Measurement scales on the continuum

In a seminal article in 1946, S. S. Stevens noted that the numerical measures then in common use exhibited three admissible groups of transformations: similarity, affine, and monotonic. Until recently, it was unclear what other scale types are possible. For situations on the continuum that are homogeneous (that is, objects are not distinguishable by their properties), the possibilities are essentially these three plus another type lying between the first two. These types lead to clearly described classes of structures that can, in principle, be incorporated into the classical structure of physical units. Such results, along with characterizations of important special cases, are potentially useful in the behavioral and social sciences.     

Induced resistance and interspecific competition between spider mites and a vascular wilt fungus

The fungal pathogen Verticillium dabliae was less likely to cause symptoms of verticillium wilt on cotton seedlings that had been previously exposed to spider mites than on unexposed cotton seedlings. Conversely, populations of the spider mite Tetranychus urticae grew less rapidly on seedlings that had been inoculated with V. dabliae than on uninoculated controls. Changes caused by pathogen or herbivore attack reduced the suitability of the host plant to a diversity of organisms. This result suggests that highly unrelated organisms that share a host plant may interact strongly.