Dissertations / Theses on the topic 'Biosecurity science and invasive species ecology'

The naturalisation and subsequent spread of non-indigenous plant species (NIPS) is a major problem for most regions of the world. Managing plant invasions requires greater understanding of factors that determine initial naturalisation and distribution of wild NIPS. By the year 2000, 2252 NIPS were recorded as wild (1773 fully naturalised and 479 casual) in New Zealand. From published literature and electronic herbaria records, I recorded year of discovery of wild populations, and regional distribution of these wild NIPS. I also recorded species related attributes hypothesised to affect naturalisation and/or distribution, including global trade, human activities, native range and biological data; and regional attributes hypothesised to affect distribution, including human population densities, land use/cover, and environmental data. I used interval-censored time-to-event analyses to estimate year of naturalisation from discovery records, then analysed the importance of historical, human activity, biogeographical and biological attributes in determining patterns of naturalisation. Typically, NIPS that naturalised earlier were herbaceous, utilitarian species that were also accidentally introduced and/or distributed, with a wide native range that included Eurasia, naturalised elsewhere, with a native congener in New Zealand. In the year 2000, 28% of wild NIPS occupied only one region, 18% occupied two regions, decreasing incrementally to 2.5 % for nine regions, but with 13.5% occupying all ten regions. I used generalised linear models (GLMs) with binomial distribution to determine predictors of whether a wild NIPS occupied ten regions or not, and GLMs with Poisson distribution for wild NIPS occupying 0 – 9 regions. As expected, the dominant effect was that species discovered earlier occupied more regions. Utilitarian wild NIPS that were also accidentally introduced and/or distributed, and wild NIPS with a native congener tended to be more widely distributed, but results for other attributes varied between datasets. Although numbers of wild NIPS recorded in regions of New Zealand were sometimes similar, composition of wild NIPS was often very different. I used nonmetric multidimensional scaling (NMDS) to determine dissimilarity in composition between regions. Then, after reducing correlation between predictor variables using principal components analyses (PCAs), I tested the importance of regional variables in determining the regional composition of wild NIPS using metaMDS. The density of human populations best explained the dissimilarity in composition, but temperature gradients and water availability gradients were also important. In the year 2000 more than 1100 (60%) of the 1773 fully naturalised NIPS in mainland New Zealand had each been recorded in Northland/Auckland and Canterbury, and at the other end of the scale, Southland and Westland each had fewer than 500 (30%). I used GLMs to analyse the importance of people and environment in determining the numbers of wild NIPS in each region. Because I conducted multiple tests on the same dataset I used sequential Bonferroni procedures to adjust the critical P-value. Only human population density was important in explaining the numbers of NIPS in the regions. Overall, humans were the dominant drivers in determining the patterns of naturalisation and spread, although environment helps determine the composition of NIPS in regions. Incorporating human associated factors into studies of wild NIPS helps improve the understanding of the stages in the naturalisation and spread process.

Invasive species are well known to cause millions of dollars of economic as well as ecological damage around the world. New Zealand, as an island nation, is fortunate because it has the opportunity to regulate and monitor travel and trade to prevent the establishment of new species. Nevertheless foreign species continue to arrive at the borders and continue to cross them, thus requiring some form of management. The control and management of a new incursion of an invasive species would clearly benefit from predictive tools that might indicate where and how quickly the species is likely to spread after it has established. During the process of spread an invasing species must interact with a complex and heterogeneous environment and the suitability of the habitat in a region determines whether it survives. Many dispersal models ignore such interactions and while they may be interesting theoretical models, they are less useful for practical management of invasive species. The purpose of this study was to create and investigate the behaviour of a spatially explicit model that simulates insect dispersal over realistic landscapes. The spatially explicit model (Modular Dispersal in GIS, MDiG) was designed as am open-source modular framework for dispersal simulation integrated within a GIS. The model modules were designed to model an an approximation of local diffusion, long distance dispersal, growth, and chance population mortality based on the underlying suitability of a region for establishment of a viable population. The spatially explicit model has at its core a dispersal module to simulate long distance dispersal based an underlying probability distribution of dispersal events. This study illustrates how to extract the frequency of long distance dispersal events, as well as their distance, from time stamped occurrence data, to fit a Cauchy probability distribution that comprises the dispersal module. An investigation of the long distance dispersal modules behaviour showed that, in general, it generated predictions of the rate of spread consistent with those of analytical partial differential and integrodifference equations. However, there were some differences. Spread rate was found to be mainly dependent on the measurement technique used to determine the invasion front or boundary, therefore an alternative method to determine the boundary of a population for fat-tailed dispersal kernels is presented. The method is based on the point of greatest change in population density. While previously it was thought that number of foci rather than foci size was more important in stratified dispersal and that finer resolution simulations would spread more quickly, simulations in this study showed that there is an optimal resolution for higher spread rates and rate of area increase. Additionally, much research has suggested that the observed lag at the beginning of an invasion may be due to lack of suitable habitats or low probability of individuals striking the right combination of conditions in a highly heterogeneous environment. This study shows an alternative explanation may simply be fewer dispersal event sources. A case study is described that involved the application of the spatially explicit dispersal model to Argentine ant spread to recreate the invasion history of that species in New Zealand. Argentine ant is a global invasive pest which arrived in New Zealand in 1990 and has since spread to both main islands of New Zealand, primarily through human mediated dispersal. The spatially explicit simulation model and its prediction ability were compared to that of a uniform spread model based on equivalent total area covered. While the uniform spread model gave more accurate predictions of observed occurrences early in the invasion process it was less effective as the invasion progressed. The spatially explicit model predicted areas of high probability of establishment (hot spots) consistent with where populations have been found but accuracy varied between 40-70% depending on the year of the simulation and parameter selection. While the uniform spread model sometimes slightly outperformed or was equivalent to the simulation with respect to accuracy early in the invasion process, it did not show the relative risk of establishment and was less effective later in the invasion when stochastic random events generated by the simulation model were averaged to represent trends in the pattern of spread. Additionally, probabilistic predictions as generated by the spatially explicit model allow the uncertainty of prediction to be characterised and communicated. This thesis demonstrates that heterogeneous spread models can give more insight and detail than one dimensional or homogeneous spread models but that both can be useful at different stages of the invasion process. The importance of compiling appropriate data on dispersal and habitat suitability to aid invasion management has been highlighted. Additionally, a number of important hypotheses that need to be addressed to increase understanding of how species interact with the complex environment, have been identified and discussed.

Knowledge of sex allocation trade-offs with tree growth in insect-pollinated woody plants is limited, particularly in invasive plants. This study examined patterns of growth and reproductive investment in a North American invasive plant species, Triadica sebifera, I hypothesized that the energy limitations of smaller trees may result in the production of more male reproductive structures that are energetically less costly. Diameter at breast height was a significant predictor of seed and catkin mass and regression can describe these relationships across sites. Seed and catkin mass were positively correlated across sites. The relationship between the seed mass:catkin mass ratio and DBH was not significant, nor was seed mass:catkin mass and total investment. Results showed a significant positive relationship between total reproductive investment and tree size across sites. Seed mass:catkin mass ratio and reproduction investment showed substantial variation among individual trees of similar size within sites.

Invasive species are a top threat to global biodiversity. Lionfish (Pterois volitans/miles) are a marine invasive predator that are now established in the Western Atlantic, Caribbean Sea and Gulf of Mexico. Studies that have documented impacts of lionfish suggest they can reduce fish recruitment and native species biomass by up to 80%. Research on lionfish impacts, biology and ecology is heavily focused in tropical and subtropical systems, with considerably less research effort occurring in the temperate regions of their invaded range, such as the South Atlantic Bight. Lionfish life history estimates are important to modeling lionfish population growth, modeling future dispersal and evaluating the efficacy of different removal strategies. Since lionfish life history will vary with a suite of environmental, biological and ecological factors, estimates of lionfish life history should be collected in all regions of their invaded range. The purpose of this study was to collect baseline information of lionfish biology and ecology in the southern portion of the South Atlantic Bight, an unstudied region for this species. As such, chapter one uses a quantitative approach to determine lionfish life history estimates important to management. Some important results of chapter one are: lionfish are recruiting at one main time throughout the year, growth changes seasonally and the population is relatively young (< 3 years of age). Chapter two takes the first step in determining lionfish impacts in this region by quantifying their diet. The main conclusion of this chapter is that round scad (Decapterus punctatus), sand perch (Diplectrum formosum) and black sea bass (Centropristis striata) are the most important prey items in the lionfish diet. Black sea bass are an important fishery in the South Atlantic Bight, and lionfish could be negatively affecting recruitment. Together, these chapters provide important insight into lionfish ecology in this region and in general.

In a large agricultural operation, such as the one at Cal Poly San Luis Obispo, disposal of deceased animals is an immense issue. The cost of transporting and rendering every dead animal is inhibitory to the general function of the agricultural operations and their thin budget. Therefore, we propose that composting mortalities could be an economical alternative. Composting is a recognized method for taking animal waste products along with carbon waste and turning it into a pathogen-free, nutrient-rich topsoil. Carcass composting is in fact performed in other countries and states to varying degrees of success. However, the California EPA limits carcass composing to only private land. Therefore, the purpose of this work was to determine the efficacy of killing pathogens by composting using bench top composting models. Ultimately, our goal is to provide “proof of concept” data in order to gain permission for a full-scale carcass compost pile to be set up at Cal Poly San Luis Obispo. Using thermo tolerant Salmonella senftenberg as an indicator organism, we performed bench top trials of traditional and carcass compost in the lab. Samples were inoculated with S. senftenberg and kept at 55°C for 15 days in accordance with the California EPA and Test Method for the Examination of Composting and Compost (TMECC). Samples were then plated and processed for multiple tube analysis and most probable number. Samples were also partitioned for a viability qPCR with propidium monoazide (PMA) to compare to the classic techniques. Using these methods we were then able to track and produce thermal death time data for S. senftenberg in both traditional and carcass compost. By comparing the types of compost, we were able to determine that the composting method presented by the California EPA and the TMECC produces safe, pathogen free compost, even when inoculated carcasses were introduced. However, even with removal of dead cells by PMA, qPCR did not outperform the classical microbiological methods for as tracking pathogen killing.

Introduced populations of Eichhornia crassipes (Pontederiaceae) possess extremely low levels of genetic diversity due to severe bottleneck events and clonal reproduction. While populations elsewhere have been well studied, North American populations of E. crassipes remain understudied. We used Amplified Fragment Length Polymorphism markers to assess genetic diversity and population structure in North American E. crassipes populations. Patterns of diversity over the past fifty years were analyzed using herbarium specimens. Furthermore, we sampled populations across the Gulf Coast of the United States throughout a year to determine contemporary genetic diversity and assess potential seasonal effects. Genetic diversity was found to be scant in the United States without population structure, agreeing with previous studies from other regions. Genetic diversity has remained consistently low over the past fifty years despite significant changes in selection pressure. However, evidence for and against population structure between seasons was found and the consequences of this are discussed.

Thesis (M.S.)--University of Toledo, 2009.
Typescript. "Submitted as partial fulfillment of the requirements for The Master of Science Degree in Biology (Ecology-track)." "A thesis entitled"--at head of title. Bibliography: leaves 28-32.

abstract: Invasive plants harm the ecological properties of natural systems, human health, and local economies. However, the negative impacts of invasive species are not always immediately visible and may be disregarded by local communities if social benefits of control efforts are not clear. In this dissertation, I use a mixed-methods approach to investigate the drivers of invasive plant distribution, potential financially feasible management techniques to control invasion, and community forest user perceptions of those techniques. In this work, I aim to incorporate the diverse perspectives of local people and increase the long-term success of invasive species control activities in socio economically vulnerable populations. Integrating a spatially and temporally diverse data set, I explore the social and ecological drivers of invasive plant abundance across 21 buffer zone community forests in the Western Chitwan Valley of Nepal. I evaluate to what extent forest user and collective manager activities, the legacies of historic activities, and ecological properties influence present-day invasive plant abundance. I built upon this study to identify areas with critically high levels of invasion then initiated a three-year, community-based management intervention to evaluate traditional and adaptive land management approaches to control invasive plants. I found that both approaches reduced invasive plant abundance relative to the surrounding, untreated forest. I then interviewed focus groups to investigate their perceived efficacy of the various treatment types and found that almost all forest users and managers preferred the adaptive approach over the traditional management approach. Notably, forest users cited the importance of the availability of forest resources and lack of harmful plants in the plots that had undergone this method. Understanding how forest users relate to and experience invasive plants has been relatively understudied but can influence forest user engagement in different management approaches. For this reason, I performed in-depth ethnoecological interviews to explore how forest users perceive, how they utilize, and to what extent they value invasive plants. This mixed-methods approach contributes to a more holistic understanding of the role that local people play in invasive plant management and restoration activities.
Dissertation/Thesis
Doctoral Dissertation Environmental and Resource Management 2020

Human society is presently beset by an array of anthropogenic social-ecological crises that threaten the sustainability of the social-ecological systems that sustain our livelihoods. While research alone will not rectify these issues, it can help to answer key questions that must be addressed to develop effective solutions. To address such questions in a cohesive, compelling manner, social-ecological research can be bounded, structured, and distilled through innumerable organizing principles or theoretical frameworks. For this dissertation, I focused on the geographic region of Tierra del Fuego and sought to draw from the array of disciplines and methods that use sound as a lens for biological, ecological, and/or social inquiry. I also endeavored to consider various temporal, spatial, and organizational scales while investigating a selection of topics with a) specific importance in the social-ecological systems of Tierra del Fuego and b) general relevance to global social-ecological challenges. Chapter 1 provides an introduction to the dissertation, and Chapter 6 serves as a conclusion.

The objective of Chapter 2, “Biogeographical and analytical implications of temporal variability in geographically diverse soundscapes”, was to provide some guidance to passive acoustic monitoring (PAM) practitioners on how to design appropriate temporal sampling schemes based on the temporal variability of the sounds one wishes to measure and the power and storage limitations of acoustic recorders. We first quantified the temporal variability of several soundscape measurements and compared that variability across sites and times of day. We also simulated a wide range of temporal sampling schemes in order to model their representativeness relative to continuous sampling.

For Chapter 3, “Sentinels for sentinels: passive acoustic and camera trap monitoring of sensitive penguin populations”, we tested the utility of PAM to monitor behavior and abundance of Magellanic (Spheniscus magellanicus) and southern rockhopper penguins (Eudyptes chrysocome) at different spatial and temporal scales. We conducted in situ observations of the acoustic behavior of each species, and we compared acoustic metrics with penguin counts from narrowly focused camera traps and larger-extent observations of colony density.

Chapter 4, “Acoustic monitoring shows invasive beavers (Castor canadensis) increase avian diversity in Tierra del Fuego”, is focused on impacts of the invasive North American beaver (Castor canadensis) on Fuegian bird communities. We sought to determine how bird communities might differ between intact riparian forests, beaver ponds, and beaver meadows created by pond drainage. We conducted PAM and classic avian point counts under each of these conditions across seasons to test for differences between impact conditions and to compare the two methodologies.

For Chapter 5, “Human-nature connection and soundscape perception: insights from Tierra del Fuego, Argentina”, we evaluated the relationship between soundscape perception and nature relatedness by conducting surveys and soliciting responses to soundscape audio prompts. We also examined the potential for any demographic influences on nature relatedness or soundscape perception in the context of local social tensions.

Eastern black walnut (Juglans nigra L.) ranks among the most highly valued timber species in the central hardwood forest and across the world. This valuable tree fills a critical role in native ecosystems as a mast bearing pioneer on mesic sites. Along with other Juglans spp. (Juglandaceae), J. nigra is threatened by thousand cankers disease (TCD), an insect-vectored disease first described in 2009. TCD is caused by the bark beetle Pityophthorus juglandis Blackman (Corthylini) and the phytopathogenic fungus Geosmithia morbida Kol. Free. Ut. & Tiss. (Bionectriaceae). Together, the P. juglandis-G. morbida complex has expanded from its historical range in southwest North America throughout the western United States (U.S.) and Europe. This range expansion has led to widespread mortality among naïve hosts J. nigra and J. regia planted outside their native distributions.

The severity of TCD was previously observed to be highest in urban and plantation environments and outside of the host native range. Therefore, the objective of this work was to provide information on biotic and abiotic environmental factors that influence the severity and impact of TCD across the native and non-native range of J. nigra and across different climatic and management regimes. This knowledge would enable a better assessment of the risk posed by TCD and a basis for developing management activities that impart resilience to natural systems. Through a series of greenhouse-, laboratory- and field-based experiments, environmental factors that affect the pathogenicity and/or survival of G. morbida in J. nigra were identified, with a focus on the microbiome, climate, and opportunistic pathogens. A number of potentially important interactions among host, vector, pathogen and the rest of the holobiont of TCD were characterized. The holobiont is defined as the whole multitrophic community of organisms—including J. nigra, microinvertebrates, fungi and bacteria—that interact with one another and with the host.

Our findings indicate that interactions among host, vector, pathogen, secondary pathogens, novel microbial communities, and novel abiotic environments modulate the severity of TCD in native, non-native, and managed and unmanaged contexts. Prevailing climatic conditions favor reproduction and spread of G. morbida in the western United States due to the effect of wood moisture content on fungal competition. The microbiome of soils, roots, and stems of trees and seedlings grown outside the host native range harbor distinct, lower-diversity communities of bacteria and fungi compared to the native range, including different communities of beneficial or pathogenic functional groups of fungi. The pathogen G. morbida was also associated with a distinct community of microbes in stems compared to G. morbida-negative trees. The soil microbiome from intensively-managed plantations facilitated positive feedback between G. morbida and a disease-promomting endophytic Fusarium solani species complex sp. in roots of J. nigra seedlings. Finally, the nematode species Bursaphelenchus juglandis associated with P. juglandis synergizes with G. morbida to cause foliar symptoms in seedlings in a shadehouse; conversely, experiments and observations indicated that the nematode species Panagrolaimus sp. and cf. Ektaphelenchus sp. could suppress WTB populations and/or TCD outbreaks.

In conclusion, the composition, function, and interactions within the P. juglandis and J. nigra holobiont play important roles in the TCD pathosystem. Managers and conservationists should be aware that novel associations outside the host native range, or in monocultures, intensive nursery production, and urban and low-humidity environments may favor progression of the disease through the effects of associated phytobiomes, nematodes, and climatic conditions on disease etiology. Trees in higher diversity, less intensively managed growing environments within their native range may be more resilient to disease. Moreover, expatriated, susceptible host species (i.e., J. nigra) growing in environments that are favorable to novel pests or pest complexes (i.e., the western U.S.) may provide connectivity between emergent forest health threats (i.e., TCD) and native host populations (i.e., J. nigra in its native range).