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61.
While the number of studies investigating the effects of species diversity on ecosystem properties continues to expand, few have explicitly examined how ecosystem functioning depends quantitatively on the degree of niche complementarity among species. We report the results of a microcosm experiment where similarity in habitat use among aquatic snail species was evaluated as a predictor of changes in community and ecosystem properties due to increasing species richness. Replicate microcosms with all possible one- and two-species combinations of a guild of six snail species were stocked with identical initial snail biomass. Microcosms with two species of snails had greater final snail biomass, lower attached algae biomass, and less total organic matter than monocultures. Snail species differed in their use of five distinct habitat types in the microcosms. Similarity in habitat use between a species pair was negatively related to the magnitude of change (e.g., deltaEF [change in ecosystem function]) in dissolved oxygen. periphyton biomass, and accrual of organic matter with a change in diversity. However, using the most stringent criterion for complementarity effects (e.g., Dmax [proportional deviation of the total polyculture yield from the highest yielding monoculture]), a relationship between species' niche similarity and changes in function with increasing species richness was only observed for dissolved oxygen. The identity of snail species present in the microcosms had strong effects on total organic matter, snail biomass, dissolved oxygen, periphyton biomass, and sedimentation rate. In this study, herbivore identity, sampling effects, and niche complementarity all appear to contribute to species richness effects on pond ecosystem properties and community structure. The analytical approach employed here may profitably be used in other systems to quantify the role of niche complementarity in species richness-ecosystem function relationships. 相似文献
62.
The aim of this study was to examine the simultaneous degradation of dissolved organic nitrogen (DON) and associated colour from wastewater containing melanoidins by an advanced oxidation process (AOP). UV irradiation of H2O2 was used as the mechanism to create the hydroxyl radical for oxidation. Melanoidins are large nitrogenous organic compounds that are refractory during biological wastewater treatment processes. The simultaneous degradation of DON and colour, present as a result of these compounds, was investigated using an AOP. The oxidation process was much more capable of removing colour (99% degradation), dissolved organic carbon (DOC) (50% degradation) and DON (25% degradation) at the optimal applied dose of hydrogen peroxide for the system (3300 mg l(-1)). This indicated that colour and DON removal were decoupled problems for the purpose of treating melanoidin by an AOP and thus colour removal can not be used as an indication of DON removal Colour was caused by organic molecules with molecular weight greater than 10 kDa. Oxidation caused a partial reduction of the DON (41-15% of the total dissolved nitrogen) and DOC (29-14% of the DOC) associated with the large molecular weight fraction (>10 kDa) and almost complete colour removal (87-3% of the total colour). The degraded DON was mostly accounted for by the formation of ammonia (31% of the nitrogen removed from the large fraction) and small molecular weight compounds (66% of the nitrogen removed from the large fraction). The degraded DOC appeared to be mostly mineralised (to CO2) with only 20% of the degraded compounds appearing as small molecular weight DOC. 相似文献
63.
Salerno Jonathan Chapman Colin A. Diem Jeremy E. Dowhaniuk Nicholas Goldman Abraham MacKenzie Catrina A. Omeja Patrick Aria Palace Michael W. Reyna-Hurtado Rafael Ryan Sadie J. Hartter Joel 《Regional Environmental Change》2018,18(3):913-928
Regional Environmental Change - Landscapes are changing rapidly in regions where rural people live adjacent to protected parks and reserves. This is the case in highland East Africa, where many... 相似文献
64.
The mechanisms through which dominance is inherited within social groups vary from direct interactions such as fighting to
non-confrontational conventions. Liostenogaster flavolineata is a primitively eusocial hover wasp in which one female, the ‘dominant’, is the only reproductive upon the nest. The remaining
females, although capable of reproduction, behave as helpers. In this study, we investigate the rules by which helpers inherit
dominance. We removed successive dominants from 56 nests and recorded accession on un-manipulated nests. The results showed
that L. flavolineata has a strict age-based inheritance queue: new dominants are the oldest female in their groups 87% of the time. Thirteen cases
of queue-jumping were found in which young individuals were able to supplant older nestmates and inherit dominance precociously.
Queue jumpers did not differ from other wasps in terms of relatedness to other group members or body size. Individuals that
had previously worked less hard than other females of equivalent rank were significantly more likely to later jump the queue.
Queue-jumping may represent a cheating strategy or could indicate that the rule for inheriting dominance is not based purely
on relative age. We also discuss possible reasons why age-based queuing has evolved and its potential to promote the evolution
of helping behaviour. 相似文献
65.
Mary Alice Coffroth Howard R. Lasker Margaret E. Diamond Jeremy A. Bruenn Eldredge Bermingham 《Marine Biology》1992,114(2):317-325
Clonal reproduction, a common life history strategy among sessile marine invertebrates, can lead to high local abundances of one to a few genotypes in a population. Analysis of the clonal structure of such populations can provide insight into the ecological and evolutionary history of the population, but requires markers that can identify individual genets. Forensic and demographic studies have demonstrated that DNA fingerprinting can provide markers that are unique for an individual genotype. We have generated DNA fingerprints for over 70 colonies of the clonal gorgonian, Plexaura A (Plexaura sp. A) collected from June 1990 through July 1991 in the San Blas Islands, Panama. DNA fingerprints within a singic individual were identical and fingerprinting resolved multiple genotypes within and among reefs. On one reef in the San Blas Islands, Panama, 59% of the colonies sampled were of one genotype and this genotype was not found on any other sampled reefs. A previous study using tissue grafts identified 13 putative clones on these reefs, while DNA fingerprints of the same colonies differentiated 17 genotypes. The present study demonstrates the utility of DNA fingerprinting for distinguishing clones and for identifying clonal structure of marine invertebrate populations. 相似文献
66.
We carried out a field study of the plume discharged by a near-shore wastewater outfall near the Akashi Strait, Japan. Using
an Acoustic Doppler Current Profiler and a tow-body CTD, we measured the near-surface salinity and temperature fields in the
region throughout an M2 tidal cycle. We filtered the data in T–S space to remove water masses other than the wastewater, and then used the adiabatic
mixing assumption to calculate the concentration of wastewater in the far field of this plume. Averaging the T–S fields of
repeated surveys over a time period during which the tidal regime did not change substantially, allowed comparison of the
time-averaged plume with the analytical solution for a plume diffusing in both the horizontal and vertical dimensions. The
resulting vertical turbulent diffusion coefficients agreed well with those resulting from Thorpe scales determined via a vertically-profiling
CTD, as well as with the canonical value for open channel flow of D
z
= 0.067hu
*. The corresponding horizontal turbulent diffusion coefficients, however, were two orders of magnitude larger than those typically
observed in straight channels, and an order of magnitude larger than those observed in meandering rivers. This is likely a
result of enhanced horizontal mixing due to barotropic eddies generated by the interaction of strong tidal flow with headlands
and levees, as well as due to the time-varying nature of tidal flow, and baroclinic spreading of the buoyant wastewater plume. 相似文献
67.
We carried out a field study of a small river plume emptying into Osaka Bay near the Akashi Strait in western Japan, to understand
the fate of its urban-runoff-laden waters. As the river is weak compared to tidal currents, we find that the behavior of the
plume is strongly influenced by phasing between tidal stage and currents (a westward-traveling progressive tidal wave). When
the tidal stage rises, sea water floods up the river, and concentrated river effluent cannot be seen in Osaka Bay. During
most of the river’s ebb, a topographic eddy transports river effluent towards the energetic Akashi Strait, while strong vertical
shear in the tidal flow mixes the effluent with seawater. However, there is a short interval of time during which the direction
of tidal flow in the Strait changes direction and the magnitude of the current is weak. At this time, shear is weak enough
to allow a stratified plume of concentrated river water to form, and this plume is driven offshore, and into Osaka Bay, by
baroclinic circulation. A sewage outfall, which is located very close to the river mouth, is subjected to these same conditions
and therefore exhibits similar behavior. Understanding the relation between tidal phase and plume behavior will be useful
to Kobe City, as well as other cities in a similar environment, for minimizing the environmental effects of their wastewater
and non-point-source runoff. 相似文献
68.
Effects of Human Activity on Global Extinction Risk 总被引:4,自引:0,他引:4
Both natural and anthropogenic factors are important in determining a species' risk of extinction. Little work has been done, however, to quantify the magnitude of current anthropogenic influences on the extinction process. The purpose of this study is to determine the extent to which measures of the intensity of human activity are related to the global variability of two measures of species' susceptibility to extinction. We observed six indices of human activities in 90 countries, and we tested their relationships to the proportion of threatened bird and mammal species in each country, as well as to mammalian population density. After correcting for area effects, latitudinal diversity gradients, and body size (for population density), 28 to 50% of the remaining variation was statistically attributable to anthropogenic variables. Different measures of anthropogenic influence were most closely related to extinction risk in birds and mammals. Human population density was the variable most closely related to the proportion of threatened bird species per country, whereas per capita GNP was more important for mammal species. Mammalian population density strongly correlates with the extent of protected area per country. Contrary to suggestions in earlier literature, our work does not support the hypothesis that habitat loss is a prime contributor to species loss because frequencies of threatened birds and mammals are not closely related to patterns of land use. 相似文献
69.
Species Richness, Endemism, and the Choice of Areas for Conservation 总被引:18,自引:0,他引:18
Jeremy T. Kerr 《Conservation biology》1997,11(5):1094-1100
Although large reserve networks will be integral components in successful biodiversity conservation, implementation of such systems is hindered by the confusion over the relative importance of endemism and species richness. There is evidence ( Prendergast et al. 1993) that regions with high richness for a taxon tend to be different from those with high endemism. I tested this finding using distribution and richness data for 368 species from Mammalia, Lasioglossum, Plusiinae, and Papilionidae. The study area, subdivided into 336 quadrats, was the continuous area of North America north of Mexico. I also tested the hypothesis that the study taxa exhibit similar diversity patterns in North America. I found that endemism and richness patterns within taxa were generally similar. Therefore, the controversy over the relative importance of endemism and species richness may not be necessary if an individual taxon were the target of conservation efforts. I also found, however, that richness and endemism patterns were not generally similar between taxa. Therefore, centering nature reserves around areas that are important for mammal diversity (the umbrella species concept) may lead to large gaps in the overall protection of biodiversity because the diversity and endemism of other taxa tend to be concentrated elsewhere. I investigated this further by selecting four regions in North America that might form the basis of a hypothetical reserve system for Carnivora. I analyzed the distribution of the invertebrate taxa relative to these regions and found that this preliminary carnivore reserve system did not provide significantly different protection for these invertebrates than randomly selected quadrats. I conclude that the use of Carnivora as an umbrella taxon is an unreliable method for invertebrate conservation. 相似文献
70.