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Capture‐recapture methods are frequently employed to estimate abundance of cetaceans using photographic techniques and a variety of statistical models. However, there are many unresolved issues regarding the selection and manipulation of images that can potentially impose bias on resulting estimates. To examine the potential impact of these issues we circulated a test data set of dorsal fin images from bottlenose dolphins to several independent research groups. Photo‐identification methods were generally similar, but the selection, scoring, and matching of images varied greatly amongst groups. Based on these results we make the following recommendations. Researchers should: (1) determine the degree of marking, or level of distinctiveness, and use images of sufficient quality to recognize animals of that level of distinctiveness; (2) ensure that markings are sufficiently distinct to eliminate the potential for “twins” to occur; (3) stratify data sets by distinctiveness and generate a series of abundance estimates to investigate the influence of including animals of varying degrees of markings; and (4) strive to examine and incorporate variability among analysts into capture‐recapture estimation. In this paper we summarize these potential sources of bias and provide recommendations for best practices for using natural markings in a capture‐recapture framework.  相似文献   

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To expand the feasibility of applying simple, efficient, non-invasive DNA preparation methods using samples that can be obtained from giant pandas living in the wild, we investigated the use of scent markings and fecal samples. Giant panda–specific oligonucleotide primers were used to amplify a portion of the mitochondrial DNA control region as well as a portion of the mitochondrial DNA cytochrome b gene and tRNAThr gene region. A 196 base pair (bp) fragment in the control region and a 449 bp fragment in the cytochrome b gene and tRNAThr gene were successfully amplified. Sequencing of polymerase chain reaction (PCR) products demonstrated that the two fragments are giant panda sequences. Furthermore, under simulated field conditions we found that DNA can be extracted from fecal samples aged as long as 3 months. Our results suggest that the scent mark and fecal samples are simple, efficient, and easily prepared DNA sources. Zoo Biol 17:499–504, 1998. © 1998 Wiley-Liss, Inc.  相似文献   

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Simple Bayesian statistical models are introduced to estimate the proportion of identifiable individuals and group sizes in photographic identification, or photo‐ID, studies of animals that are found in groups. The models require a simple random photographic sampling of animals, where the photographic captures are treated as sampling with replacement within each group. The total number of images, including those that cannot be identified, and the number of images that contain identifiable individuals are used to make inference about the proportion of identifiable individuals within each group and as the population when a number of groups are sampled. The numbers of images for individuals within each group are used to make inference about the group size. Based on analyses of simulated and real data, the models perform well with respect to accuracy and precision of posterior distributions of the parameters. Widths of posterior intervals were affected by the number of groups sampled, sampling duration, and the proportion of identifiable individuals in each group that was sampled. The structure of the models can accommodate covariates, which may affect photographic efficiency, defined in this study as the probability of photographically capturing individuals.  相似文献   

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Sustained demographic studies are essential for early detection of species decline in time for effective management response. A paucity of such background data hindered the potential for successful conservation during the global amphibian decline and remains problematic today. The current study analysed 6 years of mark‐recapture data to determine the vital demographic rates in three habitat precincts of the threatened frog, Litoria aurea (Hylidae) and to understand the underlying causes of variability in population size. Variability in population size of L. aurea was similar to many pond‐breeding species; however this level of fluctuation is rare among threatened amphibians. Highly variable populations are at greater risk of local extinction and the low level of connectivity between L. aurea populations means they are at a greater risk of further decline due to stochastic extinction events and incapacity to recolonize distant habitat. We recommend that management of this species should encourage recolonization through creation of habitat corridors and reintroduction of L. aurea to areas where stochastic extinction events are suspected.  相似文献   

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Transatlantic stock mixing in basking sharks Cetorhinus maximus is supported by low genetic diversity in populations throughout the Atlantic Ocean. However, despite significant focus on the species' movements; >1500 individual sharks marked for recapture and >150 individuals equipped with remote tracking tags, only a single record of transatlantic movment has been previously recorded. Within this context, the seredipitous re-sighting of a female basking shark fitted with a satellite transmitter at Malin Head, Ireland 993 days later at Cape Cod, USA is noteworthy.  相似文献   

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This study investigates the patterns of genetic diversity detected in allozymes, mtDNA, and microsatellites, in order to assess their relative efficacy to differentiate sympatric landlocked salmon populations and to estimate changes in genetic diversity between wild and first-generation hatchery fish. Overall, the three genetic markers indicated a genetic differentiation between two sympatric populations of Lake Saint-Jean, Québec. MtDNA and microsatellites also showed significant differences between wild and first-generation hatchery fish originating from the same river. Allozyme analysis was the most limited approach due to the low genetic diversity detected and the necessity to kill specimens. Although low polymorphism was found in mtDNA, it was the most discriminant marker between wild populations. Microsatellite analysis appears to be a promising approach due to its high sensitivity in differentiating wild populations, in detecting changes in allele composition between wild and first-generation hatchery fish and its potential for increased resolution by augmenting the number of polymorphic loci. Given the benefits and disadvantages of the three methods, the combination of mtDNA and microsatellite analyses will best address our research objectives.  相似文献   

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Reintroduction projects aim to reestablish a self‐sustaining population of an endangered species within its historical range. Adequate post‐release monitoring by gathering demographic data is important to evaluate the success of a reintroduction. Survival and reproduction rates of a reintroduced population can be compared with a self‐sustaining wild population to evaluate the success of a reintroduction. In early 2007, Nipponia nippon (Crested Ibis) was reintroduced into the Qinling Mountains (Shaanxi, Central China). In this study, we attempt to evaluate the demographic status of the reintroduced population. Age‐specific survival rates of 56 released adults and 77 wild‐born fledglings were estimated using mark‐recapture data obtained from 2007 to 2014. Survival rates for the yearlings (0.599, with 95% confidence interval [CI]: 0.467–0.719) were lower than the estimates from a wild population in Yangxian County, but the survival rates of the adults (0.678, with 95% CI: 0.603–0.745) were similar. The number of breeding pairs gradually increased since 2008, although breeding success (52.5%) was somewhat less than that of the wild population (67.6%). The stochastic estimation of population growth rate (1.084 with 95% CI: 1.069–1.098) and population size (5‐fold increase) estimated from an age‐classified Leslie matrix indicate that the reintroduced population of the Crested Ibis is more likely in regulation phase over the next 25 years. We conclude that the reintroduction of the Crested Ibis in Qinling Mountains has great promise, and progress toward a self‐sustaining population has been made under some interventions. Governments, local communities, and scientists need to facilitate habitat restoration for the long‐term survival of this endangered species.  相似文献   

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Abstract. 1. Central and Southeast Asia currently faces rapid loss and degradation of tropical and subtropical forests with potentially severe effects on its biodiversity. 2. We analysed population characteristics and dispersal of the butterfly Byasa impediens in eleven patches of a fragmented subtropical forest in Western China. 3. In an area covering 30 km2, we found an unexpected high dispersal capacity of more than 5 km, and estimated a mean dispersal distance of 1 km according to the negative exponential function. However, the inverse power function gave a better fit and predicted a reasonably large fraction of long‐distance displacements: 4% of all movements were estimated to exceed 5 km. 4. In spite of the high level of fragmentation and small sizes of some patches, we did not observe extinction or (re)colonisation events. Matching dispersal ability with the spatial grain of the resource patches in the landscape is seen as a major cause. In addition, persistence, emigration and immigration of individuals were exclusively affected by the amount of larval host plants, nectar plants and forest cover. 5. Our study indicates the importance of long‐distance dispersal and shows that species with large dispersal abilities and a somewhat broader dietary niche, such as B. impediens, can sustain in fragmented areas if patch quality is sufficient. 6. We suggest that conservation action may not only focus on particularly endangered species but also on relatively common, but often endemic, insect species. This is of particular concern given the global dominance of insects and their importance for ecosystem services, especially in an area of constantly increasing demands of agricultural products.  相似文献   

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Genetic mark–recapture requires efficient methods of uniquely identifying individuals. ‘Shadows’ (individuals with the same genotype at the selected loci) become more likely with increasing sample size, and bias harvest rate estimates. Finding loci is costly, but better loci reduce analysis costs and improve power. Optimal microsatellite panels minimize shadows, but panel design is a complex optimization process. locuseater and shadowboxer permit power and cost analysis of this process and automate some aspects, by simulating the entire experiment from panel design to harvest rate estimation.  相似文献   

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  1. Genetic techniques are important tools for conservation, but tissue sampling for DNA analysis can be particularly detrimental to small study organisms. Historically, obtaining DNA samples from small insects and butterflies has involved destructive (lethal) methods.
  2. Recent improvements to DNA purification technologies have increased the likelihood that non‐lethal sampling will be successful. In spite of this, only a few studies have evaluated the impacts of sampling on survival and behaviour.
  3. The Hermes copper, Lycaena hermes (Edwards), butterfly has a restricted distribution and generally less than 10 individuals are encountered at any one location. Non‐lethal DNA sampling would allow for genetic studies that have the potential to augment conservation decisions without causing local extirpations.
  4. We demonstrate that removing a leg from an adult male Hermes copper does not have a measureable effect on their survival, longevity or behaviour. In addition, a single leg provides a sufficient DNA sample for amplified fragment length polymorphism studies.
  5. The Hermes copper butterfly represents the smallest butterfly species for which the survival and behaviour has been assessed in relation to non‐lethal tissue sampling. This suggests that research involving smaller and more delicate species could utilise leg removal as a non‐lethal genetic sampling technique.
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Dispersal ability is known to limit the colonization by many fenland species onto restored habitat but factors determining colonization by wetland invertebrates onto restored fenland have not been previously examined. We used mark‐release‐recapture and harmonic radar tracking coupled with genetic analysis (ISSR‐PCR, inter‐simple sequence repeat—polymerase chain reaction) to assess the population structure and colonization of a brachypterous wetland carabid (Carabus granulatus) onto restored fenland. The first two methods were used to determine the dispersal rate of C. granulatus in the absence of barriers, while the genetic analysis was used to examine whether populations were separated by either distance or the water channels and drainage ditches that intersect fenland landscapes. Mark‐release‐recapture and harmonic radar tracking indicated that the most active 6% of individuals could travel over 25 m in a day and individuals found to be traveling these distances remained atypically active throughout the season. Thus, C. granulatus can disperse at a rate great enough to colonize all areas of restored fenland in the study site within 1 year in the absence of barriers. We found no evidence of genetically distinct sub‐populations of C. granulatus showing that distance and water barriers did not limit the movement of individuals from potential source populations to the restored habitat. This research indicates that where fenland is created with nearby established fenland, colonization opportunities should not be considered a limiting factor to colonization by wetland carabids, even where waterways divide sites.  相似文献   

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The endangered Rio Grande silvery minnow persists as a remnant population in a highly fragmented and regulated arid‐land river system. The species is subject to dramatic annual fluctuations in density. Since 2003, the wild population has been supplemented by hatchery‐reared fish. We report on a 12‐year (1999–2010) monitoring study of genetic diversity and effective population size (Ne) of wild and hatchery stocks. Our goals were to evaluate how genetic metrics responded to changes in wild fish density and whether they corresponded to the number and levels of diversity of hatchery‐reared repatriates. Genetic diversity and all measures of Ne in the wild population did not correlate with wild fish density until hatchery supplementation began in earnest. Estimates of variance and inbreeding effective size were not correlated. Our results suggest source–sink dynamics where captive stocks form a genetically diverse source and the wild population behaves as a sink. Nevertheless, overall genetic diversity of silvery minnow has been maintained over the last decade, and we attribute this to a well‐designed and executed propagation management plan. When multiple factors like environmental fluctuation and hatchery supplementation act simultaneously on a population, interpretation of genetic monitoring data may be equally complex and require considerable ecological data.  相似文献   

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The federally endangered species Hine's emerald dragonfly (Somatochlora hineana) is found in fens surrounding the Great Lakes region and in a small portion of the Missouri Ozarks. Most previous work has focused on the populations in the Great Lakes region. We present mark/recapture studies and genetic surveys to address the status of the Ozark populations. The densities and genetic diversity tend to be higher in the Ozarks than in the Great Lakes region. A phylogeographic analysis indicates that the Ozarks, with its unglaciated fens, is the likely source for the populations currently inhabiting the formerly glaciated Great Lakes region, and genetic diversity decreases with increasing distance from the Ozarks. This work illustrates the inadequacy of using geography alone to identify a population as marginal and of less conservation concern. We also reanalyzed genetic data on the Great Lakes populations, where several populations have been extirpated over the last several decades. We show that the populations in the Great Lakes region have already lost more than 30% of their genetic diversity over just several decades, and the phylogeographic analysis indicates that increased fragmentation is a possibility in this region due to local extirpations. Ecologically and genetically, the Ozark populations should have a high priority in management plans, and the high rate of loss of genetic diversity and potential fragmentation indicates that continued monitoring and management is needed in the Great Lakes region for this highly endangered dragonfly.  相似文献   

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One of the greatest challenges of effective conservation measures is the correct identification of sites where rare and elusive organisms reside. The recently rediscovered Hula painted frog (Latonia nigriventer) has not been seen for many decades and was therefore categorized extinct. Since its rediscovery in 2011, individuals from the critically endangered species have been found, with great effort, only in four restricted sites. We applied the environmental DNA (eDNA) approach to search for new populations of the Hula painted frog in suitable aquatic habitats. We further used the eDNA data to classify the landscape factors associated with the species distribution and to predict its suitable habitats. We sampled 52 aquatic sites in the Hula Valley during the spring of 2015 and 2016 and amplified the samples with a species‐specific qPCR assay. DNA of the Hula painted frog was detected in 22 of the sites, all of which clustered within three main areas. A boosting classification model showed that soil type, vegetation cover and the current and former habitats are all key predictors of the frog's current distribution. Intriguingly, the habitat suitability models reveal a high affinity of the species to its long‐lost habitat of the historical wetlands. Our findings encourage a series of informed searches for new populations of this threatened frog and provide guidance for future conservation management programmes. In the era of global conservation crisis of amphibians, developing the eDNA approach, a reliable detection method for many critically endangered and elusive amphibians, is of particular importance.  相似文献   

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As global warming accelerates the melting of Arctic sea ice, polar bears (Ursus maritimus) must adapt to a rapidly changing landscape. This process will necessarily alter the species distribution together with population dynamics and structure. Detailed knowledge of these changes is crucial to delineating conservation priorities. Here, we sampled 361 polar bears from across the center of the Canadian Arctic Archipelago spanning the Gulf of Boothia (GB) and M'Clintock Channel (MC). We use DNA microsatellites and mitochondrial control region sequences to quantify genetic differentiation, estimate gene flow, and infer population history. Two populations, roughly coincident with GB and MC, are significantly differentiated at both nuclear (FST = 0.01) and mitochondrial (ΦST = 0.47; FST = 0.29) loci, allowing Bayesian clustering analyses to assign individuals to either group. Our data imply that the causes of the mitochondrial and nuclear genetic patterns differ. Analysis of mtDNA reveals the matrilineal structure dates at least to the Holocene, and is common to individuals throughout the species’ range. These mtDNA differences probably reflect both genetic drift and historical colonization dynamics. In contrast, the differentiation inferred from microsatellites is only on the scale of hundreds of years, possibly reflecting contemporary impediments to gene flow. Taken together, our data suggest that gene flow is insufficient to homogenize the GB and MC populations and support the designation of GB and MC as separate polar bear conservation units. Our study also provide a striking example of how nuclear DNA and mtDNA capture different aspects of a species demographic history.  相似文献   

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  1. Dispersal is an important process for any organism, but especially for endangered species in fragmented landscapes. To enhance the dispersal of a certain species, connectivity measures are implemented, which require knowledge on the species' dispersal behaviour and habitat. It is often assumed, that the preferred reproductive habitat of a species is also used as the main dispersal habitat. Although this assumption has often been confirmed, there are also cases where it has been disproved.
  2. With a combination of a mark‐resight study and genetic analysis conducted in a fragmented agricultural landscape in Switzerland, the dispersal habitats of the threatened damselfly Coenagrion mercuriale were analysed for different distance classes. In addition, maximum dispersal distances were estimated.
  3. The mark‐resight study detected movement over short distances (≤500 m) mainly within the reproductive habitat of C. mercuriale (i.e. streams).
  4. In contrast, the genetic study detected both short‐ and long‐distance dispersal. Short‐distance dispersal occurred along streams, and discontinuity of streams hindered dispersal. Long‐distance dispersal was suggested to happen along more or less straight lines and crossing agricultural land. Genetic analysis also showed that populations were well connected and that few individuals dispersed over larger distances (≤4500 m).
  5. Our study showed that connected reproductive habitat enhanced short‐distance dispersal in C. mercuriale. Although short‐distance dispersal occurred frequently, long‐distance dispersal was rare, but important to connect more isolated populations. Therefore, it would be relevant to differentiate between these two dispersal types when planning connectivity measures.
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If animals are independently detected during surveys, many methods exist for estimating animal abundance despite detection probabilities <1. Common estimators include double‐observer models, distance sampling models and combined double‐observer and distance sampling models (known as mark‐recapture‐distance‐sampling models; MRDS). When animals reside in groups, however, the assumption of independent detection is violated. In this case, the standard approach is to account for imperfect detection of groups, while assuming that individuals within groups are detected perfectly. However, this assumption is often unsupported. We introduce an abundance estimator for grouped animals when detection of groups is imperfect and group size may be under‐counted, but not over‐counted. The estimator combines an MRDS model with an N‐mixture model to account for imperfect detection of individuals. The new MRDS‐Nmix model requires the same data as an MRDS model (independent detection histories, an estimate of distance to transect, and an estimate of group size), plus a second estimate of group size provided by the second observer. We extend the model to situations in which detection of individuals within groups declines with distance. We simulated 12 data sets and used Bayesian methods to compare the performance of the new MRDS‐Nmix model to an MRDS model. Abundance estimates generated by the MRDS‐Nmix model exhibited minimal bias and nominal coverage levels. In contrast, MRDS abundance estimates were biased low and exhibited poor coverage. Many species of conservation interest reside in groups and could benefit from an estimator that better accounts for imperfect detection. Furthermore, the ability to relax the assumption of perfect detection of individuals within detected groups may allow surveyors to re‐allocate resources toward detection of new groups instead of extensive surveys of known groups. We believe the proposed estimator is feasible because the only additional field data required are a second estimate of group size.  相似文献   

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