Invasive species often threaten biodiversity and environmental processes in their introduced range by extirpating native species due to competition for resources. Nylanderia fulva (formerly N. (=Paratrechina) sp. nr. pubens) is an ecologically dominant and economically important invasive species in the United States. This dissertation addresses aspects of the biology, behavior, management, and collection techniques for N. fulva. Specifically, topics investigated include a modified drip technique for extracting ants from their substrate, the effectiveness of a broadcast ant bait as a stand-alone treatment, the foraging preference and peak activity of workers, the reproductive potential of queens, and the ability of this species to translocate pathogenic microorganisms. The primary goal of these works was to better understand the biological idiosyncrasies of this species that may ultimately lead to the mitigation N. fulva populations. A modified drip technique was developed to quickly and efficiently extract N. fulva from their nesting substrates. Ants and their associated substrates were collected in 18.9 L buckets lined with talcum powder and transported to the laboratory. Substrates were weighted down and a cardboard tower was provided for the immigration of ants as they were forced out of substrates with a slow influx of water. Three applications of Advance Carpenter Ant Bait (ACAB) were applied to a N. fulva population in East Columbia, TX. A series of GIS interpolated maps depict achieved management and subsequent rebound of N. fulva populations. As great as 77% population reduction was achieved by 1 week post treatment, but N. fulva populations rebounded within 3-4 weeks. As a stand-alone treatment, this bait did not provide adequate ant management in treatment plots. Diet preference experiments were performed using artificial diets and food lures. These results of these trials indicated that N. fulva preferred the most carbohydrate rich diet offered through all seasons and that mint apple jelly or hot dog slices were the favored food lures. Diel foraging behavior was observed when temperatures were between 9.95 and 37.26 degrees C. Peak foraging activity occurred at 28.24 +/- 3.12 degrees C. A laboratory investigation of N. fulva suggested that as the number of queens increased, individual queen fecundity increased. This phenomenon is a novel observation among ants and suggests an alternative mechanism for intracolony dominance. Hexagyne colony fecundity of 0.25 +/- 0.12 eggs/queen/hr was the maximum fecundity observed. Results of laboratory experiments showed that N. fulva were capable of transferring E. coli up to 4.5 m in 6 hrs after acquisition from a contaminated source. Pyrosequencing of ectomicrobial assemblages revealed a suite of 518 bacteria and 135 fungi species associated with N. fulva, many of which are known pathogens of plants and animals, including humans. These results suggested that N. fulva should be regarded as both a medically and agriculturally important species.

Invasive non-indigenous species are among the principle drivers of global change, altering nutrient cycles, changing disturbance regimes, and generally threatening biodiversity. Climate change is widely expected to exacerbate invasions by relaxing abiotic barriers, such as low temperature, but the mechanistic evidence supporting this is limited. Here, I evaluate the hypothesis that low temperatures determine the northern range limit of kudzu (Pueraria montana var. lobata), an invasive Asiatic vine in North America, by assessing freezing and chilling tolerance of kudzu plants in winter, spring, summer, and fall. Kudzu was widely planted throughout the southeastern U.S. in the early 20th Century to prevent erosion. It is winter-deciduous and reproduces primarily from buds on stem nodes. In the last 40 years, kudzu has migrated northward in concert with a northward shift in the -20oC minimum winter temperature isocline, indicating that less severe winter cold is permitting northward migration. Freezing mortality during winter does not explain this correlation. Electrolyte leakage assays demonstrate that above- and belowground kudzu stems can survive to -27oC and -17oC. Insulation provided by soil and snow protects belowground stems from lethal temperatures to well north of kudzu's current range limit. Severe spring chill stops growth and photosynthesis and causes some shoot mortality, but both growth and photosynthesis recover quickly following the chill. Summer growth rates are rapid (up to 22 cm/d), responding within hours to temperature changes, and are unimpaired by nighttime lows. Photosynthesis is reduced at cool temperatures, but on cool days, kudzu leaves tend to be warmer than air temperature, so photosynthesis rates generally remain close to optimal values. In autumn, growth stops below 15oC, but leaves are retained and maintain modest photosynthetic competence until killed by frost in November. In colder climates that occur far north of kudzu's current range, reductions in the length and quality of the growing season could accumulate over time to reduce kudzu's success. There is, however, no strong evidence that low temperatures in any season will prevent kudzu from migrating throughout southern Ontario, making kudzu a good candidate for invasive species regulations.

Invasive species are an increasingly severe conservation problem that can dramatically alter native plant communities. Although ecologists have proposed many mechanisms for the dominance of invasive species, superior competitive ability is one of the longest standing hypotheses. In winter annual plant communities, germination timing affects competition among plants. I hypothesized that grass invasion has changed the costs and benefits of early and late germination, and that species with flexible germination timing would compete better with invasives. Experiments at the Bernard Field Station in Claremont, CA and germinator trials in a controlled environment were used to examine the survivorship and germination rate of three native forbs in the presence or absence of invasive grass competition. Germinator trials revealed that most Clarkia purpurea seeds germinated in fall conditions, though newer seeds had higher proportions germinate under winter conditions. Older seeds had a lower germination success, indicating a potential decrease in seed viability. In the field experiment, November germinants had higher survival rates than October germinants for Amsinckia menziesii and Phacelia distans, and both species had similar numbers of new germinants at each census. Removal of invasive grasses did not significantly affect the survival of either species, though a trend towards increased survivorship was observed in removal plots of November germinants. Taken together, these results show evidence for variation in germination timing and responses to environmental cues among native annual seeds, and also support the idea that germination timing has important consequences for survivorship, and potentially competitive interactions, with invasive grasses.

Exotic species are a great concern because of the possibility of negative effects once they become established. The exotic cactus moth, Cactoblastis cactorum has a reputation for being detrimental to Opuntia populations throughout Florida and the southeastern United States. Multiple projects are currently underway to attempt to contain and eradicate this species before it can migrate to the Opuntia-rich desert southwest and the agricultural Opuntia fields in the Mexican highlands. These projects have been undertaken without previous studies to determine what negative effects, if any, the moth is having on the common native Opuntia species. This is understandable; since it was earlier suggested that C. cactorum was doing great harm to rare and endangered species in the Florida Keys (Stiling et al. 2004). This study looks at the effects of the native moth borer, Melitara prodenialis and the exotic invader, Cactoblastis cactorum on two common Opuntia spp. within central Flo rida. Throughout the duration of this study, the coastal plants were subjected to damage solely by C. cactorum and the inland plants by M. prodenialis. The amount of moth damage was compared between three inland and three coastal sites, as well as between plants subjected to prescribed fire and those that were not within these sites. Plant mortality was determined for both the sites and burn treatments. The number of eggsticks was also compared between inland and coastal sites and burned and unburned treatments. The results of this study show that although there is a significant difference in plant mortality between inland and coastal sites (higher mortality was shown at inland locations), there is no difference in moth damage at these sites. This suggests that the exotic moth is doing similar or less damage to the cactus than is the native moth. The number of eggsticks was also greater at coastal sites. This indicates that although the exotic moth is more prolific than the native, it is still unable to cause higher cactus mortality rates. None of the data was significant between burned and unburned treatments, indicating that prescribed fire does not have any effect, negative or positive on the Opuntia.

Woody plant encroachment, that is, a substantial increase in the abundance of woody plants in a grassland or savanna, occurs in many parts of the world. It often has large effects on plant and animal populations and communities and on ecosystem properties and processes. However, little is known about the dynamics of woody plant encroachment and how these are affected by soils, by topography, and by the spatial pattern of the vegetation. Encroachment in turn can affect the spatial pattern of the vegetation. Using data from historical aerial photographs, I measured changes in woody plant cover and constructed, parameterized and compared a set of dynamic models of woody plant encroachment in central Texas savannas. These models predicted final woody cover from initial woody cover and the initial spatial configuration of woody plants. Then I incorporated soil and topography into these models to determine their effects. Finally, I examined the effects of encroachment on the spatial pattern of the vegetation. Incorporating negative density dependence in our models improved their fit, demonstrating that encroachment is density-dependent. A function that predicted the formation of new woody patches from a density-independent seed supply also improved the models' performance. The improvement in the models that resulted from incorporating the total length of woody-herbaceous edges confirmed that encroachment in this system occurs in part by the outward expansion of woody patches. The spatial pattern of the vegetation changed during woody plant encroachment. Spatial pattern (measured as degree of fragmentation) often had a non-linear relationship with cover. Furthermore, the spatial heterogeneity in fragmentation, that is, plot-to-plot variation in the degree of fragmentation, also changed during encroachment. Topography and soil type had, in general, little effect the dynamics of woody plant encroachment. Therefore, a relatively simple model of woody plant encroachment provided good predictions of woody cover at the end of the time periods. Other systems experiencing woody plant encroachment, forest succession, or invasion by non-native plants could be modeled using the same approach. / text

In Nova Scotia subtidal habitats, the invasive bryozoan Membranipora membranacea interacts with native bryozoan Electra pilosa on kelps, which offer high space availability but are highly dynamic, and on non-kelp algae, which provide low space but high stability. Settlers and colony cover of M. membranacea at various stages critical to its population dynamics, as well as relative abundance and encounter outcomes of M. membranacea and E. pilosa, were quantified on these substrates. I also examined the effects of various factors on growth rates of E. pilosa. For M. membranacea populations, the roles of kelp and non-kelp substrates varied intra- and inter-annually, as well as spatially. Membranipora membranacea was relatively more abundant on kelps than on Fucus, likely due to large colony size, faster growth, and strong overgrowth abilities. While kelps provide spatial resources for seasonal peaks in abundance of M. membranacea, non-kelp refuges can preserve local populations in time.

The introduction of harmful aquatic organisms and pathogens transferred through ships' ballast water and sediments from one coastal region to another has ecological, economic, environmental, and human impacts. The international community, through numerous binding and non-binding instruments, also sought to combat this problem. Ultimately, the International Convention for the Control and Management of Ships' Ballast Water and Sediments, 2004 was adopted by the International Maritime Organization as the dedicated legal regime intended to prevent, control and ultimately eradicate the introduction and spread of harmful aquatic organisms and pathogens through ships' ballast water and sediments. By its Regulations, the Convention sets out coastal/port and flag State obligations along with subsequently adopted technical Guidelines by which to implement it. Despite the importance of this problem, the Convention has not entered into force. This study assesses the potential of the Convention to promote achievement of the goal to prevent and eliminate this source of marine and biodiversity degradation and destruction. The study finds that the Convention constitutes a useful global legal regime within which steps can be taken to establish uniform ground rules, standards and practices to combat the introduction, transfer and spread of harmful aquatic organisms and pathogens across the world's coastal and marine areas. Nevertheless, its potential is undermined, among others, by the exemption of some categories of ships from its application, financial costs, especially to developing States, of implementing its requirements, and by the fact that its provisions do not account for other salient sources by which harmful aquatic organisms and pathogens are spread. Suggestions are made to encourage more ratification to bring the Convention into force and on remedying some of the weaknesses in the formulation of its rules. It is concluded that if it is ratified by sufficient and wide number of States as well as conscientiously implemented by States, adopting additional national laws and policies to regulate areas which are not addressed by the Convention, it would facilitate progress in the global effort to improve the protection of marine environments, ecosystems, and biodiversity, specifically, as regards the contribution towards combating the introduction and transfer of harmful aquatic organisms and pathogens via ships' ballast water and sediments. / The threat posed by harmful aquatic organisms and pathogens to the society at large is devastating. The Ballast Water Management Convention 2004 was adopted to remedy this problem. Though the Convention has potential to combat the threat, it has some ambiguities. This study concludes that if the provisions of the Convention, coupled with the recommendations made in this study are implemented at State level, we will have an international community that is free from the menace posed by harmful aquatic organisms and pathogens introduced through ships' ballast water and sediments, and a safer marine ecosystems will be ensued for us in due time.

No description available.

Invasive alien species (IAS) pose a serious threat to ecosystems and societies worldwide. Local ecological knowledge (LEK) is increasingly valued as a means of understanding environmental issues; however, its application in the context of IAS research has been limited. The overall objective of this study was to document the LEK of farmers and Weed Supervisors to gain insight into a recent IAS, Odontites serotina. I conducted semi-structured interviews with farmers and Weed Supervisors with O. serotina management experience. Results indicated that the socio-economic impacts for farmers were severe in affected rural communities. However, participants had developed promising control techniques, including the application of compost mulch. I used this LEK as well as data on species occurrence, environmental variables, and measures of propagule pressure to forecast the potential distribution of O. serotina across Manitoba. The risk map generated will be useful for guiding future monitoring and public outreach efforts.

Lake Winnipeg has been subject to intense eutrophication and invasive species such as Rainbow Smelt and Eubosmina coregoni for the last 40 years. This study demonstrated significant increases in total phosphorus, total nitrogen, chlorophyll-a, overall zooplankton abundance, and specifically Cladocera, between 1969 and the first decade of the 21st century. There were specific basin differences in the long-term changes of the Cladocera community, with the species Chydorus sphaericus and Ceriodaphnia quadrangula negatively affected by high levels of phosphorus, nitrogen and chlorophyll-a. Moreover, long-term change in the Cladocera community composition and abundance throughout the years (1969-2011) during summer was correlated with intensifying eutrophication. Additionally, weak diel vertical migration in the zooplankton community was observed for the first time in Lake Winnipeg.