The purpose of this dissertation was to investigate the usefulness and limitations of radioactive tracers as a tool for the study of microbial-meiofaunal trophic interactions under near-natural conditions. / Three methods of delivering labeled substrates to natural cores of sediments were compared. Slurried sediments disrupted the sedimentary structure and significantly altered uptake of labeled substrates by copepod species. Thus, disruption of sedimentary structure can significantly alter microbial-meiofaunal interactions and influence the results of grazing studies. / The ($\sp3$H) -thymidine technique for measuring bacterial production was evaluated. The metabolic fate of labeled thymidine in a coastal marine sediment was not consistent with assumptions necessary for measuring bacterial production or its consumption by meiofauna. / Microautoradiography was used to demonstrate that sedimentary microalgae and heterotrophic bacteria can be selectively labeled with ($\sp{14}$C) -bicarbonate and labeled organic substrates, respectively. / A study was performed to determine if radioactivity measured in copepods from grazing experiments was the result of ingestion of labeled microorganisms or the result of uptake by non-feeding processes. Uptake of label by copepods from ($\sp{14}$C) -bicarbonate was due almost exclusively to grazing on microalgae. Uptake of label by copepods from ($\sp{14}$C) -acetate, however, resulted from activity by epicuticular bacteria and was not due to ingestion of labeled bacteria. / Considered collectively, the results of these studies indicate that, when nondisruptive methods of label introduction are used, ($\sp{14}$C) -bicarbonate can be used as a reliable tracer of grazing on microalgae. Labeled organic substrates, however, do not appear to be a valid tracer form consumption of heterotrophic bacteria. Specifically, uptake by epicuticular bacteria associated with copepods account for essentially all of the radioactivity that is associated with copepods. / Source: Dissertation Abstracts International, Volume: 50-08, Section: B, page: 3250. / Major Professor: David Thistle. / Thesis (Ph.D.)--The Florida State University, 1989.

The planthopper Prokelisia marginata is the most common insect herbivore in the salt marshes of northwestern Florida, where it feeds and reproduces on smooth cordgrass, Spartina alterniflora Loisel. Relative to other sites where it has been studied, population densities of this planthopper in north Florida are low, despite high fecundity. Low nymphal survivorship, combined with high rates of adult mortality and dispersal, rapidly diminish the densities of local populations. Many factors act to alter the dynamics of planthopper populations. This study was designed to determine the magnitude of the effect of several of these factors on the demography and population dynamics of Prokelisia marginata at Apalachee Bay, Florida. / A field experiment looked at the impact of tides on planthopper populations. Artificial islands were used to create patches of the host plant. Floating islands were used to eliminate tidal inundation and waves, while populations on other islands experienced natural tidal conditions. Analysis showed that the populations did not differ significantly in size throughout the experiment and that they had similar dynamics. In the laboratory, simulated tidal inundation experiments showed that Prokelisia marginata is behaviorally adapted to withstand tidal submergence, either by retreating from the tide or by becoming submerged, and that the planthoppers are able to survive long periods under water. / A second field experiment examined the effects of spider predation on populations of Prokelisia marginata. Nymphal populations were significantly reduced in the presence of spiders, but adults were unaffected. Thus, spider predation had no effect on the population as a whole. A laboratory experiment showed that nymphs are more susceptible than adults to direct predation, and that the presence of spiders alters their life history. / The most important factor acting to reduce adult densities appears to be dispersal of the insects away from their populations. Because most of the dispersing insects probably fail to locate new sites on which to reproduce, dispersal is an important factor acting to reduce populations of Prokelisia marginata in northwestern Florida. / Source: Dissertation Abstracts International, Volume: 50-12, Section: B, page: 5443. / Major Professor: Donald R. Strong. / Thesis (Ph.D.)--The Florida State University, 1989.

Populations of the least killifish, Heterandria formosa are found in a wide variety of habitats, including habitats that differ widely in average temperature and in range of seasonal temperatures. To determine whether this ability to exist in thermally different sites is owing to phenotypic plasticity or to population differentiation I raised fish from a spring site and a pond site under common laboratory conditions. Fish were raised at one of two temperatures during gestation and at one of two temperatures from birth to sexual maturity. Gestation temperature, rearing temperature, population of origin, and gender had complex, interacting effects on critical thermal maximum and minimum at sexual maturity, on offspring survival, and on time to maturity. In particular, the populations were strongly differentiated for offspring survival and time to maturity, although the magnitude of the differences depended on the environment. Females performed better than males when genders differed. / H. formosa also exhibit superfetation, the presence of embryos in different developmental stages in the ovary at one time. There have been few comparative studies of interspecific variation in superfetation, and there have been no surveys of population variation in reproductive traits within a superfetating species. In this study I followed seasonal changes in reproductive parameters of four populations of H. formosa for all or part of 4 years. / The four populations differed in breeding phenology, level of superfetation, total volume of embryos carried, and brood size. This variation does not correspond to either general habitat similarities among the populations (ponds versus rivers), or to habitat stability. I also discovered that first, females must hold back some same-stage embryos while advancing others and second, that size of females, as measured by standard length, clearly influences the total number of embryos, brood size, and number of embryos carried in each stage. Yet despite this relationship between body size and embryo capacity, brood size is not constrained by space available for late-stage embryos. / Source: Dissertation Abstracts International, Volume: 51-02, Section: B, page: 0549. / Major Professor: Joseph Travis. / Thesis (Ph.D.)--The Florida State University, 1989.

The biology and foraging behavior of the fairyfly parasitoid Anagrus delicatus (Hymenoptera: Mymaridae) were studied to determine their effect on host population dynamics and stability. Anagrus delicatus is a short-lived solitary parasitoid that attacks the egg stage of two geographically sympatric planthoppers, Prokelisia marginata and P. dolus (Homoptera: Delphacidae). Host eggs are laid within the leaves of the grass, Spartina alterniflora, found in salt-marshes of the Atlantic and Gulf coasts of the eastern United States. / Laboratory studies indicate that upon locating a patch (S. alterniflora leaves), A. delicatus quickly and efficiently detects the presence of host eggs. Wasps remain on a patch for up to ten hours, but numbers of hosts attacked are low and variable and not much affected by host density. This low attack rate is not a consequence of differences among host species, parasitoid egg limitation, long handling times, a high ratio of parasitized to unparasitized hosts, or the presence of a host refuge. However, direct interference among parasitoids does cause a decrease in number of attacks as wasp density per patch increases. These behaviors lead to density-independent parasitism among S. alterniflora leaves. / Field studies that measured the response of natural populations of A. delicatus to experimental host patches corroborate these laboratory findings. Per capita numbers of hosts parasitized are low, variable, and a declining function of parasitoid density (parasitoid interference); and result in spatial and temporal density independence. Wasps appear to favor a foraging strategy that serves to spread eggs among a number of host patches. / I examined these parasitoid behaviors for their effect on stability in traditional host-parasitoid models. In general, patch use by A. delicatus is not stabilizing, but parasitoid interference can greatly enhance or cause interaction stability. A model developed specifically for this system that incorporates both host and parasitoid biology and behavior supports this conclusion. Due to parasitoid interference and asynchrony in host and parasitoid generation times, this model predicts that A. delicatus will cause the host population to exhibit "stable" cycles through time; exactly the pattern found in nature. / Source: Dissertation Abstracts International, Volume: 52-10, Section: B, page: 5069. / Major Professor: Joseph Travis. / Thesis (Ph.D.)--The Florida State University, 1991.

The distribution patterns of infaunal polychaetes can be influenced by several factors (e.g., predation, competition, and, or disturbance). Adult-larval interactions have been shown to be important in communities where adult densities are high. Manipulative field experiments were used to test the effects of several adult species on the settlement and recruitment of infaunal polychaetes in seagrass beds on Turkey Point Shoal, St. George's Sound in the northern Gulf of Mexico. Interpretation of observed or inferred settlement patterns in field experiments can be difficult and erroneous if little is known of larval settling behavior. I designed experiments to find cues responsible for larval settlement behavior, and to determine if these cues could also alter the spatial pattern at settlement. The deposit feeding adults Aricidea philbinae and Prionospio heterobrachia inhibited the settlement and recruitment of conspecifics both in the field and lab. The tube building adult Americonuphis magna facilitated the settlement and recruitment of A. philbinae, Sphaerosyllis taylori, and Nereis succinea in field experiments. Only Prionospio larvae seem to seek out sediments with a past history of Americonuphis magna in laboratory settling experiments. Polychaete tubes had little or no effect on polychaete settlement. Both inhibition and facilitation seem to govern recruitment sequences in these low adult density assemblages. The active larval settlement behaviors I found reveal that some mechanisms of the adult-larval interactions observed are attributable to larval behavior (both avoidance and attractance). It is evident that larval behavior and adult-larval interactions are important in structuring the small-scale patchiness in the seagrass bed community. / Source: Dissertation Abstracts International, Volume: 49-03, Section: B, page: 0623. / Major Professor: Robert J. Livingston. / Thesis (Ph.D.)--The Florida State University, 1987.

Sheepshead minnows, Cyprinodon variegatus, an estuarine fish, is heavily parasitized in the bulbus arteriosus by the heterophyid trematode Ascocotyle pachycystis, in channels and sloughs throughout the St. Mark's National Wildlife Refuge, northwestern Florida. I conducted laboratory experiments to examine the morphological and physiological effects of parasites on these fish. Unparasitized and parasitized fish were compared for differences in ventricle weight, cardiac performance, swimming performance, and oxygen consumption. / Parasitized fish hearts were hypertrophied, had larger contractile forces and shorter contractile periodicity, and decreased bulbal expansion. Swimming performance was significantly reduced at cold temperatures and low dissolved oxygen levels. Oxygen consumption increased in parasitized fish whiled swimming times to exhaustion decreased. / Field experiments were conducted in St. Mark's National Wildlife Refuge to determine seasonal variation in recruitment rates of A. pachycystis parasites into caged sheepshead minnows. Monthly fish collections were examined for intensities of infection and dispersion patterns. / Recruitment of parasites into caged fish is a warm-weather phenomenon, peaking in mid-summer and declining to zero over the winter. Susceptibility to infection is age-related. Mean intensities and prevalences are highest in the largest size classes; overdispersion is recruitment-induced, rather than mortality induced, except during the winter when it is specific to the oldest fish. / Source: Dissertation Abstracts International, Volume: 52-03, Section: B, page: 1190. / Major Professor: Joseph Travis. / Thesis (Ph.D.)--The Florida State University, 1991.

Agriculturally-altered habitats, especially oil palm plantations, are rapidly dominating the Southeast Asian landscape. Although recent studies have shown reduced species diversity associated with this commodity, data on amphibian diversity are rare. The following thesis explores the impact of oil palm plantations on amphibians in Peninsular Malaysia based on (1) amphibian biodiversity, (2) quality and use of breeding sites, (3) habitat use and (4) parasitism. Contrary to expectation, not all metrics of biodiversity differed between oil palm plantations and secondary forest sites. Amphibian community composition, however, differed greatly between the two habitat types, with oil palm communities being dominated by species known to prosper in disturbed habitats, indicating that the community is currently of limited conservation value. Within plantations, temporary pools were found to serve as important breeding habitats for amphibians so a focused study on the characteristics of these pools was carried out. Although we found differences between pools, the proportion of occupied pools did not differ significantly between plantation and forest sites. I did observe evidence of breeding site preferences of least concern, plantation amphibians, along with habitat partitioning between species, a similar pattern also seen in forest communities. I compared parasite burdens between habitats by screening for the fungus Batrachochytridium dendrobatidis (Bd) and for nematode parasite load. Bd was not detected in any of my samples and there was no difference in nematode loads between habitat types. However, patterns of nematode prevalence was affected by host type, while nematode intensity was dependent on an interaction between host and body size. The final chapter indicates that in terms of parasite, the host environment is the most important. Additionally, differences in host-parasite patterns between habitats indicate a possible underlying problem that rapid biodiversity censuses would be unable to detect.

Gene flow is a central evolutionary force that largely determines the level of differentiation among populations of organisms and thus their potential for divergence from each other. Identifying key factors that influence gene flow among populations or closely related taxa can thus provide valuable insights into how new species arise and are maintained. I undertook a comparative study of the factors that have shaped range-wide intraspecific differentiation in four related and broadly co-distributed Taiwanese bat species of the genera Murina and Kerivoula. Bats were sampled from sites across Taiwan and sequenced at two mitochondrial genes as well as genotyped at newly developed and/or existing multi-locus microsatellite markers. To improve phylogeographic inference of existing patterns of population genetic structure, I undertook spatial distribution modeling of the focal species at both the present time and at the Last Glacial Maximum. Genetic data were analysed using traditional and new methods, including Bayesian clustering, coalescent-based estimation of gene flow, and haplotype network reconstruction. My findings revealed contrasting signatures of population subdivision and demographic expansion that appear in part to reflect differences in the altitudinal ranges of the focal taxa. Mitochondrial analyses also revealed a putative sister relationship between two of the Taiwanese endemic taxa - M. gracilis and M. recondita, which - given the fact both are restricted to Taiwan - presents an unusual case of potential non-allopatric divergence. To dissect this divergence process in more detail, I used 454-Pyrosequencing to obtain ten nuclear loci sequences of these two taxa, and a third taxon from mainland Asia, M. eleryi. Based on these loci, Bayesian isolation-migration models provided no strong evidence of post-split gene flow and, therefore, did not support speciation within Taiwan. Instead, the divergence process reconstructed from ncDNA loci was found to be incompatible with the mtDNA tree, with M. recondita showing a sister relationship with M. eleryi. This conflict is best explained by the ancient introgression of mtDNA between the two insular species following their colonization of Taiwan at different times.

Despite the increased prominence of ecological measurement in fresh waters within recent national regulatory and legislative instruments, their assessment is still almost exclusively based on taxonomic structure. Integrated metrics of structure and function, though widely advocated, to date have not been incorporated into these bioassessment programmes. We sought to address this, by assessing community structure (macroinvertebrate assemblage composition) and ecosystem functioning (decomposition, primary production, and herbivory rates), in a series of replicated field experiments, at watercress farms on the headwaters of chalk streams, in southern England. The outfalls from watercress farms are typically of the highest chemical quality, however surveys have revealed long-term (30 years) impacts on key macroinvertebrate taxa, in particular the freshwater shrimp Gammarus pulex (L.), yet the ecosystem-level consequences remain unknown. Initial studies were at Europe’s largest watercress farm at St Mary Bourne, Hampshire, during the bioremediation of its complex wastewaters and changes to farm management practices. These widened to include larger scale spatiotemporal studies at other watercress farms. Detrimental ecological impacts at the start of the study were detected by the structural and functioning measures, but they did not respond to bioremediation. However, an increase in G. pulex abundance was detected, providing evidence of recovery in response to altered practices, which may be attributable to the cessation of chlorine use. The detrimental impacts were unique to the St Mary Bourne watercress farm and were not consistent across the other watercress farms in the study. Our results demonstrate the importance of integrated metrics of both ecosystem structure and functioning, to derive a more comprehensive view of aquatic ecosystems and highlights the difficulties associated with extrapolating from laboratory studies in response to stressors.

<p> Information on the movement of migratory demersal fishes such as Pacific halibut, Pacific cod, and sablefish is needed for management of these valuable fisheries in Alaska, yet available methods such as conventional tagging are too coarse to provide detailed information on migration characteristics. In this dissertation, I present methods for characterizing seasonal and annual demersal fish movement at multiple scales in space and time using electronic archival and acoustic tags. In Chapter 1, acoustic telemetry and the Net Squared Displacement statistic were used to identify and characterize small-scale movement of adult female Pacific halibut during summer foraging in a Marine Protected Area (MPA). The dominant movement pattern was home range behavior at spatial scales of less than 1 km, but a more dispersive behavioral state was also observed. In Chapter 2, Pop-up Satellite Archival Tags (PSATs) and acoustic tags were deployed on adult female Pacific halibut to determine annual movement patterns relative to MPA boundaries. Based on observations of summer home range behavior, high rates of year-round MPA residency, migration timing that largely coincided with winter commercial fisheries closures, and the demonstrated ability of migratory fish to return to previously occupied summer foraging areas, the MPA is likely to be effective for protecting both resident and migrant Pacific halibut brood stock year-round. In Chapter 3, I adapted a Hidden Markov Model (HMM) originally developed for geolocation of Atlantic cod in the North Sea for use on demersal fishes in Alaska, where maximum daily depth is the most informative and reliable geolocation variable. Because depth is considerably more heterogeneous in many regions of Alaska compared to the North Sea, I used simulated trajectories to determine that the degree of bathymetry heterogeneity affected model performance for different combinations of likelihood specification methods and model grid sizes. In Chapter 4, I added a new geolocation variable, geomagnetic data, to the HMM in a small-scale case study. The results suggest that the addition of geomagnetic data could increase model performance over depth alone, but more research is needed to continue validation of the method over larger areas in Alaska. In general, the HMM is a flexible tool for characterizing movement at multiple spatial scales and its use is likely to enrich our knowledge about migratory demersal fish movement in Alaska. The methods developed in this dissertation can provide valuable insights into demersal fish spatial dynamics that will benefit fisheries management activities such as stock delineation, stock assessment, and design of space-time closures. </p><p>