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991.
The evolution of female multiple mating, or polyandry, is difficult to comprehend and thus has been the subject of a large
number of studies. However, there is only a little evidence for genetic variation in polyandry, although the evolution of
a trait via selection requires genetic variation that enables the trait to respond to selection. We carried out artificial
selection for increased and decreased female propensity to remate as a measure of polyandry to investigate whether this trait
has a genetic component that can respond to selection in the adzuki bean beetle, Callosobruchus chinensis. Artificial selection produced responses in both directions and divergence between the selection lines in the female propensity
to remate. Although the experimental design adopted in this study selected jointly for female receptivity to remating, which
is a trait of females, and male ability to inhibit female remating—both of which are associated with female propensity to
remate—the observed response to selection was attributable only to the female receptivity to remating. This study indicates
that the female receptivity to remating has significant additive genetic variation and can evolve according to whether remating
is advantageous or disadvantageous to females in C. chinensis. 相似文献
992.
In a river, the flow directly affects the physical and chemical properties of its water, with further consequences for aquatic
biota. Land use practices and vegetation cover play a significant role in the water cycle. The wide-spread perception of forest
cover, in terms of hydrology is that forests may reduce water runoff: although in rare instances the contrary has been reported.
Water runoff varies seasonally and depends on the forest tree species. By no means can it be considered constant over large
expanses of area or for various rainfall patterns. In this paper, the results of a long-term hydrological survey conducted
in two experimental microbasins (operated by the Institute of Hydrology SAS, IH SAS) with different land use practices are
presented. The Rybárik microbasin (0.119 km2) is dominated by row crop production. The basin was 70% cultivated by the state farm and 30% by a private farm. The Lesny
microbasin (0.086 km2) is covered by a deciduous hornbeam regrowth forest (Carpinus betulus). The analysis revealed that the difference in the
runoff from the forest and the agricultural land increases with increasing precipitation; however, at some point (extreme
precipitations with low probability) the runoff from these basins is nearly equal. 相似文献
993.
T. Vega Fernández G. D'Anna A. Pérez-Ruzafa 《Journal of experimental marine biology and ecology》2009,376(1):7-16
Increased habitat complexity is supposed to promote increased diversity, abundance and biomass. This study tested the effect of the macroalgal cover on temperate reef fishes by mimicking macroalgae on artificial reefs in NW Sicily (Mediterranean Sea). Macroalgal cover affected reef fishes in different ways and independently of intrinsic temporal trends. The fish assemblages of manipulated and control artificial reef units differed in the relative abundances of the associated species, but little in species composition. In line with studies in seagrass habitats, fishes were most abundant in reefs covered by artificial macroalgae. Three species (Boops boops, Serranus scriba and Symphodus ocellatus) exhibited consistently greater abundance on vegetated reef units than on control reef units. The total number of species and the abundance of three particular species (S. scriba, S. ocellatus and Thalassoma pavo) displayed temporal trends which were independent on short and large temporal scales. Only fish total biomass and one species (Spicara flexuosa) displayed strong effects of interaction among the experimental factors. Mechanisms to explain these findings are discussed from observational evidence on habitat use and interactions among multiple species. This study highlights that manipulative experiments involving repeated sampling of fish in artificial habitats appear to be a valid approach to study fish-habitat relationships in fluctuating environments. It is also concluded that macroalgae mimics may serve as a tool for restoring lost marine vegetated habitats when current human-induced conditions prevent the recovery of pristine macroalgal stands. 相似文献
994.
ELIZABETH C. BURTON MATTHEW J. GRAY A. CHANDLER SCHMUTZER DEBRA L. MILLER 《The Journal of wildlife management》2009,73(2):269-277
ABSTRACT Global amphibian declines have been linked to various anthropogenic land uses. Recent studies have documented negative impacts of cropland agriculture and deforestation on amphibians; however, few have examined potential impacts of cattle grazing in wetlands on resident amphibians. Therefore, we measured differences in number of captures and body size of postmetamorphic amphibians, egg mass abundance, and shoreline vegetation structure and composition between 4 wetlands with direct cattle access and 4 wetlands from which cattle were excluded on the Cumberland Plateau in Tennessee, USA. We captured amphibians at wetlands from March to August 2005 and 2006 using pitfall traps. Number of green frog (Rana clamitans) metamorphs captured at nonaccess wetlands was 2.5 times and 9.8 times greater than at wetlands with cattle access in 2005 and 2006, respectively. However, number of American toads (Bufo americanus) captured was 68 times and 76 times greater at cattle-access wetlands in 2005 and 2006, respectively. In general, metamorph body size was negatively correlated with species-specific capture rate. We detected no differences in egg mass abundance between cattle land-use types. Height, percent horizontal cover, and percent vertical cover of shoreline vegetation were 74%,25%, and 84% greater, respectively, in nonaccess wetlands in 2005; vegetation trends were similar in 2006. Our results suggest that cattle impact amphibian populations but effects vary by species. Differences in postmetamorphic capture rate may be related to less emergent vegetation at cattle-access wetlands. Although body size differed between land uses for metamorphs, these trends probably were short-lived, because we did not detect differences in juvenile and adult body size between land uses for most species. Based on our findings, we suggest that fencing cattle from wetlands may be a prudent conservation strategy for some amphibian species (e.g., ranids), whereas other species (e.g., bufonids) may benefit from controlled grazing. 相似文献
995.
Martin Lee Miller Boumediene Soufi Carsten Jers Nikolaj Blom Boris Macek Ivan Mijakovic Dr. 《Proteomics》2009,9(1):116-125
There is ample evidence for the involvement of protein phosphorylation on serine/threonine/tyrosine in bacterial signaling and regulation, but very few exact phosphorylation sites have been experimentally determined. Recently, gel‐free high accuracy MS studies reported over 150 phosphorylation sites in two bacterial model organisms Bacillus subtilis and Escherichia coli. Interestingly, the analysis of these phosphorylation sites revealed that most of them are not characteristic for eukaryotic‐type protein kinases, which explains the poor performance of eukaryotic data‐trained phosphorylation predictors on bacterial systems. We used these large bacterial datasets and neural network algorithms to create the first bacteria‐specific protein phosphorylation predictor: NetPhosBac. With respect to predicting bacterial phosphorylation sites, NetPhosBac significantly outperformed all benchmark predictors. Moreover, NetPhosBac predictions of phosphorylation sites in E. coli proteins were experimentally verified on protein and site‐specific levels. In conclusion, NetPhosBac clearly illustrates the advantage of taxa‐specific predictors and we hope it will provide a useful asset to the microbiological community. 相似文献
996.
Tzu-Yi Pai S. C. Wang C. F. Chiang H. C. Su L. F. Yu P. J. Sung C. Y. Lin H. C. Hu 《Bioprocess and biosystems engineering》2009,32(6):781-790
Three types of adaptive network-based fuzzy inference system (ANFIS) in which the online monitoring parameters served as the
input variable were employed to predict suspended solids (SSeff), chemical oxygen demand (CODeff), and pHeff in the effluent from a biological wastewater treatment plant in industrial park. Artificial neural network (ANN) was also
used for comparison. The results indicated that ANFIS statistically outperforms ANN in terms of effluent prediction. When
predicting, the minimum mean absolute percentage errors of 2.90, 2.54 and 0.36% for SSeff, CODeff and pHeff could be achieved using ANFIS. The maximum values of correlation coefficient for SSeff, CODeff, and pHeff were 0.97, 0.95, and 0.98, respectively. The minimum mean square errors of 0.21, 1.41 and 0.00, and the minimum root mean
square errors of 0.46, 1.19 and 0.04 for SSeff, CODeff, and pHeff could also be achieved. 相似文献
997.
Desertification has taken place in the overgrazed grassland of the Tibetan Plateau,China,and the area of mobile sandy land has increased in recent decades.The challenging problem about desertification control is how to restore the vegetation of mobile sandy lands caused by severe desertification.Sand drifting is now regarded as the limiting factor of vegetation restoration in such lands.The initial phase of vegetation restoration is plant colonization,but it is often aborted due to sand drifting,and then vegetation restoration fails to proceed.For the sake of revegetation,the first step is to stop sand drifting to ensure plant colonization.In the northeastern Tibetan Plateau,China,feasible approaches have been found through long-term experiments,and the vegetation is being restored satisfactorily with these approaches in experimental sandy lands.The approaches comprise three types:enclosure,mechanical barriers and biological barriers.Different sandy lands require dissimilar combinations of these approaches.Enclosures may be adequate to revegetate inter-dunes or degraded grassland even in cold regions like the Tibetan Plateau,China,but it is deficient for revegetation of the shifting sand dunes unless mechanical and biological barriers are established simultaneously. 相似文献
998.
A closed-loop artificial pancreas based on model predictive control: Human-friendly identification and automatic meal disturbance rejection 总被引:1,自引:0,他引:1
Type 1 diabetes is characterized by a lack of insulin production by the pancreas, causing high blood glucose concentrations and requiring external insulin infusion to regulate blood glucose. Continuous glucose sensors can be coupled with continuous insulin infusion pumps to create a closed-loop artificial pancreas. A novel procedure of “human-friendly” identification testing using multisine inputs is developed to estimate suitable models for use in an artificial pancreas. A constrained model predictive control (MPC) strategy is developed to reduce risks of hypo- and hyperglycemia (low and high blood glucose concentration). Meal detection and meal size estimation algorithms are developed to improve meal glucose disturbance rejection when incoming meals are not announced. Closed-loop performance is evaluated through simulation studies of a type 1 diabetic individual, illustrating the ability of the MPC-based artificial pancreas control strategy to handle announced and unannounced meal disturbances. 相似文献
999.
Question: How does above‐ground net primary production (ANPP) differ (estimated from remotely sensed data) among vegetation units in sub‐humid temperate grasslands? Location: Centre‐north Uruguay. Methods: A vegetation map of the study area was generated from LANDSAT imagery and the landscape configuration described. The functional heterogeneity of mapping units was analysed in terms of the fraction of photosynthetically active radiation absorbed by green vegetation (fPAR), calculated from the normalized difference vegetation index (NDVI) images provided by the moderate resolution imaging spectroradiometer (MODIS) sensor. Finally, the ANPP of each grassland class was estimated using NDVI and climatic data. Results: Supervised classification presented a good overall accuracy and moderate to good average accuracy for grassland classes. Meso‐xerophytic grasslands occupied 45% of the area, Meso‐hydrophytic grasslands 43% and Lithophytic steppes 6%. The landscape was shaped by a matrix of large, unfragmented patches of Meso‐xerophytic and Meso‐hydrophytic grasslands. The region presented the lowest anthropic fragmentation degree reported for the Rio de la Plata grasslands. All grassland units showed bimodal annual fPAR seasonality, with spring and autumn peaks. Meso‐hydrophytic grasslands showed a radiation interception 10% higher than the other units. On an annual basis, Meso‐hydrophytic grasslands produced 3800 kg dry matter (DM) ha?1 yr?1 and Meso‐xerophytic grasslands and Lithophytic steppes around 3400 kg·DM·ha?1·yr?1. Meso‐xerophytic grasslands had the largest spatial variation during most of the year. The ANPP temporal variation was higher than the fPAR variability. Conclusions: Our results provide valuable information for grazing management (identifying spatial and temporal variations of ANPP) and grassland conservation (identifying the spatial distribution of vegetation units). 相似文献
1000.
Question: Does understory vegetation cover and richness decline along a gradient of increasing Juniperus virginiana midstory canopy cover and is that decline best correlated with litter accumulation? Location: Cross Timbers Forest in Payne County, OK, USA. Methods: We measured vegetation in forest gaps as well as forest areas without J. virginiana, at the inner and outer edge of J. virginiana canopies and near J. virginiana trunks (200 plots) and compared vegetation differences among location to light, litter, soil and microclimate variables. Results: Species richness (11 spp m?2 to 6 spp m?2) and summer vegetation cover (53.3% to 12.7%) declined with proximity to trunks. Regression indicated that richness declines (R2=0.08) and cover (R2=0.18) were best correlated with J. virginiana litter accumulation. Partial canonical correspondence analysis (pCCA) revealed two strong canonical axes, one related to litter/light and another to cover of Quercus spp. versus J. virginiana. Tree seedlings and woody vines dominated near J. virginiana. Forbs, graminoids and Quercus spp. seedlings were more common in areas without J. virginiana. Conclusions: Increasing J. virginiana and consequent litter additions alter understory biomass and composition and, through inhibiting Quercus spp. recruitment, may lead to changes in overstory composition. Decreases in herbaceous litter, which historically contributed to fuel accumulation, may have positive feedback effects on midstory encroachment by reducing the potential for prescribed burning. 相似文献