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1.
During the last decades, the critically endangered Hooded Vulture Necrosyrtes monachus has strongly declined across its African range. Although direct persecution has been suggested as a major cause of this decline, little is known about the impact of humans on reproductive output in West Africa. We studied the impact of human activities on the reproductive output of Hooded Vultures in the Garango area of Burkina Faso. Twenty and 56 nesting attempts were monitored, respectively, during the breeding season in 2013/14 and 2014/15, to determine reproductive success and identify causes of nest failure. Annual breeding success varied between 0.68 and 0.71 chicks fledged per breeding pair per year and productivity was assessed at 0.57 chicks fledged per territorial pair in 2014/15. The main threats imposed by humans were poaching of eggs, chicks and collection of nest materials, leading to 20% (13 out of 64 breeding attempts) of nest failures over the two years. An additional important reason for nest failure was the pruning and (partial) cutting of nest trees. Despite this high level of human interference, we found that Hooded Vulture nest success increased with proximity to human settlements, probably because breeding vultures benefit from protection by people against persecution and disturbance.  相似文献   

2.
Basic ecological information is still lacking for many species of African vultures. The Hooded Vulture Necrosyrtes monachus is known as a rare breeding resident in north-eastern South Africa. This study set out to monitor the nests of Hooded Vultures and, secondarily, White-backed Vultures Gyps africanus in the Olifants River Private Nature Reserve over two breeding seasons in 2013 and 2014. A total of 12 Hooded Vulture nests, placed mostly in the tree Diospyros mespiliformis, were found along the Olifants River, with an average inter- nest distance of 0.76 km. Nest success was estimated to be between 0.44–0.89 offspring pair?1 y?1 in 2013 and 0.50–0.67 offspring pair?1 y?1 in 2014, which are the first estimates for Hooded Vultures in South Africa. It is thought that nests of this species have been under-reported due to the fact that they are placed within or below the canopy of densely leafed trees and hence difficult to view from aerial surveys. African White-backed Vultures also bred along the Olifants River, with nests placed in clusters of up to six. Nesting density of this species ranged from about 1.0 to 1.2 nests km?1 and nests were predominantly placed in Ficus sycomorus trees.  相似文献   

3.
Although long‐term monitoring is viewed as an essential part of conserving wildlife populations, it is currently carried out in surprisingly few protected areas in Africa. Here, data from a 16‐year vehicle transect monitoring programme in Katavi National Park, western Tanzania, are presented. These data provide information on large mammal densities, identify declines in populations of several large mammal species as based on encounter rates, support worrying trends observed in aerial census data and shed light on the effectiveness of recent changes in legal protection. Ground and aerial surveys confirmed that waterbuck, topi, warthog, lion and spotted hyaena populations are all in decline and that this should be a cause for concern. Counting animals by driving vehicle transects is relatively easy and inexpensive to carry out, and data here show that such counts have several pay‐offs for conservation managers especially in identifying population declines; counts should be employed more often in East Africa and elsewhere.  相似文献   

4.
Emergent infectious diseases represent a major threat for biodiversity in fragmented habitat networks, but their dynamics in host metapopulations remain largely unexplored. We studied a large community of pathogens (including 26 haematozoans, bacteria and viruses as determined through polymerase chain reaction assays) in a highly fragmented mainland bird metapopulation. Contrary to recent studies, which have established that the prevalence of pathogens increase with habitat fragmentation owing to crowding and habitat-edge effects, the analysed pathogen parameters were neither dependent on host densities nor related to the spatial structure of the metapopulation. We provide, to our knowledge, the first empirical evidence for a positive effect of host population size on pathogen prevalence, richness and diversity. These new insights into the interplay between habitat fragmentation and pathogens reveal properties of a host-pathogen system resembling island environments, suggesting that severe habitat loss and fragmentation could lower pathogen pressure in small populations.  相似文献   

5.
Abundance indices of southern Gulf Leucoraja ocellata residing in Northumberland Strait, Canada, declined from 2001 to 2005, but increased during 2006 to 2008. Catch rates in 2009 were the lowest in the time series. The size of the area occupied in Northumberland Strait varied with changes in the abundance indices. Leucoraja ocellata were primarily caught in the north‐west half of the strait over sandy to gravelly seabed; a near total absence was documented from the eastern half despite suitable habitat and a previously established presence documented during research surveys conducted before 2000. In Northumberland Strait, L. ocellata occupied shallow (50% cumulative occurrence = 12 m) and warm (50% cumulative occurrence = 16·5° C) coastal waters and were not present in the cold (<1° C, >35 m) intermediate layer. Abundance and distribution data highlight the need for continuing studies to monitor the status of this population, which is classified as endangered by the IUCN and Committee on the Status of Endangered Wildlife in Canada.  相似文献   

6.
The classic 1955 and 1956 papers by Eustace Jones describe vegetation pattern, process and history in Okomu Forest, south-western Nigeria. Jones and colleagues were puzzled to find an extensive layer of charcoal and pottery below mature mahogany forests. Based on an extensive review of historical documents and the estimated ages of dying emergent tree species, Jones suggested that the forest in Okomu had regenerated after a human population decline 200–300 years previously. We made radiocarbon measurements on samples from the layer of charcoal and pottery described by Jones. In addition, we obtained δ13C measures from a soil profile cutting through the charcoal layer. The charcoal dates to about 700–750 years BP whilst the δ13C profile showed no evidence of input of organic matter from C4 grasses. These results are discussed in the light of other recent archaeological evidence of the impact of humans on the rain forests of Africa during the last 2000–3000 years. It seems that extensive archaeological remains are hidden beneath much of the African rain forest, suggesting that human disturbance has been one of the dominant factors affecting forest structure and composition in recent millennia.  相似文献   

7.
The purpose of this article is to report final results of the evaluation of a chi-square ratio test proposed by the US Food and Drug Administration (FDA) for demonstrating equivalence of aerodynamic particle size distribution (APSD) profiles of nasal and orally inhaled drug products. A working group of the Product Quality Research Institute previously published results demonstrating some limitations of the proposed test. In an effort to overcome the test's limited discrimination, the group proposed a supplemental test, a population bioequivalence (PBE) test for impactor-sized mass (ISM). In this final report the group compares the chi-square ratio test to the ISM-PBE test and to the combination of both tests. The basis for comparison is a set of 55 realistic scenarios of cascade impactor data, which were evaluated for equivalence by the statistical tests and independently by the group members. In many instances, the combined application of these 2 tests appeared to increase the discriminating ability of the statistical procedure compared with the chi-square ratio test alone. In certain situations the chi-square ratio test alone was sufficient to determine equivalence of APSD profiles, while in other situations neither of the tests alone nor their combination was adequate. This report describes all of these scenarios and results. In the end, the group did not recommend a statistical test for APSD profile equivalence. The group did not investigate other in vitro tests, in vivo issues, or other statistical tests for APSD profile comparisons. The studied tests are not intended for routine quality control of APSD.  相似文献   

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A total of 128 ticks of the genus Amblyomma were recovered from 5 marsupials (Didelphis albiventris) - with 4 recaptures - and 17 rodents (16 Bolomys lasiurus and 1 Rattus norvegicus) captured in an urban forest reserve in Campo Grande, State of Mato Grosso do Sul, Brazil. Of the ticks collected, 95 (78.9%) were in larval form and 22 (21.1%) were nymphs; the only adult (0.8%) was identified as A. cajennense. Viewed under dark-field microscopy in the fourth month after seeding, 9 cultures prepared from spleens and livers of the rodents, blood of the marsupials, and macerates of Amblyomma sp. nymphs revealed spiral-shaped, spirochete-like structures resembling those of Borrelia sp. Some of them showed little motility, while others were non-motile. No such structures could be found either in positive Giemsa-stained culture smears or under electron microscopy. No PCR amplification of DNA from those cultures could be obtained by employing Leptospira sp., B. burgdorferi, and Borrelia sp. primers. These aspects suggest that the spirochete-like structures found in this study do not fit into the genera Borrelia or Leptospira, requiring instead to be isolated for proper identification.  相似文献   

11.
Great Barrier Island (c. 27,400 ha) is the largest off-shore Island in New Zealand. Some of the most serious introduced mammalian pests of New Zealand are absent, but feral cats and rodents are present. Community based trusts are spear-heading ecological studies to support conservation and a pest eradication programme. Rodent numbers are greatest in late summer/autumn and lowest in winter/early spring. Maximum abundances were recorded in riparian and coastal vegetation, and in mature forest. Monitoring shows that trapping alone is not able to reduce rat numbers sufficiently for safety in avian re-introductions. A combination of trapping and strategically pulsed toxin baits, however, achieved low levels of rats. Ecosystem recovery is demonstrated by increases in key tree seedlings, large invertebrates and lizards in managed compared to unmanaged areas, and by the survivorship of translocated robins (Petroica longipes). The Great Barrier Island Charitable Trust is communicating these benefits, and associated risks, to the Island community, with a view to promoting pest eradication as a key component in an ecology-based economy, centred on eco-tourism.
Judy GilbertEmail:
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12.
Peter Zwick 《Hydrobiologia》1990,194(3):207-223
Upstream oviposition flights of several Plecoptera species of the genera Leuctra, Nemoura, Isoperla and Siphonoperla along the Breitenbach, Hesse, Germany are inferred from 1. oviposition occuring upstream from emergence areas; 2. size differences and size-shifts between emerging and egg-laying females; 3. concentration of oviposition in upstream sections of the emergence area. The last point relies on direct catches of egg-laying females with sticky traps, and on over-representation of old, mature females in upstream emergence traps towards the end of, or even after actual emergence periods. Criteria for age class discrimination of the respective taxa are described. The validity of the present and of other indirect evidence for directed adult flights and the significance of adult upstream displacement are discussed. Optical orientation cues are suggested. Females of Leuctra prima and Siphonoperla torrentium are shown to gain 25–50% dry weight by feeding in the terrestrial environment; general information indicates many other Plecoptera may be similar in this respect. Terrestrial adult life is shown to last for 3–8 weeks. This long time, evidence of important flight activity and feeding together suggest that the terrestrial phase is spent as an active adult, the inevitable risks of which may form an important control of population dynamics.  相似文献   

13.
鲍雅静  李政海 《生态学报》2008,28(9):4540-4546
植物功能群(plant functional groups, PFGs) 是具有确定的植物功能特征的一系列植物的组合,是生态学家为研究植被对气候变化和干扰的响应而引入的生态学概念.目前功能群研究中最核心的问题仍在于决定植物功能群划分的植物特征的选择上.以内蒙古锡林河流域草原植物群落为例,选取3个草原类型(羊草草原、大针茅草原和羊草草甸草原)及其退化梯度系列(未退化、轻度退化、中度退化、重度退化),在对植物热值进行分析测定的基础上,依据植物的能量属性-单位重量干物质在完全燃烧后所释放出来的热量值,采用人为分段的方法对草原植物进行了能量功能群的划分(高能值植物功能群、中能值植物功能群和低能值植物功能群).并探讨了这种能量功能群划分方法在草原植被动态研究中的客观性与可行性.  相似文献   

14.
Adaptive variation in social behaviour depends upon standing genetic variation, but we know little about how evolutionary forces shape genetic diversity relevant to brain and behaviour. In prairie voles (Microtus ochrogaster), variants at the Avpr1a locus predict expression of the vasopressin 1a receptor in the retrosplenial cortex (RSC), a brain region that mediates spatial and contextual memory; cortical V1aR abundance in turn predicts diversity in space use and sexual fidelity in the field. To examine the potential contributions of adaptive and neutral forces to variation at the Avpr1a locus, we explore sequence diversity at the Avpr1a locus and throughout the genome in two populations of wild prairie voles. First, we refine results demonstrating balancing selection at the locus by comparing the frequency spectrum of variants at the locus to a random sample of the genome. Next, we find that the four single nucleotide polymorphisms that predict high V1aR expression in the RSC are in stronger linkage disequilibrium than expected by chance despite high recombination among intervening variants, suggesting that epistatic selection maintains their association. Analysis of population structure and a haplotype network for two populations revealed that this excessive LD was unlikely to be due to admixture alone. Furthermore, the two populations differed considerably in the region shown to be a regulator of V1aR expression despite the extremely low levels of genomewide genetic differentiation. Together, our data suggest that complex selection on Avpr1a locus favours specific combinations of regulatory polymorphisms, maintains the resulting alleles at population‐specific frequencies, and may contribute to unique patterns of spatial cognition and sexual fidelity among populations.  相似文献   

15.
Maina JN 《Tissue & cell》2003,35(5):375-391
In the embryo of the domestic fowl, Gallus gallus variant domesticus, the lung buds become evident on day 3 of development. After fusing on the ventral midline, the single entity divides into left and right primordial lungs that elongate caudally while diverging and shifting towards the dorsolateral aspects of the coelomic cavity. On reaching their definitive topographical locations, the lungs rotate along a longitudinal axis, attach, and begin to slide into the ribs. First appearing as a solid cord of epithelial cells that runs in the proximal-distal axis of the developing lung, progressively, the intrapulmonary primary bronchus begins to canalize. In quick succession, secondary bronchi sprout from it in a craniocaudal sequence and radiate outwards. On reaching the periphery of the lung, parabronchi (tertiary bronchi) bud from the secondary bronchi and project into the surrounding mesenchymal cell mass. The parabronchi canalize, lengthen, increase in diameter, anastomose, and ultimately connect the secondary bronchi. The luminal aspect of the formative parabronchi is initially lined by a composite epithelium of which the peripheral cells attach onto the basement membrane while the apical ones project prominently into the lumen. The epithelium transforms to a simple columnar type in which the cells connect through arm-like extensions and prominently large intercellular spaces form. The atria are conspicuous on day 15, the infundibulae on day 16, and air capillaries on day 18. At hatching (day 21), the air and blood capillaries have anastomosed profusely and the blood-gas barrier become remarkably thin. The lung is well developed and potentially functionally competent at the end of the embryonic life. Thereafter, at least upto day 26, no further consequential structures form. The mechanisms by which the airways in the avian lung develop fundamentally differ from those that occur in the mammalian one. Compared with the blind-ended bronchial system that inaugurates in the mammalian lung, an elaborate, continuous system of air conduits develops in the avian one. Further studies are necessary to underpin the specific molecular factors and genetic processes that direct the morphogenesis of an exceptionally complex and efficient respiratory organ.  相似文献   

16.
The theme of the third annual Spring workshop of the HUPO-PSI was "proteomics and beyond" and its underlying goal was to reach beyond the boundaries of the proteomics community to interact with groups working on the similar issues of developing interchange standards and minimal reporting requirements. Significant developments in many of the HUPO-PSI XML interchange formats, minimal reporting requirements and accompanying controlled vocabularies were reported, with many of these now feeding into the broader efforts of the Functional Genomics Experiment (FuGE) data model and Functional Genomics Ontology (FuGO) ontologies.  相似文献   

17.
High significant differences in mean age, blood pressure and phenotype frequency distributions between the non-migrants and "emigrants" of a total unselected community sample were discovered. Use of the mean of BP scores collected from epidemiologic surveys over a period of time as an individual score allows sample attrition to produce both a genetically and demographically biased sample of a population intended to represent an unselected community of people. Multiple regression analyses estimated the contribution of an individual's age, genotype and mobility out of the sample to predicting blood pressure variation. Variation in blood pressure means among certain marker phenotype classes was greater in those who leave than in those who stay, but only the upper portion of the pressure distribution contributed to this relationship. A genetic-environment interaction is suggested.  相似文献   

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首次报道曲柄锤角细蜂属Vadana Rajmohana et Narendran,2000在我国分布,并记述采自广东的1新种:皱胸曲柄锤角细蜂Vadana rugosa,sp.nov..模式标本保存在华南农业大学膜翅目标本室.皱胸曲柄锤角细蜂Vadana rugosa,新种(图1~4)本新种与分布于印度的Vadana ...  相似文献   

20.
Kolbasov  Gregory A. 《Hydrobiologia》2000,438(1-3):185-191
A new species of the Lithoglyptes from the Seychelles is described. The external morphology of the mantle sac and the body were examined under SEM. The position of a new species within Lithoglyptes and the ultrastructural characters of different species of this genus are discussed.  相似文献   

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