Master of Science (MS), Ohio University, 2024, Biological Sciences (Arts and Sciences)

The persistence of a population depends on its ability to adapt to an array of ever-changing conditions. When genetic diversity is lost, as is the case when a population experiences a population bottleneck, adaptation by natural selection can be impeded due to a decrease in evolutionary potential—a population's ability to evolve in response to a changing environment. Thus, by studying populations' genetic recovery after bottleneck events, we can help conservation biologists promote the viability of affected populations. The Lake Erie Watersnake (Nerodia sipedon insularum), a subspecies of Common Watersnake (N. sipedon) restricted to the Lake Erie islands, underwent a severe bottleneck at the end of the 20th century followed by a rapid recovery entering the 21st century, making it well-suited for such a study. To investigate current patterns of genetic diversity in these populations following the bottleneck, genetic samples from Lake Erie Watersnakes were collected during June 2022 from 16 localities on 11 islands. Samples from the nearby mainland subspecies, the Northern Watersnake (N. s. sipedon), were also collected from 10 localities around the perimeter of the western basin of Lake Erie. Using a next-generation reduced representation sequencing method known as ddRAD, I assembled a dataset of 10,131 biallelic SNPs and estimated several standard measures of genetic variation within and between the sampled populations. Genetic variation within the Lake Erie Watersnake was higher than expected given its recent demographic history, with similar levels of heterozygosity across all island and mainland populations and low levels of inbreeding. Using the Bayesian method implemented by BayesAss3-SNPs, I found evidence of contemporary gene flow between populations. I also explored population structure using several methods, finding only a single inferred ancestral group among the sampled populations. Finally, a Mantel test for isolation by distance (IBD) showed a strong po (open full item for complete abstract)

Committee: Shawn Kuchta (Advisor); Diego Alvarado-Serrano (Advisor); M. Raquel Marchán-Rivadeneira (Committee Member); John Schenk (Committee Member); Willem Roosenburg (Committee Member) Subjects: Biology; Conservation; Evolution and Development; Genetics; Wildlife Conservation; Zoology

PhD, University of Cincinnati, 2018, Arts and Sciences: Biological Sciences

Ecological models that attempt to unite biodiversity and biogeography concepts have been used to describe and predict the distribution and abundance of species. Mechanistic ecological models theorize that demographic and distributional dynamics affect the success and persistence of the species making up the community. The community-level metapopulation model is one such model and assumes that the species at a particular island are determined by species-specific extinction and colonization rates which vary with island area and isolation from the mainland. In this dissertation, I tested the extent of the model's ability to capture the underlying mechanisms shaping the community and compare that to another mechanistic model and a null model. I used simulated island-mainland systems with varying number of islands, island sizes, and distances to mainland along with mainland communities with varying numbers of species and densities. I found that there was a limited range of system and community variables where the community-level metapopulation model could accurately describe the species richness on islands created using metapopulation dynamics better than the alternative models. Using these guidelines for system and community structure, I empirically tested evidence for metapopulation dynamics structuring small mammal, tree, and moth communities within an island-mainland system that fit the requirements. The community-level metapopulation model was not found to be better than a null model for describing the species richness patterns of all three functional taxa. The moth taxon was best described by the diversity of host plant species. Lastly, the descriptive ability of the community-level metapopulation model is dependent upon the accuracy of the underlying single-species model. An assumption of the metapopulation model that is often violated is the assumption of a constant density-area relationship. I incorporate a method to correct for variable density-area relationshi (open full item for complete abstract)

Committee: Stephen Matter Ph.D. (Committee Chair); Guy Cameron Ph.D. (Committee Member); Edward F. Conner Ph.D. (Committee Member); Arnold Miller Ph.D. (Committee Member); Kenneth Petren Ph.D. (Committee Member) Subjects: Ecology

PhD, University of Cincinnati, 2016, Arts and Sciences: Biological Sciences

Since the development of conservation science nearly four decades ago, leading conservation biologists have warned that human activities are increasingly setting the stage for a loss of life so grand that the mark on the fossil record will register as a mass extinction on par with the previous “big five” mass extinctions, including that which wiped out the dinosaurs 65 million years ago. The idea that a “sixth mass extinction” was in progress motivated me to explore the extent of recent extinction and the underpinning of the widely iterated statement that current rates of extinction are 100-1,000 times greater than the background rate. In Chapter 2, I show that the estimated magnitude difference between contemporary and background extinction does not align with the number of documented extinctions from which the estimates are extrapolated. For example, the estimate that current extinction rates are 100-1,000 times higher than background corresponds with an estimated loss of 1-10 named eukaryotic species every two days. In contrast, fewer than 1,000 extinctions have been documented over the last 500 years. Given this discrepancy, it may prove politically imprudent to use extraordinarily high rates of contemporary extinction to justify conservation efforts. Conservation efforts are sufficiently justified based on the proportion of habitat that has been destroyed or degraded in recent decades and the proportion of species threatened with extinction. In addition to examining the current extinction crisis, I evaluated potential mechanisms of extinction. Although mechanisms of population-level extinction and species-level extinction are well-resolved, little is known regarding mechanisms of the extinction of spatial population networks. A fascinating question that I was surprised had not been thoroughly investigated concerned potential effects of population-level extinction on surrounding populations of the same species: How does the extinction of one population affec (open full item for complete abstract)

Committee: Stephen Matter Ph.D. (Committee Chair); Thomas Crist Ph.D. (Committee Member); Edna Sayomi Kaneshiro Ph.D. (Committee Member); Eric Maurer Ph.D. (Committee Member); Kenneth Petren Ph.D. (Committee Member) Subjects: Ecology

Master of Science, University of Akron, 2014, Biology

A major obstacle to the preservation of animal populations is habitat fragmentation. Fragmentation often results in the isolation and subsequent loss of subpopulations. Gene flow determines the extent to which populations remain separated as independent evolutionary units, and thus affects the evolution of a species. Gene flow between small fragmented subpopulations can often have great effects on the species stability. If small populations are lost and there is no migration between subpopulations, recolonization of suitable habitat does not occur and the overall population declines. The loss of naturally occurring populations reduces gene flow, which may lead to genetic differentiation. This study investigated the population structure of the five-lined skink, Eumeces fasciatus, occupying what appear to be isolated sites in the fragmented landscape of Northeast Ohio. Populations in Akron were of particular interest because they exist in highly urbanized locales, and these lizards have rarely been recorded in Summit County. Additionally, there is a large gap in distribution record of the species statewide. Five polymorphic microsatellite markers were used to evaluate the gene flow between 5 different locations in Northeast Ohio. The gene flow estimates indicated that there is a significant pattern of isolation by distance (IBD). However, even across very broad geographical scales (170km), the IBD did not lead to a consequential divergence of populations. This data offers information on the genetic divergence of this species and contributes to our understanding of the larger problem of animal conservation in urban areas, as well as its relation to anthropogenic habitat fragmentation and degradation.

Committee: Francisco Moore Dr. (Advisor); Randall Mitchell Dr. (Advisor); Peter Niewiarowski Dr. (Committee Member) Subjects: Biology; Genetics; Wildlife Conservation; Wildlife Management

Master of Science, The Ohio State University, 2012, Environment and Natural Resources

Although habitat loss and fragmentation have troubled the Midwest for centuries, landscapes are once again changing profoundly as historically dominant agriculture is replaced by urban development. Urbanization alters both composition and structure of avian communities, yet little is known of the landscape level structure of bird populations. Because urban development may restrict movements of many species, changes in land use should affect connectivity and persistence of local populations that are distributed among remnant habitats. Metapopulations, which are comprised of demographically independent local sub-populations connected via dispersal, have the potential to promote long-term viability of small and isolated urban populations through rescue of sub-populations that are in decline. Such metapopulation dynamics require asynchrony in recruitment and survival rates among sub-populations. To understand the extent to which avian populations in urbanizing landscapes operate as metapopulations, I analyzed the population synchrony (spatial autocorrelation) of densities, rates of local extinction and recolonization for 16 species, and demographic growth rates (λ) for 2 species breeding in 14 mature riparian forest sites in central Ohio, USA from 2005-2011. Two scenarios were considered to be consistent with metapopulation structure, cases with (1) high negative spatial autocorrelation and high rates of extinction and recolonization, or (2) low spatial autocorrelation with high rates of extinction and recolonization. Only 3 of 16 species (19%) exhibited significant positive spatial autocorrelation across the entire study area. Only Acadian flycatchers in urban sites showed significant positive spatial autocorrelation of demographic growth rates. Furthermore, migrants and residents showed similar degrees of spatial autocorrelation (migrants r = 0.014 ± 0.0585 SE vs. residents r = 0.067 ± 0.0475 SE). Although autocorrelation did not differ significantly between resident (open full item for complete abstract)

Committee: Amanda Rodewald PhD (Advisor); Maria Miriti PhD (Committee Member); Robert Gates PhD (Committee Member) Subjects: Ecology; Environmental Science

Doctor of Philosophy, The Ohio State University, 2009, Evolution, Ecology, and Organismal Biology

Amphibians worldwide are facing declines due to habitat loss, disease, and other causes. Where habitat alteration is implicated, there is a need for spatially explicit conservation plans. I explore the potential for using geographic information systems (GIS) models of functional landscape connectivity as a reliable proxy for genetically derived measures of population isolation. I also use metapopulation models parameterized with genetic and demographic data to predict population persistence of salamanders in fragmented landscapes. I use genetic assignment tests to characterize isolation of marbled salamander (Ambystoma opacum) populations, and evaluate whether the relative amount of modified habitat around breeding ponds is a reliable indicator of isolation. Forest is consistently associated with decreased population isolation, whereas agriculture and development are associated with increased isolation. Models that include these variables and pond size explain 65-70% of variation in isolation across sites, and 30-45% of variation in isolation in related ambystomatids in other regions. Additionally, I address whether local populations constitute metapopulations, and estimate viability of whole metapopulations versus local populations. Estimation of persistence is strongly altered by the incorporation of genetic dispersal estimates. All populations persist using a dispersal-distance function; however, estimating dispersal with genetic data results in the loss of some or all local populations within a 100-year simulation. Overall, I conclude that anthropogenic habitat change appears to strongly influence population isolation, with agriculture being the most important isolating factor. Small, isolated populations have little probability of long-term persistence; networks of protected areas may be the best approach to conserving ambystomatid salamanders.

Committee: H. Lisle Gibbs PhD (Advisor); Laura S. Kubatko PhD (Committee Member); Amanda D. Rodewald PhD (Committee Member) Subjects: Biology; Ecology

Doctor of Philosophy, The Ohio State University, 2007, Evolution, Ecology, and Organismal Biology

I related environmental parameters to the demographics of permanent resident avian cavity nesters in Crawford County, OH. With the arrival of West Nile virus (WNV), I collected blood from selected avian species during 2002-2005 and found no Carolina chickadees (Poecile carolinensis) tested positive for WNV antibodies, while northern cardinals (Cardinalis cardinalis) had several individuals test positive for WNV antibodies. Individuals of some species were found to lose their antibodies over time. Differences in seroprevalence of Carolina chickadees and northern cardinals prompted an experiment to determine if such differences could be the result of anti-mosquito behavior by birds. Mosquitoes took the same number of blood meals from Carolina chickadees and northern cardinals. Two demographic parameters measured were reproductive success and annual survival. Reproductive success of Carolina chickadees nesting in natural cavities and house wren (Troglodytes aedon) abundance increased and decreased, respectively, with woodlot area. House wrens appeared to be the primary reason for differences in chickadee reproductive success related to woodlot area. Survival varied among years in Carolina chickadees and tufted titmice (Baeolophus bicolor), but was constant in white-breasted nuthatches (Sitta carolinensis) and downy woodpeckers (Picoides pubescens) over the study period, 1994-2005. West Nile virus may have had the greatest impact on tufted titmice. Winter severity appeared to be important for Carolina chickadee survival, while no models were useful in explaining tufted titmouse survival. White-breasted nuthatch survival was higher in isolated woodlots than in riparian sites, while downy woodpecker survival increased with woodlot area and was highest in riparian sites. Eastern screech owl (Megascops asio) survival appeared to be greatly influenced by WNV. Owls banded prior to the WNV outbreak in 2002 were never captured again. Finally, I matched various characteristics o (open full item for complete abstract)

Committee: Thomas Grubb (Advisor) Subjects: Biology, Zoology

Doctor of Philosophy, The Ohio State University, 2003, Evolution, Ecology, and Organismal Biology

I examined three aspects of forest fragmentation to determine how they impact resident and migrant bird species. The first aspect was the relationship between habitat patch area and species presence and richness. I performed an observational study along riparian woodlands to determine the abundance and distribution of bird species and avian guilds. Woodland area better predicted bird species presence than woodland width. In addition, the probability of detection was positively correlated with woodland area for 11 bird species and negatively correlated with woodland area for eight species. A management simulation of woodland riparian corridor width indicated that current management suggestions were inadequate to provide habitat for a variety of Neotropical woodland migrant bird species. In the second aspect of my research, I examined the ability of two species of birds to supplement their habitat requirements by incorporating disjunct habitat patches on either side of a watercourse into a single territory. I found the probability of eastern wood-pewees (Contopus virens) crossing water gaps to reach simulated singing conspecific to be negatively associated with vegetation gap width. Red-eyed vireos (Vireo olivaceus) demonstrated no significant trend. However, the strength of red-eyed vireo vocal responses after crossing was inversely proportional to the width of waterway. These results suggest that species may differ in their response to simulated conspecific vocalization, and that water gaps less than 30 m wide may not hinder all avian species from crossing to reach playbacks, but may still curtail territorial responses. The third aspect of my work was to determine the ability of a species to colonize empty habitat patches. I simulated patch extinction events by removing Carolina chickadees (Poecile carolinensis) from woodland fragments. I found that chickadees arrived sooner in woodlots connected to other woodland by habitat corridors. I also found that individual c (open full item for complete abstract)

Committee: Thomas Grubb (Advisor) Subjects: Biology, Ecology

PHD, Kent State University, 2013, College of Arts and Sciences / Department of Biological Sciences

The clam shrimp genus Eulimnadia is a cosmopolitan taxon comprising approximately 54 species (Brtek 1997; Martin & Belk 1989; Roessler 1990; Pereira & Garcia 2001; Durga-Prasad & Simahachalam 2004; Simahachalam 2004, 2005; Timms & McLay 2005; Babu & Nandan 2010; Rogers et al. 2010). It is the most speciose spinicaudatan genus and is of particular interest due to its exhibition of an extremely rare mating system - androdioecy (Weeks et al. 2006; Weeks 2012). Androdioecy is the co-occurrence of males and hermaphrodites in populations in the absence of true females. The evolutionary benefits of such a makeup are unclear. Males can play an important role in hermaphroditic populations to avoid inbreeding depression and to supplement male allocation in sperm-limited hermaphrodites (Wolf & Takebayashi, 2004). Yet males have difficulty invading hermaphroditic populations because of reduced mating opportunities due to the ability of hermaphrodites to self-fertilize. This requires males to more than double their mating success (i.e., successful fertilizations) relative to hermaphrodites to effectively invade the population. Theoretical models of mating system evolution that have incorporated these constraints show that androdioecy is unlikely to evolve, and that those few cases found in nature are likely to be short-term, transitional populations that are evolving from hermaphroditism to dioecy, or vice versa (Lloyd, 1975; Charlesworth, 1984). The rarity of androdioecious mating systems was exemplified when Charlesworth (1984) showed most of the species described as androdioecious to that date were actually functionally dioecious. Pannell (2002) reviewed six plant species that are truly androdioecious, and Weeks et al. (2006) reviewed androdioecy in the animal kingdom and documented this mating system in one chordate, seven nematodes, and 28 crustacean species. Weeks et al. (2006) present four additional androdioecious crustaceans. Within the Crustacea, the clam shrimp g (open full item for complete abstract)

Committee: Stephen Weeks (Advisor); Walter Hoeh (Committee Co-Chair); Lisa Park (Committee Member); Alison Smith (Committee Member) Subjects: Biology; Ecology