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Abstract: The number of individuals translocated and released as part of a reintroduction is often small, as is the final established population, because the reintroduction site is typically small. Small founder and small resulting populations can result in population bottlenecks, which are associated with increased rates of inbreeding and loss of genetic diversity, both of which can affect the long‐term viability of reintroduced populations. I used information derived from pedigrees of four monogamous bird species reintroduced onto two different islands (220 and 259 ha) in New Zealand to compare the pattern of inbreeding and loss of genetic diversity among the reintroduced populations. Although reintroduced populations founded with few individuals had higher levels of inbreeding, as predicted, other factors, including biased sex ratio and skewed breeding success, contributed to high levels of inbreeding and loss of genetic diversity. Of the 10–58 individuals released, 4–25 genetic founders contributed at least one living descendent and yielded approximately 3–11 founder–genome equivalents (number of genetic founders assuming an equal contribution of offspring and no random loss of alleles across generations) after seven breeding seasons. This range is much lower than the 20 founder–genome equivalents recommended for captive‐bred populations. Although the level of inbreeding in one reintroduced population initially reached three times that of a closely related species, the long‐term estimated rate of inbreeding of this one population was approximately one‐third that of the other species due to differences in carrying capacities of the respective reintroduction sites. The increasing number of reintroductions to suitable areas that are smaller than those I examined here suggests that it might be useful to develop long‐term strategies and guidelines for reintroduction programs, which would minimize inbreeding and maintain genetic diversity.  相似文献   

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Przewalski's Horse: Prospects for Reintroduction into the Wild   总被引:1,自引:0,他引:1  
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Abstract: Captive propagation and reintroduction programs for rare and endangered species rarely include testing of techniques prior to initiation of recovery efforts. To experimentally test the effects of rearing social, altricial birds with or without a conspecific, parental model (a puppet), we used Common Ravens ( Corvus corax ) in southwestern Idaho as surrogates for the endangered Hawaiian Crow ( Corvus hawaiiensis ) and Mariana Crow ( Corvus kubaryi ). A puppet is believed to reduce sexual and filial imprinting on human caretakers. We raised 49 ravens without a puppet and 25 ravens with a puppet. We initiated puppet-rearing when birds were 7 days of age and continued until 60 days of age, when nestlings could eat well on their own. The influence of puppet-rearing was tested as part of a factorial design that also tested for the effects of conspecific tutoring and age at release. Rearing ravens with a puppet did not affect social behaviors prior to release, dispersal from the release area, or integration with wild birds after release. Ravens raised with a puppet, however, were more fearful of caretakers and more vigilant prior to release, characteristics that may have improved their chances for survival after release. It is important for researchers to consider the species and the desired pre- and post-release behaviors to determine if rearing with a puppet is appropriate for their recovery efforts. These considerations can be taken into account by using a surrogate species prior to recovery efforts and creative management approaches in the initial phases of an endangered species recovery program.  相似文献   

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Abstract: The global amphibian crisis has resulted in renewed interest in captive breeding as a conservation tool for amphibians. Although captive breeding and reintroduction are controversial management actions, amphibians possess a number of attributes that make them potentially good models for such programs. We reviewed the extent and effectiveness of captive breeding and reintroduction programs for amphibians through an analysis of data from the Global Amphibian Assessment and other sources. Most captive breeding and reintroduction programs for amphibians have focused on threatened species from industrialized countries with relatively low amphibian diversity. Out of 110 species in such programs, 52 were in programs with no plans for reintroduction that had conservation research or conservation education as their main purpose. A further 39 species were in programs that entailed captive breeding and reintroduction or combined captive breeding with relocations of wild animals. Nineteen species were in programs with relocations of wild animals only. Eighteen out of 58 reintroduced species have subsequently bred successfully in the wild, and 13 of these species have established self‐sustaining populations. As with threatened amphibians generally, amphibians in captive breeding or reintroduction programs face multiple threats, with habitat loss being the most important. Nevertheless, only 18 out of 58 reintroduced species faced threats that are all potentially reversible. When selecting species for captive programs, dilemmas may emerge between choosing species that have a good chance of surviving after reintroduction because their threats are reversible and those that are doomed to extinction in the wild as a result of irreversible threats. Captive breeding and reintroduction programs for amphibians require long‐term commitments to ensure success, and different management strategies may be needed for species earmarked for reintroduction and species used for conservation research and education.  相似文献   

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Abstract: Some species have insufficient defenses against climate change, emerging infectious diseases, and non‐native species because they have not been exposed to these factors over their evolutionary history, and this can decrease their likelihood of persistence. Captive breeding programs are sometimes used to reintroduce individuals back into the wild; however, successful captive breeding and reintroduction can be difficult because species or populations often cannot coexist with non‐native pathogens and herbivores without artificial selection. In captive breeding programs, breeders can select for host defenses that prevent or reduce pathogen or herbivore burden (i.e., resistance) or traits that limit the effects of parasitism or herbivory on host fitness (i.e., tolerance). We propose that selection for host tolerance may enhance the success of reintroduction or translocation because tolerant hosts generally have neutral effects on introduced pathogens and herbivores. The release of resistant hosts would have detrimental effects on their natural enemies, promoting rapid evolution to circumvent the host resistance that may reduce the long‐term probability of persistence of the reintroduced or translocated species. We examined 2 case studies, one on the pathogenic amphibian chytrid fungus ( Batrachochytrium dendrobatidis [Bd]) and the other on the herbivorous cactus moth ( Cactoblastis cactorum) in the United States, where it is not native. In each case study, we provide recommendations for how captive breeders and managers could go about selecting for host tolerance. Selecting for tolerance may offer a promising tool to rescue hosts species from invasive natural enemies as well as new natural enemies associated with climate change‐induced range shifts.  相似文献   

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Eelgrass (Zostera marina L.) in the Dutch Wadden Sea historically covered an area varying from 65–150 km2 in the eulittoral as well as the sublittoral zones. At present, this area comprises less than 1 km2 eulittoral eelgrass stands, with an associated decrease in habitat diversity. The causes for this decline are presumably connected with the ‘wasting disease’ and the closure of the former Zuiderzee in the early 1930s resulting in increased tidal range and increased currents. After a slight recovery of the eelgrass populations on the intertidal flats a definite decline started in the early 1970s, possibly connected to increased turbidity. The present water quality and turbidity do not negatively influence eelgrass growth up to a depth of at least 0.6m below Mean Sea Level. Based on mesocosm experiments and field experiments it is concluded that re-establishment of eelgrass should be possible in sheltered bays and on unexposed tidal flats. The most suitable depths for a reintroduction are those between 0 and 20–40 cm below mean sea level.  相似文献   

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天目湖溶解氧变化特征及对内源氮释放的影响   总被引:7,自引:1,他引:7  
为弄清水库水体溶解氧(DO)含量的变化规律及其对水质的影响,于2006、2007年对天目湖水体DO和其他水质参数进行调查.结果表明,对于表层水体,在非夏季月份,温度增加会导致DO浓度和饱和度降低;而在夏季月份,由于浮游生物的活动,导致表层DO浓度较高,并可能出现过饱和的现象.对于中、底层水体,温度分层是影响DO浓度的关键因素.温跃层存在期间底层出现缺氧现象,温度分层消失时底层又出现复氧现象,致使在1 a之中底层DO存在缺氧-复氧-缺氧交替循环的现象.水库DO浓度对内源氮的释放有明显的影响,尤其是大坝取水口附近,由于夏季底层水体缺氧,导致沉积物中氨氮向底层水体释放,并导致同期表层水体氨氮浓度也有所升高.对于疏浚前后水体氨氮的调查分析表明,底泥疏浚可以有效地减少夏季内源氮的释放,从而降低了DO浓度变化对氮释放的影响强度.  相似文献   

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Abstract: Captive breeding and reintroduction programs are rarely evaluated, and assessment criteria vary widely. We used the following criteria to evaluate a bighorn sheep ( Ovis canadensis ) augmentation program: (1) survival and recruitment rates in the captive population, (2) survival of released animals, (3) recruitment of released animals, (4) growth rate of the reintroduced or augmented population, and (5) establishment of a viable wild population. Captive bighorn survival and recruitment was high, averaging 0.98 (SD = 0.05) and 71.0% (SD = 19.4), respectively. Annual survival of free-ranging captive-reared bighorn ( n = 73, x = 0.80, SD = 0.11) did not differ (   Z = −0.85, p = 0.40; n = 14) from survival of wild-reared bighorn ( n = 43, x = 0.81, SD = 0.12). Recruitment was unusually low for both captive-reared (  x = 13.7%, SD = 0.24) and wild-reared ewes (  x = 13.7%, SD = 0.20). Although reintroduction did not result in population growth or establishment of a viable population, it helped prevent extirpation of the reinforced deme, preserved metapopulation linkage, and aided habitat preservation. Chronic low recruitment and low adult survivorship precluded achievement of criteria 3–5. Environmental conditions in the release area also appeared to hinder program success. Standard evaluation criteria for ongoing reintroductions allow for informative assessments and facilitate comparisons needed to refine reintroduction science as a recovery tool for threatened or endangered populations.  相似文献   

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Improving the Evaluation of Conservation Programs   总被引:5,自引:0,他引:5  
Abstract: The evaluation of conservation programs is rare but increasingly important in improving their effectiveness. Regular evaluations of conservation programs and the implementation of recommendations resulting from such assessments are infrequent because of resistance by participants and lack of funding. Evaluations may be internal or external, depending on the purpose of the review and how broadly it is focused. We strongly recommend external peer review of long-term complex conservation programs every 5 years, supported by more frequent (annual) internal reviews. Criteria for success must encompass both biological and social measures and include learning and the application of new knowledge to management. Evaluations must also go beyond monitoring to assess the value of the program. We emphasize the need to include the organization and function of a conservation program (the process) in any evaluation in addition to substantive criteria for success, which usually involve biological measures (numbers). A dysfunctional program organization and process can as effectively cripple a conservation effort as can a major biological catastrophe. We provide examples of different types of conservation program evaluations, including moderated workshops and case-study analysis, and provide advice on the logistics and organization of the review, emphasizing the importance of the evaluation process itself to a successful outcome. One important aspect of an evaluation is having an individual with leadership ability and considerable expertise to organize the format and oversee the review process itself. Second, it is essential at the outset to ensure agreement among the program participants and the review committee on the goals and objectives of the conservation program, what is to be evaluated, and the criteria for defining success. Finally, the best evaluations are inclusive and involve all participants and stakeholders.  相似文献   

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MHC Polymorphism and the Design of Captive Breeding Programs   总被引:3,自引:0,他引:3  
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Abstract:  Despite many successful reintroductions of large mammalian herbivores throughout the world, remarkably little attention has focused on how these actions affect native and exotic vegetation at reintroduction sites. One such herbivore is tule elk ( Cervus elaphus nannodes ), which was on the brink of extinction in the mid 1800s, but now has numerous stable populations due to intensive reintroduction efforts. Here, we summarize results from a 5-year exclosure experiment that explored the effects of tule elk on a coastal grassland in northern California. Elk significantly altered the species composition of this community; the response of annual species (dominated heavily by exotic taxa) was dramatically different from perennial species. Elk herbivory increased the abundance and aboveground biomass of native and exotic annuals, whereas it either had no effect on or caused significant decreases in perennials. Elk also decreased the cover of native shrubs, suggesting that these herbivores play an important role in maintaining open grasslands. In addition, elk significantly reduced the abundance and biomass of a highly invasive exotic grass , Holcus lanatus, which is a major problem in mesic perennial grasslands. Our results demonstrate that the successful reintroduction of a charismatic and long-extirpated mammal had extremely complex effects on the plant community, giving rise to both desirable and undesirable outcomes from a management perspective. We suspect that these kinds of opposing effects are not unique to tule elk and that land managers will frequently encounter them when dealing with reintroduced mammals.  相似文献   

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A comparative study of the solubilization of Fe, Zn, Cu and Mn from a river sediment by solutions of a residue from agricultural industry and a synthetic polymer (SP) is presented. The agricultural residue shows a higher mobilising effect than the SP. The presence of the latter causes in most cases an initial solubilization and a readsorption afterwards, with a tendency to an equilibrium for long reaction times. The effect of the agricultural residue is not uniform for all metals studied, with a significant formation of metal‐organic complexes for Cu and Zn. In the presence of the SP, the proportion of complexes formed is significant only for Zn.  相似文献   

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转基因生物环境释放风险评估的原则和一般模式   总被引:1,自引:0,他引:1  
风险评估是转基因生物环境释放依法管理的一项重要内容 ,也是生物安全研究的核心内容之一。本文在分析和比较国内外有关转基因生物风险评估方法的基础上 ,结合作者近年来对转基因生物风险评估的专题研究 ,对转基因生物环境释放风险评估的基本原则和一般模式进行了全面的描述。这种模式一般包括危险识别、风险估算和风险评价 3个连续过程 ,并可分解为 7个具体步骤  相似文献   

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