7 research outputs found
Inventory and Characterization of the Riparian Zone of the Current and Jacks Fork Rivers
The ecological, recreational, and economic value of the 134 mile (216 km) riparian corridor within the Ozark National Scenic Riverways (ONSR) is of great interest to land managers and conservationists. Recent interest in applying ecosystem management to forest systems has necessitated a fresh look at the tools and methods in use to assess existing patterns of plant community structure and diversity. The purpose and objective of the study described in this report was to initiate a series of vegetation studies that could be integrated with existing research and management infonnation on the riparian vegetation in the ONSR. Defining the compositional and spatial attributes of the riparian corridor were at the core of our research efforts. We used multivariate analysis and ordination techniques to characterize the composition and distribution of woody and herbaceous vegetation within the ONSR
Benefits and costs of defense in a neotropical shrub
Journal ArticleBenefits and costs are central to optimality theories of plant defense. Benefit is the gain in fitness to reducing herbivory and cost is the loss in fitness to committing resources to defense. We evaluate the benefits and costs of defense in a neotropical shrub, Psychotria horizontalis. Plants were either exposed to herbivores or protected within a cage of fine mesh in three gardens planted in large light gaps on Barro Colorado Island, Panama
Beneficios y costos de defensa en un arbusto del neotrópico
Journal ArticleLOS beneficios y costos son de importancia capital para las teorfas de optimization de las defensas de las plantas. El beneficio es la ganancia de aptitud para reducir el herbivorismo; el costo es la perdida de aptitud al comprometer recursos en defensa. Evaluamos los beneficios y los costos de defensa, en el arbusto neotropical Psychotria horizontalis. Las plantas estuvieron expuestas a los herbivoros, o protegidas dentro de una malla, en tres jardines situados en un claro grande de luz, en la isla de Barro Colorado, en Panama. Se sembraron dos esquejes de cada uno de 35 clones, por parejas, segiin la masa inicial, y se asignaron al azar a un jardin y al tratamiento de exposici6n o de protection. La tasa anual de herbivorismo fue de 37% en las plantas expuestas y de 17%, en las protegidas
The Establishment of Genetically Engineered Canola Populations in the U.S.
Concerns regarding the commercial release of genetically engineered (GE) crops include naturalization, introgression to sexually compatible relatives and the transfer of beneficial traits to native and weedy species through hybridization. To date there have been few documented reports of escape leading some researchers to question the environmental risks of biotech products. In this study we conducted a systematic roadside survey of canola (Brassica napus) populations growing outside of cultivation in North Dakota, USA, the dominant canola growing region in the U.S. We document the presence of two escaped, transgenic genotypes, as well as non-GE canola, and provide evidence of novel combinations of transgenic forms in the wild. Our results demonstrate that feral populations are large and widespread. Moreover, flowering times of escaped populations, as well as the fertile condition of the majority of collections suggest that these populations are established and persistent outside of cultivation
Benefits of Transgenic Insect Resistance in Brassica Hybrids under Selection
Field trials of transgenic crops may result in unintentional transgene flow to compatible crop, native, and weedy species. Hybridization outside crop fields may create novel forms with potential negative outcomes for wild and weedy plant populations. We report here the outcome of large outdoor mesocosm studies with canola (Brassica napus), transgenic canola, a sexually compatible weed B. rapa, and their hybrids. Brassica rapa was hybridized with canola and canola carrying a transgene for herbivore resistance (Bt Cry1Ac) and grown in outdoor mesocosms under varying conditions of competition and insect herbivory. Treatment effects differed significantly among genotypes. Hybrids were larger than all other genotypes, and produced more seeds than the B. rapa parent. Under conditions of heavy herbivory, plants carrying the transgenic resistance were larger and produced more seeds than non-transgenic plants. Pollen derived gene flow from transgenic canola to B. rapa varied between years (5%–22%) and was not significantly impacted by herbivory. These results confirm that canola-weed hybrids benefit from transgenic resistance and are aggressive competitors with congeneric crops and ruderals. Because some crop and crop-weed hybrids may be competitively superior, escapees may alter the composition and ecological functions of plant communities near transgenic crop fields