Master of Science, University of Toledo, 2022, Biology (Ecology)

Grass Carp (Ctenopharyngodon idella) is a large, invasive herbivore that may harm Lake Erie's ecology and economy. A large-scale, multi-agency collaboration to remove as many Grass Carp as possible from the basin has increased effort every year since 2017. However, removal has fallen short of the Lake Erie Committee's goal of 390 fish per year since its enactment. A biological indicator, such as mortality, can assess changes in population demographics and may provide a more sensitive way than total catch to determine whether control efforts are effective. I modeled mortality rates from 2014-2021 using a multilevel linear model to estimate annual mortality, relative to the overall mean, from the entire time-series of data. The data were grouped by the number of fish in each age class within each year. This analysis suggests that mortality rates increased after 2017. Positive correlations between mortality and the number of fish harvested per year suggest that removal may be driving increases in the mortality rate. This research directly addressed fishery managers needs to better understand Grass Carp population dynamics and supports the adaptive management framework identified in the Lake Erie Grass Carp Adaptive Response Strategy.

Committee: Christine Mayer (Committee Chair); Patrick Kocovsky (Committee Member); William Hintz (Committee Member); Mark DuFour (Committee Member) Subjects: Ecology

Master of Science (M.S.), University of Dayton, 2017, Biology

Terrestrial-to-aquatic linkages are an important vector for the transfer of nutrients from one habitat to another. Therefore, the biology of headwater streams is strongly influenced by the surrounding terrestrial riparian vegetation. Amur honeysuckle (Lonicera maackii) is an invasive shrub that thrives in disrupted habitats including stream riparian zones. Although, extensive research has shown the detrimental effects of L. maackii on terrestrial systems, little research has been done on how cross boundary subsidies such as leaves and woody debris are impacted by the dense and often overarching L. maackii invasion in headwater stream riparian zones. Therefore, the aim of this study is to understand the influence of a gradient of L. maackii density in riparian habitats on the contribution of organic subsidies in stream systems in Southwestern Ohio. Across the established gradient of L. maackii invasion leaf litter biomass, fruit biomass, falling twig biomass, terrestrial and aquatic fine woody debris (0.5-9.9 cm diameter) volume and count, and terrestrial and aquatic coarse woody debris (>9.9cm diameter) volume were accessed. We hypothesized that sites with a higher density of L. maackii would have a decreased total leaf litter biomass deposition due to the dense overarching riparian L. maackii over the stream increasing the potential of litter getting caught in the canopy. Additionally, based on the intentionally established gradient of sites we also expected L. maackii leaf biomass to increase as invasion intensity increased. Lastly, we hypothesized that woody biomass in the form of both fine and coarse woody debris would decrease along the invasion gradient due to the dense shrub architecture. The only significant treatment effects in regards to site were found for L. maackii only leaf litter biomass (p = <0.0001), count of aquatic fine woody debris (p = 0.03292), and fruit biomass (p = 0.00597). In all cases the observed treatment effect did not follow our hypot (open full item for complete abstract)

Committee: Ryan McEwan Ph.D. (Committee Chair); Albert Burky Ph.D. (Committee Member); Mark Nielsen Ph.D. (Committee Member) Subjects: Biology; Ecology

Master of Science in Environmental Science, Cleveland State University, 2017, College of Sciences and Health Professions

Ranunculus ficaria L., an ephemeral perennial invasive plant brought over from Europe, is becoming widespread throughout the Northeastern United States. This herbaceous buttercup is able to create extensive dense mats that limit native species growth. Taking advantage of an early growing season and rapid reproduction rates, this species can create dense monocultures, which threatens native communities and ecosystems. Elimination of native spring ephemerals results in decreased biodiversity. A better understanding of how R. ficaria responds to site characteristics is needed to prioritize management efforts toward high-risk sites. Ranunculus ficaria abundance and reproductive output (seed, bulbil and tuber production rates) were examined in plots spanning a disturbance gradient away from a river. Site characteristics (PAR, aspect, soil pH, soil moisture, texture and nutrient content) were investigated to examine their role in plant performance. I hypothesized that soil characteristics (pH and nutrient availability) drive R. ficaria plant performance; specifically I expected higher biomass and reproductive output to be associated with higher soil pH. I also expected reproductive output and R. ficaria biomass would be highest in moist floodplain at intermediate distances from rivers. Many soil nutrients and characteristics were significantly related to biomass and reproductive output; specifically phosphorus, calcium and LTI (Lime Test Index) all showed significantly positive relationships with plant biomass and bulbil counts, while soil pH was significantly positively related to biomass. Bulbil and tuber counts were significantly higher in soils of high percent silt. These findings suggest that soil characteristics (pH, texture) and nutrients (P, Ca) are strongly linked to plant performance, supporting my hypothesis. Reproductive output and R. ficaria biomass were not significantly greater at intermediate distances from rivers, in contrast to my hypothesis. A (open full item for complete abstract)

Committee: Emily Rauschert Ph.D. (Advisor); Julie Wolin Ph.D. (Committee Member); Pete Clapham Ph.D. (Committee Member) Subjects: Ecology; Environmental Science

Master of Science, University of Akron, 2015, Biology

Past research suggests that avian nests in exotic shrubs are more susceptible to depredation and represent an ecological trap. In this study, we explore the relationship between exotic plants, nest predation, and nest-site selection to test the hypothesis that nests in exotic plants are more susceptible to depredation then nests in native plants. We used the Hooded warbler (Setophaga citrina), a forest-understory obligate, as a model species for this study. In 2013 and 2014, we monitored nests in forest parks in Summit County, Ohio. In these parks, Hooded warblers primarily selected exotic plants for nesting sites (73% of 133 nests). The preferred species for nesting sites for Hooded Warblers were Rosa multiflora, the genus Lonicera, Lingustrum vulgare, and native saplings (24%, 13%, 27% and 26% respectively). We analyzed the influence of nest-site choice on nest success at the nest and patch scale, and found no relationship between nesting success and exotic species. Similar to previous studies, we found no evidence that typical habitat measurements, except for nest height influenced. However, we found that nests initiated later in the season were more likely to survive to fledging. Including clutch initiation date into our model of nest fate suggested that nests placed in exotic shrubs had worse nesting success than nests placed in native plants. However, this pattern switched mid-way through the season to suggest that nests within exotic shrubs were more successful than nests in native plants. The natural nest experiment suggested a pattern of differential nesting success between nests in privet and rose. Recognizing this pattern we set out to test it with an artificial nest experiment. The results of this experiment showed there is a significantly higher chance of a nest fledging from rose than nests in privet. All together, these results do not support the hypothesis that nests in exotic plants are ecological traps and are more susceptible to depredation. In d (open full item for complete abstract)

Committee: Randall Mitchell Dr. (Advisor); Gregory Smith Dr. (Advisor); Matthem Shawkey Dr. (Advisor) Subjects: Ecology

Master of Science in Biological Sciences, Youngstown State University, 2010, Department of Biological Sciences and Chemistry

A biological community can become invaded by non-resident species when the resources necessary for establishment and growth coincide with invader propagules. There are many ecological factors that affect below- and aboveground resource availability in a community and this research integrates both spatially and temporally varying components. In a managed grassland, we measured the interactive effects of disturbance patch size (DPS), grazing intensity (GI), and soil resource availability (SRA) on the invasion success of smooth pigweed Amaranthus hybridus (L.) and velvetleaf Abutilon theophrasti (L.). Importantly, we considered two life history stages of each focal invader (i.e., emerged and established seedlings) because invasion success may depend on when resource shifts coincide with particular life history stages. Our empirical data generally support the following predictions: 1) thresholds in ISP exist across DPS, the magnitude of which increases with higher SRA levels, 2) the life history stage of the invader strongly affects ISP in smaller sized patches containing high SRA, 3) regardless of invader size, grazing effects are large in small DPSs in high SRA area 4), in the absence of grazing, SRA within a given DPS can have opposing effects on ISP. Integrating disturbance type and intensity across other ecological dimensions is important in elucidating the mechanisms of community invasibility as well as offering sound recommendations to managers of native grassland communities.

Committee: Ian Renne PhD (Advisor); Thomas Diggins PhD (Committee Member); Felicia Armstrong PhD (Committee Member) Subjects: Agriculture; Biology; Ecology; Plant Propagation

Master of Science (MS), Wright State University, 2012, Biological Sciences

Our goal was to characterize the interactive feedback between garlic mustard (Alliaria petiolata) and European earthworm species in southwest Ohio. Earthworm community composition, abundance and biomass were compared between 0.1 m2 plots of garlic mustard, cut-leaved toothwort (Cardamine concatenate), wild ginger (Asarum canadense), or no plant cover. Exotic earthworms were present in the study site. Earthworm abundance and biomass did not correlate with garlic mustard percent cover. There was a greater density of earthworms in the fall than in the spring. Worm abundance differed between garlic mustard and wild ginger plots and cut-leaved toothwort and control plots, suggesting that earthworms may prefer to be located under plants that produce high biomass. Worm biomass did not differ between the plants. There was a greater abundance of endogeic worms below all plants, while anecic worms contributed the most biomass. Our results do not support strong feedback between garlic mustard and European earthworms.

Committee: Thomas Rooney PhD (Advisor); James Runkle PhD (Committee Member); Don Cipollini PhD (Committee Member) Subjects: Biology; Ecology

Master of Science (MS), Ohio University, 2011, Environmental and Plant Biology (Arts and Sciences)

Shade-tolerant invasive plant species are threatening deciduous forest communities of the eastern United States, but their method of invasion remains unclear. We test the idea that arrival of one such species, the non-native annual grass Microstegium vimineum {Nees}(Poaceae), is facilitated by movement of humans or animals by direct observation of distributions along movement corridors over two years. Weak colonization of experimental plots shows that Microstegium is limited by seed availability, and to a lesser extent litter cover, in the absence of human or animal movement. Inconsistent extension of populations along off-road-vehicle trails, small roads, and stream sides did not indicate increased movement of seeds by vehicles, road equipment, and water in my field sites. Saturation of isolated roadside sites demonstrates that within-site colonization is very rapid relative to colonization between sites. Little extension along footpaths and horse trails implies that pedestrian and horse movements are not important mechanisms of invasion. Dispersal experiments indicate that adhesion may be a feasible dispersion technique for Microstegium vimineum, and may dictate the spatial patterns of colonization. These results suggest that Microstegium invasions are spatially hierarchical, with different mechanisms acting on different scales, and that invasion may take place in series of explosions of growth and periods of little or no growth. Management focused on controlling dispersal and focusing efforts on the local scale will be most effective at controlling the spread of this species.

Committee: Matlack Glenn PhD (Advisor); Phillip Cantino PhD (Committee Member); Harvey Ballard PhD (Committee Member) Subjects: Ecology