Department: Evolution, Ecology, and Organismal Biology ![[clear]](close-x.png "Remove this limiter")
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2.
Andrews, Adam Lee.
The role of female preference in sexual dimorphism of Japanese medaka (Oryzias latipes).
Degree: MS, Evolution, Ecology, and Organismal Biology, 2005, Ohio State University
► The aim of my thesis is determine the role of female choice…
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▼ The aim of my thesis is determine the role of female choice in sexual dimorphism in Japanese medaka (Oryzias latipes). I attempted to obtain this information with three questions. 1) What are the consequences to offspring viability of female choice for male phenotypes? That is, why might such phenotypes have evolved? 2) In what phenotypic characters do male and female medaka differ? Are these dimorphic traits consistent between strains? How are phenotypes altered when the gender or genotype of an individual is changed? 3) Does female mate choice in medaka drive the sexual dimorphism found in this species, or is it likely the result of intrasexual competition? In the first chapter, I reviewed the studies that correlated male phenotypes with some measure of female reproductive success. Over a range of taxa, I found that variation in traits in which the sexes differed, such as body size, spur size, body color, song repertoire, and ornamentation had reproductive consequences for females. It stands to reason then that if these traits are indicators of male quality, then females may select males so as to maximize their reproductive fitness. With these traits in mind, I measured both size and color traits of male and female medaka in Chapter 2. I found medaka to be sexually dimorphic in body and anal fin color, as well as fin size and body shape. Fin and body size differences were generally conserved between strains, indicating that selection is acting upon the species to diversify the sexes. In order to determine whether this selection pressure is that of female choice, or whether it might be from male-male competition, I conducted behavioral assays in which females were able to demonstrate a preference between two males, who were subsequently measured in the sexually dimorphic traits (Chapter 3). The only correlation I found was a weak self-referential one in which females prefer male with a similar nape color (red channel) to their own. Otherwise, I found no correlation between any of the measured traits and female preference, indicating that the dimorphism is likely the result of intrasexual selection, rather than female choice.
Advisors/Committee Members: Downhower, Jerry F.
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3.
Archibald, Jenny Kay.
Systematics, hybridization, and character evolution within the southern African genus, Zaluzianskya (Scrophulariaceae s.s., tribe Manuleeae).
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2003, Ohio State University
► Zaluzianskya (Scrophulariaceae s.s., tribe Manuleeae) is a southern African genus with four…
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▼ Zaluzianskya (Scrophulariaceae s.s., tribe Manuleeae) is a southern African genus with four sections, whose floral diversity is particularly evident. This work examines Zaluzianskya at population and genus-wide levels. Sympatric and allopatric populations of Z. microsiphon (day-flowering) and Z. natalensis (night-flowering) were examined using ISSR markers in combination with ordination analyses of morphology. Although unexpected due to differences in flowering time between these species, putative hybrids have been found. The high genetic similarity between these species made it difficult to recover patterns of gene flow. However, it appears that genetic material from Z. microsiphon may be introgressing into Z. natalensis. The first broad phylogenies for Zaluzianskya were resolved using nuclear (ITS) and chloroplast (rpl16 and trnL-trnF) sequences. Analyses of separate and combined data sets were largely congruent, resolving three main clades. The only significant incongruence involved the single species included from section Macrocalyx. This species is placed sister to section Nycterinia by ITS but within that section by cpDNA. Consequently, the monophyly of section Nycterinia is undecided. It is certain, however, that sections Zaluzianskya and Holomeria are not monophyletic. Additionally, one of the purported outgroups (Reyemia) was nested within Zaluzianskya with strong support. Based on this and morphological affinity, this ditypic genus should be submerged within Zaluzianskya. Finally, the status of Z. microsiphon is uncertain, with three populations clearly separated in the phylogeny. Potentially this represents three lineages with convergent morphology due to pollinator selection. Alternatively, hybridization may have distorted Z. microsiphons placement on the phylogeny. Character evolution was also examined, to find morphological synapomorphies for the new infrageneric groups and to consider the evolution of floral diversity within Zaluzianskya. Several traits support various levels in the phylogeny, including petal shape, stamen placement, tube length, nectary adnation, stem indumentum, and calyx lobing. Reconstruction of some traits was complicated by the uncertain status of Z. microsiphon. For example, the evolution of flowering time, floral symmetry, and throat indumentum is more labile if Z. microsiphon is divided. The evolution of habit (annual vs. perennial) and distribution (within relatively arid vs. mesic regions) appear associated although concentrated-changes tests did not reveal a significant correlation.
Advisors/Committee Members: Wolfe, Andrea D.
Keywords: floral evolution; ISSR; Reyemia; ethological isolation; biogeography; ITS; Zaluzianskya; Scrophulariaceae; rpl16; trnL-trnF; hybridization; South Africa; Kwazulu-Natal; PCA
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4.
Artman, Vanessa L.
Effects of prescribed burning on forest bird populations in southern Ohio.
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2000, Ohio State University
► Prescribed burning treatments were applied experimentally as a repeated series of low-intensity…
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▼ Prescribed burning treatments were applied experimentally as a repeated series of low-intensity surface fires in mixed-oak (Quercus spp.) forests of southern Ohio. I researched the short-term effects of frequent and infrequent burning regimes on habitat structure, breeding bird population levels, nesting productivity, and nest site selection. Repeated burning resulted in incremental reductions in leaf litter cover and densities of shrubs and saplings. These habitat features recovered to some extent within two years after burning, but a second fire after two years of recovery resulted in similar changes in habitat conditions as repeated fires without recovery. Of thirty bird species monitored, population levels of four bird species were negatively affected by prescribed burning and population levels of two bird species were positively affected by prescribed burning. Population levels of ovenbirds (Seiurus aurocapillus), worm-eating warblers (Helmitheros vermivorus), and hooded warblers (Wilsonia citrina), each of which nest on the ground or in low shrubs, declined incrementally in response to repeated burning. Their population levels did not recover within one year after burning, and reductions were similar whether repeated fires were applied on a frequent or infrequent basis. Rates of nesting success for these three bird species did not change significantly in response to prescribed burning, but levels of seasonal fecundity, representing a combination of nesting success, fledging success, and likelihood of renesting, appeared to be lower in burned than unburned areas. Population levels of northern cardinals (Cardinalis cardinalis) were also negatively affected by the fires as densities fluctuated from year to year in unburned areas but remained low in burned areas. Population levels of eastern wood-pewees (Contopus virens) and American robins (Turdus migratorius) increased in response to burning, apparently because burning improved their foraging habitat but these increases were evident only after several years of repeated burning. Eastern wood-pewees were common in unburned areas, suggesting that these areas also provided suitable habitat conditions for this bird species. Densities of midstory-nesting bird species, including the Acadian flycatcher (Empidonax virescens), red-eyed vireo (Vireo olivaceus), and wood thrush (Hylocichla mustelina), did not change in response to the fires despite reductions in midstory vegetation. Midstory-nesting bird species appeared to compensate for the changes in habitat conditions by selecting nest sites where fire intensities were lower. Rates of nesting success did not differ between burned and unburned areas for these bird species suggesting that their continued use of recently burned areas had no consequences (positive or negative) in terms of reproductive success.Although prescribed burning is important for restoring habitat for nongame bird species in other regions, my research shows that nongame bird populations in southern Ohio experience minimal benefits from prescribed burning. Several bird species were adversely affected by prescribed burning and these effects were similar whether repeated burning was applied at frequent or infrequent intervals. My research thus underscores the need to objectively assess whether prescribed burning should be applied on an extensive basis within the region, particularly in considering the need to ensure sustainability of multiple resources within the context of long-term forest management.
Advisors/Committee Members: Downhower, Jerry F.
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5.
Back, Christina L.
Effects of Common Reed (Phragmites australis) Invasion and Glyphosate and Imazapyr Herbicide Application on Gastropod and Epiphyton Communities in Sheldon Marsh Nature Reserve.
Degree: MS, Evolution, Ecology, and Organismal Biology, 2010, Ohio State University
► Phragmites australis, the common reed, is an invasive macrophyte in many eastern…
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▼ Phragmites australis, the common reed, is an invasive macrophyte in many eastern North American wetlands. Reed often rapidly forms dense, near-monotypic stands by replacing native vegetation, which lowers plant diversity and alters wetland habitat structure. Accordingly, herbicides such as imazypr-based Habitat® and glyphosate-based AquaNeat® are often applied to reed stands in an attempt to control its establishment and spread. Although these herbicides are apparently not toxic to benthic organisms, they may indirectly affect them by altering available habitat structure via increased detrital litter, increased light penetration to surface waters and increased water temperature. Understanding the impacts of widespread herbiciding on benthic communities, as well as the impact of different herbicides on habitat conditions, should help wetland managers design control plans to reduce reed and conserve system biodiversity. I compared gastropod (i.e., snails) and epiphyton communities, and habitat conditions among large, replicated plots of unsprayed Phragmites, glyphosate-sprayed Phragmites, imazapyr-sprayed Phragmites and unsprayed Typha angustifolia (narrow-leaf cattail) in early the summer 2008 in a Lake Erie coastal marsh. I studied gastropods because they can greatly influence trophic structure in freshwater systems by consuming benthic algae and by serving as prey to sportfish. Moreover, I included Typha angustifolia in the study because it is another invasive plant common to many Lake Erie coastal wetlands. Relative abundances of gastropods were similar among treatments on 24 June and 30 June, but differed on 8 July. On 8 July, Fossaria spp. were particularly abundant in herbicide-treated plots, and Promenetus umbilicatellus was abundant in AquaNeat®- treated plots. Snail densities were greater in plots containing metaphyton (filamentous green algae) than in plots without metaphyton, and juvenile and small snails were abundant in metaphyton mats. Metaphyton presence was linked to increases in light penetration caused by herbiciding. Epiphytic algal densities, and chlorophyll a levels, an indicator of algal biomass, were low in all treatments, and diatom-dominated epiphyton communities were similar among treatments. Dry mass of benthic organic matter (BOM), which can provide available substrate for epiphyton growth and habitat for snails, was also similar among treatments. Dissolved oxygen and water depths were similar among treatments, but water depths significantly declined with sampling date. A combination of low and highly variable water levels, low oxygen levels, and eutrophic conditions apparently shape snail and algal community structure in this marsh. My results suggest that both glyphosate- and imazapyr-containing herbicides have little effect on the herbivore-producer relationship and gastropod diversity in Sheldon marsh 1-year post-spraying.
Advisors/Committee Members: Holomuzki, Joseph R.
Subjects: Ecology
Keywords: Phragmites; gastropods; herbicides; glyphosate; imazapyr
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11.
Briland, Ruth.
Optimizing Larval Fish Survival and Growth through an Analysis of Consumer and Resource Interactions in Percid Culture Ponds.
Degree: MS, Evolution, Ecology, and Organismal Biology, 2010, Ohio State University
► Management of aquaculture systems should be based on ecologically sound principles and…
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▼ Management of aquaculture systems should be based on ecologically sound principles and experimentation to determine species- and site-specific management practices that both optimize fish production and extend our understanding. Herein, we exemplify an approach to meet this goal, evaluating the effectiveness of three common management levers: pond fertilization regimen, pond filling and stocking schedule, and fry stocking rate, on larval production of two popular percid fish, walleye (Sander vitreus) and saugeye (S. vitreus x S. canadense), at Senecaville State Fish Hatchery in Ohio. These levers are based on established ecological principles and hypotheses concerning fish recruitment, including resource-driven or “bottom-up” control, the match-mismatch hypothesis, and predator-driven or “top-down” control, respectively. Our experiments demonstrate that “top-down” effects (i.e., fish predation on zooplankton) drive fish growth, and we recommend that fry stocking density be reduced to les than 20 percid fry/m3 to yield suitable fish size at harvest. At higher stocking rates, percid planktivory can deplete zooplankton prey resources, resulting in poor fish growth and unacceptably small percid size at harvest. The other two management levers (i.e., manipulating fertilization rate and pond filling and stocking schedules) had little impact on percid production; however, these ecological management levers may be critical for successful fish production at other hatcheries, given different environmental conditions (e.g., source water productivity) or fish taxa. Overall, we illustrate an ecologically sound approach to assess management protocols for fish production in aquaculture settings that can be broadly applied to culture of many species at a variety of culture locations.
Advisors/Committee Members: Ludsin, Stuart.
Subjects: Aquaculture; Ecology; Fish production; Freshwater ecology
Keywords: larval fish ecology, aqucuaculture, walleye, saugeye
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12.
Bronson, Cynthia L.
Patterns and processes within a non-ecotone hybrid zone: the chickadees of Ohio.
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2002, Ohio State University
► This dissertation uses an avian hybrid zone as a study system in…
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▼ This dissertation uses an avian hybrid zone as a study system in which to explore potential causes for the configuration and movement of such zones. Stable hybrid zones are commonly considered to reflect a balance between selection and dispersal. Both exogenous and endogenous selection factors have been advanced to explain barriers to gene flow across narrow hybrid zones. Exogenous selection involves adaptation to local environments. In contrast, endogenous selection involves adaptation or coadaptation on the genomic level regardless of the external environment. The focal avian species of this dissertation, black-capped (Poecile atricapilla) and Carolina (Poecile carolinensis) chickadees, are permanent residents in Ohio. Currently, their distributions abut in an east-west hybrid zone in the northern aspect of the state. The black-capped chickadee resides north of the hybrid zone and the Carolina chickadee south. Based on historical data, the hybrid zone has moved northward about 100 km in the past 70 years. The first phase of this dissertation characterized, in a limited manner, a transect of the hybrid zone and identified patterns in reproductive success across the zone. A distinctive trough in reproductive success in the hybrid zone was observed and correlated with both location and parental genetics. The second phase consists of a controlled experiment. The genetics of the chickadees within the hybrid zone (endogenous selection) and the location of the hybrid zone (exogenous selection) were tested against each other to determine which was more influential on the observed pattern of decreased reproductive success within the hybrid zone. In support of endogenous selection, transplanted hybrid pairs produced fewer nestlings and fledglings than did transplanted pairs of either parental species. The final phase consists of a controlled, aviary experiment to determine if female mate preference might be a causal mechanism for the northward movement of the hybrid zone. The relative importance of morphological appearance (possibly denoting species identity) and social dominance of males were assessed. Without apparent knowledge of dominance, females preferred black-capped chickadee males. With knowledge of dominance, females preferred the dominant male which, when the dyad was of comparable size, was the Carolina male.
Advisors/Committee Members: Grubb, Jr., Thomas C.
Subjects: Biology, Zoology
Keywords: Poecile atricapilla; Poecile carolinensis; hybrid zone; selection; reproductive success
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13.
Bunnell, David B. Jr.
Exploring mechanisms underlying recruitment of white crappie in Ohio reservoirs.
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2002, Ohio State University
► Organisms that produce many, small offspring generally exhibit variable population size, owing…
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▼ Organisms that produce many, small offspring generally exhibit variable population size, owing to variation in production and survival of offspring. Using a life- history approach, we focused on ecological mechanisms underlying the production and survival of white crappie Pomoxis annularis, a popular North American sport fish exhibiting high variability in recruitment to maturity (i.e., age-2). Offspring production begins with adult energy allocation to reproduction. Female white crappies initiate ovary development during autumn, 6 months before spring spawning. To understand why females develop ovaries early, we used optimality and simulation models. Results revealed that early ovary development is an adaptation to uncertainty in spring feeding conditions. To investigate how mean condition and egg production of the adult population influence larval density and age-2 catch per effort (CPE), we sampled white crappie from 14 reservoirs. Although mean condition influenced ovary characteristics, only population egg production influenced larval density and age-2 CPE. Thus, population egg production can limit recruitment success. After larvae hatch, numerous mortality events occur before recruitment to age-2. We focused on two periods: between the larval and juvenile stage and during the first winter of life. In reservoirs, we evaluated how zooplankton density, water temperature, and larval density influenced larval growth and survival. Growth increased with zooplankton density, whereas survival was unrelated to any measured variable. We then evaluated how food, fish size, and winter severity influenced winter survival in the lab. Winter severity regulated survival with only 47% of the juveniles surviving the severe winter, and 97% surviving the mild winter. Although temperatures less than 4 degrees Celsius caused mortality in the lab, fish may occupy warmer habitat during Ohio winters in the field. Overall, white crappie recruitment is likely set by the egg or larval stage, though considerable winter mortality remains a possibility. With this caveat, we recommend that managers use catch restrictions to increase adult biomass and subsequent egg production to improve poor recruitment. Higher egg production should increase larval density and ultimately the number of fish recruiting to both maturity and the sport fishery.
Advisors/Committee Members: Stein, Roy A.
Subjects: Biology, Ecology
Keywords: white crappie; life history; larvae; juveniles; recruitment; maternal effects; winter temperatures; stock - recruit; energy allocation; optimality
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14.
Campbell, Lesley G.
Rapid evolution in a crop-weed complex (Raphanus spp.).
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2007, Ohio State University
► The development and adoption of transgenic crops with novel traits has raised…
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▼ The development and adoption of transgenic crops with novel traits has raised awareness of the potential for weed populations to evolve increased weediness after hybridization with cultivated relatives. I explored the evolutionary and ecological consequences of gene flow between crop radish (Raphanus sativus) and its weedy relative (wild radish, R. raphanistrum). Hybridization may generate the genetic and phenotypic variation necessary for an evolutionary response by weeds. First, I imposed artificial selection on wild and hybrid lineages for four generations for early flowering a potentially advantageous trait for weeds. Hybrid lineages evolved more rapidly under selection for early flowering and rapidly recovered a wild-type phenology and fertility. Second, I established replicated wild and hybrid populations in agricultural landscape and measured their evolutionary response to natural conditions after three generations. Natural conditions favoured larger plants in both wild and hybrid populations. However, because an advantageous trait, large size, had been transferred to hybrid populations, hybridization resulted in significantly larger hybrid than wild weeds and accelerated weed evolution. Further, I asked whether environmental context affected the success of hybrid relative to wild radish. Using a response surface competition experiment, I examined the consequences of competition on life history and lifetime fecundity of hybrid and wildplants. Hybrid plants were less competitive than wild plants. With increasingly competitive conditions, differences in hybrid and wild life history and fecundity were reduced. Therefore, competition may promote the introgression of crop alleles into weed populations. In a second experiment, I examined the consequences of geographic location on fecundity of hybrid and wild plants by conducting two common garden experiments in disparate locations within the geographic range of wild radish (Michigan, California). In Michigan, hybrids had lower fecundity than wild plants, but, in California, hybrids had significantly greater fecundity and survival than wild plants, suggesting hybrids may displace wild relatives in some environments. In summary, I present new evidence for a role of hybridization in the evolution of agricultural weeds by measuring the rate of hybrid evolution relative to wild ancestors and exploring the environmental contexts that facilitate crop trait introgression into weed populations.
Advisors/Committee Members: Snow, Allison A.
Keywords: hybridization; crop-to-wild gene flow; introgression; natural selection; artificial selection; phenotypic evolution; ferality; competition
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15.
Caprette, Christopher L.
Conquering the cold shudder: the origin and evolution of snake eyes.
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2005, Ohio State University
► I investigated the evolutionary origin and diversity of snakes by examining one…
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▼ I investigated the evolutionary origin and diversity of snakes by examining one complex structure, the eye. Using light and transmission electron microscopy, I contrasted the anatomy of the eyes of diurnal northern pine snakes and nocturnal brown treesnakes. Among the observed differences, brown treesnakes have much larger lenses than those of northern pine snakes for similar sized eyes. Northern pine snakes have a simplex, all-cone retina, while brown treesnake retinas have both rods and cones. The cone ellipsoids of northern pine snakes contain microdroplets that act as light guides, and there were similar droplets in brown treesnake rods, although their function is not clear. The density of photoreceptors and neural layers in brown treesnake retinas predict that brown treesnakes should have the same visual acuity under scotopic conditions that northern pine snakes have under photopic conditions. Next, I quantified orbital area, binocular overlap, eye size, lens size, and the refractive powers of the lens and spectacle among colubrid and crotalid snakes. The size-adjusted orbital area fit preditions based upon ecology, but binocular overlap did not for colubrid snakes. Pit vipers had much smaller orbital areas than colubrid snakes, but significantly greater binocular overlaps. The eastern cottonmouth, an aquatic pit viper, had a much greater average orbital area than its body size predicted, which may be due to its unique ecology. The eyeballs of both colubrids and pit vipers were significantly subspherical, as were the lenses of several species, and the lens contributed significantly more to the total refraction than the spectacle in all but one species, the brown treesnake, in which the spectacle had greater refractive power. Lastly, snakes evolved from lizards, but their eyes are substantially different. I compared the anatomy of vertebrate eyes across many taxa to evaluate alternative hypotheses concerning the evolution of the distinctive features of snake eyes. My analyses retrieved groupings consistent with ecological adaptation rather than accepted phylogenetic relationships. Moreover, snakes clustered with primitively aquatic vertebrates, whereas fossorial lizards and mammals clustered together. Those results support the hypothesis that snakes evolved from aquatic ancestors.
Advisors/Committee Members: Hetherington, Thomas E.
Keywords: Serpentes; Snakes; Eyes; Evolution; Morphology; Adaptation
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16.
Collingsworth, Paris Dever.
Assessing the Potential for Differential Contributions of Spawning Stocks to Lake Erie Yellow Perch Populations.
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2009, Ohio State University
► To determine how the heterogeneous environments in the western and central basins…
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▼ To determine how the heterogeneous environments in the western and central basins of Lake Erie influence reproduction and recruitment of yellow perch, I conducted a series of field and laboratory studies to measure the energetic and performance traits of various life stages. In Chapter 2, we examine the spawning behavior of yellow perch in the western basin by relating the presence and abundance of adult yellow perch during the spawning season to environmental variables. Here, we also estimated the timing of yellow perch spawning in this area by comparing the relative abundance of gravid and spent females through time and in relation to changing environmental conditions. In Chapter 3, we measured spatial variation in female reproductive traits among multiple spawning aggregations in the western and central basins of Lake Erie. We then demonstrate how spatial differences in demographic parameters influence population-level reproductive effort using a deterministic egg model to simulate total egg production under different mortality scenarios. In Chapter 4, we compared juvenile yellow perch traits at the end of their first summer across the western and central basins of Lake Erie. In Chapter 5, we measured elemental concentrations in the otoliths of larval yellow perch sampled from different regions of the western basin of Lake Erie and attempted to discriminate fish sampled from different regions using multi-element signatures. Finally, in Chapter 6, we reared juvenile yellow perch under different elemental concentrations crossed with three temperatures to determine the interactive influence of ambient elemental concentrations and temperature on otolith chemical composition. From an ecological perspective, this research was an attempt to identify factors that may influence annual population fluctuations in yellow perch. From an applied, management perspective, we were attempted to identify recruitment mechanisms that can be manipulated to better manage yellow perch in Lake Erie. Fish recruitment is a process driven by the complex interactions of many abiotic and biotic factors and many of these factors, such as environmental conditions, are uncontrollable. The identification of recruitment mechanisms that can be affected via management initiatives would be invaluable to managers and greatly advance our ability to manage fish populations.
Advisors/Committee Members: Marschall, Elizabeth.
Subjects: Ecology
Keywords: yellow perch; Lake Erie; reproduction
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17.
Conroy, Joseph David.
Testing the algal loading hypothesis: the importance of Sandusky River phytoplankton inputs to offshore Lake Erie processes.
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2007, Ohio State University
► Studies of tributary-lake interactions most often consider only tributary nutrient stimulation of…
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▼ Studies of tributary-lake interactions most often consider only tributary nutrient stimulation of offshore phytoplankton growth. However, in freshwater ecosystems, input of tributary phytoplankton may directly affect offshore processes, such as nutrient cycling, phytoplankton-bloom formation, and hypolimnetic hypoxia. To explore these interactions, we propose the Algal Loading Hypothesis which predicts (1) tributaries contain phytoplankton; (2) tributary phytoplankton are light-limited due to high nutrient concentrations and high light attenuation; (3) offshore phytoplankton are nutrient-limited due to low nutrient concentrations and low light attenuation; and, (4) as tributary phytoplankton move offshore, productivity increases in response to greater light availability, using tributary-stored nutrients to drive offshore productivity. We used field sampling during April-September 2005 and 2006, phytoplankton physiological measures, and computer simulations to test these predictions and to determine the effect of loaded phytoplankton on offshore phytoplankton dynamics and hypolimnetic oxygen depletion in the Sandusky system (Sandusky River, Bay, and subbasin) of Lake Erie. We found extremely high phytoplankton biomasses in the Sandusky River and Bay (Chapter 2) including an invasive cyanobacterial phytoplankter, Cylindrospermopsis(Chapter 5). Phytoplankton biomass was best predicted by the ratio of total inorganic nitrogen to total phosphorus (Chapter 2) whereas Cylindrospermopsisbiomass correlated with increased temperatures and shallow depths (Chapter 5). River and bay phytoplankton communities were not phosphorus limited but the offshore phytoplankton community was (Chapter 3). Phytoplankton communities at all sites were not strictly light limited; however, simulated phytoplankton productivity was most sensitive to light availability. For example, when we simulated increased light for the bay phytoplankton community, productivity increased > 200% (Chapter 3). Hypolimnetic oxygen depletion rates, however, were not affected by bay input of particulate organic matter but were most strongly influenced by basin morphometry (Chapter 4). Overall, we found support for the predictions of the Algal Loading Hypothesis with the exception of light limitation for tributary phytoplankton. Input of tributary phytoplankton “primed” for growth offshore must be considered when attempting to manage offshore water quality, especially in a system extensively modified by human activity, such as Lake Erie.
Advisors/Committee Members: Culver, David Alan.
Keywords: Lake Erie; phytoplankton; Cyanobacteria; Sandusky River; Sandusky Bay; phosphorus; oxygen
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18.
Corey, Sarah J.
Understanding Amphibian Vulnerability to Extinction: A Phylogenetic and Spatial Approach.
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2009, Ohio State University
► In the global extinction crisis currently underway, threats to biodiversity are not…
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▼ In the global extinction crisis currently underway, threats to biodiversity are not simply limited to species with particular risks in particular cases. Biodiversity will be increasingly affected by the wholesale decline of entire clades. In the face of this crisis, with amphibians ranking at the top of all vertebrates in the rate of extinctions, there is a great need for macroecological studies addressing three key areas of species declines. The processes that put species at great risk for extinction may be associated with 1) environmental factors, 2) spatially structured, or geographic effects, and 3) evolutionary predispositions to those processes (phylogenetic structure in vulnerability). I present a collection of work to address primarily the phylogenetic and geographic components of species vulnerability. First, I construct a theoretical foundation for using phylogenetic comparative methods for conservation assessments, emphasizing the importance of evolutionarily specific parameters and trees. I prescribe a greater conservation focus on understanding the severity of clade-level threats and potential data deficient species vulnerability, and identify evolutionary scenarios with the greatest return on resource investments. Second, I identify autocorrelated threats in the amphibian tree of life representing potential evolutionary predispositions to enigmatic rapid declines and Redlist threatened status in the superfamily Hyloidea. Third, I focus in on a family in Hyloidea, Hylidae, and use multiple phylogenetic comparative methods to identify phylogenetic signal in processes that selectively threaten lineages in the tree. I find phylogenetic signal (a predisposition to vulnerability) in pollution, habitat loss, species with multiple threatening processes, Redlist threatened status, and enigmatic rapid declines, concentrated in the clade Hylini. Among the comparative methods employed is a new application for conservation of a more flexible measure of phylogenetic signal accounting for selection using an Ornstein-Uhlenbeck model. Fourth, I use a landscape perspective to discover what spatial and environmental factors predict threats to amphibians in Venezuela. I find that traditional measures of human impact (population density and ecological footprint) effectively predict higher numbers of threatened amphibians, but indigenous peoples population density does not predict threats. Accounting for spatial dependence in the landscape reveals that cultural stewardship, i.e., parks on indigenous versus nonindigenous land, cannot predict threatened species distributions, failing to validate typical conservation concerns over indigenous population impacts to parks and biodiversity. Using a local spatial autocorrelation metric, I also find that the northwest region of Venezuela is a hotspot of geographic irreplaceability, for spatially autocorrelated threatened species, endemics and data deficient species. Overall, my collection of work addresses key themes in the amphibian extinction crisis using a macro-analytic approach: evolutionary predisposition to threats, anthropogenic threatening processes and spatial autocorrelation (or clumping) of threatened species. My work supports the emerging consensus that the extinction crisis is widespread, in terms of impact to phylogenetic diversity and geographic regions, but my findings also point to advantages for conservation policy and management gained by prioritizing vulnerable clades and geographic regions that stand to lose the most diversity and hold the greatest potential management payoffs.
Advisors/Committee Members: Rodewald, Amanda.
Subjects: Biology; Ecology
Keywords: phylogenetic comparative methods; phylogenetic signal; Hylidae; Amphibian conservation; phylogenetic autocorrelation; landscape ecology; Venezuela; extinction crisis; Moran's I, Ornstein-Uhlenbeck process
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19.
Coupe, Bradford Houston.
Mate-location behavior of Timber (Crotalus horridus) and Sidewinder (Crotalus cerastes) Rattlesnakes.
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2005, Ohio State University
► For many animals mate location is a matter of following widely broadcast…
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▼ For many animals mate location is a matter of following widely broadcast signals (e.g., visual, auditory) to the signaler. However, due to their morphology or habitat many animals are not able to broadcast signals widely. In these cases little is known about the methods used in mate location. I discuss three hypothesized mate-location methods potentially used in these situations by timber (Crotalus horridus) and sidewinder (Crotalus cerastes) rattlesnakes. (1) It has been suggested that scent-trailing of lipid-based pheromones left by females is an integral part of snake mate location. (2) Because many snakes are long-lived (some >25 years) and have a capacity for spatial memory, it is likely that males can use prior experience to remember female locations. (3) Males might use an efficient search strategy by moving in a pattern that will maximize their chances of encountering a female. A fourth method, males patrolling their home range for females, is suggested by movements made by some male sidewinders. Individuals of both species were tracked using radiotelemetry. I describe the movements made by males that brought them in contact with females. I also discuss various aspects of sidewinder spatial biology and their relevance to mate-location methods. In addition, I developed an individual-based, spatially explicit simulation of mate-location methods using parameters appropriate for sidewinders. Each hypothesized mate-location method is compatible with at least some of the data. As sidewinder males were able to follow female trails for >100 m, it is clear that trail following is an important mate-location method that is likely used in conjunction with the other methods. Thus, I think males are searching for female trails rather than for females themselves. In the model, both prior experience (with map-and-compass navigation) and efficient searching (straight-line) performed well, with males having a >40% chance of finding a female during a search. Timber and sidewinder males might use different mate-location methods as many sidewinder movements did not appear as directed as those of timbers.
Advisors/Committee Members: Hetherington, Thomas E.
Keywords: timber rattlesnake, Crotalus horridus, sidewinder rattlesnake, Crotalus cerastes, mate-location behavior, mate-search behavior, spatial ecology
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20.
Criswell, Joni M.
Multimodal Communication in the Panamanian Golden Frog (Atelopus zeteki).
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2008, Ohio State University
► Animals may combine different types of signals (e.g. acoustic, visual, etc.) for…
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▼ Animals may combine different types of signals (e.g. acoustic, visual, etc.) for multimodal communication. Anuran amphibians (frogs and toads) are well known for their use of acoustic signals in communication. Some anurans also may use visual signals for this purpose. The genus Atelopus (family Bufonidae) produces conspicuous movements of the forelimb and forefoot (semaphores) and provides an excellent opportunity to study multimodal (acoustic and visual) communication in an anuran amphibian. Results of experiments using model frogs that can produce semaphores suggest that vocalizations and semaphoring actions do indeed function together in biomodal communication in A. zeteki. Target males produced significantly more behavioral responses when acoustic and visual signals were combined compared to signals presented individually. Results of these experiments suggest that semaphores may be important in providing information on the position of males. Data suggest that A. zeteki (which lacks a tympanic middle ear) is relatively ineffective at localizing sound sources, and that visual semaphore signals may facilitate the location of a vocalizing territorial male. Although semaphores occur in communication in A. zeteki, male frogs responded almost equally well to any type of model motion and not just the specific semaphore action. The semaphore is a modified stepping action, and potentially represents an exaptation for functioning in territorial communication occurring between resident and intruding males. Studies examined the pattern of co-occurrence of semaphores and pulsed vocalizations in male A. zeteki. Signals were more likely to be followed by the same type of signal, and time delays between signals were quite variable. Analysis of the pattern of co-occurrence of semaphores and vocalizations did not provide any additional insight into the role of these signals in multimodal communication. Field observations established that juvenile A. zeteki also actively semaphore. In fact, semaphoring rates of juveniles were significantly higher than those of adults. However no clear function of juvenile semaphoring was apparent from the field observations. Tests also examined the potential use of other types of visual signals (vocal sac inflation and body color pattern) in this species. However, no evidence was found that such potential visual signals modify the territorial behavior of male A. zeteki.
Advisors/Committee Members: Hetherington, Thomas.
Subjects: Behaviorial sciences; Biology; Zoology
Keywords: multimodal communication, multimodal signaling, visual signaling
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21.
Datwyler, Shannon Lynn.
Evolution and dynamics of hybridization in Penstemon subgenus Dasanthera (Scrophulariaceae S.L.).
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2001, Ohio State University
► Penstemon subgenus Dasanthera is a small group of 16 taxa distributed at…
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▼ Penstemon subgenus Dasanthera is a small group of 16 taxa distributed at high elevations in western North America. Hybridization is common in the subgenus when two or more species occur in sympatry. In this study, I examined evolutionary trends and the importance of hybridization and gene flow to the evolution of the subgenus. Phylogenetic relationships among members of Penstemon subgenus Dasanthera were assessed using ITS and matK sequence data, and inter-simple sequence repeat (ISSR) markers to elucidate biogeographic relationships and morphological trends in the subgenus. These data support previous hypotheses suggesting that the Cascade-Sierra Nevada lineage is derived from the northern Rocky Mountain lineage. Furthermore, there is a shift in growth form from deciduous perennials to evergreen, woody subshrubs concurrent with migration to the Cascade-Sierra Nevada mountains. Within the Cascade-Sierra lineage, P. newberryi and P. rupicola display a series of floral shifts that may represent adaptations for hummingbird pollination. The molecular data presented here also demonstrate the utility of dominant marker data for reconstructing phylogenetic relationships among closely-related species.To examine the potential outcomes of hybridization in the subgenus, ISSR and morphological markers were used to assess hybrid zone structure and patterns of gene flow between Penstemon davidsonii and P. rupicola on Wizard Island in Crater Lake National Park, Oregon (USA). On Wizard Island, a hybrid zone was found on the southwest portion of the island, in addition to unintrogressed populations of both species throughout the island. I surveyed three hybrid subpopulations from different localities in the hybrid zone to examine population structure throughout the hybrid zone. In each subpopulation, plants were categorized based on morphological characters diagnostic for P. davidsonii and P. rupicola. Using molecular data, the proportion of P. davidsonii-typical and P. rupicola-typical ISSR bands was calculated for each putative hybrid. Comparisons were made between hybrid categories and unintrogressed populations of P. davidsonii and P. rupicola using an approximation of Fisher's Exact Test to test for directionality of gene flow. These results indicate an asymmetrical pattern of gene flow and the potential for introgressive hybridization in these species. The observed asymmetry in the pattern of gene flow on Wizard Island could be the result of either endogenous selection pressures, in the form of pre-pollination barriers (ethological isolation) or post pollination barriers (pollen-tube growth rate or seed-siring ability), or exogenous selection in the form of differential fitness of hybrids in hybrid zones. I tested for differences in both pollinator visitation rates and pollinator behavior during visitation, and differential seed siring ability for P. davidsonii and P. rupicola on the observed pattern of gene flow on Wizard Island. Although the same suites of pollinators visit both P. davidsonii and P. rupicola, the frequency of visitation varies between the two species. Penstemon rupicola is visited primarily by pollen-collecting insects, including syrphid flies and sweat bees, that probably do not serve as effective pollinators, whereas P. davidsonii is visited primarily by leafcutter bees that may be good pollinators. From these studies, it is not clear how pollinator visitation affects gene flow in hybrid zones. Fruit set and seed set data demonstrate that P. rupicola shows a greater seed-siring ability relative to P. davidsonii for heterospecific crosses. However, seed germination rates were higher for P. davidsonii than for P. rupicola for all cross types, and highest for heterospecific crosses. These results suggest that P. davidsonii serves as a better maternal parent with regard to seed germination. The data presented suggest that the factors influencing hybrid zone structure on Wizard Island are complex, and probably include a combination of pre-pollination barriers, post-pollination barriers, and selection for fitness traits in the hybrid zone.
Advisors/Committee Members: Wolfe, Andrea D.
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22.
Dodenhoff, Danielle J.
AN ANALYSIS OF ACOUSTIC COMMUNICATION WITHIN THE SOCIAL SYSTEM OF DOWNY WOODPECKERS (PICOIDES PUBESCENS).
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2002, Ohio State University
► In contrast to many avian species, woodpeckers use both non-vocal and vocal…
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▼ In contrast to many avian species, woodpeckers use both non-vocal and vocal signals for territorial advertisement. Males and females used these signals at similar overall rates (signals hour-1), but their drum rates (drums hour-1) varied over six breeding stages. Results of neighbor-stranger playback experiments indicated downy woodpeckers were able to recognize individuals by rattle and pik calls, but failed to express a differential behavioral response between neighbor and stranger drums. Downy woodpeckers have been documented to raise their young in monogamous pairs. However, I observed at four of thirteen cavities a female downy woodpecker helping a monogamous pair during the 1998-2001 breeding seasons, Kraus Woods, Delaware Co, OH. I used multilocus minisatellite DNA fingerprinting to test for relatedness of individuals within groups. The average proportion of bands shared between females and helpers was 0.22, while the average proportion of bands shared between males and helpers was 0.41. The proportion of bands shared between mates, and between males and non-mated, non-helper females was 0.15. Primary breeding females were present within the territory the previous year, but primary breeding males were not observed the previous year. I recorded and analyzed acoustic features of pik calls, rattle calls and drums from color banded downy woodpeckers during the 1998-2001 breeding seasons. Using discriminant function analysis, there was sufficient variability between individuals to correctly classify individuals by their drum or pik calls, but rattle calls had the highest correct classification of individuals. The frequency characteristics of rattle calls varied between individuals, while the temporal characteristics varied between breeding stages. The some of the frequency parameters of the rattle call significantly changed between the two years sampled. The weaker response by mates to a mate’s call of the previous year indicated changes in call characteristics between years did change the how the calls were perceived by individuals.
Advisors/Committee Members: Nelson, Douglas A.
Subjects: Biology, Zoology
Keywords: acoustic communication, downy woodpecker, individual recognition, nest helpers, sound analysis, picidae
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25.
Elliott, Jennifer Theresa.
Territorial defense and mate attraction in isolated and social white-breasted nuthatches (Sitta carolinensis): tests of stochastic dynamic programming models.
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2005, Ohio State University
► Stochastic dynamic programming (SDP) models have been used to examine the trade-off…
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▼ Stochastic dynamic programming (SDP) models have been used to examine the trade-off dynamics of survival- and reproduction-promoting behaviors in birds during the non-breeding season. The models assume that dawn and dusk choruses are components of adaptive daily routines of singing and foraging under unpredictable environmental conditions. I examined predictions from SDP models using white-breasted nuthatches (Sitta carolinensis). First, I performed an observational study where I observed nuthatch pairs isolated in small woodlots (isolated pairs) or in large woodlots where several pairs resided (social pairs). I was interested in whether nuthatch vocalizations followed patterns predicted by SDP models, and whether there were differences between vocal and other behaviors of social and isolated nuthatch pairs. I found that while nuthatch vocalizations were as predicted by the models, especially song which peaked at dawn and dusk, foraging did not occur as predicted. Social environment of the birds appeared to influence behaviors, as isolated pairs called and sang less than social pairs, and isolated females foraged more than social females. In the second component of my dissertation, I performed a mate-removal experiment to investigate hypotheses from SDP models. I found a trade-off between singing and foraging, and this trade-off changed over the winter. Upon removal of a mate, males increased the frequency of two song types. My results did not support predictions regarding patterns of singing and foraging, as male song peaked at dawn and showed a decline throughout the day, while foraging peaked at dusk. In the third component, I investigated how nutritional state influences mate-attraction and foraging behaviors of white-breasted nuthatches. I removed the female of nuthatch pairs to induce males to sing at dawn. Then each male was caught and subjected in captivity to two feeding regimes, ad libitum food or food-deprivation for two hours prior to dusk. Upon release at dawn, males sang more type I whinnies when well fed compared to when food-deprived. In late winter, males sang more type II whinnies when well fed. Well-fed males tended to forage more and rest less. White-breasted nuthatch mate-attraction and foraging behavior appear to be state-dependent.
Advisors/Committee Members: Grubb, Thomas C.
Subjects: Biology, Ecology
Keywords: foraging; whinnies; WHITE-BREASTED NUTHATCHES; birds
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26.
Field, Kristin L.
Effects of sex ratio on ontogeny of sexual behavior and mating competence in male guppies, poecilia reticulata.
Degree: PhD, Evolution, Ecology, and Organismal Biology, 2004, Ohio State University
► Early social interactions can shape future reproductive behavior, which has been well…
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▼ Early social interactions can shape future reproductive behavior, which has been well studied in organisms with parental care (e.g., sexual imprinting in birds). Evidence suggests that socially mediated behavioral development can occur also in species without parental care or during stages following independence from parents. I discuss implications of “developmental ecology,” a new conceptual framework that extends the classic imprinting paradigm to incorporate interactions among group members as being potentially important for individual behavioral ontogeny (Chapter 1). I conducted three laboratory experiments to determine whether social group composition could produce different behavioral trajectories in male guppies, Poecilia reticulata, and whether these behaviors persist with new social experience. For each experiment, males were tested in novel social environments following maturation under different rearing conditions. Maturation in all-male groups induced male-male courtship, which continued in mixed-sex groups (Chapter 2). Further, males that had already developed typical heterosexual behavior tended to increase male-directed courtship after experience in all-male groups. In order to determine whether socially inducible same-sex courtship affected reproductive competence, males reared in all-male or mixed-sex groups were given the opportunity to breed (Chapter 3). This experiment did not detect any difference between numbers of offspring produced by males that exhibited same-sex courtship in early environments compared to males that had always courted females. Thus, data did not support the hypothesis that socially mediated preference for the sex to which males direct courtship reduces mating competence later in life. More realistic, yet still biased, sex ratios promoted differences in behavioral patterns in males, which disappeared following new experience in even sex ratios (Chapter 4). This experiment suggested that maturation with other males might be beneficial for future encounters with potential mates. Overall, this project provides evidence that group composition can promote the development of different patterns of sexual behavior and that some, but not all, trajectories may be modified with new experience. Although these results were revealed under artificial conditions, they provide a starting point from which to base ecologically relevant studies, and they have implications for captive populations used in behavioral studies and conservation programs.
Advisors/Committee Members: Waite, Thomas A.
Keywords: developmental ecology; sex ratio; behavioral plasticity; phenotypic plasticity; cowbirds (Molothrus ater); early social environment; imprinting; mate choice; social context
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27.
Flower, Charles Elliot.
Seasonal carbohydrate allocation in Big Tooth Aspen (Populus Grandidentata Michx.) and Northern Red Oak (Quercus Rubra L.) from northern lower Michigan.
Degree: MS, Evolution, Ecology, and Organismal Biology, 2007, Ohio State University
► Forest carbon storage in the upper Great Lakes displays considerable interannual variability,…
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▼ Forest carbon storage in the upper Great Lakes displays considerable interannual variability, which is largely climate dependant. Annual net ecosystem production (NEP) at the University of Michigan Biological Station (UMBS) in northern lower Michigan varied over 100 % from 1999-2003 (Gough et al., 2007 b). Meteorological and ecological measurements of NEP show that forest growth lags behind canopy photosynthesis, indicating that late season C uptake is stored over winter and applied to spring growth. The objective of this study was to quantify the relationship between late season carbohydrate storage and growth the following year. We tracked seasonal changes of non-structural carbohydrates (starch and soluble sugars) in leaves, twigs, stems, and coarse roots of the dominant canopy species bigtooth aspen (Populus grandidentata Michx.) and northern red oak (Quercus rubra L.) in 2005 and 2006. Seasonal variation of storage carbohydrates in both species was related to canopy photosynthesis, reproductive events, and leaf phenology. In 2005, we observed an inverse correlation between spring twig starch and soluble sugar concentrations in Q. rubra, suggesting a conversion of starch to soluble sugars. During leaf out, Q. rubra experienced a >50 % and >20 % depletion of starch in coarse roots and stems, respectively. It was this early season reallocation of C stored in reserve organs that fueled spring growth, leaf production, and acorn swelling. Likewise, in 2005, P. grandidentata exhibited an inverse correlation between stem starch concentrations and twig soluble sugar and starch concentrations, suggesting a reallocation to spring growth and leaf production. In 2006, P. grandidentata root bark exhibited a strong depletion of soluble sugars during the period of biomass growth. Furthermore, in both 2005 and 2006, starch concentrations in P. grandidentata root bark were significantly lower prior to the growing season compared to after the initiation of growth suggesting a seasonal reloading during the photosynthetic period. A gradual accumulation of daytime soluble sugars in leaf tissue of Q. rubra and P. grandidentata over the growing season also was observed. Furthermore, interannual variation in tree growth appears correlated with non-structural carbohydrate concentrations at the end of the previous growing season.
Advisors/Committee Members: Curtis, Peter S.
Keywords: Carbohydrates; Seasonal Variation; Carbon Allocation; Oak; Aspen
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28.
Fries, Anthony Charles.
The molecular evolution of mitochondrial oxidative phosphorylation genes in the Order Passeriformes.
Degree: MS, Evolution, Ecology, and Organismal Biology, 2009, Ohio State University
► Differences in organismal life-history characteristics are often related to variation in an…
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▼ Differences in organismal life-history characteristics are often related to variation in an organisms’ energy expenditure. For example, tropical bird species show a significantly slower “pace of life” in terms of increased longevity, reduced fecundity and faster maturation when compared with temperate species and this slower pace is correlated with a reduced basal metabolic rate (BMR). Differences in BMR could have a genetic basis yet the mechanisms governing energy expenditure remain unclear. Genes encoding proteins involved in crucial energetic pathways present logical candidates to explore the role of selection as a cause of energetic differences between species. The distribution of certain bird families in both tropical and temperate environments offers a unique opportunity to study the molecular evolution of these physiological adaptations through paired comparisons of mitochondrial DNA evolution among confamilial species. Here, I explored the role of evolution of mitochondrial proteins as a genetic cause for variation in mass-organismal energy expenditure by examining the role of selection on the 13 mitochondrial genes encoding proteins involved in the oxidative phosphorylation system (OXPHOS). I sequenced the OXPHOS mitogenome of 14 species of birds from the Order Passeriformes in paired confamilial groupings from both temperate and tropical environments and analyzed the molecular evolution of these genes as well as how the amino acid differences I observed may influence life-history traits between the regional groupings. Overall, I found an overwhelming signature of purifying selection operating on these genes across each complex of the OXPHOS system. However, variation in the level of functional conservation does vary between the ND and CO OXPHOS complexes. In addition I found 26 sites with elevated dN/dS ratios that occur in functionally important regions but do not show patterns of substitutions consistent with a role in metabolic governance. Therefore, the evolutionary history of oxidative phosphorylation genes in the mitochondrial genome of passerines does not suggest that amino acid substitution patterns between confamilial species influences differences in energy expenditure and that these genes exhibit significantly high levels of purifying selection that varies between OXPHOS complex regions.
Advisors/Committee Members: Gibbs, H. Lisle.
Subjects: Biology; Genetics; Molecular biology
Keywords: Evolution, birds, mitochondria, positive selection, oxidative phosphorylation
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29.
Frost, Paul Christopher.
Zooplankton in Western Lake Erie: before and after Zebra Mussels.
Degree: MS, Evolution, Ecology, and Organismal Biology, 1997, Ohio State University
► Zebra mussels (Dreissena polymorpha) constitute a threat to western Lake Erie's sport…
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▼ Zebra mussels (Dreissena polymorpha) constitute a threat to western Lake Erie's sport fisheries through their reported effects on phytoplankton and zooplankton. This project tested whether phytoplankton and zooplankton communities changed after the 1987 establishment of Dreissena into western Lake Erie.Previous researchers predicted zebra mussel grazing would depress phytoplankton and zooplankton abundance in near-shore and shallow waters of Lake Erie. Spatial patterns of phytoplankton and zooplankton abundance from samples taken in 1995 did not coincide to those predicted to be produced under the influence grazing dreissenids. In addition, zooplankton biomass in 1995 after Dreissena's introduction was lower than estimates from 1970 but remains equivalent to estimates from 1983-84. Together these results indicate that pelagic phytoplankton and zooplankton may not be controlled just by zebra mussels but instead are simultaneously influenced by multiple factors, including those associated with external nutrient loading and lake size.We tested whether crustacean production (mg m3 d-1) has declined since Dreissena's introduction into western Lake Erie. Because comparable crustacean production estimates from the 1970's and 1980's were unavailable, we used regressions, derived from current results, to back calculate historical productivity. Zooplankton production was highly correlated (r2 = 0.96-0.99) to crustacean biomass and water temperature, providing an effective method to estimate historical production using only these two variables. Consequently, we estimated pre-Dreissena, crustacean productivity using historical biomass and water temperature data obtained from previous studies of western Lake Erie. Levels of crustacean production, 1995-6, were well below maximum 1970 and 1975 values, a period characterized by high phosphorus loading and no zebra mussels. Current zooplankton productivity does appear equivalent to that found near the Bass Islands in 1988-9, a period of reduced phosphorus and very low zebra mussel abundance. No evidence in this study indicates that zooplankton have dramatically declined since Dreissena's colonization.
Advisors/Committee Members: Culver, David A.
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30.
Fussman, Jennifer Lynn.
Foraging ecology of Kirtland's Warblers in managed and natural breeding habitat.
Degree: MS, Evolution, Ecology, and Organismal Biology, 1997, Ohio State University
► This study examines prey availability as a factor influencing breeding habitat selection…
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▼ This study examines prey availability as a factor influencing breeding habitat selection by Kirtland's Warblers (Dendroica kirtlandii), and characterizes the foraging behavior of this endangered species. Kirtland's Warblers nest on the ground in early-successional jack pine forests in northern Lower Michigan. The species may reject old jack pine stands for nesting due to decreased prey density in lower branches and ground vegetation of old stands. Insects were captured in young and old nesting habitat and in mature jack pine too old to be attractive for breeding, and birds were observed foraging in young and old nesting habitat. Insect biomass in low vegetation was less in old nesting habitat than in young nesting habitat, and was much less in mature habitat. Kirtland's Warblers in old nesting habitat did not forage higher than those in young nesting habitat, suggesting that the decrease in insect biomass in old nesting habitat is not great enough to affect the birds. Managed plantations and natural wildfire-regenerated jack pine stands were very similar in terms of insect abundance, diversity, and distribution, and warbler behavior. Warblers foraged most often on jack pines, but also used ground vegetation and pin oak trees as foraging substrates. The proportion of foraging attempts in oak varied widely among stands, suggesting that warblers use oak in proportion to its availability. Female Kirtland's Warblers foraged significantly lower than males, following a general trend for species of parulid warblers.
Advisors/Committee Members: Grubb, Jr., Thomas C.
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