The installation of marine renewable energy devices (MREDs) is progressing rapidly along many coastlines. It has been suggested that MRED arrays could provide stepping-stones for larval dispersal, mediating species range expansions or invasions. As common members of hard-substrate fouling communities and likely colonisers of MREDs, the larval dispersal processes of barnacles (Cirripedia: Thoracia) in the Firth of Lorn (Scotland) are assessed at scales ranging from mm to 10s – 100s km. At the scale of the organism itself, significant differences in larval mass densities and sinking velocities were observed between species of cirripedes, suggesting that larval physiology and morphology play an important role in water column vertical positioning. The importance of vertical positioning to horizontal transport and dispersal of larvae was identified in field surveys of the horizontal and vertical distributions of cirripede larvae, which revealed the interplay of wind-driven and tidally-oscillating currents in determining transport distances. Numerical simulations of larval dispersal based on a threedimensional hydrodynamic model then demonstrated that larvae with shallower abundance distributions often experienced greater horizontal transport, but that net dispersal distances were often greater for larvae deeper in the water column. Overall, simulated transport and dispersal distances were greatest for particles released at habitats further from the coast, such as MREDs, suggesting that the connectivity of these adult populations may be enhanced. Together, larval morphology, vertical positioning, and the coastal proximity of adult habitat could serve as useful indicators of larvae capable of reaching nearby newly installed offshore structures. For locations designated for MRED development in the Firth of Lorn, it is suggested that species with dispersal abilities similar to the cirripedes in this study could feasibly use these structures as stepping-stones for dispersal and range expansion, which could have important consequences when fouling communities are comprised of commercially important or invasive species.

The rate of global urbanization is increasing at an alarming pace, as the human population has grown to over 7 billion people—from 1.6 billion people in the 1900s—, half of which reside in urban areas. This increase has necessitated the expansion of urban habitat and increased consumption of natural resources. While the effects of urbanization on species diversity is well-documented (increasing urbanization decreases species diversity), its effects on species interactions have been less studied. Plant-animal interactions, such as seed dispersal, may be especially sensitive to urbanization. For plants, animal-based seed dispersal depends on several aspects, including 1) the rate of interactions with seed dispersers, 2) the probability of seed dispersal from an interaction event, 3) the identity and the number of seed disperser species –especially regarding differential ability to scarify seeds through digestion, and 4) the probability of germination after seed dispersal. Urbanization may affect seed dispersal dynamics by altering the frequency of interactions and/or the identity and diversity of seed dispersers. Consequently, the probability of seed dispersal and the ability of seeds to germinate and survive after being dispersed may be negatively affected by urbanization. In this study we ask specifically: 1) Will birds visit T. radicans at a greater rate in urban or natural habitats? 2) Will the diversity of dispersers be higher in urban or natural habitats? 3) Do seeds from urban or natural sites have a greater probability of dispersal? 4) Will seeds from urban or natural habitat be more likely to germinate? To compare differences in rate of visitation and disperser diversity between urban and natural habitats, individual T. radicans plants in two urban and two natural sites were observed for interactions by birds. Dispersal probability was estimated by marking fruits with a UV fluorescent dye and estimating a proportion of dispersed seeds at the end of the season. Seeds dispersed = total fruits marked – number of recovered fruits. Germination success will be estimated by collecting defecated—thus scarified—seeds in natural and urban sites as well as collecting non-dispersed seeds (that will be treated with either water or sulfuric acid). Seeds will be cold stratified 90 days before planting in constant 28oC and 16:8 L:D conditions. Preliminary results indicate that the rate of visitation, species diversity, and probability of seed dispersal are all significantly higher in urban sites. This trend suggests that T. radicans in urban habitat may be more successful than in natural habitat, however further research is necessary to confirm this.

Anthropogenic habitat disturbance is the leading cause of global biodiversity decline. Urbanization in particular is one of the most drastic forms of habitat disturbance, and it is associated with a decrease in both plant and animal diversity. Changes in biodiversity can affect the interactions between the remaining species within an ecosystem, which can, in turn, affect the provision of essential ecosystem services such as seed dispersal and pollination. Despite the wealth of studies examining the effects of urbanization on biodiversity, however, relatively few studies have investigated how urbanization impacts the interactions between species and the ecosystem services provided by them. Seed dispersal is one such ecosystem service which provides an ideal study system for investigating these effects. The goal of this study was to assess the impact of urbanization on avian seed dispersal networks in southern Appalachia. Specifically, we investigated the impact on species richness, interaction richness, and several network metrics related to ecosystem function (H2, interaction evenness, and weighted nestedness). The study was conducted across two fall – winter observation periods to coincide with the period of peak fruit production, from September – January in 2021-2022 and 2022-2023. Data was collected from 9 study sites during multiple visits via direct observation of bird-fruit interactions, with a total of 635 interactions recorded from 32 bird species on 18 fruiting plant species. Although data analysis is currently ongoing, initial results seem to indicate that there is no significant difference in species richness or interaction richness between natural and urban sites. This has interesting implications, as it suggests that plant-frugivore networks are relatively robust to disturbance caused by urbanization, which is promising for the continued provision of ecosystem services in urban areas.

Mosquitofish (Gambusia holbrooki) are native to the southeastern United States but invasive elsewhere, and are dominant predators in many ecosystems that they inhabit. Information on dispersal behavior will help better understand and predict mosquitofish metapopulation dynamics and invasions. I experimentally tested dispersal behavior of individual mosquitofish under a range of laboratory conditions relevant to field situations. Preliminary experiments showed that gender, lighting conditions, hunger and acclimation time did not significantly affect net dispersal rate. Power analysis based on this preliminary experiment determined that 6 replicate fish were sufficient for each subsequent experiment; I used 24 fish, and each fish was tested one time. Three factors that potentially could affect net swimming rate were tested: habitat of origin (permanent vs. temporary waters), water depth (3-24 mm), and the interaction between water depth and leaf litter type (upland and wetland). Fish from a temporary pond dispersed significantly faster than fish from a permanent pond, and fish dispersed significantly faster in deeper water than in shallower water. However, leaf litter significantly inhibited fish dispersal at all depths tested. Based on these experiments, G. holbrooki disperse more readily through relatively open and deeper (several centimeters) pathways between habitats such as roadside ditches, drainage canals and trails in flooded conditions. My results are useful for understanding mosquitofish dispersal behavior based on the abiotic and biotic factors examined in this experiment. I predict that mosquitofish can spread from a point of introduction at about 800 m per day, given and unobstructed path of only > 6 mm depth.

In most eukaryotes, aerobic respiration requires interactions between autosomally- encoded genes (Ninteract genes) and mitochondrial DNA, RNA, and protein. In species where females are philopatric, contrasting distributions of genetic variation in mito- chondrial and nuclear genomes creates variation in mitonuclear interactions that may be subject to natural selection. To test this expectation, we turned to a group with extreme female philopatry: the macaque monkeys. We examined four genomic datasets from (i) wild caught and (ii) captive populations of rhesus macaque, which is the most widely distributed non-human primate, and (iii) the stump-tailed macaque and (iv) a subspecies of longtail macaque, both of whose mitochondrial DNA is introgressed from a highly di- verged ancestor. We identified atypically long runs of homozygosity, low polymorphism, high differentiation and/or rapid protein evolution associated with Ninteract genes com- pared to non-Ninteract genes. These metrics suggest a subset of Ninteract genes were independently subject to natural selection in multiple species. Selection on mitonuclear interactions is thus a factor in macaque genome evolution that could have influenced as- pects of macaque societies including species diversity, ecological breadth, female-biased adult sex ratio and demography, sexual dimorphism, and mitonuclear phylogenomics. / Thesis / Master of Science (MSc)

This research examined the behavior of avian scavenger bone dispersal in a New England environment. The furthest distance that avian species can carry bone elements can be used by search investigators by providing possible distances maximum dispersal. The sizes of bones dispersed by avian species provides context on how bone elements differing in size are transported from the initial site of deposition. The project utilized two locations with elements of varying sizes (large, intermediate, and small) with tracking tags attached to determine the distance and pattern of scavenger displacement. Scavenging was also recorded with motion-sensing game cameras that allowed for differentiation between which species scavenged on which elements, allowing for the distance carried to be associated with individual species. The most common avian scavengers were the northern cardinal (Cardinalis cardinalis), downy woodpecker (Dryobates pubescens), and blue jay (Cyanocitta cristata). The furthest element that was displaced and recovered was a pig rib approximately 62 meters from its initial placement location and it was moved by a crow (Corvus brachyrhynchos). The second furthest element displaced was a pig rib moved approximately 41.5 meters by a Cooper’s hawk (Accipiter cooperii). In addition, six other elements were removed from the platform by birds and not recovered due to possible displacement outside of the search radius and tracking application radius. Overall, 55.0% of elements were recovered within 1 meter of their initial placement location. For elements dispersed under 1 m, Rayleigh z-statistical tests (z =1.328; α = 0.05) for the site location in a wooded area indicated that directionality was not statistically significant, while the location in the wetlands was determined to be statistically significant (z = 20.656; α = 0.05). In addition, a Watson’s U2 Two-Sample Test of Homogeneity (U2 = 0.374) revealed the two groups of average directions are significantly different at α = 0.05. This indicates a difference in direction of displacement between the platforms. For Platform 1 (forested location), the results of the Mann-Whitney U-Test (z = -2.638) indicated that the distances of displacement between the spring and summer seasons are significantly different between the two seasons at α = 0.05. For Platform 2 (wetland location), the results of the Mann-Whitney U-Test (z = -0.859) indicate the distances of displacement between the two seasons were not significantly different between the two seasons at the α = 0.05 value. In addition, Kruskal-Wallis H tests revealed that there was no statistically significant difference between the platform location and the number of site visits for the majority of species. Only two species, cardinals (z = -2.04; α = 0.05) and song sparrows (z = -2.208; α = 0.05), were determined to have a statistically significant difference between the location and the number of site visits.

No description available.

Identifying the processes and mechanisms that govern communities of organisms is the main goal of community ecology. Locally operating mechanisms such as environmental filtering, in which the environment determines what species are found in a given location, as well as regional processes such as dispersal have all been identified as potential drivers of community processes. However, the relative importance of these drivers may vary temporally and spatially. In dendritic stream networks, headwater streams are isolated when compared to more centrally located mainstem stream sections. I investigated the potential for stream networks to influence the relative influence of local and regional processes via a survey and field experiment based approaches. I found that headwater streams can influence mainstem stream communities, potentially as a result of the dispersal of organisms or abiotic materials. Additionally, I demonstrated that macroinvertebrate communities in headwater streams respond more strongly to manipulations of local environment than do mainstem streams, both in terms of community composition as determined taxonomically and as functional traits. These results indicate that headwater streams may be affected differently than mainstem streams by anthropogenic activity and as such, management strategies and restorations may need to be specifically tailored to address the relative influences of local and regional processes at varying points within a stream network. / Ph. D.

Metacommunity ecology explicitly incorporates processes at multiple spatial scales to explain the assembly and dynamics of a community. In a metacommunity, local communities interact with one another through the dispersal of individuals across a region. As such, metacommunities are molded by two sets of processes: local and regional. Local factors are those that directly impact a single local community, such as environmental conditions, competition, and predation. On the other hand, regional factors affect communities across a landscape and include mechanisms such as, immigration and emigration. The potential interactions between local and regional factors make metacommunity dynamics a unique body of theory when compared to classic community theory. However, while the direct influence of dispersal on metacommunity dynamics continues to be a well-researched topic, how dispersal interacts with local factors to shape metacommunity dynamics is a more open topic. In particular, one continuing gap in my knowledge is how dispersal interacts with biotic effect how it may affect metacommunities. One type of local biotic process that can directly affect communities is a strong interactive species, i.e., a species that affects community structure and diversity, and to the best of my knowledge, the interaction between dispersal and strongly interactive species has not been directly addressed experimentally. In the following study, I investigated the interaction of dispersal and a strong interactive species on metacommunity diversity and assembly. I chose Daphnia magna as my strong interacting species due to its biological and physical traits. Dispersal is known to create predictable patterns of diversity as it increases in a metacommunity. We made logical predictions based off of my knowledge of these patterns, and my inclinations regarding how dispersal would interact with a strong interacting species. The following predictions were made in relation to the control: 1) Alpha diversity would be the highest during low dispersal as new species would be introduced and maintained above the extinction threshold. I also predicted beta diversity would decrease with increased dispersal due to the homogenization of communities. 2) In the presence of D. magna, beta diversity would only increase during low dispersal due to possible rescue effects. 3) Temporal variability would decrease for the low dispersal treatment and increase for the high dispersal treatment in the absence of D. magna. 4) Temporal variability would overall increase across all treatments in the presence of D. magna. To carry out the study, I assembled outdoor mesocosms using a 2x3x3x4 factorial design (Daphnia Treatment: no addition of D. magna, addition of D. magna; Dispersal Treatment: no dispersal, low dispersal, high dispersal; three buckets were equivalent to one metacommunity; 4 replicates). There was a significant interaction between D. magna and dispersal. Over time, beta diversity decreased as communities became homogenized; however, the no dispersal treatment homogenized at a slower rate compared to the other treatments. In addition, D. magna appeared to create local selection for certain taxa resulting in the increase of Bosmina and Simocephalus while other taxa decreased, for example Streblocerus. This trend was likely due to the feeding and grazing habits of D. magna which is known to outcompete other large zooplankton for larger phytoplankton taxa. Lastly, D. magna directly influenced temporal variability of metacommunities in the experiment. In particular, the low dispersal treatment increased in temporal variability in the presence of D. magna. Again, this result could likely be attributed to D. magna effects selecting for certain taxa, or by the re-introduction of new or dying species with each dispersal through rescue effects. Overall, the results in my study supported majority of my predictions. It is clear that D. magna had an effect on communities as taxa abundances increased and beta diversity in the no dispersal treatment did not decrease as quickly. This result suggests that the introduction of D. magna as an invasive to non-local waters could pose a threat to local community dynamics. It is important to understand how a strong interactive species can affect communities across a landscape as they can greatly alter diversity and composition. Future studies should focus on expanding the dispersal gradient and incorporating a local strong interactive species and non-local strong interactive species to understand how they may change community dynamics. / Master of Science

Biological invasions represent both an urgent conservation problem and an opportunity to advance ecological theory. Development of pertinent research questions and proactive management strategies require knowledge of which introduced species are present and of spatiotemporal trends in the distribution of natives and invaders. In Chapter 2 we developed a quantitative framework to identify spreaders and decliners and estimate invasion chronologies based on a historical fish presence data set for upper and middle New River (UMNR) tributaries. Our framework accounts for spatiotemporal variability in sampling effort by aggregating presences by watershed and expressing range size as a function of the number of watersheds sampled per time period. The majority (55%) of fish species present in the study area were introduced, 51% of which were spreaders. Most spreaders (84%) appeared to be spreading exponentially. The rate of new introductions detected in the study area has slowed since the mid-20th century. Two natives, the mound-spawning bluehead chub Nocomis leptocephalus and its strong nest associate (reproductive mutualist), mountain redbelly dace Chrosomus oreas, were among the most rapid spreaders. Four natives showed evidence of decline. Our framework leverages historical presence data to reconstruct temporal trends in species distributions. It sets the stage for further study of factors driving stream fish invasions and declines in the Appalachian region, and is transferable to diverse taxonomic groups and geographic regions. Species traits and human activities mediating stream-fish invasions remain poorly understood. In Chapter 3 we modeled the contribution of species traits to invasion success of UMNR tributary fishes during the colonization and spread stages. Biological traits accurately explained colonization and spread success, whereas ecological traits resulted in less accurate models. Colonization success was positively related to time since introduction, benthic feeding, an equilibrium life history, and nest spawning. Successful spread was positively related to winter air temperature in the native range and an equilibrium life history. Variables estimating human use and propagule pressure were non-informative. Traits that influenced invasion success were consistent with the hypothesis that human land-use practices have increased the invasibility of highland watersheds by creating novel conditions suited to lowland and equilibrium invaders. / Master of Science