Optimal foraging and community structure: implications for a guild of generalist grassland herbivores

A particular linear programming model is constructed to predict the diets of each of 14 species of generalist herbivores at the National Bison Range, Montana. The herbivores have body masses ranging over seven orders of magnitude and belonging to two major taxa: insects and mammals. The linear programming model has three feeding constraints: digestive capacity, feeding time and energy requirements. A foraging strategy that maximizes daily energy intake agrees very well with the observed diets. Body size appears to be an underlying determinant of the foraging parameters leading to diet selection. Species that possess digestive capacity and feeding time constraints which approach each other in magnitude have the most generalized diets. The degree that the linear programming models change their diet predictions with a given percent change in parameter values (sensitivity) may reflect the observed ability of the species to vary their diets. In particular, the species which show the most diet variability are those whose diets tend to be balanced between monocots and dicots. The community-ecological parameters of herbivore body-size ranges and species number can possibly be related to foraging behavior.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47765/1/442_2004_Article_BF00377109.pd

Causes of false-positive HIV rapid diagnostic test results

HIV rapid diagnostic tests have enabled widespread implementation of HIV programs in resource-limited settings. If the tests used in the diagnostic algorithm are susceptible to the same cause for false positivity, a false-positive diagnosis may result in devastating consequences. In resource-limited settings, the lack of routine confirmatory testing, compounded by incorrect interpretation of weak positive test lines and use of tie-breaker algorithms, can leave a false-positive diagnosis undetected. We propose that heightened CD5+ and early B-lymphocyte response polyclonal cross-reactivity are a major cause of HIV false positivity in certain settings; thus, test performance may vary significantly in different geographical areas and populations. There is an urgent need for policy makers to recognize that HIV rapid diagnostic tests are screening tests and mandate confirmatory testing before reporting an HIV-positive result. In addition, weak positive results should not be recognized as valid except in the screening of blood donors