Browsing by Author "Kanno, Yoichiro, advisor"
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Item Open Access An experimental test of intra- and inter-specific competition between invasive western mosquitofish (Gambusia affinis) and native plains topminnow (Fundulus Sciadicus)(Colorado State University. Libraries, 2022) Lewis, Samuel, author; Kanno, Yoichiro, advisor; Salerno, Jonathan D., committee member; Sanderson, John S., committee member; Preston, Daniel L., committee member1. Invasive species are a major threat to freshwater conservation. Species coexistence in invaded habitats depends on the relative strength of intra- versus inter-specific competition, where inter-specific competition from invasive species to native species is often stronger than intra-specific competition, jeopardizing their coexistence.2. In this study, I conducted a laboratory experiment to test for the relative competitive strength between native plains topminnow (Fundulus Sciadicus) and invasive western mosquitofish (Gambusia affinis) at 16, 22, and 28 °C. Data were analyzed using the isodar theory, which assumes that animals are ideally distributed to maximize their fitness and thus their distributions measure the quality and quantity of habitat patches. This was supplemented by behavioral observations of intra- and inter-specific competition. 3. Contrary to my predictions, I did not find evidence that competition was asymmetrical from the invasive mosquitofish to the native plains topminnow. Instead, more individuals occupied their shared preferred habitat (a slow-moving pool) in sympatry compared to allopatry, and the isodar analysis demonstrated that intra-specific competition was significantly stronger than inter-specific competition at all temperature levels. This analysis of habitat selection was corroborated by behavioral observations that aggression was most frequent between plains topminnow in sympatry. 4. This study indicates that aggression might not always be the key mechanism of invasion, even for one of the most successful aquatic invasive species widely known for their aggressive behavior. In mosquitofish, other ecological traits such as fast reproductive cycle and tolerance to a wide range of environmental conditions might be responsible for their invasion success globally. This suggests that mosquitofish may not be a driver in native species declines, but rather an opportunistic invader in degrading ecosystems.Item Open Access Genetic analysis reveals bidirectional fish movement across the Continental Divide via an interbasin water transfer(Colorado State University. Libraries, 2021) Harris, Audrey Catherine, author; Kanno, Yoichiro, advisor; Winkelman, Dana, advisor; Oyler-McCance, Sara, committee member; Morrison, Ryan, committee memberInterbasin water transfers are becoming an increasingly common tool to satisfy municipal and agricultural water demand, but their impacts on the movement and gene flow of aquatic organisms are poorly understood. The Grand Ditch is an interbasin water transfer that diverts water from tributaries of the upper Colorado River on the west side of the Continental Divide to the upper Cache la Poudre River on the east side of the Continental Divide. I used single nucleotide polymorphisms to characterize population genetic structure in cutthroat trout (Oncorhynchus clarkii) and determine if fish utilize the Grand Ditch as a movement corridor. Samples were collected from two sites on the west side and three sites on the east side of the Continental Divide. I identified two genetic clusters, but they did not align with the west and east sides of the Continental Divide. Spatial distributions of admixed individuals indicated that the Grand Ditch facilitated bidirectional fish movement across the Continental Divide, a major biogeographic barrier. Many others have demonstrated the ecological impacts of interbasin water transfers, but this study is one of the first to utilize genetics to understand how interbasin water transfers affect connectivity between previously isolated watersheds. I also discuss implications on native trout management and the need for balancing water demand and biodiversity conservation.Item Open Access Intraspecific variation in reproductive ecology and success of a keystone stream fish, bluehead chub(Colorado State University. Libraries, 2019) Kim, Seoghyun, author; Kanno, Yoichiro, advisor; Angeloni, Lisa, committee member; Bestgen, Kevin R., committee member; Winkelman, Dana L., committee memberTo view the abstract, please see the full text of the document.Item Open Access Seasonal trophic niche dynamics of mottled sculpin and juvenile brown trout in a regulated Rocky Mountain river(Colorado State University. Libraries, 2023) Platis, Nitsa, author; Kanno, Yoichiro, advisor; Johnson, Brett, advisor; Kampf, Stephanie, committee memberIn temperate ecosystems, resource availability fluctuates seasonally due to changes in environmental conditions and productivity throughout the year. Intra- and inter-specific trophic niche overlap under resource limitation is a measure of competitive interactions and influences species coexistence and community dynamics, but patterns of this overlap are highly variable among regions and communities. In this study, we analyzed stomach content samples and stable isotope signatures to evaluate seasonal trophic niche dynamics of mottled sculpin Cottus bairdii (80-130 mm total length) and juvenile brown trout Salmo trutta (80-200 mm) in the Blue River, Colorado, USA, where aquatic production varies seasonally and has been reduced due to upstream dams. Prey biomass (i.e., benthic macroinvertebrates) peaked in spring and declined through summer and autumn. Stomach content and stable isotope analysis results revealed diet composition of mottled sculpin and brown trout shifted seasonally in response to changes in resource availability. In autumn, both species exhibited the highest frequency of empty stomachs and expanded population trophic niches due to increased inter-individual diet variation despite decreased individual trophic niche breadth. Interspecific trophic niche overlap was relatively high across all seasons, but the lowest degree of overlap occurred in autumn of both years. Isotopic analysis revealed similar trends of wider isotopic niches and reduced overlap in autumn compared to spring. Taken together, our data indicate that seasonal variation impacts individual and population-level trophic niche dynamics, as well as interspecific niche overlap between mottled sculpin and juvenile brown trout. These two species occur sympatrically in many coldwater streams throughout North America, and our findings indicate trophic segregation under resource limitation may serve as a mechanism that facilitates their coexistence.Item Open Access Spatial asynchrony and cross-scale climate interactions in populations of a coldwater stream fish(Colorado State University. Libraries, 2023) Valentine, George P., author; Kanno, Yoichiro, advisor; Hooten, Mevin B., advisor; Morrison, Ryan R., committee memberClimate change affects animal and plant populations over broad geographic ranges due to spatially autocorrelated abiotic conditions known as the "Moran Effect". However, populations do not always respond to broad-scale environmental changes synchronously across a landscape. We used a retrospective analysis of time-series count data (5-28 annual samples per site) at 170 stream segments dispersed over nearly 1,000 km to characterize the population structure and scale of spatial population synchrony in a coldwater stream fish (brook trout, Salvelinus fontinalis), which is sensitive to temperature and flow alterations, across its southern native range. Spatial synchrony differed by life stage and geographic region: it was stronger in the juvenile life stage than the adult life stage and in the northern sub-region than the southern sub-region. Spatial synchrony of trout populations extended to 100-150 km but was much weaker than that of climate variables such as temperature, stream flow, and precipitation. Early life stage abundance changed over time due to annual variation in summer temperature and winter and spring stream flow conditions. Climate effects on abundance differed between sub-regions and among local populations, indicating multiple cross-scale interactions where climate interacted with local habitat to generate only a modest pattern of population synchrony over space. We conclude that heterogeneous responses to climate variation lead to only a modest level of spatial synchrony among local trout populations, which leads to varying susceptibility to climate change. This response heterogeneity indicates that some local segments characterized by population asynchrony and resistance to climate variation could represent unique populations of this iconic native coldwater fish that warrant attention in their conservation planning in a changing climate. Identifying such priority populations and incorporating them into landscape-level conservation planning is imperative to their conservation. Our approach is applicable to other widespread aquatic species sensitive to climate change.Item Open Access Using population ecology to advance stream community assembly(Colorado State University. Libraries, 2019) Pregler, Kasey C., author; Kanno, Yoichiro, advisor; Bailey, Larissa, committee member; Koons, David, committee member; Poff, LeRoy, committee memberTo view the abstract, please see the full text of the document.