Herbivory can have many effects on plant fitness, including altering plant-pollinator interactions and sexual reproduction in angiosperms. Pollinator-mediated interactions may be impacted when herbivores alter plant traits, such as floral display size, that can influence pollinator visitation rates, and, ultimately, the reproductive component of plant fitness. Here I describe an investigation into the indirect effects of feeding by beetles released as a biological control agent, Galerucella calmariensis and G. pusilla, on plant-pollinator interactions and reproductive output in the invasive plant Lythrum salicaria L. (purple loosestrife). During the summer of 2011, three treatments (low, ambient and mechanical herbivory) were applied to 105 plants during the pre-flowering period of growth. At the onset of flowering, a series of pollinator observations were conducted over the course of approximately 1.5 weeks. Several aspects of floral display were affected by the herbivory treatments, including increased inflorescence and flower production in the ambient and mechanical herbivory treatments, relative to the low herbivory treatment. Treatment type did not have a significant effect on the number of pollinator foraging bouts, but had marginally significant effects on the number of flowers probed per pollinator foraging bout and per 30-minutes. Moreover, treatment had a significant effect on the number of switches among the inflorescences on a single plant. I discuss the possibility that the differences in pollinator visitation were mediated by differences in the architecture and the size of floral display. There were no detectable differences in fruit or seed production (i.e., female fitness) among treatments. However, as I discuss, differences in pollinator visitation may affect other unmeasured aspects of fitness, such as the level of inbreeding or the number of seeds sired through male function.

In order to predict future range shifts for invasive species it is important to explore their ability to acclimate to the new environment and understand physiological and reproductive constraints controlling their distribution. My dissertation studied mechanisms by which temperature may affect the distribution of two of the most aggressive plant invaders in North America, Bromus tectorum and Bromus rubens. While Bromus tectorum is dominant in the “cold desert” steppes of the Intermountain region of western North America, B. rubens is one of the severe grass invaders in the “hot deserts” of southwestern North America. I first evaluated whether winter freezing tolerance is the mechanism responsible for the distinct northern range limits of Bromus species. Bromus rubens has a slower rate of freezing acclimation that leads to intolerance of sudden, late-autumn reductions in temperature below -12°C, Bromus tectorum, by contrast, cold hardens rapidly and is not impacted by the sudden severe late-autumn cold. Photosynthetic response to temperature does not explain their current range separation. Bromus species differ little in their photosynthetic temperature responses and the acclimation pattern of photosynthesis. Both species acclimated to a broad range of temperature through the amelioration of Pi regeneration limitation at sub-optimal temperatures and improved carboxylation capacity above the thermal optimum which probably resulted from increased thermostability of Rubisco activase. The effect of elevated temperatures during flowering on the seed yield of Bromus species demonstrates that neither species produces seed at 36°C and above. These thresholds are close to temperatures encountered during flowering in their natural environment. In summary, climatic changes will cause northward range expansion of Bromus species due to less severe autumn and winter, while reproductive failure could cause range contraction at their southern margins.

With steady growth in global commerce and intensified ship traffic worldwide, comes the increased risk of invasion by non-indigenous organisms. Annually, >7000 vessels traveled across Galveston Bay, Texas from 2005-2010. These vessels discharged ~106 million metric tons of ballast water, equivalent to ~3.4% of the total volume of the Bay. A majority of these discharging vessels originated from around the Gulf of Mexico and the Caribbean Sea. By evaluating the source and frequency of inoculations from various locations, we are striving to assess the invasibility risk to Galveston Bay by way of ballast water. We identified organisms from Galveston Bay, ballast water samples and growout experiments using molecular methods. To our knowledge, this is the first utilization of molecular methods to identify the phytoplankton community within Galveston Bay. Within Galveston Bay, we identified 15 genera of dinoflagellates, 2 of which have previously gone undetected including Takayama and Woloszynskia. Thirteen ballast water samples yielded twenty genera of Protists, Fungi or Animalia from at least ten different phyla. With more than seven genera identified, dinoflagellates were the most diverse group: including the known toxin producer Pfiesteria and Scrippsiella which has not previously been detected in Galveston Bay. The most common diatoms in the ballast water samples were Actinocyclus, Ditylum, Nitzschia, Stephanopyxis and Thalassiosirales. At the termination of the growout experiments eight genera of phytoplankton were identified including: Dinophysis, Gymnodinium, Gyrodinium, Heterocapsa, Peridinium, Scrippsiella, Chaetoceros and Nitzschia. With these findings, Galveston Bay has the potential to be both a recipient and donor region of dinoflagellates. Dinoflagellates, capable of forming harmful algal blooms leading to fish and shellfish kills, are being transported to Galveston Bay via ballast water. Our results suggest that Galveston Bay is at risk for invasive species introductions via ballast water and support the idea that a monitoring system within the ports as well as the bay should be put in place. The actions would help to maintain the current health of this ecosystem and aide in preventing a negative impact in the event of successful establishment of a non-indigenous species of phytoplankton transported to Galveston Bay via ballast water.

Conservation in Canada is increasingly driven by land use planning processes. Approaches to governing nature conservation have shifted dramatically from protecting isolated pristine areas to greater attention to the remaining fragments of greenspace in urban, semi-urban and rural areas. The ways that societies govern and use nature are always changing, and these physical management actions are connected to deeply rooted cultural norms and values about the ideal relationship between humans and nature. In the land use planning approach to conservation, citizens and governments find value and construct meaning for remaining nature rather than beginning with normative considerations of what is most worthy of protection. At the root of this conservation planning trend is a growing appreciation for hybrid nature that is valued as natural in spite of the past or present influences upon it. This represents a dramatic shift from the traditional values involved in North American nature conservation, where nature was most valued for its perceived separation from human influence and protected to maintain its untouched qualities. In light of these ideological shifts in the ways that Canadians value and in turn manage nature, is there a corresponding change in the ways that conservation activists perceive environmental value and evaluate naturalness? An increasing number of studies demonstrate that public valuation of nature is not limited to pristine environments: even highly disturbed environments can be valued as natural and are not perceived as a form of lesser nature. Conceptions of what is natural and what is not are highly subjective and variable; in particular, the body of work on the social dimensions of both invasive species and ecological restoration demonstrates the ways in which people construct naturalness in accord with their values and cultural context. By exploring the extent to which people perceive invasive species as reducing naturalness and how ecological restoration is perceived to restore it, these subjects serve as excellent conceptual lenses for exploring constructions of nature. This study explores the subtle variations in environmental values and perception of naturalness among a study population who self-identify as pursuing the same goal: ensuring the continued protection of the Oak Ridges Moraine. The Moraine is a partly urbanized landform in southern Ontario that is situated within a complex hybrid socio-ecological landscape. It is also the subject of an active and high profile conservation movement that has spanned over 40 years. Using a combination of interviews and Q Method, this study explored how citizens engaged in Oak Ridges Moraine conservation perceive both the current and ideal state of naturalness on the Moraine, with specific emphasis on how the discourses these citizens use to frame the Moraine invoke the concept of naturalness Findings from this study reveal that Moraine activists represent a conservation paradox: they value the natural, non-human qualities of the landform, yet at the same time identify the Moraine as a hybrid landscape with both social and ecological qualities. In particular, respondents indicated a strong interest in naturalness in the context of invasive species and ecological restoration, yet at the same time identified the naturalness of the Moraine to be a lesser priority in the face of urban development pressures. In this way, citizens engaged in Moraine conservation respond to the hybrid quality of the Moraine landscape by moving beyond the binary distinction between nature and society, situating themselves as both apart from and a part of the landscape at the same time. This finding demonstrates how values for conserving nature are affected by hybridity between social and ecological systems, and suggests how embracing the paradox of hybrid nature can contribute to understanding and managing complex socio-ecological systems.

Russian thistle (Salsola tragus L.) invaded areas of native montane grassland important to winter survival of bighorn sheep (Ovis canadensis Shaw) were studied in Jasper National Park, Alberta, Canada. The biology of Russian thistle and its control in the Park were studied in the field and greenhouse. Russian thistle in grasslands were 9.1 cm tall with 37.5 seeds per plant, whereas larger plants in naturally disturbed habitats were 29.8 cm tall with 1562.4 seeds per plant. Plants travelled up to 4,180 m during dispersal. With soil seed contact, litter depth did not inhibit performance or survivability; without soil contact, thick litter reduced germination and plant performance. Russian thistle responded positively to increased greenhouse temperature and drier conditions. Seven control treatments involving herbicide, seeding mixes, hand pulling, and grazing exclusion were assessed. Grazing exclusion was the best field management option, increasing litter and biomass, while reducing Russian thistle density and biomass. / Land Reclamation and Remediation

Caulerpa taxifolia is a marine alga notorious for its introduction and subsequent colonization of the Mediterranean Sea. It is recognized as one of the 100 worst invasive species, and it is suggested that much of its expansion may have been at the expense of native seagrass beds. To date, the bulk of research on C. taxifolia has centred on quantifying expansion and methods of eradication. There are few quantitative data on the relationship between C. taxifolia growth and environmental characteristics (e.g. light, temperature, nutrients). Furthermore, once C. taxifolia has been introduced to a system it is exceptionally difficult and expensive to eradicate. Accordingly the implications, both positive and negative, of this new habitat type must be considered in the context of the new habitat mosaic into which it fits. Australia is unique in that it has both native and invasive populations of C. taxifolia. These populations offer not only an opportunity to examine the dynamics of C. taxifolia beds and their associated communities at different latitudes and temperature and light regimes, but especially in the context of a high diversity marine coastal environment. The objectives of this thesis were to use native (Moreton Bay, Queensland) and invasive (Pittwater, New South Wales and Port River, South Australia) populations of C. taxifolia to: 1) quantify the relationship between environmental drivers (light, temperature, nutrients) and C. taxifolia growth, and 2) examine differences in habitat use and function between seagrass, C. taxifolia, unvegetated substrate. Most of the locations in Australia where large C. taxifolia beds occur are adjacent to urban areas that have a degraded water quality. Manipulative experiments in Moreton Bay demonstrated that nutrients stimulate C. taxifolia growth, however, light availability and seasonality appear to influence the response of C. taxifolia growth to nutrients. Short-term manipulative experiments were conducted across a range of seasons and locations, to capture the effects of temperature on growth. Temperature was the dominant factor affecting rate of stolon extension in both native and invasive locations. Colonization potential of C. taxifolia appears to be driven by ambient water quality (light and nutrients) and bed expansion is driven by temperature in systems where nutrients are saturating. Epifaunal communities sampled by beam trawl were dominated by the families Palaeomonidae, Terapontidae, Scorpaenidae, Monacanthidae, Syngnathidae, Gobiidae, and were largely similar between seagrasses and C. taxifolia; however, syngnathids were absent from C. taxifolia beds. I examined habitat use patterns between seagrass (Zostera muelleri), C. taxifolia, and unvegetated substrate. Fish preferred seagrass to C. taxifolia; however, in the absence of a seagrass fish used C. taxifolia. While C. taxifolia may have similar structural benefits to some seagrasses, there are fewer food resources available within C. taxifolia beds. Furthermore, grazing may be limited to a few specialist grazers. Within the habitat mosaic, C. taxifolia will provide some benefit over an unvegetated substrate; however, that benefit might mask losses in system quality or resilience by decreasing the threshold level for change within the community. Therefore, should a perturbation occur (e.g. sudden drop in water temperature, filamentous algal bloom) a system comprised solely of seagrass could withstand such stress; however, a habitat mosaic of seagrass and C. taxifolia could have a rapid and dramatic loss in its ability to sustain a diverse faunal community. Ultimately, it is most important to protect the system from anthropogenic degradation so it is more resilient to environmental changes.

Thesis (M.S.)--Miami University, Dept. of Botany, 2008. / Title from first page of PDF document. Includes bibliographical references (p. 22-29).

Thesis (M.S.)--Indiana University, 2008. / Department of Earth Sciences, Indiana University-Purdue University Indianapolis (IUPUI). Advisor(s): Pierre-Andre Jacinthe, Lenore P. Tedesco, Philippe G. Vidon. Includes vita. Includes bibliographical references (leaves 95-99).

Thesis (M.S.)--Miami University, Dept. of Botany, 2005. / Title from first page of PDF document. Document formatted into pages; contains [1], iv, 65 p. : ill. Includes bibliographical references (p. 38-40).

Thesis (M.S.)--Miami University, Dept. of Botany, 2006. / Title from first page of PDF document. Includes bibliographical references.