Hypogastrura dasiensis and Protachorutes pyrenaeus. The greatest diversity was observed in the soils of Rhododendron, above all at Nuria. Collembola were most poorly represented in the pine forest of Vallibierna, where the endemic Hypogastrura meridionalis was the dominant species. Multivariate analyses indicated that the latter species characterizes this pine forest and separates it from all other biotopes studied. The evenness (E) was most pronounced in Nuria, where Folsomia manolachei was the characteristic species.  相似文献   

5.
Recent advances in Collembola systematics   总被引:5,自引:0,他引:5  
Louis Deharveng 《Pedobiologia》2004,48(5-6):415-433
  相似文献   

6.
Molecular data are shedding new light on our understanding of genetic diversity and biological diversity in general. We examine results of recent genetic studies on African birds that document endemic diversity in small, isolated montane forests of Africa. These studies show that levels of genetic differentiation in these isolated montane regions are substantial and indicate little or no gene flow with their closest populations. Although this pattern of locally distributed montane taxa is not something that has gone unnoticed by traditional taxonomists, we argue that many of the small, often outlying areas run the risk of being devalued in conservation planning because these areas generally have comparatively low levels of overall diversity and endemism (especially at the species level). We strongly suspect that other organisms will possess similar patterns of differentiation in Afro-montane regions of Africa and we argue that this information can be effectively brought to bear to highlight the conservation significance of these smaller areas.  相似文献   

7.
During the Pleistocene, climatic fluctuations due to glacial and interglacial periods greatly modified the distribution of boreal organisms. One direct effect of these distribution shifts is that, along the southern edge of the range of some boreal species, populations persist only in isolated patches of suitable habitats, surrounded by less suitable areas. Isolated populations in marginal habitat are vulnerable to several threats, including climate change, anthropogenic threats, and stochastic events. We developed habitat-suitability models using Ecological Niche Factor Analysis for populations of the smooth snake, Coronella austriaca, at the southernmost limit of the species range. These models were based on historical and current records of occurrence, coupled with remote sensing data including elevation, slope, and climatic variables. Our results indicated that C. austriaca in the Iberian Peninsula occurred in areas associated with high slope and precipitation, low temperatures, and low variation in seasonal temperature and precipitation compared to areas of non-occurrence. At a broad scale, the areas classified as highly suitable for the species in the southern Iberian Peninsula were small and fragmented. At a local scale, extensive field work demonstrated that C. austriaca occurs in low densities in these areas. In addition, we detected several human-induced threats like habitat loss, favoured by temperature increase and rainfall reduction. Several life-history traits, such as dietary specialization and low frequency reproduction, also may contribute to the vulnerability of these populations to local extinctions. Although the most suitable southernmost areas are included in protected reserves, specific guidelines for management are needed to assess conservation needs.  相似文献   

8.
We used the results of the Spanish Otter Survey of 1994-1996, a Geographic Information System and stepwise multiple logistic regression to model otter presence/absence data in the continental Spanish UTM 10×10-km squares. Geographic situation, indicators of human activity such as highways and major urban centers, and environmental variables related with productivity, water availability, altitude, and environmental energy were included in a logistic model that correctly classified about 73% of otter presences and absences. We extrapolated the model to the adjacent territory of Portugal, and increased the model's spatial resolution by extrapolating it to 1×1-km squares in the whole Iberian Peninsula. The model turned out to be rather flexible, predicting, for instance, the species to be very restricted to the courses of rivers in some areas, and more widespread in others. This allowed us to determine areas where otter populations may be more vulnerable to habitat changes or harmful human interventions.  相似文献   

9.
The forests and highlands along the southern portion of the Nigeria-Cameroon border and on the island of Bioko have long been recognized as being biologically diverse. This region (referred to as the Biafran forests and highlands) is a center of endemism for a wide variety of taxa including, but not limited to, primates, anuran amphibians, birds, freshwater fish, butterflies, dragonflies, and trees. Though these groups have diverse distributions, conservation efforts have to date largely been focused on lowland areas. We conducted a GIS-based analysis of point locality records for three groups characterized by high endemism (primates, anuran amphibians, birds) in order to examine both their spatial and altitudinal distribution throughout the study area. We also evaluated the distribution of existing and potential protected areas relative to highland areas and the distribution of endemics. Our analysis suggests that the existing protected area system provides poor coverage of montane habitats and their associated endemic taxa. Complementarity analysis suggests that, if the protected area network were expanded to include a small number of highland sites, coverage of endemic taxa could be significantly improved. Many of these important highland sites are currently under intense pressure from habitat loss and hunting. If the full range of biodiversity present in the Biafran forests and highlands is to be preserved, new protected areas should be gazetted that take the varied distributions of the regions endemic taxa into account.  相似文献   

10.
Biodiversity in Africa, Madagascar and smaller surrounding islands is both globally extraordinary and increasingly threatened. However, to date no analyses have effectively integrated species values (e.g., richness, endemism) ‘non-species’ values (e.g., migrations, intact assemblages), and threats into a single assessment of conservation priorities. We present such an analysis for the 119 ecoregions of Africa, Madagascar and smaller islands. Biodiversity is not evenly distributed across Africa and patterns vary somewhat among taxonomic groups. Analyses of most vertebrates (i.e., birds, mammals, amphibians) tend to identify one set of priority ecoregions, while plants, reptiles, and invertebrates highlight additional areas. ‘Non-species’ biological values are not correlated with species measures and thus indicate another set of ecoregions. Combining species and non-species values is therefore crucial for assembling a comprehensive portfolio of conservation priorities across Africa. Threats to biodiversity are also unevenly distributed across Africa. We calculate a synthetic threat index using remaining habitat, habitat block size, degree of habitat fragmentation, coverage within protected areas, human population density, and the extinction risk of species. This threat index is positively correlated with all three measures of biological value (i.e., richness, endemism, non-species values), indicating that threats tend to be focused on the region’s most important areas for biodiversity. Integrating biological values with threats allows identification of two distinct sets of ecoregion priority. First, highly imperilled ecoregions with many narrow endemic species that require focused actions to prevent the loss of further habitat leading to the extinction of narrowly distributed endemics. Second, less threatened ecoregions that require maintenance of large and well-connected habitats that will support large-scale habitat processes and associated area-demanding species. By bringing these data together we can be much more confident that our set of conservation recommendations serves the needs of biodiversity across Africa, and that the contribution of different agencies to achieving African conservation can be firmly measured against these priorities.  相似文献   

11.
This article documents the conservation status of the herpetofauna in the Pacific lowlands and adjacent Balsas Basin and Chiapas Depression regions and the presents the results of modelling species spatial distributional patterns through GARP analysis, to identify hotspots of species richness, endemic and geographically restricted species in the study area. It also compares the distribution of these hotspots with the distribution of protected areas and intact seasonally tropical dry tropical forests, the dominant vegetation type in the study area and experiencing high deforestation rates. A total of 301 reptiles and amphibian species occur in the study area accounting for a third of the Mexican herpetofauna, and recording high levels of endemism and endangerment. Hotspots of species richness and endemism were located in coastal Jalisco, a considerable portion of the Colima state, as well as scattered areas in Michoacán, Guerrero, and Oaxaca. These areas should receive highest priority for protection. Unfortunately, there was a minimum correspondence when comparing the distribution of actually and proposed protected areas with hotspots identified. Fortunately, areas of high species richness, endemism and restricted species coincided with those where intact seasonally tropical dry tropical forests still exists. These areas should receive high priority in future plans for seasonally tropical dry tropical forests protected areas. It is hoped that this paper will call attention to the need for establishing a network of protected areas in the study area, as has been proposed by previous studies.  相似文献   

12.
Some snakes are highly vulnerable to extinction due to several life history traits. However, the elusive behavior and secretive habits of some widespread species constrain the collection of demographic and ecological data necessary for the identification of extinction-prone species. In this scenario, the enhancement of ecological modelling techniques in Geographical Information Systems (GIS) is providing researchers with robust tools to apply to such species. This study has identified the environmental factors that limit the current distribution of Vipera latastei, a species with secretive behavior, and has evaluated how human activities affect its current conservation status, identifying areas of best habitat suitability in the Iberian Peninsula. Ecological-niche factor analysis (ENFA) indicated low marginality (0.299) and high tolerance (0.887) scores, suggesting strong tendency for the species to live in average conditions throughout the study area and to inhabit any of the environmental conditions. The analysis also revealed that this viper tends to select particular Mediterranean habitats, although topographic factors (altitude and slope) were the major environmental constraints for the Iberian distribution pattern of the species. The presence of other parapatric viper species in the north of the Iberian Peninsula (V. aspis and V. seoanei) and two human-related variables (landscape transformation and human density) also had a negative relation with the occurrence of V. latastei. All factors can explain its absence in northern Iberia and its fragmented distribution as currently is found mostly in mountains and relatively undisturbed low-altitude areas. The historical destruction and alteration of natural Mediterranean habitats and several life-history traits of the species contribute to its vulnerability to extinction. The ENFA analysis proved to be an outstanding method to evaluate the factors that limit the distribution range of secretive and widespread species such as V. latastei, updating evaluation of their conservation status.  相似文献   

13.
Many tropical countries contain large numbers of species with small geographical ranges, here, for convenience, termed endemics. South America, for example, harbours 440 endemic land birds having ranges of less than 50 000 km2. These comprise about a quarter of the terrestrial avifauna of the continent. Such species are exceptionally vulnerable to deforestation and their preservation will require siting future parks or reserves in just the right places. Using Colombia and Ecuador as an illustration, we describe a simple procedure for locating areas of concentrated endemism that would be optimal for future protection. Unfortunately, there is little correspondence between the points of maximal endemism and the locations of existing and projected reserves in the two countries. The advantages and limitations of using satellite photos for habitat evaluation in centres of endemism are also discussed.  相似文献   

14.
Crop wild relatives (CWR) and wild harvested plant species (WHP) constitute an important element of a nation’s plant genetic resources (PGR) available for utilisation. Although their natural populations are threatened like other wild species by habitat lost and fragmentation, little attention has generally been paid to their systematic conservation. The development of checklists and inventories is considered by the convention on biological diversity (CBD) and the global strategy for plant conservation (GSPC) as the first step in any national strategy for conservation and sustainable use of plant diversity. Methodological approaches to the development of a national inventory of wild PGR are discussed in the light of a case-study for the CWR and WHP growing in mainland Portugal. The resultant inventory comprises 2319 taxa, of which 97.5% are CWR, 21.4% are WHP and 19.0% are both CWR and WHP. Approximately 6.1% are endemic to mainland Portugal; 24.1% occur in 1 to 4 Portuguese administrative regions; 15.6% are threatened, but only 5.9% are covered by legislative protection. Taxonomic misalignments and the dispersed nature of biological literature were the major impediments to the production of the national inventory, but once the inventory was established it has proven to be a powerful tool in conservation management.  相似文献   

15.
The biodiversity of the Albertine Rift   总被引:4,自引:0,他引:4  
The Albertine Rift is one of the most important regions for conservation in Africa. It contains more vertebrate species than any other region on the continent and contains more endemic species of vertebrate than any other region on mainland Africa. This paper compiles all currently known species distribution information for plants, endemic butterfly species and four vertebrate taxa from the Albertine Rift. The literature on fish species richness and endemism is also reviewed to assess the importance of the larger lakes in the Rift for conservation. We use data from 38 protected and unprotected areas to prioritise sites within the Albertine Rift for conservation based upon their numbers of endemic and globally threatened species. Virunga and Kahuzi Biega National Parks and Itombwe Massif in Democratic Republic of Congo, Bwindi Impenetrable and Kibale National Parks in Uganda, and Nyungwe National Park in Rwanda rank highest in terms of numbers of both endemic and globally threatened species. Six conservation landscapes are described that include most of these sites and it is argued that a focus on these landscapes may be a more holistic method to ensure the safety of the priority areas of the Albertine Rift.  相似文献   

16.
Pantepui is a biogeographical province composed of a group of approximately 50 tabular mountain summits, or tepuis, in the southeast of Venezuela. This region, also known as Guayana Highlands (GH), lies between 1500 and 3014 m elevation and has an approximate extension of 6000 km2. The summits of the tepuis are characterized by exceptional vascular plant diversity and high endemism. However, it is expected that ongoing global warming will produce upward displacements of summit taxa, which may cause the extinction of certain species due to habitat loss. This study assessed the potential extinction risk of the >600 Pantepui endemic vascular plant species during the 21st century due to global warming, revealing that 30–50% of endemic species would lose their habitat by the end of this century. In light of these results, prioritization of threatened species for conservation purposes became necessary. This was achieved through the calculation of an Environmental Impact Value (EIV) for each species, and a subsequent division of these species into priority categories, which should be used in a chronological sequence to guide decision-making and future research aimed at establishing the most suitable conservation strategies. A number of in situ and ex situ conservation alternatives were discussed. In situ conservation by means of designating protected areas does not appear a viable option because of the upward habitat displacement involved in this case. Conversely, seed banks, living plant collections and managed relocation were suggested in this chronological order to preserve the species studied here.  相似文献   

17.
Five main conclusions arise from this review of the responses of species to anthropogenic disturbance in Madagascar: First, species’ reactions to anthropogenic disturbance are generally negative, but remain poorly known. Our knowledge is patchy among and within higher taxonomic groups; we are still largely gathering case studies. Second, taxonomic groups vary considerably in which proximate factors are most important. Third, several groups show differing responses within different ecoregions. Whether these differences are consistent across groups requires further testing. Fourth, related species often have divergent reactions to disturbance, even within lower taxonomic groupings (families or genera). Thus, we cannot rely on phylogenetic relatedness or even ecological similarity to infer similarity in responses. Finally, disturbance typically reduces species diversity (especially of native and/or endemic species), but also causes species turnover, typically with forest specialists replaced by grassland generalists, and endemics replaced by non-endemics (including invasives). Given these knowledge gaps, we stress the urgency of applied studies that assess species’ ecology, behaviour and health across disturbance gradients, including purely anthropogenic landscapes. Remaining natural vegetation and protected areas will be unable to preserve Madagascar’s biodiversity under the impact of climatic change; we must understand responses of plants and animals to disturbance in order to create buffer zones and corridors combining secondary, degraded and natural habitats.  相似文献   

18.
19.
Historical data on the distribution and status of the purple gallinule (Porphyrio porphyrio) in Portugal were collected by bibliographic research, from museum catalogues and from questionnaires to wetland managers, ornithologists and birdwatchers. The population suffered severe decline and range contraction at the end of the 19th century and most of the 20th century, due mainly to habitat loss and degradation and excessive hunting. However, the population has begun to recover in the last decade mainly through direct protection of the species and of the remaining habitat, together with creation of artificial wetlands and a reintroduction programme, and probably also due to immigration from Spain. The population size has increased about 10-fold and the range has expanded to most of its former area. The estimated Portuguese breeding population in 2002 was 49-67 pairs. Densities varied between 0.05 and 7 individuals/ha in recently colonized areas and stable (saturated) areas, respectively. Although the population is recovering, its small size, high fragmentation and several natural and anthropogenic threats lead us to consider it still a species of major concern in Portugal.  相似文献   

20.
The Alexander Archipelago of Southeast Alaska encompasses over 2000 named islands that extend along 600 km of the North Pacific Coast. This review summarizes recent research on mammals of this largely unexplored region. Field inventories followed by preliminary molecular genetic analyses of selected mammals demonstrate substantial spatial structure consistent with both the dynamic geologic history of this boreal region and the highly insular landscape. New views of taxonomic diversity, biogeographic history, and contemporary population connectivity lay a framework for managing and conserving this complex biome. First, repeated Pleistocene glacial advances along the coast fragmented species, leaving clear genetic signatures and a strongly diversified fauna. Organisms recolonized the coast following deglaciation from multiple northern (Beringia), southern (West Coast and Continental) or North Pacific Coastal refugia. Several species are composed of multiple, genetically distinctive lineages (in some cases, incipient or new species) due to independent colonization histories from distinct, divergent source populations. Second, the insular landscape of the Alexander Archipelago has produced highly endemic populations. These centers of endemism should be thoughtfully managed as hotspots of lineage diversity. Until a better understanding of connectivity among these divergent populations is developed, each island should be considered an independent biological unit. Finally, industrial logging, mining, human encroachment, tourism, wildlife consumption, and invasive species should be stringently monitored and regulated with respect to impact on island endemics and ecosystems. A new conservation paradigm for the Tongass National Forest should be developed that is built around the recognition of the complexity of this incomparable island archipelago of the North Pacific. In particular, recognition of high diversity and endemism should be central to management plans.  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