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141.
We evaluated the population genetic structure of seven microsatellite loci for old growth and second growth populations of eastern white pine (Pinus strobus). From each population, located within Hartwick Pines State Park, Grayling, Michigan, USA, 120-122 contiguous trees were sampled for genetic analysis. Within each population, genetic diversity was high and inbreeding low. When comparing these populations, there is a significant, but small (less than 1%), genetic divergence between populations. Spatial distance between populations or timber harvest at the second growth site were reasonable explanations for the observed minor differences in allele frequencies between populations. Spatial autocorrelation analysis suggested that, for the old growth population, weak positive structuring at 15 m fits the isolation by distance model for a neighbourhood size of about 100 individuals. In comparison, genotypes were randomly distributed in the second growth population. Thus, logging may have decreased spatial structuring at the second growth site, suggesting that management practices may be used to alter natural spatial patterns. In addition, the amount of autocorrelation in the old growth population appears to be lower for some of the microsatellites, suggesting higher numbers of rare alleles and that higher mutation rates may have directly affected spatial statistics by reducing structure.  相似文献   
142.
Avian disease at the Salton Sea   总被引:3,自引:3,他引:0  
Milton Friend 《Hydrobiologia》2002,473(1-3):293-306
A review of existing records and the scientific literature was conducted for occurrences of avian diseases affecting free-ranging avifauna within the Salton Sea ecosystem. The period for evaluation was 1907 through 1999. Records of the U.S. Department of Agriculture, Bureau of Biological Survey and the scientific literature were the data sources for the period of 1907–1939. The narrative reports of the U.S. Fish and Wildlife Service's Sonny Bono National Wildlife Refuge Complex and the epizootic database of the U.S. Geological Survey's National Wildlife Health Center were the primary data sources for the remainder of the evaluation. The pattern of avian disease at the Salton Sea has changed greatly over time. Relative to past decades, there was a greater frequency of major outbreaks of avian disease at the Salton Sea during the 1990s than in previous decades, a greater variety of disease agents causing epizootics, and apparent chronic increases in the attrition of birds from disease. Avian mortality was high for about a decade beginning during the mid-1920s, diminished substantially by the 1940s and was at low to moderate levels until the 1990s when it reached the highest levels reported. Avian botulism (Clostridium botulinum type C) was the only major cause of avian disease until 1979 when the first major epizootic of avian cholera (Pasteurella multocidia) was documented. Waterfowl and shorebirds were the primary species affected by avian botulism. A broader spectrum of species have been killed by avian cholera but waterfowl have suffered the greatest losses. Avian cholera reappeared in 1983 and has joined avian botulism as a recurring cause of avian mortality. In 1989, avian salmonellosis (Salmonella typhimurium) was first diagnosed as a major cause of avian disease within the Salton Sea ecosystem and has since reappeared several times, primarily among cattle egrets (Bubulcus ibis). The largest loss from a single epizootic occurred in 1992, when an estimated 155000 birds, primarily eared grebes (Podiceps nigricollis), died from an undiagnosed cause. Reoccurrences of that unknown malady have continued to kill substantial numbers of eared grebes throughout the 1990s. The first major epizootic of type C avian botulism in fish-eating birds occurred in 1996 and killed large numbers of pelicans (Pelecanus occidentalis & P. erythrorhynchos). Avian botulism has remained as a major annual cause of disease in pelicans. In contrast, the chronic on-Sea occurrence of avian botulism in waterfowl and shorebirds of previous decades was seldom seen during the 1990s. Newcastle disease became the first viral disease to cause major bird losses at the Salton Sea when it appeared in the Mullet Island cormorant (Phalacrocorax auritus) breeding colony during 1997 and again during 1998.  相似文献   
143.
Schmitz  Martin  Platt  Wiliam  DeCoster  James 《Plant Ecology》2002,160(2):137-148
Environmental heterogeneity, especially that related to topography, has been proposed to influence numbers of plant species in different sized areas. Despite little variation in elevation, large numbers of vascular plant species occur in some habitats. This study explored possible relationships between number of plant species and substrateheterogeneity in two species-rich habitats, subtropical pine savannas and short-hydroperiod prairies, in the Long Pine Key region of Everglades National Park (Florida, U.S.A.). We examined relationships between numbers of vascular plant species and topographic heterogeneity by measuring numbers of species and elevations in differ-ent sizes of nested plots that spanned five orders of magnitude (0.1 m2 to 1000 m2 ) and that were located along two transects extending from pine savannas into short-hydroperiod prairies in different areas of Long Pine Key. We also classified substrates and soil depths in 1 m 2 sized submodules within the nested plots. Pine savannas occurred at higher elevations than adjacent short-hydroperiod prairies. Although differences occurred in substrate types and distribution within 1 m 2 plots, numbers of species were not associated with these differences. Vari-ances in elevations were similar in the smallest plots, but increased with area more rapidly in pine savannas than in short-hydroperiod prairies. Plot size explained about 85% of the variation in species numbers, which increased from 2040 per 1 m 2 to 80120 per 1000 m2 . An interaction between habitat and scale explained 5% of the variation; more species occurred in shorthydroperiod prairies than pine savannas at scales <10 m2 , but the re-verse occurred at scales >10 m2. The number of species in pine savannas at scales of 1 m2and 10 m2was positively associated with variation in elevations; no significant relationships were obtained in short-hydroperiod prairies, which lack the fine-scale topographic variation of pine savannas. Our data indicate that substrate het-erogeneity, measured as variation in elevations, is not likely to be involved in the co-occurrence of many species within small areas of these savannas, but may influence numbers of species at larger scales of observation, es-pecially in pine savannas. Why many plant species occur within very small areas in these savannas remains un-answered.  相似文献   
144.
Summary Recent research at the Haeckel Haus at the University of Jena goes far to confirm Haeckel’s role as an ideological progenitor of fascist ideology. This is true not only for Germany, but also for the birth of fascist thought in Italy and France. Haeckel’s Monism is the main inspiration for the origin of French and Italian fascism as well as other vital manifestations of modernist culture. In general, the history of science reveals more fully than any other theoretical approach, the roots of fascism as well as avant-garde modernism.  相似文献   
145.
Chimpanzees (Pan troglodytes) often groom in gatherings that cannot simply be divided into unilateral dyadic grooming interactions. This feature of grooming is studied at two different levels: grooming cliques and grooming clusters. Grooming cliques are defined as directly connected configurations of grooming interactions at any given moment, and when any member of a clique successively grooms any member of another clique within 5min and within a distance of 3m, all the members of both cliques are defined as being in the same grooming cluster. Twenty-seven types of cliques are observed, with the largest one consisting of seven individuals. Mutual and/or polyadic cliques account for more than 25% of all cliques. The size of grooming clusters varies from two to 23 individuals, and almost 70% of the grooming time is spent in polyadic clusters. Although adult males groom the longest in relatively smaller clusters (size=2-4), adult females groomed the longest in clusters of five or more individuals. A review of the literature implies that mutual and polyadic cliques occur less often in other primate species than in chimpanzees. The importance of overlapping interactions for these kinds of gatherings and its possible significance in the evolution of sociality is discussed in this article.  相似文献   
146.
In response to the Surgeon General's request for more research on racial disparities in mental health care, especially research that includes high-need populations (e.g., the homeless, incarcerated, children in foster care, and substance abusers), we examined racial disparities in the provision of mental health counseling, psychotherapy, and pharmacotherapy in hospital outpatient settings using nationally representative data from the 1997 National Hospital Ambulatory Medical Care Survey (NHAMCS). After controlling for diagnosis and other factors, we found that African Americans were less likely than whites to receive mental health counseling and psychotherapy, but more likely than whites to receive pharmacotherapy. We also found that substance abuse clinics were more likely than primary care and specialty mental health clinics to provide mental health counseling and psychotherapy. However, specialty mental health clinics were the only clinics to provide pharmacotherapy. Future research should examine racial disparities in a variety of settings, controlling for diagnosis as well as other factors.  相似文献   
147.
The Israel National Skin Bank (INSB) was founded jointly by the Israel Defense Forces (IDF) Medical Corps and the Ministry of Health in 1986. The prime purpose of the Skin Bank is to treat burn victims incurred at war or during mass casualty incidences. The INSB Protocol is comprised of international skin bank protocols and our previous and present research results. They provide the framework for selecting optimal guidelines for procurement, processing, preservation, storage and evaluation of transplantation performance of viable skin grafts. For evaluation and direct comparison of graft performance of glycerolized or cryopreserved skin stored for long periods, we have applied a mouse recipient model developed by us. This model assesses graft performance before the rejection process takes place. The in vivo design has inherent clinical relevance, which is especially appealing. Cryopreserved skin performed better than glycerolized skin (p > 0.027), but fresh skin performed significantly better than cryopreserved skin (p > 0.003), as analyzed by the Mann–Whitney non-parametric test. Then graft performance of skin specimens were cryopreserved by programmed or stepwise freezing and stored at -80°C or in liquid nitrogen for 1 and 6–10 months was evaluated. The average score of skin preserved by programmed freezing and stored in liquid nitrogen is the highest for both storage periods. This method has a highly significant advantage (p < 0.007) over the others for 6–10 months storage, evaluated by graft adherence. Several interaction factors determine the quality of cryopreserved skin. Highly significant is the interaction factor/'combined effect' of sample variability with the method of cryopreservation or with the storage period. Finally, the results of paired comparison of selected histology criteria of cryopreserved to fresh skin indicated that storage of skin for up to 5 years did not impair significantly its performance compared to fresh skin, whereas, after six years of storage, there was a highly significant (p < 0.001) impairment in skin quality. We offer a simplified in vivo model and analysis for cryopreserved skin graft performance, suggesting that the evaluation procedures, which are issues of great interest in skin banking, may help future skin banks to make informed choices and decisions regarding quality issues.  相似文献   
148.
Herbivore damage is known to cause the premature loss of mature leaves. However, the effects of herbivory on abscission during the early stages of leaf development remain unexplored, even though herbivores frequently prefer unlignified, immature leaves. In a field experiment, we removed 50% of the tissue from leaves at various stages of development on seedlings of Shorea hopeifolia (Dipterocarpaceae), a dominant rain forest tree in Indonesian Borneo. Four weeks following simulated herbivory, >88% of unlignified expanding leaves had been abscised, compared to only 20% of fully expanded, unlignified leaves and 0% of recently lignified, mature leaves. In a separate experiment over 9 wk, simulated herbivory did not increase abscission rates of mature leaves, even when 75% of leaf tissue was removed. Because most (58%) of S. hopeifolia seedlings under natural conditions had lost 1% or less of the tissue from their mature leaves, herbivore damage probably has little effect on the abscission of mature leaves. In contrast, the tendency for damaged expanding leaves to abscise may explain why 49% of S. hopeifolia seedlings had already lost their youngest leaf. If similar patterns occur in other species, herbivore attacks on developing leaves may contribute substantially to both leaf loss and the cumulative impact of herbivory on the growth and survival of whole plants.  相似文献   
149.
Abstract. The concept of mapping potential replacement vegetation (PRV) is proposed as a parallel to potential natural vegetation (PNV). Potential replacement vegetation (PRV) is an abstract and hypothetical vegetation which is in balance with climatic and soil factors currently affecting a given habitat, with environmental factors influencing the habitat from outside such as air pollution, and with an abstract anthropogenic influence (management) of given type, frequency and intensity. For every habitat, there is a series of possible PRV-types corresponding to the different anthropogenic influences, e.g. grazing, mowing, trampling or growing cereals. The PRV-concept is especially useful in large-scale mapping (scales > 1 : 25 000) of small areas where replacement vegetation is the focus of attention for managers and land-use planners, for example in nature reserves where the aim is conservation of replacement vegetation managed in a traditional way, or in restoration ecology where the concept may be used for defining restoration goals and evaluating the success of restoration efforts. At smaller scales, PRV-mapping may be useful for revealing the biogeographical patterns of larger areas which may be different from the corresponding PNV patterns, because replacement vegetation and natural vegetation may respond to environmental gradients at different scales. An example of medium-scale PRV-mapping through the coincidence of diagnostic species of vegetation types, based on species distribution grid data, is presented. In cultural landscapes, the advantage of using the PRV-concept instead of PNV is its direct relationship to the replacement vegetation. In the habitat mapping with respect to the replacement vegetation, the PRV concept yields more valuable results than the mapping of actual vegetation, as the latter is strongly affected by spatially variable anthropogenic influences which may be largely independent from climatic and soil factors.  相似文献   
150.
Abstract. A phenological map has been prepared for the Podyjí/Thayatal National Park, located on the border between the Czech Republic and Austria. The area is characterized by V-shaped river valleys deeply incised into a gently undulating landscape. Five stages of phenological development were defined, based upon phenological spectra of plant communities in late April; 96 sites, more or less regularly spaced over the area, were assigned to one of these stages using field observations of these spectra. Potential direct solar irradiation was calculated from a digital elevation model for a 25 m x 25 m grid extending over the study area. A method was developed for interpolation of phenological observations by weighted regression of phenology on the irradiation model. This interpolation enables the prediction of the local stage of phenological development across the study area without levelling out phenological patterns dependent upon small-scale topographic variation. Spring phenological events appear to be more advanced in the valleys (except for steep north-facing slopes) than in the adjacent landscape. Possible climatic processes underlying this pattern are discussed with emphasis on temperature inversions in the river valleys. Cold-air-drainage inversions reported from the valleys are probably too infrequent and of too short duration to delay plant phenology. The combined effects of advanced phenology and the increased risk of spring frost injury due to these inversions in the valleys may be an explanation for local distributional patterns of flora and vegetation.  相似文献   
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