CiteULike: neteler Schweitzer

Extending Genomics to Natural Communities and Ecosystems

Thomas Whitham — 2008-05-03T20:41:38-00:00

Science, Vol. 320, No. 5875. (25 April 2008), pp. 492-495.

An important step in the integration of ecology and genomics is the progression from molecular studies of relatively simple model systems to complex field systems. The recent availability of sequenced genomes from key plants is leading to a new understanding of the molecular drivers of community composition and ecosystem processes. As genome sequences accumulate for species that form intimate associations in nature, a detailed view may emerge as to how these associations cause changes among species at the nucleotide level. This advance could dramatically alter views about the structure and evolution of communities and ecosystems. 10.1126/science.1153918

Habitat factors influencing distributions of Anaplasma phagocytophilum and Ehrlichia chaffeensis in the Mississippi Alluvial Valley.

JS Manangan — 2008-04-19T06:03:05-00:00

Vector borne and zoonotic diseases (Larchmont, N.Y.), Vol. 7, No. 4. (2007), pp. 563-573.

Human monocytotropic ehrlichiosis (HME), caused by the bacterium Ehrlichia chaffeensis, and human granulocytic anaplasmosis (HGA), caused by the bacterium Anaplasma phagocytophilum, are two emerging tick-borne zoonoses of concern. Factors influencing geographic distributions of these pathogens are not fully understood, especially at varying spatial extents (regional versus landscape) and resolutions (counties versus smaller land units). We used logistic regression to compare influences of physical environment, land cover composition, and landscape heterogeneity on distributions of A. phagocytophilum and E. chaffeensis at multiple spatial extents. Pathogen presence or absence was determined from white-tailed deer (Odocoileus virginianus) serum samples collected from 1981 to 2005. Ecological predictor variables were derived from spatial datasets that represented deer density, elevation, land cover, normalized difference vegetation index (NDVI), hydrology, and soil moisture. We used three strategies (a priori, exploratory, and spatial extent) to develop models. Best fitting models were applied within a geographic information system to create predictive probability surfaces for each bacterium. Ecological predictor variables generally resulted in better fitting models for E. chaffeensis than A. phagocytophilum (90.5% and 68% sensitivity, respectively), possibly as a result of differences in the natural histories of tick vectors. Although alternative model development strategies produced different models, in all cases bacteria presence or absence was affected by a combination of soil moisture or flooding variables (thought to affect primarily tick vectors) and forest cover or NDVI variables (thought to affect primarily mammalian hosts). This research demonstrates the potential for modeling the distributions of microscopic tick-borne pathogens using coarse regional datasets and emphasizes the importance of forest cover and flooding as environmental constraints, as well as the importance of considering ecological variables at multiple spatial extents.

Ableitung von phänologischen Verlaufsmustern aus MODIS-Zeitserien und Möglichkeiten der Anwendung

RR Colditz — 2006-06-22T13:46:55-00:00

(2005), pp. 94-99.

Zeitlich hochaufgelöste operationelle Satellitendaten wie NOAA AVHRR und MODIS eignen sich besonders zur Extraktion und Analyse zeitlicher Verlaufsmuster. Insbesondere die MODIS-Daten stellen eine geeignete Ressource aktueller Daten dar und ermöglichen durch die detaillierten Qualitätsinformationen eine verbesserte Erstellung von Zeitserien. Diese Studie extrahiert zeitliche Signaturen aus MODIS NDVI- und LAI-Daten mittels zweier Landbedeckungsklassifikationen aus dem Jahr 2002 für die Beispielregionen Usbekistan und westliches Afrika. Die abgeleiteten Verlaufsmuster werden zeitlich analysiert und zur Landbedeckungsklassifikation mittels eines Nearest Neighbour Ansatzes auch für andere Jahre angewendet. Somit ist unter der Berücksichtigung phänologischer Variationen ein jährliches Klassifikationsupdate möglich.