Master of Science, The Ohio State University, 2024, Earth Sciences

The health of Caribbean coral reef ecosystems has declined rapidly in recent decades due to climate change and local human stressors. Although there are robust data sets following the onset of large-scale monitoring in the late-1970s, less is known about reef health before this time. Furthermore, most of this monitoring work has focused on such organisms as corals, parrotfish, and echinoderms; much less is known about how changing environments are reflected in other important coral reef community members (e.g., molluscs). Reef matrix cores can help fill this knowledge gap, as they provide records of reef communities and environments over the past centuries to millennia, prior to large-scale human disturbance. To obtain a more accurate baseline of reef ecosystem structure and functioning and to track ecosystem change over the past one and a half millennia, I assessed changes in the taxonomic and functional group composition of subfossil assemblages of bivalves, gastropods, corals, and urchins preserved in 3.5 m-long cores from three reefs within the central lagoon of Belize. Bivalve and gastropod composition was assessed using relative abundance of shells, whereas urchin and coral composition was assessed using the accumulation rate of spines and coral fragments measured by weight. These cores record a shift in the dominant substrate relationship in bivalves from epifaunal to infaunal over time, which becomes most prominent in the late-1800s, indicating a loss of hard substrate (i.e., corals). Additionally, this epifaunal decline coincides with an increase in soft-substrate-indicating gastropods (e.g., Cerithium spp.) and the gorgonian coral associated bivalve Dendostrea spp. In contrast, urchin composition shows little change through the equivalent time interval, with the currently common Echinometra spp. dominating throughout the cores. These trends mirror those that have been observed previously from reef matrix cores in Caribbean Panama, as well as Belizean verte (open full item for complete abstract)

Committee: Jill Leonard-Pingel (Advisor); Loren Babcock (Committee Member); Andréa Grottoli (Committee Member) Subjects: Geological; Paleoecology; Paleontology

MS, Kent State University, 2023, College of Arts and Sciences / Department of Earth Sciences

Phyllocarid mandibles are an underutilized morphological component of phyllocarid morphology which can aid in identification at the species or genus level. Mandibles from various species of Dithyrocaris from throughout the United States were described and compared to those of Paraechinocaris punctata. Morphological characteristics from these specimens concerning denticle arrangement, crown morphology, as well as size and shape of the corpus mandibulae, revealed that significant differences exist between genera and species within the same genus. Thus, mandible morphology is shown to be useful in identification at the genus and species level.

Committee: Rodney Feldmann (Advisor); Joseph Ortiz (Committee Member); Carrie Schweitzer (Advisor) Subjects: Geology; Paleontology

MS, Kent State University, 2022, College of Arts and Sciences / Department of Earth Sciences

Faunal turnover is a pattern of diversification and extinction that occurs in taxa throughout the geologic record. Patterns of repeated faunal turnovers are referred to as faunal progression. Understanding the driving factors behind faunal progression, which may be niche partitioning, competition between groups, movement to new environments, or extinction and radiation due to environmental factors, may be key to understanding the pasts and futures of our modern fauna. Within Decapoda, clawed lobsters, podotrematous crabs, and heterotrematous crabs experienced faunal progression. These groups diversified and faced high rates of extinction in succession. The transition between podotrematous crabs and heterotrematous crabs is the most recent such turnover and is therefore of particular interest when trying to understand the potential causes of decapod faunal progression as a whole. Section Raninoida, commonly called ‘frog crabs', constitutes a major monophyletic group of crabs with podotrematous body forms, and closely follows broader trends of diversification and decline within the podotremes from the Cretaceous to the present day. Additionally, modern raninoids are highly specialized back burrowers, despite several extinct families displaying traits indicative of generalist lifestyles which would seem more likely to survive. Data on rock type, age, location, and carapace morphology for each species within section Raninoida were analyzed for trends in diversity, taxon longevity, paleoenvironment type, and paleogeographic occurrences using Microsoft Excel, Python, PAST, and ArcGIS. Paleomaps were generated to visualize type specimen occurrences and overall diversity through time. Declines in raninoid diversity aligned with mass extinction events and major climate shifts, especially those of cooling climate. Likewise, diversification within the section occurred in warm, greenhouse climates. Thus, a major factor in patterns of faunal turnover is likely to be enviro (open full item for complete abstract)

Committee: Carrie Schweitzer (Advisor); Rodney Feldmann (Committee Member); Joseph Ortiz (Committee Member) Subjects: Paleontology

Master of Science (MS), Ohio University, 2022, Geological Sciences

Type Cincinnatian strata are among the best preserved Upper Ordovician deposits in the world and record a range of depositional environments as well as various biotic and abiotic changes, making them an ideal natural laboratory in which to study biotic and abiotic processes. The most substantial biotic change in the Type Cincinnatian Series is a biotic invasion known as the Richmondian Invasion. The first pulse of the Richmondian Invasion is referred to as the Clarksville Phase (Aucoin and Brett, 2016) and is the focal point of this study which quantifies the impact the Clarksville Phase had on the ecology and diversity of the fauna of the Cincinnati basin. A suite of methods were employed to quantify the invader impact including detrended correspondence analysis, cluster analysis, rarefaction, Simpson's index of dominance, guild analysis, and comparison of environmental preferences and tolerances through time. Results indicate the Clarksville Phase had numerous impacts on the fauna of the Cincinnati Sea including modification of occupied habitat, ecospace utilization, gradient structure, community structure, community composition, and biodiversity. Habitat occupation changed considerably following the introduction of the invaders with taxa shifting both their environmental tolerances and preferences. Ecospace utilization shifted as previously low diversity guilds were filled out with novel taxa. Faunal differentiation across the depth gradient increased with the introduction of the invaders. Generic richness increased within the basin, generic evenness decreased, and community composition became more complex. The results of this study contribute to our understanding of the Richmondian Invasion and our general understanding of earth history as well as provide new insights about the potential long term ecological and biodiversity impacts of biotic invasions today.

Committee: Alycia Stigall (Advisor); Gregory Springer (Committee Member); Katherine Fornash (Committee Member) Subjects: Ecology; Geobiology; Paleoecology; Paleontology

Master of Science (MS), Ohio University, 2013, Geological Sciences (Arts and Sciences)

Changes in niche stability levels in deep time are evaluated by assessing the niche dynamics of a diverse suite of invertebrate taxa from the Late Ordovician Cincinnatian series of North America. During this interval, periodic sea-level fluctuations, storm events, and extrabasinal species invasions disrupted stable shallow-marine communities as taxa responded to both rapid and gradual environmental changes. Variations in relative niche stability through time and across clades are determined using ecological niche modeling (ENM) to produce and compare models for 11 invertebrate genera (crinoids, trilobites, bivalves, gastropods, bryozoans and corals) at high spatial and temporal resolution. The maximum entropy (Maxent) algorithm was used to generate ecological niche models for each genus for 9 time-slices across three sequences. Previous studies provided sedimentologically derived environmental layers, and geo-referenced occurrence data were compiled from primary field research augmented by published data. To evaluate niche stability, models were compared geospatially (in two-dimensional G-space), and in environmental space (n-dimensional E-space) between time-slices. Environmental parameters, which define individual niche models, were also tested for statistical dissimilarity between time-slices. These analyses were designed such that high degrees of similarity and range-overlap indicate niche stability, whereas statistical dissimilarity and low percentage range overlap indicate niche evolution. Complementary ENM studies of brachiopod species across this interval have documented higher levels of niche evolution during intervals of rapid sea-level rise and during the Richmondian Invasion. To determine if niche responses were congruent across clades, this analysis focuses on the niche dynamics of non-brachiopod taxa at the genus level and comparison of niche stability patterns between different clades, feeding styles, and at different taxonomic scales. The res (open full item for complete abstract)

Committee: Alycia Stigall PhD (Advisor); Douglas Green PhD (Committee Member); David Kidder PhD (Committee Member) Subjects: Ecology; Geology; Paleontology