Readers may make verbatim copies of this document for non-commercial purposes by any means, provided that this copyright notice appears on all such copies. This paper presents a dynamic principal-agent model of aquatic species invasions in which a manager, concerned about the spread of invasive species across lakes by boaters, sets interseasonal management controls on a lake-by-lake basis, and ...

P olyploidy is a prominent chromosomal/genetical feature in most flowering plant groups (1, 2). Change in the number of chromosome sets (and thus gene dosage) is an important factor in the genesis of new species, in part because plants with higher ploidal levels often have ecological tolerances that differ from those of their progenitors. Plant evolutionists have been very interested in the ori...

Throughout many years of studying mycopopulation of weeds, we have found fungi of the Diaporthe/ Phomopsis complex interesting to research. After years of examining plants of Achillea millefolium L., some of them exhibited symptoms of infection typical for Diaporthe/Phomopsis species. A. millefolium was usually found in uncultivated, pasture and forest flora, but also in or nearby sunflower fie...