Browsing by Subject "North Hennepin Community College"

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    Assessment of Eurasian Phragmites australis Haplotype M Cryptic Invasion in the Minnesota and Mississippi River Valleys of Minnesota
    (2009-04-08) Weaver, Robbyn
    Phragmites australis (Cav.) Trin. ex Steud. is an aquatic grass species found in wetlands throughout North America. The cryptic invasion of these environments by the introduced Eurasian Phragmites australis haplotype M over the past two centuries has recently been reported. In recent decades, the aggressive expansion of clonal Phragmites australis populations in many Minnesota wetlands has been noted. Wetland scientists have often speculated that these invasive populations may represent non-native strains that are morphologically indistinguishable from the native type, now recognized as Phragmites australis subsp. americanus. In this study, we use RFLP analysis to investigate the extent of Eurasian Phragmites australis haplotype M establishment in the Minnesota and Mississippi River Valley corridors of Minnesota, and within the drainage way of Interstate Highway 94 in central Minnesota.
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    Geographic Isolation, Environmental Disturbance, and Local Adaptation in a Clonal Aquatic Plant, Lemna minor
    (2009-04-08) Malikowski, Nicole; Diederichs, Jessica
    In a multiyear study we conducted laboratory reciprocal transplant experiments with Lesser Duckweed Lemna minor from two manmade ponds. Runoff Pond (RP) is a catch basin for parking lot runoff and has no outlet. Shingle Creek Pond (SCP) is connected to Shingle Creek. Lemna minor forms clones as fronds grow and separate from the mother plant. We hypothesized that a reduced influx of genotypes in RP relative to SCP would lead to local adaptation of Lemna minor to RP conditions, and greater genetic diversity in SCP would result in greater phenotypic plasticity. In 2004 both hypotheses were supported. Lemna minor from RP performed better (rate of per capita growth and senescence) in RP water. Lemna minor from SCP had similar characteristics in both sources of water. Runoff Pond was significantly disturbed by dredging following the experiment. In 2005, SCP plants outperformed RP plants in both sources of water. Prior to the experiment in 2006, SCP experienced environmental disruption when construction occurred along Shingle Creek upstream of SCP. Despite environmental disturbance, SCP Lemna minor again outperformed RP Lemna minor, faring better in RP water than SCP water. Interestingly, Lemna minor from a nearby lake outperformed SCP and RP plants in both sources of water. In 2008 SCP and RP Lemna minor exhibited a pattern similar to 2004. Overall, SCP Lemna minor exhibited greater ability to respond to environmental change than RP Lemna minor, and significant local adaptation was not observed.
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    Response of Fathead Minnows (Pimephales promelas) to a Chemical Alarm Signal
    (2009-04-08) Murphy, Charles
    The fathead minnow, Pimephales promelas, and common shiner, Luxilus cornutus, are cyprinid fishes native to Minnesota. Both species produce a chemical alarm signal, hypoxanthine-3-N-oxide (H3NO), in response to injury to the skin. H3NO may therefore indicate that a predatory fish is nearby. The objective of this study was to examine the behavior of fathead minnows in the presence and absence of chemical alarm signal isolated from conspecifics. Behaviors were studied under several conditions: solitary fatheads, single species schools of 12 fatheads, or mixed species schools of nine fatheads and three common shiners. Two synchronized digital camcorders were used to monitor the vertical and horizontal movement of individuals or schools, proximity of individuals, and size of shoals. In the absence of alarm chemical signal fatheads and common shiners exhibited different behaviors. Both solitary fatheads and shoals exhibited greater vertical movement than common shiners, which aggregated near the bottom of the tank. Solitary fatheads displayed reduced movement both vertically and horizontally in response to H3NO. Although vertical movement of fathead shoals was reduced after the addition of chemical alarm signal, horizontal motion continued in most trials. Fatheads in shoals adopted a testing or sampling behavior. Individuals made looping motions, moving a few centimeters vertically and quickly returning to the bottom of the tank. In summary, the behavioral response of fathead minnows was different when solitary or in shoals.
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    Role of Host Plant Variation, Avian Predators, and a Parasitoid in Populations of a Gall Fly, Eurosta solidaginis
    (2009-04-08) Muncy, Sarah; Tague, Erin Elizabeth; Jedlicki, Ryan
    Tall goldenrod, Solidago altissima, is the host plant of a stem-galling fly Eurosta solidaginis. The fly larvae inhabit spherical galls that form on plants. Black-capped chickadees, downy woodpeckers, and a parasitoid Eurytoma gigantea are important causes of mortality in E. solidaginis. Galls were collected from abandoned fields near Mendota Heights and Brooklyn Park, MN. Larval mass, gall size, and rate of parasitism differed between populations. To elucidate plant characteristics that contribute to higher rates of gall fly oviposition, individual goldenrod clones were identified in the Brooklyn Park population. Among clones plant density, plant height, and clone area were not correlated with percentage galled plants. Clones of similar area, plant density, and plant height with exceptionally high proportions of galled plants were examined further. Basal stem diameter, gall height, gall diameter, larval mass, and rate of parasitism differed significantly among the clones equally susceptible to gall fly oviposition. Previous research has found that larger galls are more likely to suffer avian predation and smaller galls experience higher rates of parasitism. From indirect evidence it has been concluded that birds avoid galls containing a parasitoid. Alternatively, birds may simply preferentially attack larger galls. To remove the confounding factor of gall size, we are conducting avian feeding trials with gall fly and parasitoid larvae removed from galls.
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    Sexual Dimorphism and Mate Choice in the Ambush Bug (Phymata americana)
    (2009-04-08) Vang, Feng
    The ambush bug is a heteropteran predatory insect with cryptic coloration. Unusual among insects, males remain coupled with a female for several to many hours after mating, resulting in a large investment in each mating opportunity for males. Unpaired males, unpaired females, and coupled males and females were collected on goldenrod in late summer in east central Minnesota over two seasons. Each insect was weighed, and the pronotum width, abdomen width, abdomen length, and rear leg length were measured with a digital stereoscopic microscope. Unpaired males and coupled males were not significantly different for any of the parameters. Abdomen width was significantly greater in coupled females than single females the first year, although mass, pronotum width, and abdomen length of paired and unpaired females were not different. In the second year, paired females were not larger than single females with pronotum width significantly greater in single females. Females were larger than males for all parameters. Size-assortative mating was not observed in either year. Scramble competition for mates occurs in male ambush bugs. Since darker (melanistic) males may reach a temperture necessary for flight more quickly under cool but sunny conditions, we assessed the degree of thoracic pigmentation in coupled and single males with image capture software. The coloration of paired and unpaired males did not differ with respect to size of pigmented area or hue.