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41.
Adaptive host choice and avoidance of superparasitism in the spawning decisions of bitterling (Rhodeus sericeus) 总被引:5,自引:0,他引:5
C. Smith John D. Reynolds William J. Sutherland Pavel Jurajda 《Behavioral ecology and sociobiology》2000,48(1):29-35
Choice of a site for oviposition can have fitness consequences. We investigated the consequences of female oviposition decisions
for offspring survival using the bitterling, Rhodeus sericeus, a freshwater fish that spawns inside living unionid mussels. A field survey of nine bitterling populations in the Czech
Republic revealed a significantly lower rate of release of juvenile bitterling from Anodonta cygnea compared to three other mussel species. A field experiment demonstrated that female bitterling show highly significant preferences
for spawning in A. anatina, Unio pictorum, and U. tumidus. Within a species, female bitterling avoided mussels containing high numbers of bitterling embryos. Mortality rates of bitterling
embryos in mussels were strongly density dependent and the strength of density dependence varied significantly among mussel
species. Female preferences for mussels matched survival rates of embryos within mussels and females distributed their eggs
among mussels such that embryo mortalities conformed to the predictions of an ideal free distribution model. Thus, female
oviposition choice is adaptive and minimizes individual embryo mortality.
Received: 6 October 1999 / Received in revised form: 7 January 2000 / Accepted: 13 March 2000 相似文献
42.
Operational sex ratio versus gender density as determinants of copulation duration in the walnut fly,Rhagoletis juglandis (Diptera: Tephritidae) 总被引:5,自引:0,他引:5
In laboratory and field studies of the walnut fly, Rhagoletis juglandis Cresson (Diptera: Tephritidae), we assessed the effect of operational sex ratio on copulation duration and partitioned the
sex ratio effect into component effects due to male density and female density. In our first laboratory experiment, results
were clearly consistent with theoretical expectation: increases in male density were associated with significant increases
in copulation duration while increases in female density were associated with significant decreases in copulation duration.
These component effects yielded a striking composite effect of operational sex ratio (OSR) on copulation duration in which
male-biased ratios were associated with low frequencies of short copulations and female-biased ratios were associated with
high frequencies of short copulations. Consistent with a priori expectations concerning costs of territorial behavior, the
effect of male density on copulation duration was stronger than that of female density. There was no significant interaction
between the effects of gender density on copulation duration: each gender density contributed additively to the composite
OSR effect on copulation duration. In contrast to the effect of OSR, overall density had little effect. Field data corroborated
these findings fully and showed additionally that OSR in the vicinity of fruit tended in nature to be male-biased. In a second
laboratory experiment, we measured copulation duration for individuals exposed alternately to male-biased and female-biased
ratios. Individual flies consistently copulated for longer in male-biased environments than in female-biased ones. We propose
that this plasticity permits individuals to track changes in local sex ratio over space and time and respond appropriately.
Received: 15 November 1995/Accepted after revision: 27 April 1996 相似文献
43.
Richard J. Douglass 《Environmental management》1989,13(3):355-363
Rodents can be useful in detecting environmental impacts because they are easy to study (easy to capture and handle), they can occur in densities adequate for statistical analysis, and they are ecologically important. In this study the usefulness of rodent populations for ecological monitoring was investigated by examining the effect of variation on the possibility of detecting differences among populations of rodents on 10 trapping grids. The effects of sampling frequencies and dispersal on detecting differences in population parameters among grids was also investigated, as was the possibility of inferring population parameters from correlations with habitat data. Statistically significant differences as small as 4.3Peromyscus maniculatus/ha were detected between grids. Of 10 populations, this comprised 12% of the highest-density population and 44% of the lowest-density population. Smaller and more differences among grids were found by examining only animals surviving from previous months. Dispersal confounds detection of direct impacts to populations, especially during the breeding season. Infrequent sampling fails to detect impacts that occur between sampling periods and will indicate impacts when observed changes result from natural variation. Correlations between population parameters and habitat variables exist but should only be used in predicting, not measuring, impacts. It is concluded that some rodent populations can be used in ecological monitoring. However, intensive sampling is required to account for variation and dispersal. 相似文献
44.
It is believed that diversity of plant communities has a positive effect on their productivity. The benefits of diversity are described by “biodiversity indices”, comparing yield of mixtures with yields of monocultures of constituent species. These indices are supposed to capture also the main mechanisms leading to increased yield. We have constructed a spatially explicit individual based model, simulating even-aged stand development, and compared the behaviour of selected biodiversity indices (overyielding, selectivity and complementarity) with expectations based on life history traits of constituent species. The results are based on comparisons of two species mixtures with corresponding monocultures. We designed three scenarios of changes in the two species life history differentiation, and compared the behaviour of the indices with expectation based on it. In the first scenario, selectivity was driven by increasing size inequality of the two species, mostly in accordance with expectations. The second scenario presents increasing shade tolerance of the smaller species that increased complementarity, again mostly as expected. In the last scenario, shortening of length of stress tolerance of the weaker species surprisingly increased values of the biodiversity indices. For each setting, we varied sowing density and spatial pattern of the constituent species. The behaviour of the indices was influenced by both factors, but the effect of density was more pronounced. In particular, at high sowing densities, the most important interactions happened in the very early stages of mixture development, and the behaviour of the indices was often counter-intuitive. 相似文献
45.
电收尘器高性能电晕极性能探讨 总被引:1,自引:0,他引:1
极线是电尘器的核心部分之一,是电场中产生电晕电流的部件,它的性能好坏直接影响到电收尘器的性能。从电收尘的理论考虑,为进一步探索研究电晕线的性能,此次试验我们与日本住友重机株式会社共同对国内外数十种电晕线进行测试试验,以不同电晕线缺乏何形状、不同电晕极间距、以及不同极板间距,测出各种电压、电流数据从中比较出最佳电晕极的几何形状,以及最佳电晕间距。 相似文献
46.
A population model is presented that accounts for spatial structure within habitat patches. It is designed for social species of wildlife that form social group home ranges that are much smaller than patch size. The model represents social group home ranges by Voronoi regions that tessellate a patch to form a Voronoi diagram. Neighbouring social groups are linked with habitat-confined shortest paths and form a dispersal network. The model simulates population dynamics and makes use of Voronoi diagrams and dispersal networks as a spatial component. It then produces density maps as outputs. These are maps that show predicted animal densities across the patches of a landscape. A construction procedure for the particular Voronoi diagram type used by the model is described. As a test case, the model is run for the squirrel glider (Petaurus norfolcensis), a small arboreal marsupial native to Australia. A time series of density maps are produced that show squirrel glider density changing across a landscape through time. 相似文献
47.
48.
49.
Thomas H. Henderson K. Ulrich Mayer Beth L. Parker Tom A. Al 《Journal of contaminant hydrology》2009,106(3-4):195-211
A popular method for the treatment of aquifers contaminated with chlorinated solvents is chemical oxidation based on the injection of potassium permanganate (KMnO4). Both the high density (1025 gL− 1) and reactivity of the treatment solution influence the fate of permanganate (MnO4) in the subsurface and affect the degree of contaminant treatment. The MIN3P multicomponent reactive transport code was enhanced to simulate permanganate-based remediation, to evaluate the pathways of MnO4 utilization, and to assess the role of density contrasts for the delivery of the treatment solution. The modified code (MIN3P-D) provides a direct coupling between density-dependent fluid flow, solute transport, contaminant treatment, and geochemical reactions. The model is used to simulate a field trial of TCE oxidation in a sandy aquifer that is underlain by an aquitard. Three-dimensional simulations are conducted for a coupled reactive system comprised of ten aqueous components, two mineral phases, TCE (dissolved, adsorbed, and NAPL), reactive organic matter, and including ion exchange reactions. Model parameters are constrained by literature data and a detailed data set from the field site under investigation. The general spatial and transient evolution in observed concentrations of the oxidant, dissolved TCE, and reaction products are adequately reproduced by the simulations. The model elucidates the important role of density-induced flow and transport on the distribution of the treatment solution into NAPL containing regions located at the aquifer–aquitard interface. Model results further suggest that reactions that do not directly affect the stability of MnO4 have a negligible effect on solution density and MnO4 delivery. 相似文献
50.
沈阳市大气细菌与真菌粒子的关系 总被引:3,自引:1,他引:3
用ANDERSEN生物粒子采样器对沈阳市大气细菌和真菌粒子的密度、密度分布、粒度分布及两者关系进行了观察和。结果表明,沈阳市大气年平均密度细菌粒子为7228个/m^3,真菌粒子为1797个/m^3,细菌为真菌的4.1倍。细菌粒子密度和粒度均呈正偏态分布,真菌粒子密度和粒度均呈对数正态分布。〈8.2μm的可吸入粒子,细菌为4326个/m^3,占其总数的61.4%;真菌为1583个/m^3,占其总数的 相似文献