Generalist plant pathogens may have wide host ranges, but many exhibit varying degrees of host specialization, with multiple pathogen races that have narrower host ranges. These races are often genetically distinct, with each race causing highest disease incidence on its host of origin. We examined host specialization in the seed pathogen Pyrenophora semeniperda by reciprocally inoculating path...

Bradley N. Johnson Tami L. Stubbs Land Management and Water Conservation Research Unit, USDA Agricultural Research Service, 215 Johnson Hall, Washington State University, Pullman, WA, 99164-6421 Pseudomonas fluorescens strain D7 (P. f. D7; NRRL B-18293) is a root-colonizing bacterium that inhibits downy brome (Bromus tectorum L. BROTE) growth. Before commercialization as a biological control ag...

Modification of habitat structure due to invasive plants can alter the risk landscape for wildlife by, for example, changing the quality or availability of refuge habitat. Whether perceived risk corresponds with actual fitness outcomes, however, remains an important open question. We simultaneously measured how habitat changes due to a common invasive grass (cheatgrass, Bromus tectorum) affecte...

Desert annuals are a critically important component of desert communities and may be particularly responsive to increasing atmospheric (CO2 ) because of their high potential growth rates and flexible phenology. During the 10-year life of the Nevada Desert FACE (free-air CO2 enrichment) Facility, we evaluated the productivity, reproductive allocation, and community structure of annuals in respon...

M any natural landscapes have undergone dramatic permanent alterations as a result of human activities, including conversion to cultural landscapes; such changes are readily observed and understood. However, extensive ecological change can also occur in regional landscapes that are maintained in a seminatural state, changes that go largely unrecognized because the regional landscape retains an ...

Throughout the western United States, the invasive annual grass, medusahead (Taeniatherum caputmedusae L. Nevski), is rapidly invading grasslands once dominated by native perennial grasses, such as bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) A). It is also invading grasslands dominated by less undesirable invasive annual grasses, especially cheatgrass (Bromus tectorum L.). Understandi...

historical records of cheatgrass Bromus tectorum invasion in North American sagebrush-steppe Sumanta Bagchi*, David D. Briske, Brandon T. Bestelmeyer and X. Ben Wu Department of Ecosystem Science and Management, Texas A&M University, 2138 TAMU, College Station, TX 77843, USA; USDA-ARS, Jornada Experimental Range and Jornada Basin LTER, New Mexico State University, MSC 3JER, Box 30003, Las Cruce...

We investigated the effects of chemical variation in thyme (Thymus vulgaris L.) on its interactions with competitors, herbivores, and herbivore predators. Four different thyme monoterpene phenotypes (chemotypes) were grown in a 4x2x2 factorial of chemotype, caging (sham half-cages vs. full cages), and competition (control vs. the grass Bromus madritensis L.). Cages reduced numbers of arthropod ...