Browsing by Subject "Dispersal"

Now showing 1 - 6 of 6
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    Ecology and ecosystem impacts of common buckthorn (Rhamnus cathartica): a review
    (2007) Knight, Kathleen S; Kurylo, Jessica S; Endress, Anton G; Stewart, J. Ryan; Reich, Peter B
    In this review, we synthesize the current knowledge of the ecology and impacts of Rhamnus cathartica L., a shrub from Europe and Asia that is a successful invader in North America. Physiological studies have uncovered traits including shade tolerance, rapid growth, high photosynthetic rates, a wide tolerance of moisture and drought, and an unusual phenology that may give R. cathartica an advantage in the environments it invades. Its high fecundity, bird-dispersed fruit, high germination rates, seedling success in disturbed conditions, and secondary metabolite production may also contribute to its ability to rapidly increase in abundance and impact ecosystems. R. cathartica impacts ecosystems through changes in soil N, elimination of the leaf litter layer, possible facilitation of earthworm invasions, unsubstantiated effects on native plants through allelopathy or competition, and effects on animals that may or may not be able to use it for food or habitat.
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    The effect of relative humidity on acaricide efficacy against and dispersal characteristics of the mold mite Tyrophagus putrescentiae
    (2013-06) Freitag, Jessica Anne
    This study determined the effects of relative humidity on mold mites (Tyrophagus putrescentiae) with regard to acaricide efficacy and dispersal characteristics. The mold mite is a stored product pest that can infest retail habitats. Mold mite survival depends on relative humidity (RH), and RH levels may affect efficacy of residual acaricides. In a simulated retail habitat, increasing humidity levels generally decreased acaricide efficacy. Results indicated that some acaricides may create a barrier against this mite. A second study analyzed mold mite dispersal characteristics. Mite infestations may remain undetected until mites leave the food package. Arenas provided an enclosed food reservoir incubated at high RH, and an open space incubated at one of three RH levels. Mite activity was monitored daily until dispersal characteristics were determined. Explosive dispersal, a mass-migration within 24 h, was observed. Therefore, direct sampling of habitat may be necessary to detect infestations before explosive dispersal has occurred.
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    Estimating seed dispersal distances with incomplete genetic data:new methods, power analyses and a case study of the tropical tree Tabebuia rosea
    (2012-12) Vargas Timchenko, Marta Isabel
    Genetic data linking seeds directly to parents through maternal seed tissue are often hailed as the best way to obtain information on seed dispersal distances. However, DNA quality in maternally derived seed tissue is often low, leading to high rates of genotyping errors, and usually much discarding of data. This study tested and applied methods for gleaning information on seed dispersal distances from incomplete and error-prone genetic data, using the tropical tree Tabebuia rosea as a case study. Genotyping error rates were calculated and then incorporated these rates into a model to estimate seed dispersal distances using all available data. Simulations were used to evaluate the effects of both genotyping error rates and the number of seeds genotyped upon dispersal estimates. Results demonstrate the importance of calculating error rates, and the value of including incomplete genetic data in analyses in order to increase power and obtain better parameter estimates.
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    Flight capacity of emerald ash borer Agrilus planipennis (Coleoptera: Buprestidae) and its parasitoid Tetrastichus planipennisi (Hymenoptera: Eulophidae), in response to several experimental treatments
    (2014-12) Fahrner, Samuel Joseph
    Emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is an invasive beetle native to eastern Asia. Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) is one of three hymenopteran parasitoids currently being introduced into North America as part of a classical biological control program against emerald ash borer. Here, custom-built, computer-monitored flight mills were used to measure the effects of age, feeding status, mating status, sex, and size on flight metrics of T. planipennisi. The flight mill was then used to measure flight metrics of emerald ash borer and T. planipennisi across a range of temperatures and relative humidity. The relationship between flight energetics, specifically flight distance, with temperature was then integrated with landscape temperatures at ten locations throughout the continental United States to compare relative dispersal capacity for emerald ash borer and T. planipennisi. The goal of this research was to elucidate factors that mediate the flight capacity of both insects and, for T. planipennisi, to infer the pre- and post-release conditions that may optimize flight capacity.
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    Improving Stink Bug Management in The Midwest: Understanding Dispersal Capacity and Developing Sampling Plans
    (2020-12) Carlesso Aita, Rafael
    Stink bugs are an emerging threat for horticultural and field crops in the North Central Region of the United States. This threat can be attributed to the increase in abundance of Pentatomidae species native to North America over the years, and to the spread of invasive stink bugs throughout this region, in particular, the brown marmorated stink bug, (Halyomorpha halys). There is a lack of decision-making frameworks that provide more efficient sampling for stink bugs in soybean for this region, and there is a need to understand the dispersal capacities of laboratory-reared H. halys. Therefore, my research developed more efficient sampling for herbivorous stink bugs in this region and assessed the dispersal capacity of H. halys under laboratory conditions. First, I developed a binomial or decision-making sequential sampling plan for herbivorous stink bugs by using data from 11 states of the North Central Region. Results showed that using a tally threshold of 3 stink bugs per 25 sweeps for action thresholds corresponding to the current action thresholds of 5 (soybean grown for seeds) and 10 (soybean grown for grain) stink bugs per 25 sweeps, provided the best sampling outcomes in terms of efficiency and accuracy. In addition, we showed that 18 and 12 sample units, for action thresholds of 5 and 10 stink bugs per 25 sweeps respectively, would be needed for reliable decision-making sampling. The development of a binomial sequential sampling plan for stink bugs in soybean should provide increased efficiency with regards to the number of sample units required to reach a management decision. Secondly, I assessed the effects of starvation, age, mating status, and pre-flight weight on flight parameters of laboratory-reared H. halys using flight mills. Although some statistical differences were observed across the experiments, these differences represented minimum ecological significance. These results could reflect the resilience of H. halys as a successive invasive species to North America and could help predict the dispersal potential of this species in Minnesota. The results of my thesis will provide valuable information to fine-tune integrated pest management strategies for stink bugs in the North Central Region, enabling more efficient scouting for growers and consultants as well as better forecasting the dispersal capacity of an important invasive species to the region.
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    Production and Wind Dispersal of Canada Thistle (Cirsium arvense L.) Achenes
    (Minnesota Department of Transportation, 2008-09) Becker, R.L.; Haar, M.J.; Kinkaid, B.D.; Klossner, L.D.; Forcella, F.
    Quantity, quality and dispersal distance of wind-blown achenes and pappi were determined during the peak time of dispersal over twelve site-years in Minnesota during 2006 and 2007. Approximately twice as many pappi than achenes were trapped. Wind blown pappi tend to travel near the ground. Most achenes fell near the parent plants and their population density declined exponentially with increasing distance. Over 80% of pappi collected did not have an achene attached. Concomitantly, seed production in Canada thistle was monitored for 8 site-years in Minnesota. Averaged across years and locations, female Canada thistle shoots that flowered produced an average of 38% empty, 17% shrunken, and 44% normal achenes. Male shoots produce about half the number of seedheads compared to female shoots. A low level of hermaphroditic expression was observed in male shoots. Though seed production by female Canada thistle is extremely variable, when sufficient pollen is available, Canada thistle clearly has the potential to generate significant contributions to seedbanks to maintain invasive stands. However, dispersal by wind is for the most part, local. Long distance dispersal of significant numbers of healthy achenes would be a rare event.