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Life Sciences	50%

Selected Abstracts

Distribution, abundance, and individual strategies: a multi-scale analysis of dasyurid marsupials in arid central Australia

ECOGRAPHY, Issue 3 2006
Adele S. Haythornthwaite
We investigated the effects of different environmental factors on the distribution and abundance of 6 species of dasyurid marsupials using a multiple-scale analysis. Data collected in the spinifex dunefields of the Simpson Desert, Australia, were analysed at 3 spatial scales spanning more than 5 orders of magnitude: "metasite" (covering an area of 1000,2000 km2), site (2,12 km2) and grid (0.01 km2). Temporal variability was also investigated, using data collected in March, April, and May in 4 consecutive years from 1997 to 2000. Both abiotic and biotic factors influenced the capture rates of different species at different times and spatial scales. At the coarsest spatial scale, Dasycercus cristicauda (mulgara) was consistently limited in its distribution by the intensity of rainfall, probably as an indirect result of increased grazing pressure from pastoral activity and a higher density of feral predators in high rainfall areas. However, at the finest spatial scale, this partly carnivorous species was scarce in areas of dense spinifex, perhaps because such habitats yield lowest returns during foraging, and was more common in areas where small invertebrate prey were abundant. Factors affecting the distribution of the most abundant dasyurid species in the study area, Sminthopsis youngsoni (lesser hairy-footed dunnart), could not be identified at any scale; we conclude that this reflects the opportunistic foraging strategies and flexible habitat requirements of this insectivorous species. Both Ningaui ridei (wongai ningaui) and Sminthopsis hirtipes (hairy-footed dunnart) were less abundant throughout the study region. For N. ridei, a spinifex specialist, predictors of occurrence could be identified only at the finest scale of analysis; at the grid level, a close positive association was detected in 2 of the 4 study years between capture rate and spinifex cover. For S. hirtipes, all 3 levels of spatial analysis revealed a negative association between capture rate and both rainfall and spinifex density. For the rarely-caught S. crassicaudata (fat-tailed dunnart) and Planigale tenuirostris (narrow-nosed planigale), no clear results were obtained at any spatial scale, and we interpret this to indicate that the study region represents sub-optimal habitat for these species. Given that different factors affected the distribution and abundance of dasyurids at different spatial scales over time, we conclude that a multiple-scale approach to population and community analysis is vital to accurately identify which environmental processes shape population and community dynamics. Understanding the interplay between regional and local processes will be crucial for management of existing species populations and for prediction of their distributions and abundances in future. [source]

Microsatellite variation and fine-scale population structure in the wood frog (Rana sylvatica)

MOLECULAR ECOLOGY, Issue 5 2001
Robert A. Newman
Abstract We investigated genetic population structure in wood frogs (Rana sylvatica) from a series of Prairie Pothole wetlands in the northern Great Plains. Amphibians are often thought to exist in demographic metapopulations, which require some movement between populations, yet genetic studies have revealed strong subdivision among populations, even at relatively fine scales (several km). Wood frogs are highly philopatric and studies of dispersal suggest that they may exhibit subdivision on a scale of , 1,2 km. We used microsatellites to examine population structure among 11 breeding assemblages separated by as little as 50 m up to , 5.5 km, plus one population separated from the others by 20 km. We found evidence for differentiation at the largest distances we examined and among a few neighbouring ponds, but most populations were strikingly similar in allele frequencies, suggesting high gene flow among all but the most distant populations. We hypothesize that the few significant differences among neighbouring populations at the finest scale may be a transient effect of extinction,recolonization founder events, driven by periodic drying of wetlands in this hydrologically dynamic landscape. [source]

Multiscale morphology of the galaxy distribution

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2007
Enn Saar
ABSTRACT Many statistical methods have been proposed in the last years for analysing the spatial distribution of galaxies. Very few of them, however, can handle properly the border effects of complex observational sample volumes. In this paper, we first show how to calculate the Minkowski Functionals (MFs) taking into account these border effects. We then present a multiscale extension of the MF which gives us more information about how the galaxies are spatially distributed. A range of examples using Gaussian random fields illustrate the results. Finally, we have applied the Multiscale Minkowski Functionals (MMFs) to the 2dF Galaxy Redshift Survey data. The MMF clearly indicates an evolution of morphology with scale. We also compare the 2dF real catalogue with mock catalogues and found that , cold dark matter simulations roughly fit the data, except at the finest scale. [source]

Hydrological seasonal forecast over France: feasibility and prospects

ATMOSPHERIC SCIENCE LETTERS, Issue 2 2010
J.-P. Céron
Abstract This article presents a first evaluation of a hydrological forecasting suite at seasonal time scales over France. The hydrometeorological model SAFRAN-ISBA-MODCOU is forced by seasonal forecasts from the DEMETER project for the March,April,May period. Despite a simple downscaling method, the atmospheric forcings are reasonably well represented at the finest scale. The computed soil moisture shows some predictability with large regions of correlation above 0.3. Probabilistic scores for soil moisture and river flows for four different catchments are higher than that for atmospheric variables. These results suggest to go further for building an operational hydrological seasonal forecast system. Copyright © 2010 Royal Meteorological Society [source]