Correlation of climatic factors and dengue incidence in Metro Manila, Philippines

Dengue is a serious public health problem in Metro Manila, Philippines. Increasing dengue incidence has been attributed to climate change; however, contradicting reports show inconclusive relationships between dengue and climatic factors. This study investigates temperature and rainfall as climatic factors affecting dengue incidence in Metro Manila from 1996 to 2005. Monthly dengue incidence and climatic data for Metro Manila were collected over a 10-y period (1996-2005). Climatic factors temperature and rainfall were linked with dengue incidence through regression analysis. A predictive model equation plots dengue incidence (Y) versus rainfall (X), which suggests that rainfall is significantly correlated to dengue incidence (r2 = 0.377, p < 0.05). No significant correlation between dengue incidence and temperature was established (p > 0.05). Evidence shows dengue incidence in Metro Manila varies with changing rainfall patterns. Intensified surveillance and control of mosquitoes during periods with high rainfall are recommended.     

Indices of Grassland Biodiversity in the Chihuahuan Desert Ecoregion Derived from Remote Sensing

Abstract: We used a relatively simple and direct remote-sensing approach to determine biodiversity values in arid ecosystems and thus identify potential conservation sites. We developed indices based on regression models between grass, shrub, litter, exposed-soil groundcover components, and Landsat thematic mapper satellite imagery reflectance values over a reference site in the northern Chihuahuan Desert in New Mexico. This site supports low-disturbance desert grasslands that have been excluded from livestock grazing for 55 years and moderate-disturbance grasslands that have been under a continuous grazing regime for over 100 years. Greater richness and abundance of noninvasive and nonruderal plant species were associated with the low-disturbance grasslands that had lower shrub abundance, increased litter and grass cover, and lower exposed soil. Using the thematic mapper indices, we computed an additive grassland biodiversity index such that, as exposed soil and shrub values go down, litter and grass values go up, as does the biodiversity index. When the biodiversity index was applied to the reference-site landscape, grasslands previously identified for their high conservation value were detected. As a further test, we applied the indices to a site in Chihuahua, Mexico, that supports similar grasslands but for which there are few other data on condition and conservation values. The soil, grass, and shrub indices were moderately effective in describing the range of variation at the Mexico site, but the litter equation was not. Still, higher biodiversity value in terms of nonruderal plant diversity tended to correspond to higher grass cover and lower soil exposure and a higher overall biodiversity index. Some localized calibration with geologic substrate may be required along with an assessment of the temporal constraints, but generally the index shows promise for quickly and efficiently detecting desert grasslands of high biodiversity conservation value.     

Effect of spatial variation on salinity tolerance of macroinvertebrates in Eastern Australia and implications for ecosystem protection trigger values

Salinisation of freshwater has been identified as a serious environmental issue in Australia and around the world. Protective concentrations (trigger values) for salinity can be used to manage salinity impacts, though require locally relevant salinity tolerance information. 72-h acute salinity tolerance values were determined for 102 macroinvertebrates collected from 11 locations in four biologically distinct freshwater bio-regions in Northeast Australia and compared with sensitivities observed in Southeast Australia. The salinity tolerance of individual taxa was consistent across Northeast Australia and between Northeast and Southeast Australia. However, two distinct communities were identified in Northeast Australia using distributions of the acute tolerance values and a calculated index of salinity sensitivity. Salinity trigger values should therefore be representative of local or regionally relevant communities and may be adequately calculated using sensitivity values from throughout Eastern Australia. The results presented provide a basis for assessing salinity risk and determining trigger values for salinity in freshwater ecosystems at local and regional scales in Eastern Australia.     

VISUALIZATION OF TRENDS AND FLUCTUATIONS IN CLIMATIC RECORDS1

ABSTRACT: Small systematic changes in climatic records are often poorly visualized by standard time series plots because they are usually hidden by the magnitude and variability of the data values themselves. A visualization approach based on the rescaled adjusted partial sums (RAPS) which overcomes the above-stated shortcomings is presented. This visualization highlights trends, shifts, data clustering, irregular fluctuations, and periodicities in the record. Additional information on the number, magnitude, shape, frequency, and timing of fluctuations and trends can also be inferred. The visualization approach can be used for preliminary visual inspection of a time series, to gain a feel for the data, and/or to guide and focus subsequent statistical tests and analyses. It is not intended as a substitute for standard statistical analysis. Alternatively, the visualization approach can be used to display findings of a time series analysis. The capabilities and limitations of the approach are discussed and illustrated for two time series of annual rainfall values.     

Nitrate levels in shallow groundwater of upstate New York,USA

This paper summarizes research evaluating nitrate levels in shallow groundwater of upstate New York, USA. Water from abandoned dug wells in six different land-use categories was analyzed for nitrate. Findings indicate that regardless of overlying land-use, shallow groundwater is susceptible to high levels of nitrate. Over 60 percent of the water samples tested, including at least one sample from each land-use category, had nitrate levels in excess of the United States drinking water standard of 10 mg 1^–1. Due to the potential threat of elevated nitrate levels, efforts should be made to eliminate abandoned dug wells in shallow groundwater as a source of water supply.Glenn Harris is with the Environmental Studies Programme of St Lawrence University in Canton, New York. Brian Henry is with the Department of Entomology at the University of Georgia in Athens, Georgia. Jeffrey Deyette is with the joint International Relations and Resource and Environmental Management Programme at Boston University in Boston, Massachusetts. This research was performed as a Community Service Project sponsored by the Mergardt Fund while Mr Henry and Mr Deyette were students under the supervision of Dr Harris at St Lawrence University.     

Model estimation of land-use effects on water levels of northern prairie wetlands.

Wetlands of the Prairie Pothole Region exist in a matrix of grassland dominated by intensive pastoral and cultivation agriculture. Recent conservation management has emphasized the conversion of cultivated farmland and degraded pastures to intact grassland to improve upland nesting habitat. The consequences of changes in land-use cover that alter watershed processes have not been evaluated relative to their effect on the water budgets and vegetation dynamics of associated wetlands. We simulated the effect of upland agricultural practices on the water budget and vegetation of a semipermanent prairie wetland by modifying a previously published mathematical model (WETSIM). Watershed cover/land-use practices were categorized as unmanaged grassland (native grass, smooth brome), managed grassland (moderately heavily grazed, prescribed burned), cultivated crops (row crop, small grain), and alfalfa hayland. Model simulations showed that differing rates of evapotranspiration and runoff associated with different upland plant-cover categories in the surrounding catchment produced differences in wetland water budgets and linked ecological dynamics. Wetland water levels were highest and vegetation the most dynamic under the managed-grassland simulations, while water levels were the lowest and vegetation the least dynamic under the unmanaged-grassland simulations. The modeling results suggest that unmanaged grassland, often planted for waterfowl nesting, may produce the least favorable wetland conditions for birds, especially in drier regions of the Prairie Pothole Region. These results stand as hypotheses that urgently need to be verified with empirical data.     

Signaling and priming communication: Independent roles in the reproductive isolation of spatially-separated populations of rodents

Summary This research concerned the relative potential for signaling and priming incompatibilities to promote reproductive isolation in rodents. Signaling is defined here as involving behavioral responses, while priming involves endocrine responses. Compatibility of both types of communications was tested between two widely separated and markedly diverging populations of deermice, and between equally separated but much less divergent populations of house mice. Signaling compatibility was assessed by comparing the amount of aggression toward young females by adult males when the two sexes were of the same vs the different stock of the same species. Priming compatibility was tested by measuring the relative amounts of uterine growth induced in young females by exposure to adult males.No signaling or priming incompatibilities were detected during cross-testing of the house mouse stocks. A degree of developing reproductive isolation was observed between the two deermouse populations, however, and this isolation was reinforced by independently occurring incompatibilities of both the signaling and the priming type. The signaling incompatibility was particularly dramatic, manifesting itself in the killing of young females by adult males.The present results provide the first demonstration of a priming incompatibility supporting reproductive isolation in diverging populations of a mammal. Furthermore, our results suggest that signaling and priming systems are independently subject to evolutionary change even when both systems probably operate through the same sensory modality.