Browsing by Author "Hufbauer, Ruth, committee member"

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Open Access
Causes and consequences of plant climate adaptation
(Colorado State University. Libraries, 2019) Monroe, John Grey, author; McKay, John, advisor; Ghalambor, Cameron, committee member; Hufbauer, Ruth, committee member; Sloan, Dan, committee member; Des Marais, Dave, committee member
Climatic conditions such as temperature and drought can sources of strong selection on natural populations. In plants, whose sessile nature forces them to adapt to local climate conditions, extensive evidence of local adaptation has been observed. However, the consequences of this adaptation on ecosystem processes such as carbon cycling remain poorly understood. Additionally, the molecular basis of adaptation is often unresolved and the specific climatic factors that drive adaptive evolution unclear. Addressing these knowledge gaps has become increasingly urgent as climate change threatens to rapidly alter selection regimes. Fortunately, conceptual and technical advances provide new opportunities to characterize and integrate environments, phenotypes, and genes, and thus advance our understanding of the causes and consequences of climate adaptation. In Chapter 2 of this dissertation, I consider the consequences of climate adaptation through the lens of ecoevolutionary dynamics. Integrating environments and phenotypes by considering ecosystem impacts of adaptive evolution, I review empirical evidence that contemporary climate adaptation could significantly alter the carbon cycle. In Chapter 3, I investigate the molecular basis of adaptation to winter temperatures in the model plant Arabidopsis thaliana by integrating genes and environments through the framework of landscape and population genetics. Specifically, I address the hypothesis that loss-of-function in a family of transcription factors contributes to adaptation to warmer climates. In Chapter 4, I develop methods combining whole genome sequence data, long term remote sensing, and reverse genetics to study drought as an agent of selection on flowering time and identify loss-of-function variants contributing to this evolution in Arabidopsis thaliana. Together, this work has inspired my interest in combining conceptual, computational, experimental innovations into an integrated research program to understand climate adaptation.
Open Access
Conservation genetics and phylogeography of a disjunct prairie plant: Clematis fremontii (Ranunculaceae)
(Colorado State University. Libraries, 2022) Krakowiak, Alaina, author; Simmons, Mark, advisor; Ackerfield, Jennifer, committee member; Hufbauer, Ruth, committee member; McGlaughlin, Mitchell, committee member
Premise: Clematis fremontii has a unique disjunct distribution with populations found in multiple distinct and widely separated mixed-grass and xeric limestone prairie habitats in the Great Plains, Ozarks, and Southeast. It is considered rare and endangered in much of its range. This study assesses genetic differentiation and diversity of C. fremontii in and among these disjunct areas in order to 1) inform conservation strategies, and 2) better understand the biogeographic processes that shaped its current range. Methods: 116 samples collected from 17 populations across the species' range plus 10 outgroup samples of C. ochroleuca were sequenced using a double digest restriction-site associated DNA (ddRAD) approach. Genetic diversity and structure were analyzed using STRUCTURE, multivariate ordination, and other statistical approaches. hierarchical relationships were estimated with Tetrad, TNT, and a neighbor-net analysis. Results: All populations showed moderate genetic diversity, and geographic regions showed moderate genetic differentiation from one another. Analyses generally demonstrated that initial divergence was between groups occurring east and west of the Mississippi River, but we found further structuring among disjunct regions. We also found evidence for secondary contact between eastern and western groups, particularly in the Georgia population. Conclusions: Small, isolated populations of Clematis fremontii have higher levels of genetic diversity than we expected, but habitat loss still poses a major threat. Current levels of genetic diversity could indicate an extinction lag. Restoration and population augmentation efforts are needed for this species to persist long-term. Additionally, our data supports the hypothesis that separation of eastern and western C. fremontii populations dates to relatively recent Pleistocene events. This could be a vicariance event, such as meltwater mega-flooding of the Mississippi River, or an eastward expansion from a more widespread western group during an interglacial period. Our data did not support the hypotheses of ancient vicariance via the formation of the Mississippi embayment or very recent expansion dating to the Hypsithermal Interval. We also found that C. fremontii accumulated genetic variation upon isolation in xeric limestone prairie habitats, similar to a rapid radiation.
Open Access
Effects of early snowmelt on plant phenophase timing and duration across an elevation gradient
(Colorado State University. Libraries, 2021) Wilmer, Chelsea, author; Kampf, Stephanie, advisor; Steltzer, Heidi, advisor; Hufbauer, Ruth, committee member
Plant phenology is an important indicator of the effects of climate change, yet the relative importance of both the drivers of plant phenology and the importance of individual phenophases in how plants respond to climate change is not well understood. Here we assess the impact of early snowmelt, a critical climate perturbation in mountain regions, on the timing and duration of individual plant phenophases across an elevation gradient in Crested Butte, Colorado. We observed a sequence of plant phenophases, new leaves, full leaf expansion, first open flower, and full leaf color change at five sites at distinct elevations (2774 m, 2957 m, 3167 m, 3475 m, 3597 m) across three mountain life zones (montane, subalpine, and alpine) in 2017 and 2018. In the spring of 2018, we used solar radiation absorbing fabric to accelerate the timing of snowmelt and observed the differences in timing for early snowmelt plots relative to control plots. The two study years had different snowmelt timing with 2018 being much earlier than 2017, so we analyzed the data to evaluate the effect of year using unmanipulated plots only, and also, separately the snowmelt manipulation, on phenophase start dates and durations. Phenophase timing was advanced at nearly all sites in 2018 and was not clearly linked to shifts in duration, which were variable. The snowmelt manipulation did not shift the timing of phenophases at the lowest elevation in our elevation gradient and the effect of the experiment on the timing of phenophases decreased as elevation increased. Even though snowmelt was significantly accelerated in the manipulation plots in 2018 at the lowest elevation the timing of phenophases were not advanced. This may indicate a threshold beyond which early snowmelt no longer advanced leaf emergence. Earlier snowmelt in mountain regions can shift the timing and duration of plant growth, though not consistently, which will have consequences on how plants affect the movement of water and retention of nutrients and metals in mountain watersheds.
Open Access
Experimental tests of risky augmentation scenarios using Trinidadian guppies
(Colorado State University. Libraries, 2017) Kronenberger, John Andrew, author; Angeloni, Lisa, advisor; Funk, Chris, advisor; Ghalambor, Cameron, committee member; Hufbauer, Ruth, committee member
Increased isolation of populations, and the subsequent reduction in genetic diversity, can exacerbate global biodiversity loss by contributing to inbreeding depression and reducing the ability of organisms to adapt to rapid environmental change. This has prompted some conservation biologists to consider augmenting isolated populations with immigrants as a means of demographic and genetic rescue. Augmentations are typically highly successful, but they are also controversial due to the risk of outbreeding depression or the introduction of maladapted alleles when immigrants are genetically or adaptively divergent. For my Master's thesis, I tested risky augmentation scenarios using mesocosm populations of Trinidadian guppies (Poecilia reticulata) in two separate controlled experiments. In my first experiment (Chapter 1), I augmented mesocosm populations derived from a single recipient source with genetically or adaptively divergent immigrants to assess their short-term demographic effects. Mesocosms that were augmented maintained greater abundance and recruitment than controls that were not. There was also a trend for populations to receive a greater benefit from immigrants that were genetically divergent than those that were adaptively divergent. I expanded upon these results in my second experiment (Chapter 2), in which I augmented mesocosm populations from two different recipient sources with immigrants spanning a greater range of divergence and monitored them over a longer time frame, including an additional control and genetic monitoring to determine the relative impact of demography and genetics. Despite no evidence for demographic rescue, I found genetic rescue in one recipient population. Divergent immigrants did not have a negative effect in almost all cases, and any positive effect they had depended on the genetic diversity, immigrant fitness, and recipient life-history traits. Together, these experiments provide strong evidence that immigrants can bolster population fitness despite being divergent, thereby supporting the use of augmentation as a management technique in dire situations when no safe immigrant sources are available.
Open Access
Field population genetics of global Puccinia striiformis f. sp. tritici populations in wheat reveal a dynamic molecular battlefield
(Colorado State University. Libraries, 2021) Lyon, Rebecca, author; Trivedi, Pankaj, advisor; Broders, Kirk, committee member; Pearce, Stephen, committee member; Hufbauer, Ruth, committee member
To view the abstract, please see the full text of the document.
Open Access
Green roof effects on floral phenology and floral nectar resources
(Colorado State University. Libraries, 2023) Ruszkowski, Kyle M., author; Bousselot, Jennifer, advisor; Hufbauer, Ruth, committee member; Krishnan, Sarada, committee member
This study investigates the potential for green roofs to support pollinator diversity and abundance in urban ecosystems through the altered floral phenology and floral abundance of plants. I compare floral phenology and the floral abundance of green roof plants to plants grown at grade on the Front Range in Fort Collins, Colorado, and how these changes may affect pollinator biodiversity in urban ecosystems. I employed an independent block design, with one green roof and one ground-level garden, approximately 120 meters apart, with replicate plants of 4 species at each garden. I found the abundance of flowers to be variable, depending on the plant species. However, all species of plants tested bloomed earlier when grown on the green roof than when grown at grade. We found pollinator abundance and diversity to be low at both the green roof and at grade. Nectar quantity and quality are diverse across a landscape and affect the health and behavior of some pollinators. I evaluated nectar volume and nectar sugar concentration between plant replicates grown on a green roof and grown at grade. Volume was measured in situ and sugar concentration was measured both in situ using a refractometer and, in a laboratory, using UPLC-RI. We found that there was no clear difference between nectar volumes of plants grown on the green roof and at grade while nectar sugar concentrations were generally higher in green roof plants.
Open Access
Influence of habitat complexity on diversity and community structure of arboreal spiders in grassland-shrub systems
(Colorado State University. Libraries, 2023) Knutson, Eric M., author; Charkowski, Amy, advisor; Aldridge, Cameron L., committee member; Trivedi, Pankaj, committee member; Hufbauer, Ruth, committee member
Revealing the ecological drivers of species distribution is one of the central issues in ecology. The ecological niche concept recognizes that distribution of species is influenced by abiotic (e.g., temperature, landscape characteristics, and nutrients) and biotic (e.g., food availability) factors through both direct and indirect mechanisms. Many of these niche factors can influence the spatial position of plants in a landscape. Plant communities often determine the physical structure of the environment (microclimate, plant architecture) and therefore, have a considerable influence on the distribution of animal species, such as arthropods, and on local community structure. For instance, vegetation structure provides spatial complexity by creating microenvironments that may enable more interactions with other species that live on plants or allow resource partitioning. In grasslands, much of the arboreal habitat is in the form of shrubs, but the role and importance of shrubs in distribution and diversity of arthropods in grasslands is unknown. Spiders are a useful indicator for examining the role of shrubs in arthropod ecology because they are genetically and behaviorally diverse predators and prey that can be captured and counted with a single method. Spiders are a key component of invertebrate communities of grasslands and arboreal spiders of grasslands provide a unique ecological system to study habitat association and community assemblage. However, most spider studies in prairie ecosystems have focused on ground dwelling taxa or those associated with agroecosystems. Only limited data exist for shrub-dwelling species and few studies have compared arboreal spider occupancy across different grassland shrub species. I endeavored to understand this system in more detail by investigating how arboreal spider community structure responds to native shrub species, plant community composition and landscape complexity. Since landscape complexity can be evaluated at multiple scales, landscape characteristics can be significant predictors of presence and abundance for a variety of taxa. I collected and identified 3,053 specimens to family, genus or species level and found that presence of certain shrub species predicted spider species occurrence and suggested diversity community structure patterns. I found that habitat association to combinations on shrub species indicated habitat specific niche partitioning of arboreal spiders in two Colorado grassland systems. Because shrub species occurrence is largely dependent on elevation and moisture gradients, spider occupancy may also be tied to similar gradients correlated with these landscape factors. Changes in the topography of the sampling area affected the local plant communities of shrubs across a recognized elevational gradient, which correlated to habitat zones for arboreal spiders in the local area.
Open Access
Investigation of flowering phenology, pollinator and invertebrate biodiversity value on urban green roofs and an evaluation of ornamental horticulture crops for pollinator value
(Colorado State University. Libraries, 2024) Guidi, Michael A., author; Bousselot, Jennifer, advisor; Hufbauer, Ruth, committee member; Krishnan, Sarada, committee member
Urban green space, green infrastructure, and horticultural installations are gaining recognition for their potential to foster biodiversity. Green roofs are challenging growing environments for plants, characterized by extreme substrate temperatures, high light intensity, limited moisture availability, and limited substrate depth. Plants have a variety of physiological responses to these unique conditions, but little is known about how green roof growing conditions affect ecological characteristics like plant flowering phenology. Similarly, studies are only just beginning to uncover the degree to which green roofs can provision habitat and support urban biodiversity. We evaluated the flowering phenology and made in-situ pollinator observations of 15 plant taxa growing both on green roof systems and at ground level at the Denver Botanic Gardens over two growing seasons. Using the same study sites, we sampled invertebrate diversity on green roof sites and ground level using pitfall traps. Finally, using a large citizen-science dataset, we evaluated differences in pollinator visitation with a specific focus on plant nativity, cultivated origin, growth form. We found that flowering phenology is substantially earlier on green roofs compared to ground level. We also observed a greater number of pollinators on green roofs early in the season, compared to ground level, presumably due to the availability of flora resources among the observed plant taxa. We observed significantly higher substrate temperatures along with wider diurnal temperature amplitude during the growing season that may contribute to this pattern. Invertebrate abundance was substantially higher at ground-level, species richness was similar between the intensive green roof and ground-level, and we observed substantially lower abundance and richness on the extensive green roof. Divergence in flowering phenology between individual plants of the same species on green roofs and plants at ground-level may have implications for organisms that rely on floral resources in urban environments. Earlier flower initiation on green roofs may provide pollinators with unique foraging opportunities and aid targeted conservation where early-season floral resources are limited. Similarly, results from invertebrate sampling suggest that green roofs, especially intensive roofs with high vegetation coverage, species richness, and habitat heterogeneity may offer invertebrate habitat on par with ground-level urban gardens and may even support unique groups of invertebrate taxa. Our results from our citizen science pollinator observations demonstrate that non-native plants showed similar visitation compared to native plants, but origin was important with selections and species having significantly higher pollinator visitation compared to hybrid plants. Shrubs and herbaceous perennials demonstrated high pollinator visitation compared to other plant growth forms.
Open Access
Manipulation of resource allocation to increase fecundity in Mimulus gemmiparus
(Colorado State University. Libraries, 2016) Chu, Kevin, author; Steingraeber, David, advisor; Funk, Chris, committee member; Hufbauer, Ruth, committee member
Mimulus gemmiparus W. A. Weber, a Colorado endemic, is a rare species that is at risk of becoming endangered. Reproduction in M. gemmiparus is solely by vegetative propagules (bulbils), which function analogously to seeds; sexual reproduction has not been observed in the wild. Manipulation of resource allocation in this plant may shift resources allocated for sexual reproduction to vegetative growth; the investment in increased vegetative growth should result in a direct increase in fecundity. Two experiments were conducted to examine the effects of redistribution of resources and change in meristem fate. The first experiment used plants grown in greenhouse conditions; seemingly nonfunctional floral buds or floral buds and shoot apical meristems were removed to potentially increase bulbil production. The second experiment used plants grown indoors under growing lamps to produce plants that were similar in size to those found in their natural habitats; their shoot apical meristems were removed to potentially induce branching and thus increase vegetative growth to increase bulbil production. Removal of floral buds or removal of both floral buds and shoot apical meristems in a greenhouse environment doubled the number of bulbils produced per plant, increased by approximately two-thirds the total bulbil biomass per plant, increased the ratio of bulbil count to stem biomass, and increased the ratio of bulbil biomass to stem biomass; however, there was a trade-off between having greater number of bulbils and individual bulbil biomass. Solely removing the shoot apical meristem in a low-light environment had no effect on bulbil production; although branching was induced, the primary branches remained small and did not elongate. Secondary branches were formed only on plants that had their shoot apical meristem removed. The total numbers of shoot axes per plant were not significantly different between the control and treatment group; the induction of branching seemingly produces a compensatory effect, but not overcompensation for the removal of the shoot apical meristem. In both experiments, stem biomass did not differ between the control and treatment group(s). Lighting condition in the environment the plants grew in had the greatest effect on stem development, and manipulation of meristems to form new shoots did not increase plant size. Bulbil yield may be increased in greenhouse conditions by manipulation of allocation from sexual reproduction to vegetative growth.
Open Access
Phenotype to genotype and back in emerging and established crop species
(Colorado State University. Libraries, 2023) Woods, Patrick O'Neal David, author; McKay, John, advisor; Hufbauer, Ruth, committee member; Funk, Chris, committee member; Sloan, Dan, committee member
Understanding the relationship between the phenotype and genotype is a fundamental goal of genetics. Through the years, two primary approaches have been developed for studying the phenotype-genotype relationship: forward genetic and reverse genetics. Forward genetics enables the potential discovery of numerous candidate genes controlling a phenotype while reverse genetics allows for the mechanistic validation of a single gene's role in controlling a phenotype. Applying these two approaches to crops enables the discovery of genetic targets that can be used for crop improvement through breeding. In this dissertation, I focused on understanding the phenotype-genotype relationship in both the emerging crop Cannabis sativa and the established crop Maize. In Chapter 1, I used both a forward a reverse genetics approach to identify and validate candidate genes controlling agriculturally important traits (agronomic and biochemical) in Cannabis sativa. In Chapter 2, I used a reverse population genetics approach to identify the genetics underlying local adaptation in feral and domesticated populations of Cannabis sativa. In Chapter 3, I used a forward genetics approach to identify candidate genes controlling variation in root system architecture in Maize. Collectively, this work demonstrates how modern genomic techniques can be applied to both new and old crop systems to identify genetic targets for use in crop innovation through breeding.
Open Access
Relationships between anatomy and climate in members of the subfamily Pooideae
(Colorado State University. Libraries, 2019) Spitzer, Daniel B., author; Ocheltree, Troy, advisor; Meiman, Paul, committee member; Hufbauer, Ruth, committee member
As climate continues to change, it will become increasingly important to accurately predict the landscape-level response of plant functional groups to climatic shifts. Relationships between vascular anatomy and climate distribution have been revealed in woody plant species, but little research has been done on this subject in the Poaceae family. These relationships were studied in 21 grass species from 5 genera in the subfamily Pooideae by analyzing their anatomical traits and climate data from each species' range. Analysis showed multiple correlations among anatomical traits, such as a positive correlation between the ratio of vessel wall thickness to vessel diameter (t/b ratio) with vein density. These relationships suggest that anatomical traits are closely linked to each other and to vein density, which may be confer some advantage or be in response to selective pressure. Some correlations between climate traits and anatomical traits were found, but the strength of these relationships was less than expected and were often the result of the interaction of multiple climate variables with a single anatomical variable. This may be because of broad, multi-year averaged data obscuring important temporal and spatial factors, as well as phenological variation across species not being accounted for. Future research should focus on microclimatic conditions species occupy and noting phenology for each species to better identify the climate conditions species are adapted to.
Open Access
The ecology and evolution of plant-insect interactions among hybrid populations of the invasive plant, tamarisk (Tamarix sp.), in the western United States
(Colorado State University. Libraries, 2012) Williams, Wyatt I., author; Norton, Andrew, advisor; Friedman, Jonathan, committee member; Hufbauer, Ruth, committee member; Nissen, Scott, committee member; Bauerle, William, committee member
Tamarisk is one of the most abundant invasive tree species in the western United States. Several species belonging to the genus Tamarix were imported intentionally to the U.S. in the mid-nineteenth century. Currently, most U.S. populations are comprised of a hybrid swarm between T. ramosissima and T. chinensis and other species. Negative consequences of hybrid tamarisk invasion include alteration of ecosystem functioning and decreases in native biodiversity. Very few natural enemies attack this invasive plant, contributing to its success on the landscape. In an attempt to provide top-down population control, a specialized herbivore that coevolved with tamarisk in its native range was intentionally released in the introduced range (i.e. biological control). I investigated interactions between tamarisk hybrids and herbivores in order to better understand the dynamics that contribute to the control of this exotic weed. In Chapter 1, which was published in Volume 57 of The Southwestern Naturalist, I describe how a native stem-boring beetle was found attacking tamarisk populations in eastern Colorado, western Kansas, and southwest Nebraska. This is an important discovery because very few native insects have been reported to consume this plant and never at the levels of the stem-borer. The beetle may reduce tamarisk growth and fecundity on the Great Plains, providing evidence for the biotic resistance hypothesis. In Chapter 2, I investigate the interaction between drought and herbivory by the biological control agent, Diorhabda carinulata. Under which environmental conditions or geographical locations can biological control be maximized? Finally, in Chapter 3, I speculate whether hybrid tamarisk individuals or populations differ in plant performance and herbivore defense traits. Since the biological control agent coevolved with one parent species, T. ramosissima, I hypothesized that some hybrids may be more or less susceptible to attack by this herbivore. Success of biological control may hinge upon the level of species introgression, and if hybridization occurs predictably across the landscape, managers can exploit this information for tamarisk control. My research not only attempts to improve control strategies, but also addresses fundamental questions in plant-insect ecology and evolution.