Browsing by Author "Fausch, Kurt D., committee member"
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- ItemOpen AccessAnalysis of the groundwater/surface water interactions in the Arikaree River Basin of eastern Colorado(Colorado State University. Libraries, 2010) Banning, Ryan Oliver B., author; Durnford, Deanna S., advisor; Fausch, Kurt D., committee member; Oad, Ramchand Naraindas, committee memberThe decline of stream baseflows along Colorado's high plains streams is degrading aquatic and riparian habitat. Historic strongholds for many plains fish species no longer exist. In Eastern Colorado, center-pivot irrigation is common and clearly contributing to the decline of baseflow in some stream basins. The purpose of this study is to develop a defensible conceptualization of the stream-aquifer system in the Arikaree River basin of eastern Colorado, in part using the results of a preliminary groundwater model developed to predict groundwater levels, analyze stream depletion and examine the effects of irrigation well retirements on groundwater and stream levels. The groundwater conceptualization and model represent the Arikaree River groundwater system of Southern Yuma County where there is significant hydrogeological connection between the Ogallala and alluvial aquifers. Analytical and numerical models presented in this thesis calculate seasonal stream-depletion of the Arikaree River due to nearby wells and similar potential effects of riparian vegetation. Finally, the author examines the river basin water budget in Southern Yuma County to determine possible pumping effects on the amount of available water for streamflow and habitat.
- ItemOpen AccessInfluence of abiotic and biotic factors on the response of benthic macroinvertebrates to metals(Colorado State University. Libraries, 1995) Kiffney, Peter Michael, author; Clements, Will, advisor; Fausch, Kurt D., committee member; Kondratieff, Boris C., committee member; Chapman, Phillip, committee memberStream ecologists are well aware that chemical, biological, and physical characteristics of lotic systems vary spatially and temporally. With this in mind, I designed a series of experiments and field studies to examine the role of spatial variation in stream benthic macroinvertebrate communities in response to metals. Specifically, I tested the hypothesis that stream invertebrate communities from pristine streams of different size and altitude varied in their response to metals. To evaluate how metals affected biotic interactions, I manipulated invertebrate density, predation intensity, and metals in stream microcosms. Using stream invertebrate communities, I also designed an experiment and field survey to identify reliable bioindicators of metal contamination in western streams. Results from microcosm experiments and field studies showed that benthic invertebrate populations from high-altitude streams were more sensitive to the effects of metals than invertebrate populations from low-altitude streams. For example, Baetis sp. and Rhithrogena hageni from Little Beaver Creek (LBC), Colorado, (high-altitude stream) were significantly more sensitive to zinc than the same species from the South Fork of the Poudre River (SFP) (low-altitude stream) in stream microcosms. Results from field surveys showed that densities of most groups of aquatic insects (e.g., Ephemeroptera, Plecoptera, Trichoptera) were lower at high-altitude metal contaminated streams than those same groups at low-altitude streams. Other factors, such as variation in water temperature or nutrient concentrations between high- and low-altitude streams, could be lll responsible for these differences. However, because invertebrate responses were similar under controlled and field conditions, I hypothesize that differences in abundances between reference and contaminated locations was a result of metals. To determine if body size contributed to the variation in sensitivity of insects to metals, size measurements were made on species collected from LBC (high-altitude) and SFP (low-altitude). Measurements were also made on species from control and metal-treated stream microcosm. Most species were smaller at LBC (high-altitude stream) than the same species from SFP (low-altitude stream). For example, the mayfly Baetis tricaudatus and the caddisfly Arctopsyche grandis were significantly larger at SFP than LBC. In addition, insect body size was larger in metal-dosed microcosms than in controls. Brachycentrus sp., B. tricaudatus, R. hageni, Eohemerella infrequens, and P. badia were significantly larger in metal-treated microcosms than in controls. Logistic regression indicated survival in metal-dosed microcosms was less for small individuals than for larger individuals of the same species. These results suggest that some insect species from high-altitude streams were smaller than those from low-altitude streams, and that survival was greater for larger lifestages. Thus the variation in response of macroinvertebrates between different altitude streams observed in earlier studies may be due to differences in body size. The effects of low levels of metals (half the chronic levels of Cd, Cu, and Zn) on some species varied in relation to invertebrate density (low and high density) and invertebrate predation (no predators added and predators added). The abundance of Hydropsyche sp. was significantly lower in metal-dosed, high density treatments than in control, high density treatments. Moreover, the effects of an invertebrate predator (Hesperoperla pacifica) on Hydropsyche sp. was significantly greater in metal-dosed microcosms than in controls. These results suggest that metals interact with biotic factors to influence stream invertebrate community structure, and that effects occurred at metal concentrations lower than chronic criteria value. Toxicity experiments in stream microcosms showed that the abundance and species richness of aquatic insects were significantly reduced at 1x, 5x and 10x the United States Environmental Protection Agency chronic levels of cadmium, copper, and zinc (1x=1.1, 5.0, and 110 μg/L Cd, Cu, and Zn, respectively). Mayflies were the most sensitive group, as the abundance of Baetis sp. and Rithrogena hageni were significantly reduced in the Ix treatment. The response of Drunella grandis was size dependent, as small lifestages were significantly more sensitive than large lifestages. Stoneflies were also affected, but their response was more variable with abundances of some species (Pteronarcella badia) being reduced in the Ix treatment, whereas other species were unaffected (Sweltsa sp.). Heptageniid mayflies were consistently less abundant downstream of sources of metal contamination in the Arkansas and Eagle rivers, whereas the response of other measures were more variable. For instance, species richness and total density were greater at a metal-contaminated site on the Arkansas River compared with an upstream reference site. Therefore, results from this experiment and field survey suggest that changes in abundance of heptageniid mayflies may provide a reliable indicator of metal-contamination in western streams.
- ItemOpen AccessIntra- and interspecific variation along environmental gradients: adaptation, plasticity, and range limits(Colorado State University. Libraries, 2012) Torres Dowdall, Julián R., author; Ghalambor, Cameron K., advisor; Angert, Amy L., committee member; Fausch, Kurt D., committee member; Poff, N. LeRoy, committee member; Thomas, Stephen, committee memberUnderstanding the processes underlying patterns of intraspecific variation, and how these processes in turn shape the distributional limits of species is a fundamental goal of evolutionary ecology. The study of species distributed along environmental gradients provides a framework for testing how changing conditions lead to local adaptation, phenotypic plasticity, and ultimately shape distributional limits. Yet, environmental gradients are complex, being composed of a diversity of abiotic and biotic factors that act on individual species and shape the interactions between them. Thus, empirical studies aimed to understand patterns of intraspecific divergence and interspecific diversity need to evaluate the effects of both abiotic and biotic factors varying along gradients. Evolutionary ecologists have become increasingly interested in trying to understand the costs and limits to trait variation along environmental gradients and what factors prevent species from evolving larger geographic ranges. Theory predicts that species distributed along environmental gradients should track conditions through local adaptation or adaptive phenotypic plasticity, and that a disruptive factor along the gradient (e.g. increase in the steepness of the gradient, the presence of a competitor, etc.) could result in the formation of distribution limits as conditions become unsuitable for populations persistence. Empirical studies analyzing large-scale patterns of phenotypic variation have provided support for the formation of clines in response to environmental gradients. However, less evidence has accumulated for the formation of such patterns at local scales and clear disruptive factors leading to distributional limits remain elusive. My dissertation takes an evolutionary ecological perspective to understand how environmental gradients shape patterns of variation within and between species. Here, I attempt to understand how abiotic and biotic factors interact to drive patterns of phenotypic variation. To approach this question, I used as a study system two closely related, ecologically similar, and parapatric species of poeciliids distributed along rivers on the island of Trinidad, West Indies. In the first part of this dissertation, I focus on the patterns of intraspecific variation in the Trinidadian guppy (Poecilia reticulata) along a predation risk gradient. I used this species to explore the spatial scale at which local adaptation occurs (Chapter 1), and to investigate the role of adaptive phenotypic plasticity in allowing species to track local optima (Chapter 2). I found that local adaptation in Trinidadian guppies occurs at a smaller spatial scale than previously shown. My results also suggest that adaptive plasticity plays an important role in allowing Trinidadian guppies to track local optima along a gradient of predation risk. Furthermore, I found divergence in patterns of plasticity between Trinidadian guppy populations adapted to low- or to high-levels of predation pressure. My results suggest that this difference in adaptive phenotypic plasticity evolved as a by-product of adaptation to local environmental conditions. In the second part of my dissertation I change my focus from patterns of intraspecific variation to patterns of interspecific variation along environmental gradients. I examine how the Trinidadian guppy and its sister species, the swamp guppy (P. picta), are distributed along a complex environmental gradient in lowland rivers of Trinidad (Chapter 3), and performed a series of experiments aimed to determine what factors drive their distributions (Chapter 4). As Trinidadian rivers approach the ocean, several factors change in comparison to upstream localities, including changes in productivity, physicochemical conditions, and community composition. I found that the Trinidadian guppy and the swamp guppy show an overlapping parapatric distribution along the interface between brackish-freshwater in the lowland rivers of Trinidad. The swamp guppy is usually found in downstream sections of the rivers, both in fresh- and brackish water. On the other hand, the Trinidadian guppy is only found in freshwater, dropping off abruptly at the brackish-freshwater interface. Field and laboratory experiments suggest that brackish water environments are physiologically stressful for the two study species, as survival and growth rate in this environment were lower compared to that observed in freshwater. Also, these experiments indicate that the Trinidadian guppy is competitively dominant over the swamp guppy across all salinity conditions. Thus, I showed that asymmetric competition limits the competitively subordinate swamp guppy to the harshest end of the salinity gradient, and that stressful salinity conditions limits the dominant Trinidadian guppy to the less stressful freshwater end of the gradient.
- ItemOpen AccessPhylogeography and character congruence within the Hoplias malabaricus Bloch, 1794 (Erythrinidae, Characiformes, Ostariophysi) species complex(Colorado State University. Libraries, 1996) Dergam, Jorge A., author; Behnke, Robert, advisor; Black, William C., IV, committee member; Kondratieff, Boris C., committee member; Fausch, Kurt D., committee member; Stack, Stephen, committee member
- ItemOpen AccessReproduction and recruitment dynamics of flathead chub Platygobio gracilis relative to flow and temperature regimes in Fountain Creek, Colorado(Colorado State University. Libraries, 2015) Haworth, Matthew R., author; Bestgen, Kevin R., advisor; Fausch, Kurt D., committee member; Bledsoe, Brian P., committee memberA paucity of basic ecological information for flathead chub Platygobio gracilis has made effective conservation planning difficult for this declining species. The objective of this study was to contribute insight to the poorly understood reproductive ecology of flathead chub, and enable prediction of effects of future hydrologic alterations in Fountain Creek, Colorado, to avoid or mitigate negative impacts from these actions. To accomplish this I investigated the influence of flow and water temperature regimes on reproduction and recruitment dynamics of flathead chub in Fountain Creek from May 2012 to October 2013 through collection of eggs, and analysis of otoliths from larvae and juveniles. Presence of flathead chub eggs and larvae in drift nets and Moore egg collectors indicated a protracted spawning season spanning a four-month period from mid-May to mid-September. Species composition of fish hatched from eggs reared in the laboratory showed the majority of eggs captured in drift nets were flathead chub. This enabled identification of peak reproduction periods based on captures of eggs in preserved samples. Reproduction began in each year when water temperatures exceeded 15°C, and highest egg densities occurred in later May and June in both 2012 and 2013. Unlike literature suggestions of need for flow spikes to induce reproduction, spawning occurred during both steady low flow conditions and to a lesser extent, under fluctuating flows caused by convective storms. Larvae hatching also peaked in May and June but, unlike egg production, was restricted to periods of stable low flows of about 1-2 m³/s. Recruitment, in this study defined as the addition of an individual to the population by survival to the juvenile stage, occurred only in a subset of the egg production season during periods of low and steady flows, usually in late May and June. In contrast, egg production preceding or during flow spikes that reached approximately 20 m³/s produced few recruits, presumably because eggs and weak-swimming larvae were transported downstream or destroyed. Recruitment sometimes occurred prior to flow spikes, but the minimum duration of relatively steady flows required was about three weeks. Both episodic and frequent high magnitude flow events had large and negative impacts on recruitment of flathead chub, and potentially population dynamics of the species in Fountain Creek. This is mostly counter to the prevailing paradigm that high flows are required for many plains-adapted minnow species to reproduce, a hypothesis formulated mostly from observations in flow-depleted streams where such patterns may be an artifact of an altered environment. This study was successful in identifying environmental conditions suitable for flathead chub reproduction and recruitment related to temperature and flow regimes in Fountain Creek. Managers should use these insights to predict how future hydrologic alterations may affect the flathead chubs so the population in Fountain Creek can be conserved.