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 31 毫秒
1.
Levels of genetic diversity and population genetic structure of the rare, endangered terrestrial orchid Liparis japonica were examined for eight natural populations (n = 185) in Northeast China using six AFLP primer pairs, where this species has experienced severe habitat loss and fragmentation. Based on 406 DNA bands, a high level of genetic diversity was found at the species level with the PPB of 85.47 %, while the genetic diversity at the population level was low (PPB = 47.48 %). A significantly high degree of population differentiation was found with 42.69 % variation existed among populations as measured by AMOVA, indicating potential restricted gene flow. The genetic distances between populations were independent of the corresponding geographic distances, and the genetic relationship of individuals had no significant correlation with their spatial distribution. The restricted gene flow might be impacted by reduced population size, habitat destruction and fragmentation. The results in this study suggested that habitat protection and keeping a stable environment are critical for the conservation of L. japonica species.  相似文献   

2.
注意植物迁地保护中的遗传风险   总被引:6,自引:0,他引:6  
康明  叶其刚  黄宏文 《遗传》2005,27(1):160-166
稀有濒危植物迁地保护的长期目标之一就是要保护物种的遗传多样性和进化潜力。介绍了稀有濒危植物在植物园迁地保护过程中存在的一系列遗传风险。由于引种或取样的不足,容易导致被保存的物种缺乏足够的遗传代表性;盲目的引种、不合理的定植以及材料的来源不清则会导致稀有濒危植物的遗传混杂、近交衰退或杂交衰退;人为选择和生长环境的改变也容易造成濒危物种对迁地保护的遗传适应。在实际的迁地保护工作中,这些遗传风险往往被忽视。植物迁地保护中遗传风险将严重影响稀有濒危物种的回归和恢复。植物园应当重视濒危植物的遗传管理,以降低或避免迁地保护中的遗传风险。Abstract: Conserving genetic diversity of rare and endangered species and their evolutionary potential is one of the long-term goals of ex-situ conservation. Some potential genetic risks in ex-situ conservation in botanical gardens are presented. The preserved species may lack genetic representativity because of poor sampling. Inappropriate plantations, inadequate records and unclear kinships jeopardize endangered species to genetic confusion, inbreeding depression or outbreeding depression. Artificial selection and habitat conversion also potentially result endangered plants in adapting to ex-situ conservation, which had been usually overlooked. All the genetic risks can decrease the success of reintroduction and recovery. Therefore, appropriate genetic management should be carried out in botanical gardens to decrease or avoid genetic risks in ex-situ conservation.  相似文献   

3.
Restoration of habitat for endangered species often involves translocation of seeds or individuals from source populations to an area targeted for revegetation. Long-term persistence of a species is dependent on the maintenance of sufficient genetic variation within and among populations. Thus, knowledge and maintenance of genetic variability within rare or endangered species is essential for developing effective conservation and restoration strategies. Genetic monitoring of both natural and restored populations can provide an assessment of restoration protocol success in establishing populations that maintain levels of genetic diversity similar to those in natural populations. California’s vernal pools are home to many endangered plants, thus conservation and restoration are large components of their management. Lasthenia conjugens (Asteraceae) is a federally endangered self-incompatible vernal pool annual with gravity- dispersed seeds. Using the molecular technique of intersimple sequence repeats (ISSRs), this study assessed levels and patterns of genetic variability present within natural and restored populations of L. conjugens. At Travis Air Force Base near Fairfield, California, a vernal pool restoration project is underway. Genetic success of the ecologically based seeding protocol was examined through genetic monitoring of natural and restored populations over a three-year period. Genetic diversity remained constant across the three sampled generations. Diversity was also widely distributed across all populations. We conclude that the protocol used to establish restored populations was successful in capturing similar levels and patterns of genetic diversity to those seen within natural pools. This study also demonstrates how genetic markers can be used to inform conservation and restoration decisions.  相似文献   

4.
Primula reinii var. rhodotricha is a perennial herb endemic to the limestone slope of Mt. Buko, located approximately 50 km northwest of central Tokyo, Japan. In recent years, its natural population size has decreased markedly due to limestone mining, and this species has been assigned to the ‘Critically Endangered (CR)’ category on the latest Japanese Red List. Although a remnant population of this species has been protected by a mining company outside their historical distribution range on Mt. Buko, the ex situ conservation of this endangered plant has been difficult because of insufficient low seed production. The genetic status of ex situ P. reinii var. rhodotricha and related species were investigated to develop an effective conservation plan for this species. Microsatellite analysis indicated that the ex situ population harbors lower genetic diversity than sister taxa, providing molecular evidence for the recent critical status designation of the ex situ population, whereas the presence of rare alleles may imply further potential for seed reproduction by outcrossing. Therefore, an appropriate propagation strategy that considers genetic diversity is needed for restoration and recovery of this critically endangered ex situ primrose population.  相似文献   

5.
Assessing the genetic consequences of habitat fragmentation is a crucial step in conservation planning for species in endangered habitats. We tested for the impact of natural habitat fragmentation on gene flow and genetic diversity in seven northern breeding locations of the sagebrush Brewer’s sparrow, Spizella breweri breweri. Genetic analyses using five highly variable DNA microsatellite loci suggested that individuals sampled within a sagebrush landscape fragmented by natural elements such as coniferous forest, comprise a single genetic population and that gene flow among them is unimpeded. We posit that juvenile dispersal links seemingly isolated breeding locales of this species, and discuss implications of our findings for conservation of migratory songbirds in the northern portion of their ranges in light of potential shifts in distribution due to climate change.  相似文献   

6.
The following paper describes patterns of diversity across major habitat types in a relatively well preserved coastal dune system in central Italy. The research addresses the following questions: (a) whether different habitats defined on the base of a land cover map support similar levels of biodiversity in terms of vascular flora richness and number of rare and endangered species, and (b) how each habitat contributes to the total species diversity of the coastal environment. A random stratified sampling approach based on a detailed land cover map was applied to construct rarefaction curves for each habitat type and to estimate total species richness. In addition, the number of exclusive, rare and endangered species was calculated for each habitat type. Results highlight the importance of the coastal dune zonation (embryo-dune, main dune, transition and stabilized dune) in species conservation because they harbour progressively higher species richness. However, differences among these habitats were not significant, so no particular species rich “hotspots” could be evidenced. On the contrary, rarefaction curves show that the upper beach (strand) habitat sustains significantly smaller number of species, but surprisingly, it shows the highest rarity values and highest proportion of endangered species. Therefore, for the establishment of successful biodiversity conservation programs in these coastal environments, it is imperative not only to conserve biologically rich hotspots but also to include species poor habitats containing endangered or unique elements. Thus, the complete coastal vegetation mosaic including all coastal habitats is important to adequately characterize the plant species diversity of coastal dune ecosystems.  相似文献   

7.
Hopea bilitonensis is an extremely rare and predominantly selfing dipterocarp in Peninsular Malaysia. A comprehensive research was initiated to assess the ecological genetics of H. bilitonensis to elucidate specific ecological and genetic requirements and subsequently to recommend conservation strategies. The objective for conservation of a rare plant such as H. bilitonensis differs from that of a common plant. For common plants, the conservation strategies are to prevent the species from becoming endangered. In contrast, for rare plants, the final race against extinction is being fought. Tropical forests are rich in plant species diversity and obtaining adequate knowledge to set conservation strategies for the majority of these species might be difficult. Thus, it is suggested that for the conservation of tree species, the species can be grouped according to their life history traits. The information generated for a species can then be adapted to species that have similar types of life history traits. We have recently generated the ecological genetics information for a rare and predominantly outcrossed dipterocarp (Shorea lumutensis). This study on H. bilitonensis will provide ecological genetics information for the conservation of rare and predominantly selfing dipterocarps.  相似文献   

8.
Californian vernal pools, a patchy, island-like habitat, are endangered as a result of habitat destruction. Conservation of the remaining vernal pool habitat is essential for the persistence of several endangered species. We present the first study examining DNA-level genetic diversity within and among populations of a vernal pool plant species. We investigated genetic variation across eight populations of the US federally endangered vernal pool endemic Lasthenia conjugens (Asteraceae) using intersimple sequence repeat (ISSR) markers. Genetic diversity within the species was high (Nei's gene diversity estimate was 0.37), with moderate differentiation among populations (Bayesian F ST analog of 0.124). Using an amova analysis, we found that the majority of the genetic variation (84%) was distributed within populations. There is a significant relationship between geographical distance and pairwise genetic differentiation as measured by the Bayesian estimate θB. The alternative hypotheses of historic geological processes within the Central Valley and contemporary gene flow are discussed as explanations of the data. Because of the vulnerability of the populations, we calculated a probability of loss for rare alleles (fragments) in the populations. Calculations show that sampling only one of the eight populations for ex-situ conservation or restoration will capture approximately 54% of the sampled rare fragments. We believe that one of the sampled populations has become extinct since it was sampled. When removing this population from the above-mentioned calculations, sampling one population will capture only 41.3% of the sampled rare fragments. We recommend sampling strategies for future conservation and restoration efforts of L. conjugens.  相似文献   

9.
Though translocations of rare populations should be considered only as the last resort for species’ conservation, when habitat destruction is imminent, it may be the only means to preserve a species. With over half the known, wild federally endangered Crenulate leadplant (Amorpha herbacea var. crenulata), Fabaceae, growing on unprotected land slated for development, preserving this unprotected population was critical. We rescued whole plants, cuttings, and seeds for an experimental translocation. Into a restored pine rockland, once dominated by the invasive exotic tree Brazilian pepper (Schinus terebinthifolius), we transplanted plants from different sources and of different sizes. Plants used were rescued from an unprotected site, seedlings, and 1‐, 2‐, and 7‐year‐old plants from Fairchild Tropical Botanic Garden’s ex situ collection, creating a novel population in a new habitat. We also evaluated which propagule type and source had the best survival, growth, and reproduction. After 40 months, overall transplant survival was 71%. Large whole plants, rescued and nursery grown, had the best survival rates (86 and 78%), whereas cuttings had 67% survival and seedlings had only 26% survival. The restored site, once nearly a monoculture of S. terebinthifolius, is now dominated by 104 native plant species, including 17 naturally recruited state listed, plus the one translocated federally endangered plant species. In addition, one federally threatened snake species was observed on the site. These studies demonstrate that botanic garden collections not only play a vital role in the conservation of species’ genetic diversity but also can be used as source material for habitat restoration.  相似文献   

10.
Many endangered species worldwide are found in remnant populations, often within fragmented landscapes. However, when possible, an understanding of the natural extent of population structure and dispersal behaviour of threatened species would assist in their conservation and management. The brush-tailed rock-wallaby (Petrogale penicillata), a once abundant and widespread rock-wallaby species across southeastern Australia, has become nearly extinct across much of the southern part of its range. However, the northern part of the species’ range still sustains many small colonies closely distributed across suitable habitat, providing a rare opportunity to investigate the natural population dynamics of a listed threatened species. We used 12 microsatellite markers to investigate genetic diversity, population structure and gene flow among brush-tailed rock-wallaby colonies within and among two valley regions with continuous habitat in southeast Queensland. We documented high and significant levels of population genetic structure between rock-wallaby colonies embedded in continuous escarpment habitat and forest. We found a strong and significant pattern of isolation-by-distance among colonies indicating restricted gene flow over a small geographic scale ( <10 km) and conclude that gene flow is more likely limited by intrinsic factors rather than environmental factors. In addition, we provide evidence that genetic diversity was significantly lower in colonies located in a more isolated valley region compared to colonies located in a valley region surrounded by continuous habitat. These findings shed light on the processes that have resulted in the endangered status of rock-wallaby species in Australia and they have strong implications for the conservation and management of both the remaining ‘connected’8 brush-tailed rock-wallaby colonies in the northern parts of the species’8 range and the remnant endangered populations in the south.  相似文献   

11.
Assessing patterns of genetic variation in rare endangered species is critical for developing both in situ and ex situ conservation strategies. Pinus dabeshanensis Cheng et Law is an endangered species endemic to the Dabieshan Mountains of eastern China. To obtain fundamental information of genetic diversity, population history, effective population size, and gene flow in this species, we explored patterns of genetic variation of natural populations, in addition to an ex situ conserved population, using expressed sequence tag-simple sequence repeats (EST-SSR) markers. Our results revealed moderate levels of genetic diversity (e.g., HE = 0.458 vs. HE = 0.423) and a low level of genetic differentiation (FST = 0.028) among natural and conserved populations relative to other conifers. Both contemporary and historical migration rates among populations were high. Bayesian coalescent-based analyses suggested that 3 populations underwent reductions in population size ca. 10,000 yr ago, and that two populations may have experienced recent genetic bottlenecks under the TPM. Bayesian clustering revealed that individuals from the ex situ population were largely assigned to the ‘red’ cluster. Additionally, our results identified private alleles in the natural populations but not in the ex situ population, suggesting that the ex situ conserved population insufficiently represents the genetic diversity present in the species. Past decline in population size is likely to be due to Holocene climate change. Based on the genetic information obtained for P. dabeshanensis, we propose some suggestions for the conservation and efficient management of this endangered species.  相似文献   

12.
Luan S  Chiang TY  Gong X 《Annals of botany》2006,98(3):583-589
BACKGROUND AND AIMS: Nouelia insignis Franch., a monotypic genus of the Asteraceae, is an endangered species endemic in Yunnan and Sichuan Provinces of China. Most of the populations are seriously threatened. Some of them are even at the brink of extinction. In this study, the genetic diversity and differentiation between populations of this species were examined in two drainage areas. METHODS: DNA fingerprinting based on inter-simple sequence repeat polymorphisms was employed to detect the genetic variation and population structure in the species. KEY RESULTS: Genetic diversity at species level was high with P=65.05% (percentage of polymorphic loci) and Ht=0.2248 (total genetic diversity). The coefficient of genetic differentiation among populations, Gst, which was estimated by partitioning the total gene diversity, was 0.2529; whereas, the genetic differentiation between populations in the Jinsha and Nanpan drainage areas was unexpectedly low (Gst=0.0702). CONCLUSIONS: Based on the genetic analyses of the DNA fingerprinting, recent habitat fragmentation may not have led to genetic differentiation or the loss of genetic diversity in the rare species. Spatial apportionment of fingerprinting polymorphisms provides a footprint of historical migration across geographical barriers. The high diversity detected in this study holds promise for conservation and restoration efforts to save the endangered species from extinction.  相似文献   

13.
As ancient gymnosperm and woody plants, cycads have survived through dramatic tectonic activities, climate fluctuation, and environmental variations making them of great significance in studying the origin and evolution of flora biodiversity. However, they are among the most threatened plant groups in the world. The principal aim of this review is to outline the distribution, diversity, and conservation status of Cycas in China and provide suggestions for conservation practices. In this review, we describe the taxonomy, distribution, and conservation status of Cycas in China. By comparing Chinese Cycas species with its relatives worldwide, we then discuss the current genetic diversity, genetic differentiation of Cycas, and try to disentangle the potential effects of Quaternary climate changes and topographical events on Cycas. We review conservation practices from both researchers and practitioners for these rare and endangered species. High genetic diversity at the species level and strong genetic differentiation within Cycas have been observed. Most Cycas species in southwest China have experienced population retreats in contrast to the coastal Cycas's expansion during the Quaternary glaciation. Additionally, human activities and habitat fragmentation have pushed these endangered taxa to the brink of extinction. Although numerous efforts have been made to mitigate threats to Cycas survival, implementation and compliance monitoring in protection zones are currently inadequate. We outline six proposals to strengthen conservation measures for Cycas in China and anticipate that these measures will provide guidelines for further research on population genetics as well as conservation biology of not only cycads but also other endangered species worldwide.  相似文献   

14.
山茶科3种中国特有濒危植物的遗传多样性研究   总被引:17,自引:0,他引:17  
猪血木(Euryodendron excelsum)、圆籽荷(Apterosperma oblata)和杜鹃红山茶(Camellia changii)均为我国特有的山茶科珍稀濒危植物。本研究应用随机扩增多态性DNA(RAPD)检测方法,比较了这3个物种的遗传多样性。利用20-24个随机引物从猪血木、圆籽荷和杜鹃红山茶居群中分别获得206-305条RAPD谱带,多态位点百分率(PPL)分别为51.80%、80.26%和38.83%;居群间遗传分化指数GST分别为0.3566、0.1713、0.1242。结果显示:自然分布较广的圆籽荷的遗传多样性高于另外两种自然分布区狭窄的种类。3个物种的遗传变异均主要存在于居群内,但猪血木居群间的遗传分化明显高于圆籽荷和杜鹃红山茶,这可能与其生境的严重片断化有关。根据3个物种不同的遗传结构特点,建议加强现有自然居群的就地 保护,促进居群自然更新;收集不同分布点的种源,尽快建立广东山茶科珍稀濒危植物的保育中心,深入开展人工快繁研究,扩大这些种群的数量。  相似文献   

15.
遗传多样性与濒危植物保护生物学研究进展   总被引:40,自引:3,他引:37  
尽管对于濒危物种的遗传学人们已经进行了大量研究,但是种群遗传学在植物保护中的实际地位尚存在很大争议。濒危物种的遗传多样性可能会由于遗传漂变、近交的作用而丧失;但这种丧失更可能是濒危的结果而不是濒危的起因。遗传多样性水平与物种生存力之间没有任何必然的联系。但植物种群遗传结构如果由于自交不亲和等位基因的丧失和与亲缘种杂交造成的遗传同化而发生改变,那么它对物种生存力会产生明显负作用。  相似文献   

16.
In order to preserve endangered plant populations and recover their evolutionary potential and ecological behavior, some restoration measures generally involve the reinforcement of the population size in existing natural populations or the reintroduction of new populations. Genetic monitoring of both natural and restored populations can provide an assessment of restoration protocol success in establishing populations that maintain levels of genetic diversity similar to those in natural populations. The highly threatened Spanish species Silene hifacensis (Caryophyllaceae) has only three natural reduced mainland populations in the Iberian Peninsula, following decline and extinction that occurred during the late 20th century. Preterit restoration strategies were essentially based on the implantation of new populations and reinforcement of certain existing populations using transplants mostly cultivated in greenhouses. In the present contribution, levels and patterns of genetic variability within natural and restored populations of Silene hifacensis were assessed using the molecular technique AFLP. Our results pointed out significant genetic diversity differences across the three existing natural populations though their population fragmentation and progressive loss of individuals have not had an impact on the global genetic diversity of this species. For restored populations, their levels of genetic diversity were similar and even higher than in natural populations. As a result, the past restoration protocols were successful in capturing similar and even higher levels of genetic diversity than those observed within natural pools. However, inbreeding processes have been detected for two restored populations. Finally, the main source of plant material for the long-time restored transplants appears to be the natural population of Cova de les Cendres. This study demonstrates, once again, how genetic markers are useful tools to be taken in consideration for endangered plant species conservation plans.  相似文献   

17.
对中国特有珍稀濒危植物绣球茜(Dunnia sinensis Tutcher)开展了分布范围、种群大小、生境特征、繁殖技术和保护状况研究。研究结果表明,绣球茜主要分布于广东省境内龙门县南昆山省级自然保护区、台山市北峰山森林公园、台山市古兜山林场和阳春市八甲峨凰嶂省级自然保护区、新会市崖西镇鹅坑水库、珠海高栏岛东侧海岸、电白县罗坑镇马房村等7个地点的公路边坡次生疏林或荒坡上,其所在群落的植物多样性较低,绣球茜是阳生性种类,其主要伴生种是芒萁(Dicranopteris linearis Underw)。绣球茜所在群落的土壤为酸性赤红壤,土层较薄,养分含量较高。该种野外个体约有2380株,因公路、水库和工厂建设导致绣球茜丧失栖息地是导致其种群减少的主要原因。本文所研究的4个地点的绣球茜种群,有台山市北峰山和龙门县南昆山的2个种群处于衰退中。根据世界自然保护联盟(International Union for Conservation of Nature,IUCN)标准,该种可列为极濒危级(CR)。绣球茜的种子在湿润河沙+泥炭生境下自然发芽率仅8%,生根剂ABT、萘乙酸、IBA吲哚-3-丁酸浸泡后的扦插条存活率为分别为13.3%、20.0%和20.0%。建议:(1)对该种加强就地保护,对保护区外的分布点设立保护小区,同时防止保护小区内乔木层郁闭影响绣球茜的更新;(2)对所有分布点的植株进行有遗传多样性代表性的迁地保护;(3)开展全球变化背景下的野外回归;(4)在引种驯化的基础上开展种苗生产和栽培基质等商品化生产研发。研究结果对这类需要适度干扰的珍稀濒危植物的保护和可持续利用有参考价值。  相似文献   

18.
The aim of this study was to estimate the degree and distribution of genetic diversity within Central-European populations of Thesium ebracteatum—one of the most endangered plant species in Europe. By analyzing allozymes from 17 populations, we estimated the distribution of genetic diversity and suggest the most valuable populations for conservation. Analysis of molecular variance results showed the highest variance existed between populations (54 %), whereas the mean variance within populations was 46 %. A surprisingly low degree of variance (less than 1 %) was found between the six studied regions. We also observed no correlation between geographical and genetic distance, which supports the idea that individual populations are strongly isolated. T. ebracteatum undergoes extensive clonal growth and may survive for very long periods of time without generative reproduction. Consistent with this, we found a strong and significant relationship between genetic diversity and population size. All populations occupying an area greater than 300 m2 showed high genetic diversity, whereas small populations contained less genetic diversity. Therefore, conservation priorities could generally be decided based on population size. Because this species is a weak competitor, existing localities should also be managed to prevent species loss from habitat degradation, by mowing or from time to time otherwise disturbing population areas to create open areas for growth.  相似文献   

19.

Revealing patterns of genetic diversity and barriers for gene flow are key points for successful conservation in endangered species. Methods based on molecular markers are also often used to delineate conservation units such as evolutionary significant units and management units. Here we combine phylo-geographic analyses (based on mtDNA) with population and landscape genetic analyses (based on microsatellites) for the endangered yellow-bellied toad Bombina variegata over a wide distribution range in Germany. Our analyses show that two genetic clusters are present in the study area, a northern and a southern/central one, but that these clusters are not deeply divergent. The genetic data suggest high fragmentation among toad occurrences and consequently low genetic diversity. Genetic diversity and genetic connectivity showed a negative relationship with road densities and urban areas surrounding toad occurrences, indicating that these landscape features act as barriers to gene flow. To preserve a maximum of genetic diversity, we recommend considering both genetic clusters as management units, and to increase gene flow among toad occurrences with the aim of restoring and protecting functional meta-populations within each of the clusters. Several isolated populations with especially low genetic diversity and signs of inbreeding need particular short-term conservation attention to avoid extinction. We also recommend to allow natural gene flow between both clusters but not to use individuals from one cluster for translocation or reintroduction into the other. Our results underscore the utility of molecular tools for species conservation, highlight outcomes of habitat fragmentation onto the genetic structure of an endangered amphibian and reveal particularly threatened populations in need for urgent conservation efforts.

  相似文献   

20.
We evaluated whether ecosystem engineers can accomplish two conservation goals simultaneously: (1) indirectly maintain populations of an endangered animal through habitat modification and (2) increase riparian plant diversity. We tested for effects of a prominent ecosystem engineer, the beaver Castor canadensis, on populations of St. Francis' satyr butterfly Neonympha mitchellii francisci and plant species richness and composition. We performed our test by surveying riparian vegetation communities in all stages of beaver‐influenced wetland succession. We found that beavers created wetland habitats that supported plant species not found elsewhere in riparian zones and increased plant species diversity across the landscape by creating a novel combination of patch types. Our results confirmed what others have found about engineering effects on plant diversity, but these results further demonstrated a case where ecosystem engineers indirectly maintain populations of rare animals by modifying the composition and diversity of plant communities within wetlands. Our research demonstrates how an ecosystem engineer can influence habitat availability and composition of plant communities important for an endangered insect, and maintain overall plant species diversity by increasing habitat heterogeneity.  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