No description available.

Phalaris arundinacea L. is an aggressive species that can dominate wetlands by producing monotypic stands that suppress native vegetation. In this study invasion windows were created for native species in monotypic stands of P. arundinacea with either fire or herbicide. Three native species groups, herbaceous plants, herbaceous seeds, and woody shrubs, were planted into plots burned or treated with herbicide in the early spring. Fire did not create an effective invasion window for native species; there was no difference in P. arundinacea root and shoot biomass or cover between burned and control plots (p ≥ 0.998). Herbicide treatment created an invasion window for native species by reducing P. arundinacea root and shoot biomass for two growing seasons, but that invasion window was fast closing by the end of the second growing season because P. arundinacea shoot biomass had nearly reached the shoot biomass levels in the control plots (p = 0.053). Transplant mortality, frost, and animal herbivory prevented the herbaceous species and woody seedlings from becoming fully established in the plots treated with herbicide during the first year of the experiment. Transplanted monocots had a greater survival than dicots. By the second growing season the herbaceous group had the greatest mean areal cover (5%), compared to the woody seedlings (3%) and seed group (0%). Long-term monitoring of the plots will determine whether the herbaceous transplants will compete effectively with P. arundinacea and whether the woody species will survive, shade the P. arundinacea, and accelerate forest succession.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22898号 / 農博第2441号 / 新制||農||1083(附属図書館) / 学位論文||R3||N5318(農学部図書室) / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 松浦 健二, 教授 大門 高明, 教授 寺内 良平 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Solenopsis invicta is an invasive ant that has caused detrimental impacts to ecosystems and economies in the Southeastern United States, recently including Virginia. In this study, we explored the invasion ecology of S. invicta through two main objectives. First, we established a comprehensive distribution map of S. invicta in Virginia through multiple survey techniques. We then compared our findings with published models quantifying the potential spread of S. invicta and created our own species distribution model. In 2020-2021, S. invicta occurrences were found in 7 counties beyond the current Quarantine and our data show that S. invicta has spread further than predicted. Our own species distribution model suggests that the distribution area for S. invicta is likely to increase under the projected climate change. This study provides insights into the range expansion of S. invicta at the border of its suitable habitat and allow for improvements to models of its spread under these conditions. Additionally, it provides useful information to inform county extension agents to know where they are to expect new infestations of S. invicta. Second, we investigated the impacts of pesticide residue on the behavior of S. invicta through neonicotinoid exposure. We found detectable levels of neonicotinoids in the soil of the ant mounds as well as in the ants themselves. In addition, we investigated the effects of dietary exposure to imidacloprid on foraging behavior in a laboratory setting. We found that unexposed colonies were able to locate the food source more quickly during the second trial while exposed ants were unable to improve their performance. We also found that more exposed ant workers were unable to successfully navigate the maze as compared to unexposed workers. Our results suggest impaired learning of maze tasks and impaired navigational skills in neonicotinoid-exposed ants. / Master of Science in Life Sciences / The red imported fire ant (RIFA) is an invasive ant species found throughout the Southeastern United States that has negatively impacted ecosystems and economies. In the past few decades, RIFA has invaded the Coastal Plain of Virginia, resulting in legislation that restricts the movements of soil, plant products, and some equipment in and out of several southeastern counties and independent cities. To develop better management practices, there is a critical need to understand the spread, establishment, and impacts of RIFA in greater detail. We aimed to do this by surveying the current distribution of RIFA in Virginia and investigate the impact of insecticide use on their spread and behavior. In 2020-2021, we found RIFA occurrences in 7 counties beyond the current Quarantine, which is further than previously predicted. We then built a model using climatic variables that predicts the distribution of RIFA and found their habitable range is likely to increase under the projected climate change. Additionally, we investigated the impacts of common agricultural pesticides on the behavior of RIFA. We found these chemicals present in both the soil of the ant mounds and in the ants themselves. We also found that dietary exposure to imidacloprid, a neonicotinoid pesticide, altered the foraging behavior of RIFA. This study provides useful information to advise county extension agents to know where they are to expect new infestations of RIFA. Our results also suggest that human activity alters the invasion ecology of recent arrivals such as the red imported fire ant.

Thesis (PhD (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / Dispersal plays an essential role in determining the distribution of populations of species, especially species expanding their ranges. Two disciplines are concerned with gaining understanding of spread of species, namely restoration ecology and invasion biology. Con- ceptual understanding of dispersal, its mechanisms and its management is essential to both disciplines. Nevertheless, the disciplines have quite opposite objectives: in restoration ecol- ogy, spread of indigenous species into transformed landscapes is promoted, while invasion biology aims to prevent the (further) spread of alien species into pristine or restored habi- tats. Despite these two opposite objectives of facilitating spread and preventing spread of their respective target species, these disciplines have essentially the same requirements in terms of information needed for restoration. In this thesis, I will present two modelling studies—one looking at the impact of two different seed-feeding alien control agents on the spread of Hakea sericea, the other investigating the recolonisation by Dicerothamnus rhinocerotis of an old field dominated by Cynodon dactylon. Based on these studies, I will draw conclusions for the management in each case. In a second step, I will compare these two seemingly-different studies and draw conclusions on how these two disciplines can learn from each other, and how conclusions drawn and management recommendations developed for the one discipline can be translated for the other. The invasion biology study concluded that seed-feeding biocontrol agents do have a considerable impact on the velocity of the spread of the target species. In addition, management recommendations included the possibility of substituting seed-feeding biocontrol agents with an increased fire frequency where the negative impact on natural vegetation, on the site invaded by the target species, is acceptable. The restoration study concluded that the main impact on the velocity of spread, and the speed of the return of the shrub species onto the old fields, is the availability of micro-sites. A sensitivity analysis showed the even a slight change from 1% to 2% increases the velocity and pattern of spread dramatically. The other parameters playing an important role are the mean rate of establishment and the time span between

The degree to which biotic interactions influence invasion success may partly depend on the evolutionary relationship between invaders and native species. In particular, since host-use by enemies such as invertebrate herbivores and fungal pathogens tends to be phylogenetically conserved, exotic plants that have close native relatives in the invaded range should be more likely to interact with enemies. In this thesis, I explore this idea using a series of experiments and field surveys at nested taxonomic levels. My results indicate that exotics from multiple plant families experience lower damage if their average phylogenetic distance from locally co-occurring native family members is higher. I then demonstrate that within the Asteraceae, foliar and capitular damage are lower on exotic compared to native species. Both damage types had a relatively large phylogenetic component, but did not decline with phylogenetic distance to native or exotic confamilials. Finally, I show that communities with versus without close relatives are unlikely to differ in resistance to the novel invader, Solidago virgaurea: biotic resistance imposed by competitors, generalist vertebrates, and specialist invertebrates resulted in similar patterns of damage and mortality regardless of the presence of congeneric natives. In some cases, effects of biota were positive: growth of S. virgaurea seedlings in soils collected near congeneric natives was enhanced more than in soils from communities where congenerics were absent. Overall, these results suggest that biotic interactions between exotic and native species can be phylogenetically structured, although trends based on distance measures tend to be weak. In some cases, damage does decline with phylogenetic distance to native species; however this trend is unlikely to be a strong force limiting invasion or structuring plant communities. These results have significant implications for current theories of invasion biology including the "Enemy Release Hypothesis" and "Darwin's Naturalization Hypothesis", as well as for community phylogenetics.

The degree to which biotic interactions influence invasion success may partly depend on the evolutionary relationship between invaders and native species. In particular, since host-use by enemies such as invertebrate herbivores and fungal pathogens tends to be phylogenetically conserved, exotic plants that have close native relatives in the invaded range should be more likely to interact with enemies. In this thesis, I explore this idea using a series of experiments and field surveys at nested taxonomic levels. My results indicate that exotics from multiple plant families experience lower damage if their average phylogenetic distance from locally co-occurring native family members is higher. I then demonstrate that within the Asteraceae, foliar and capitular damage are lower on exotic compared to native species. Both damage types had a relatively large phylogenetic component, but did not decline with phylogenetic distance to native or exotic confamilials. Finally, I show that communities with versus without close relatives are unlikely to differ in resistance to the novel invader, Solidago virgaurea: biotic resistance imposed by competitors, generalist vertebrates, and specialist invertebrates resulted in similar patterns of damage and mortality regardless of the presence of congeneric natives. In some cases, effects of biota were positive: growth of S. virgaurea seedlings in soils collected near congeneric natives was enhanced more than in soils from communities where congenerics were absent. Overall, these results suggest that biotic interactions between exotic and native species can be phylogenetically structured, although trends based on distance measures tend to be weak. In some cases, damage does decline with phylogenetic distance to native species; however this trend is unlikely to be a strong force limiting invasion or structuring plant communities. These results have significant implications for current theories of invasion biology including the "Enemy Release Hypothesis" and "Darwin's Naturalization Hypothesis", as well as for community phylogenetics.

Invasions from coho salmon were first reported in the Cape Horn Biosphere Reserve (CHBR) in 2019 which is the most southern distribution registered to date. The CHBR is known for its high number of endemic species and unique biodiversity, such as the native fishes Galaxias maculatus and Aplochiton taeniatus. There are now three invasive salmonid species in the rivers of CHBR and are a potential threat to the native fish taxa. Stable isotope and gut content analysis were used to understand resource utilization by both native galaxiid and invasive salmonid taxa, as well as aquatic macroinvertebrates and riparian spiders. The natural laboratory study approach applied to this research, allowed for comparisons of differences within streams that contain conditions in which fish do not occur naturally, to sites in which high densities of invasive salmonid exist. Analysis of the trophic niche and diet in this study showed the importance of marine resource use by the native galaxiid and coho salmon juveniles supported with elevated δ15N and δ34S ratios. Diet analysis also confirmed there was the highest similarity between the coho salmon juveniles and the native fish. Altered behavior and habitat use was shown through the isotope and diet analysis for the galaxiid in snow melt streams which could be due to the high density of invasive salmonids in these streams. The invasive salmonids were found to impact aquatic macroinvertebrate populations, specifically larger bodied Trichoptera abundance. Aquatic insect emergence was negatively correlated to salmonid densities. The aquatic insect emergence revealed alterations with significantly higher biomass of aquatic insect emergence in upstream sites without invasive fish. Lastly, aquatic insect predator (Hydrobiosidae: Rheochorema sp.) exhibited a suppressed trophic position in rivers with invasive salmonids. An unexpected finding from the study was the refugium stream habitat conditions that has been shown to be important for conserving the native fish in the CHBR. We conclude that the impacts from invasive species are significant enough to disrupt lower trophic levels especially aquatic insects. The altered aquatic emergence and insect behavior have the potential to disrupt food webs and ecosystem functioning in the southernmost protected ecoregion in the world.

Predicting the impacts of non-native species remains one of the greatest challenges to invasion ecologists. Because of their insularity, freshwater systems are particularly vulnerable to invasions, especially from non-native predators. The research in this thesis explores the role of abiotic and biotic factors in mediating the distribution and impact of Bythotrephes longimanus, a predatory cladoceran that has been introduced to freshwater systems in North America. Although the general impacts of this invasion have been documented, little is known about the factors that modulate them. Using a combination of field surveys and experiments, I tested several hypotheses concerning the influence of interactions with native species, as well as the role of heterogeneity in the light environment, in mediating the impact of Bythotrephes. Results demonstrated that biotic resistance by native macroinvertebrate predators does not play a limiting role in the establishment success of Bythotrephes. However, the within-lake distribution of Bythotrephes was influenced by these macroinvertebrates, suggesting that the native predator context matters when trying to understand the impacts of non-native predators. This was demonstrated with a mesocosm experiment in which the impact of Bythotrephes was constrained by the native Chaoborus larvae. In terms of the abiotic environment, in situ feeding experiments demonstrated that refuges from impact could exist for some prey taxa, as the outcome of predation by Bythotrephes was dependent on light availability and some prey taxa were more successful at evading predation under low light conditions. Finally, results show that adaptive behaviour by prey is also an important determinant of impact, as migrating Daphnia can escape predation effects by Bythotrephes. The combination of light-limited predation and a shallow distribution by Bythotrephes selects for prey that occupy relatively deeper positions during the day. As a whole, this research highlights the importance of complex interactions in mediating the impact of Bythotrephes and may help to explain some of the variation that has been documented among invaded lakes. A better understanding of these complex interactions can improve our ability to anticipate impacts as Bythotrephes continues to spread, as well as provide insight on some of the long-term effects following invasion. / Thesis (Ph.D, Biology) -- Queen's University, 2013-06-17 09:26:35.221