Scholarship & Research
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/1
Browse
2 results
Search Results
Item Coexistence between a native (Valvata humeralis) and a non-native (Potamopyrgus antipodarum) gastropod in the Middle Snake River, Idaho : implications for invasive species impact(Montana State University - Bozeman, College of Letters & Science, 2012) Gates, Kiza Kristine; Chairperson, Graduate Committee: Billie L. Kerans; Billie. L. Kerans was a co-author of the article, 'Spatial, temporal, and diet partitioning combine with environmental stochasticity to enable coexistence between an invasive and a native gastropod' in the journal 'Biological invasions' which is contained within this thesis.; Billie. L. Kerans was a co-author of the article, 'Biotic interaction gradients between native and invasive species' in the journal 'Ecology' which is contained within this thesis.; Billie. L. Kerans was a co-author of the article, 'Competitive and facilitative mechanisms of a biotic interaction gradient' in the journal 'Oecologia' which is contained within this thesis.The dominant competitive abilities of many invasive species are frequently assumed to preclude biologically similar native species over time, but there has been little research exploring how interactions between invasive and native species may change with changes in biotic and abiotic conditions. Introduction of the invasive New Zealand mud snail Potamopyrgus antipodarum in the Snake River in the late 1980's raised many concerns for the native gastropods of this region; however, the native gastropod Valvata humeralis has maintained large populations and continued to coexist with P. antipodarum. I investigated the coexistence of P. antipodarum and V. humeralis in the Vista reach of the Middle Snake River. Diet, spatial, and temporal partitioning of V. humeralis were explored in populations that were invaded by P. antipodarum and uninvaded. A field growth experiment was used to measure the net intra- and interspecific effects of V. humeralis and P. antipodarum at varying densities and species proportions. Results of the field growth experiment were compared with field survey data. A laboratory growth experiment and a stoichiometric experiment were used to identify the interaction mechanisms between species. Valvata humeralis juveniles appeared to shift diet in the presence P. antipodarum. There was evidence of spatial partitioning from P. antipodarum by V. humeralis at the among population scale but not the within population or patch scales. The field growth experiment indicated that interspecific net effects of P. antipodarum on V. humeralis changed in direction with increasing P. antipodarum density. Field surveys showed a similar pattern. The laboratory growth experiment indicated that direct interference competition was the negative mechanism of the species interaction and confirmed field experimental results. Stoichiometric analyses suggested that P. antipodarum juveniles require more phosphorus than V. humeralis juveniles, but that stoichiometric facilitation was not likely an interaction mechanism. Facilitated growth of V. humeralis in the presence of P. antipodarum may have been caused by increased access to food and/or P. antipodarum digestive food conditioning. Results suggest that the impact of an invasive species on the native community may be a complex interplay between invader density, native species behavior, invader nutrient use, and environmental conditions.Item Myxospore detection in soil and angler movement in Southwestern Montana : implications for whirling disease transport(Montana State University - Bozeman, College of Letters & Science, 2007) Gates, Kiza Kristine; Chairperson, Graduate Committee: Christopher S. GuyMovement of anglers among rivers in southwestern Montana presents a potential pathway for the spread of whirling disease and other aquatic nuisance species (ANS) on soil laden angling equipment. The objectives of this study were to 1) determine the effectiveness of a density extraction to isolate myxospores from soil and the effectiveness of polymerase chain reaction (PCR) at detecting M. cerebralis myxospores in soil; 2) quantify movement of resident and non-resident anglers in southwestern Montana and soil quantity carried on angling equipment; and 3) determine myxospore adherence to wading equipment materials. Myxospores were extracted from soil using a soil particle density separation technique. A single blind study was used for PCR experiments with varying quantities of myxospores and soil. Angler movement was assessed with a survey at fishing access sites on six southwestern Montana rivers. Soil samples were taken during the survey from boots and waders with a pressure sprayer to assess quantity of soil carried on angling equipment. Myxospore adherence to wading materials (lightweight, neoprene, rubber, and felt) was tested by exposing myxospores to material and rinsing with a pressure sprayer.