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Natural hybridization is a relatively common feature of vascular plant species and has been demonstrated to have played an important role in their evolution. Nonetheless, it is not clear whether spontaneous hybridization occurs as a general feature of all plant families and genera or whether certain groups are especially prone to spontaneous hybridization. Therefore, we inspected five modern biosystematic floras to survey the frequency and taxonomic distribution of spontaneous hybrids. We found spontaneous hybridization to be nonrandomly distributed among taxa, concentrated in certain families and certain genera, often at a frequency out of proportion to the size of the family or genus. Most of these groups were primarily outcrossing perennials with reproductive modes that stabilized hybridity such as agamospermy, vegetative spread, or permanent odd polyploidy. These data suggest that certain phylogenetic groups are biologically predisposed for the formation and maintenance of hybrids.

Few empirical data exist to examine the influence of regional scale environmental gradients on productivity patterns of plant species. In this paper we analyzed the productivity of several dominant grass species along two climatic gradients, mean annual precipitation (MAP) and mean annual temperature (MAT), in the Great Plains of the United States. We used climatic data from 296 weather stations, species production data from Natural Resource Conservation Service rangeland surveys and a geographic information system to spatially integrate the data. Both MAP and MAT were significantly related to annual above-ground net primary production (ANPP). MAP explained 54 % to 89 % of the variation in ANPP of two C4 short-grasses, Bouteloua gracilis and Buchloë dactyloides, and two C4 tall-grasses, Andropogon gerardii and Schizachyrium scoparium (= Andropogon scoparius). MAT explained 19 % to 41 % of the variation in ANPP of two C4 grasses, B. gracilis and B. dactyloides, and 41 % to 66 % of the variation in ANPP of two C3 grasses, Agropyron smithii and Stipa comata. ANPP patterns for species along both gradients were described by either linear, negative exponential, logistic, normal or skewed curves. Patterns of absolute ANPP (g/m2) for species differed from those of relative ANPP (%) along the MAP gradient. Responses were similar for species with common functional characteristics (e.g. short-grasses, tall-grasses, C3, C4). Our empirical results support asymmetric responses of species to environmental gradients. Results demonstrate the importance of species attributes, type of environmental gradient and measure of species importance (relative or absolute productivity) in evaluating ecological response patterns.

Weather in the Corn Belt and northern plains and the elimination of traditional commodity programs have refocused attention on farmland valuation. This study uses a statistical formulation of information provided by individual regressors to examine the sensitivity of farmland values to changes in inflation, returns on agricultural assets, and the cost of capital. The results indicate that inflation provides the most information on changes in farmland values; however, the regional results indicate that regions that tend to be more sensitive to changes in the return on agricultural assets also rely more heavily on government payments.

Oil concentration and fatty acid composition were determined in achenes of two annual Helianthus species (112 populations) and 11 perennial species (103 populations) from the Great Lakes region and the Central Great Plains of the U.S. The highest average oil concentration was observed in annual H. petiolaris Nutt. with 28.8%, followed by H. annuus L. with 25.4%. Among the perennial species, H. hirsutus Raf. had the highest average oil concentration with 29.8%. The highest average palmitic (C16: 0) and stearic (C18:0) fatty acids were observed in H. tuberosus L. (6.5 and 3.5%, respectively), while the lowest values were observed in H. pauciflorus Nutt. ssp. subrhomboideus (4.2 and 2.1, respectively). The highest oleic acid (C18:1) was observed in H. annuus (24.7%) and the highest linoleic (C18:2) was observed in H. pumilus Nutt. with 71.3%. Sufficient variability appears to be present in the wild species for enhancement of oil and fatty acid characteristics for cultivated sunflower. /// La concentración de aceite y la composición del ácido graso fueron determinados en aquenios de dos especies de Helianthus anuales (112 poblaciones) y 11 especies perennes (103 poblaciones) procedentes de la región de los Grandes Lagos y de las Grandes Planicies Centrales de los EE.UU. El promedio mayor de concentración de aceite se observó en la anual H. petiolaris Nutt. con 28,8%, seguida por H. annuus L. con 25,4%. Entre las especies perennes, la H. hirsutus Raf. tuvo el promedio mayor de concentración de aceite con 29,8%. El promedio mayor de concentración de ácidos grasos, palmítico (C16:0) y esteárico (C18:0) fueron observados en la H. tuberosus L. (6,5% y 3,5%, respectivamente), mientras los valores más bajos fueron observados en la H. pauciflorus Nutt. ssp. subrhomboideus (4,2 y 2,1, respectivamente). El mayor ácido oléico (C18:1) se observó en la H. annuus (24,7%) y el mayor ácido linoléico (C18:2) se observó en la H. pumilus Nutt. con 71,3%. Parece haber suficiente variabilidad en las especies silvestres, para lograr un mejoramiento de las características de aceite y ácido graso del girasol cultivado.

This study examines the effects of both farm price support programs and federally subsidized crop insurance programs upon the profitability, capital structure, and financial survival rates of High Plains wheat producers. The alternative farm programs are analyzed in an intertemporal dynamic setting. Results indicate that the producer's first response to risk is to restrict the use of debt. Price support programs and crop insurance are substitutes in reducing producer risk. The availability of crop insurance in a setting with price supports allows producers to service higher levels of debt with no increase in risk.

A pilot fetal alcohol syndrome (FAS) surveillance was carried out in four American Indian communities in the Northern Plains by the Aberdeen Area Indian Health Service to determine the incidence of FAS and to evaluate the feasibility of establishing continuing surveillance for FAS. Baseline data on the incidence of FAS would be used by the Indian Health Service to develop and evaluate preventive interventions, including treatment programs for pregnant women who drink alcohol. Four of the 1,022 children included in the project were found to have FAS, a rate of 3.9 per 1,000 live births. The rate is believed to underestimate the true rate of FAS because some low birth weight children were not screened, parents or guardians were reluctant to bring children suspected of FAS for evaluation, clinicians were hesitant to diagnose possible alcohol-damaged children for fear of labeling the child, and some children with FAS died before the diagnosis of FAS could be confirmed. If the rate of FAS is similar for the 39 percent of the infants not screened and for the 25 percent of suspected infants who were not evaluated, a rate of 8.5 cases of FAS per 1,000 live births may be postulated. The authors recommend routine screening of prenatal patients for substance abuse and establishing a tracking system for low birth weight infants suspected to have FAS or other alcohol-related developmental disorders, in an effort to establish more accurate FAS rates. Such a surveillance system would identify women at risk of having alcohol-affected infants so that appropriate treatment and counseling could be provided, possibly reducing the severity of adverse effects of alcohol on their fetuses

Wheat, barley, flaxseed, and oilseed sunflower acreage respond to different economic variables. Wheat and barley acreage must be divided among program-complying, program-planted, and nonprogram-planted acreage because these categories respond to different variables and respond to own expected-revenue and price-risk variables in opposite ways. Flaxseed, sunflower, and nonprogram-planted acreage of wheat and barley have highly significant, positive responses to their own expected revenue and negative responses to their own-price risk. Flaxseed and sunflower acreage have been more responsive to their lagged values than to expected revenues for wheat.

Biotic response to the buildup of greenhouse gases in Earth's atmosphere is considerably more complex than an adjustment to changing temperature and precipitation. The fertilization effect CO2has on some plants, the impact UVB radiation has on health and productivity of organisms, and the resulting changes in competitive balance and trophic structure must also be considered. The intent of this paper is to review direct and indirect effects of anthropogenic greenhouse gases on wildlife, and to explore possible effects on populations of birds and their habitats in the northern Great Plains. Many of the potential effects of increasing greenhouse gases, such as declining plant nutritional value, changes in timing of insect emergence, and fewer and saltier wetlands, foreshadow a decline in avian populations on the Great Plains. However, other possible effects such as increased drought resistance and water use efficiency of vegetation, longer growing seasons, and greater overall plant biomass promise at least some mitigation. Effects of multiple simultaneous perturbations such as can be expected under doubled CO2scenarios will require substantial basic research to clarify.

The purple coneflower referred to as Echinacea (Brauneria) pallida in the numerous ecological publications of John E. Weaver on the Central North American Grasslands over a 50-year period (1919-1968) was actually E angustifolia DC. Interestingly, Weaver used the specific epithet pallida throughout his career, even though the floristic manuals that covered all or part of his study area and most other Great Plains plant ecologists of the period used angustifolia.

This article examines the interactions between land quality, crop choice, and technological change using a framework that integrates cross-sectional and intertemporal aspects of diffusion. The empirical results indicate that (a) the acreages allocated to different crops vary significantly over land quality, (b) crops tend to be grown on specific ranges of land quality, (c) the introduction of center pivot technology induced significant changes in cropping patterns, (d) land quality-augmenting technologies tend to be utilized primarily on lower qualities of land, and (e) irrigation development has been quite sensitive to tax policies.