Browsing by Author "Kempnich, Michael"
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Item A comparative study of the invertebrate community and its longitudinal diversity(2012-03-05) Benson, Madeline; Kempnich, Michael; Meyers, Paul; Parikh, SanatInputs into riverine ecosystems are highly variable with respect to longitudinal location within the system. These inputs help to shape the animal community within the river or stream, and have been hypothesized to be correlated with invertebrate diversity and community composition (Rosi-Marshall and Wallace 2002). In order to test this relationship, we sampled the benthic invertebrate community from three reaches of the Mississippi River near and within Itasca State Park, Minnesota. These samples were used to quantify invertebrate diversity and functional feeding group types (FFG). Significant differences were found between the community composition of each site with the Headwaters site showing the highest levels of invertebrates which feed upon allochthonous material, and the Downstream site showing the highest amount of invertebrates which feed upon autochthonous material (p=1.84*10-12). The Headwaters site also demonstrated the highest levels of community diversity, due to the myriad of niches created by varying river conditions. The results of this study suggest that the invertebrate community composition is dependent on the primary inputs into the system, whether from allochthonous or autochthonous sources.Item Transmission of Barley/Cereal yellow dwarf viruses by aphid vectors(2013) Kempnich, Michael;Barley and Cereal yellow dwarf viruses (B/CYDVs) negatively impact the fitness of host plants and have a destabilizing effect on established ecosystems. Plant and B/CYDV pathogen interaction dynamics can be significantly altered by increasing worldwide nitrogen and phosphorous input. Viruses rely on interactions between host plants, insect vectors and environmental factors in order to spread. Relationships between virus transmission and both the level of and ratio between host nitrogen and phosphorous resources are difficult to establish, especially in natural systems, and remain poorly understood. In order to assess the relationships between host resources and vectored-disease spread in controlled conditions, we developed a method of inoculation of healthy plants using aphid vectors that previously fed on virus infected fresh plant leaves. While we originally tested an inoculation method in which aphids fed on a homogeneous virus inoculum obtained by grinding and clarifying infected plant tissues, this resulted in low aphid survival and low virus transmission rate in our lab conditions. We will use the inoculation technique developed in this study to test the effects of host nutrient levels and ratios on virus transmission rate. The results obtained under laboratory conditions will allow us to make predictions on the broad connections between human nutrient loading and rates of viral infection.