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<p>Plants often grow in communities closely surrounded by neighbouring plants. Plants can actively and intensely compete for resources and also anticipate competition by sensing environmental cues from the presence and identity of neighbours. Moreover, it’s been proposed that the evolution of both increased and decreased competitive ability may serve as a mechanism for invasiveness. However, still little is known about how plants integrate competitive responses when sensing multiples cues of competition and which individual competitive traits respond to the identity of competitors. In addition, whether and why the evolution of competitive traits may contribute to the ability of introduced species to become invasive is also poorly understood.</p> <p>Here I present a body of work that examined the competitive responses of a native and an invasive plant species to cues of competition and the identity of neighbours. I also examined how experimental manipulation of pot volume, to control belowground resources, affects plant growth and allocation. In one study I tested the competitive responses of the North American native, <em>Impatiens pallida</em>, to cues signalling the presence of neighbours above and belowground simultaneously in competitive environments composed of either siblings or strangers. I demonstrate that<em> I. pallida</em> can recognize siblings and shows more aggressive competitive behaviours towards strangers than kin.</p> <p>In two other studies, I compared the competitive responses of the invasive and native ecotypes of <em>Alliaria petiolata</em> to changes in density, as well as to the presence and identity of neighbours. I found that invasive ecotypes produced less competitive phenotypes especially under high density. Moreover, I found that invasive ecotypes performed better when sharing rooting space with neighbours that were siblings.</p> <p>Taken together, these results demonstrate the ability of these plant species to respond to the identity of neighbours and provide strong evidence in support of the evolution of reduced competitive ability hypothesis in invasive plant species potentially mediated by the action of kin selection in invasive ecotypes.</p> / Doctor of Philosophy (PhD)

Invasive plants can displace native species, deteriorate native forest, and change plant communities and ecosystem functions. Native plant populations are fundamentally impacted by invasive species because of the interactions between invasive species and native plants. This study focuses on understanding the extent, mechanisms and consequences of interaction between a non-indigenous invader Ailanthus altissima and its functionally similar native species Robinia pseudoacacia in the Mid-Appalachian region, from an individual scale to a regional scale. These two subject species are common and coexist in early-successional eastern deciduous forest. The interactions between these two common species are important to community structure and canopy tree regeneration. To address the type and extent of interactions of these two species, a greenhouse experiment utilizing various species proportions, nutrient levels and seed sources was performed. In addition, a common-garden experiment with various species densities and proportions over three consecutive growing seasons was performed in a more natural condition than that of the greenhouse experiment. We found at the seedling stage, the dominant interaction was competition, and R. pseudoacacia was the winner both above- and belowground. The allelopathic compounds of A. altissima may have inhibited nodulation of R. pseudoacacia. Ailanthus altissima seedlings from its native region had slightly stronger competitive abilities compared with the seedlings from its invaded range. In the common garden experiment, R. pseudoacacia plants grew quicker than A. altissima, but A. altissima inhibited the growth of R. pseudoacacia by interspecific competition. The negative impact of A. altissima on R. pseudoacacia became larger as time progressed. To assess the community-level consequences of the two species, we conducted a forest mapping and a complete target-tree-based forest survey, and analyzed regional-scale data from the Forest Inventory Analysis Data Base. The two target species were significantly associated with themselves and with each other. Community species composition and diversity were significantly different across sites. A negative impact of both species on the understory community diversity and tree regeneration at the neighborhood scale was detected; while at a regional level, tree diversity in the FIA plots with either A. altissima or R. pseudoacacia was higher than the reference plots. / Ph. D.

The increasing scope and speed of biological invasions around the world is a major concern of the modern environmental conservation movement. Although many ecological impacts of biological invasions are still not well understood, there is a general consensus that exotic, invasive species are a primary driver of extinctions globally. By altering ecosystem structure and function, invasive species also affect human quality of life; however, not all impacts lead to negative outcomes. Given that invasive species have diverse impacts on society, their management in human-dominated landscapes is a wicked problem wherein the resolution is as much an issue of social value as technical capacity. The purpose of my research was to understand the propensity for engaging private landowners in an effort to eradicate an invasive species on an inhabited island. Specifically, I investigated private landowner perspectives on eradicating the North American beaver (Castor canadensis) from the Tierra del Fuego (TDF) island archipelago in Argentina and Chile. The beaver was introduced in 1946 and has since become a central conservation issue due to its long-lasting changes to local hydrology, nutrient cycling, riparian vegetation, food webs, and aquatic and terrestrial species assemblages. Because eradication requires near complete cooperation from stakeholders and no research had been conducted to understand the perspectives or willingness of private landowners to cooperate, my objectives were to: 1) characterize the links private landowners make between the presence of beavers and impacts to the ecosystem services in their riparian areas, and 2) explore the role of a market-based incentive program to increase landowner cooperation in eradication efforts. Through semi-structured interviews, I elicited landowner mental models of how beavers impact the ecosystem services they receive from their riparian lands. I found that TDF ranchers prioritized provisioning ecosystem services, and held diverse and idiosyncratic beliefs about how beavers influence these outcomes. TDF ranchers may not recognize the beaver as a highly salient problem because they do not connect them to reductions in ecosystem services that are important to them. Among those who do perceive beavers affecting important ecosystem services, there is no clear, unified understanding of how the beavers disturb the ecosystem and key ecosystem services. Additionally, in a broadly administered survey, I used a factorial vignettes to examine the role of program structure and other program-related factors on landowners' willingness to participate in a voluntary eradication program. Overall, landowners were willing to cooperate in an incentive program to eradicate beavers. They were positively motivated by greater financial compensation, an increased expectation that the program would be successful, and the program assuming full responsibility for its implementation. Other factors returned mixed results indicating that further research may be required. In diverse, human-inhabited, and privately-owned landscapes, conservation requires collective action—i.e., the high threshold of participation needed for eradication to be achieved. Understanding the knowledge systems that cause landowners to perceive value or risk serves as a first step in understanding behaviors, and can also serve as a framework for crafting more effective outreach, as current communication about the beaver and the proposed eradication may not resonate with private landowners. Further, barriers to inaction can be overcome by understanding landowner needs and how program-related factors influence the potential for cooperation. In sum, by putting human needs at the forefront of program design, conservation planners can better understand stakeholder perspectives, reduce barriers to participation, and ultimately increase cooperation and improve conservation outcomes. / Master of Science

<p dir="ltr">Using historic acoustic bat data collected by the Indiana Department of Natural Resources, we constructed Bayesian occupancy models to gain insights into bat communities and populations across Indiana. Through use of informative prior distributions, we addressed two important considerations for bat conservation with our occupancy models: 1) exploring a compensatory community dynamic causing the expansion of evening bat (<i>Nycticeius humeralis</i>) populations in Indiana following the establishment of white-nose syndrome (WNS), and 2) estimating a percent decline of summertime hoary bat (<i>Lasiurus cinereus</i>) populations in Indiana due to wind energy development. We found evidence for a potential compensatory community dynamic in the evening bat system, in which losses of the Indiana bat (<i>Myotis sodalis</i>) and the little brown bat (<i>Myotis lucifugus</i>) due to WNS may be resulting in new realized niche space for evening bats, thereby contributing to a compensatory community dynamic. In our hoary bat system, we found evidence of a regional summertime decline of 8.9% annually since 2012. These findings have important conservation implications considering imperiled nature and conservation priorities for bats in North America. </p>

Many municipalities around Sweden use public access spatial data from Artportalen to track and fight invasive species, but anyone can upload data to Artportalen and not all of it becomes verified. They could potentially enhance their efforts by incorporating street view technology for more reliable data. One municipality that uses Artportalen data is Jönköping, which suffers from Reynoutria japonica. I randomly selected 50 areas around Jönköping with reports of R. japonica and went through them using Street View. The purpose of this study is to test if Street View can be used to improve the reliability of Artportalen data and if it can fully replace other methods to do so. I counted each individual of R. japonica I could identify and compared it to the number of reports in each area. Among the 50 areas only 26 were reachable in Google Street View and some plants were impossible to identify if they were R. japonica or not. When looking at the areas that could be reached it showed no difference between Reports in Artportalen and what was found in Street View if you included the unidentifiable plants. When excluding unidentified plants or when including areas that could not be reached it showed a significant difference. Using Google Street View to complement Artportalen data for R. japonica comes with benefits and limitations. Many areas were impossible to reach, but where accessible, it proved effective in identifying misreports and finding unreported plants without the need to visit the location. Street View data can enhance the reliability of distribution data used for monitoring invasive species without ever needing to travel, however it cannot fully replace other methods of enhancement and for the best reliability, a combination of Street View and on-site visits is necessary. / Många kommuner runt om i Sverige använder offentligt tillgängliga geodata från Artportalen för att spåra och bekämpa invasiva arter, men vem som helst kan ladda upp data till Artportalen och inte all data blir verifierad. Kommunerna skulle potentiellt kunna förbättra sina insatser genom att använda Street View teknologi för att få mer tillförlitliga data. En kommun som använder sig av data från Artportalen är Jönköping, som lider av den invasiva växten Reynoutria japonica. Syftet med den här rapporten är att testa om Street View kan användas för att komplimentera data från Artportalen och om det kan helt byta ut andra metoder att göra samma sak. Jag valde slumpmässigt ut 50 områden runt Jönköping med rapporter om R. japonica och gick igenom dem med Street View. Jag räknade varje individ av R. japonica jag kunde identifiera och jämförde det med antalet rapporter i varje område. Bland de 50 områdena var det bara 26 som kunde nås med Google Street View och vissa växter var omöjliga att identifiera om de var R. japonica eller inte. När man tittade på de områden som kunde nås visade det ingen skillnad i antal växter mellan rapporterna i Artportalen och vad som hittades i Street View om man inkluderade de oidentifierbara växterna. När man exkluderade oidentifierade växter eller när man inkluderade områden som inte kunde nås visade det en signifikant skillnad. Att använda Google Street View för att komplettera Artportalen-data för R. japonica har både fördelar och begränsningar. Många områden var omöjliga att nå, men där de var 2 tillgängliga visade det sig effektivt för att identifiera felrapporter och hitta orapporterade växter utan att behöva besöka platsen. Street View-data kan förbättra tillförlitligheten av distributionsdata som används för att övervaka invasiva arter utan att man någonsin behöver resa, men det kan inte fullt byta ut andra metoder att öka tillförlighet och för bästa resultat är en kombination av Street View och platsbesök nödvändig.

<p dir="ltr">Succession is a foundational idea in ecology and serves as way to study ecological community assembly. Here, we test the three alternative mechanisms for succession: (I) facilitation, where species arrival order is not random and can be categorized as falling into distinct stages of succession such as early and late species; (ii) tolerance, where species arrival is random, but species interactions that promote coexistence or exclusion determine the community structure through time, and; (iii) inhibition, where species arrival is once again random, but species hold space until they die, and only then can there be a change in species composition through colonization of gaps. To do this, we used a 70-year time series of succession in an oak-hickory forest system in northwest Indiana called the Ross Biological Reserve. Every ten years tree species identity and abundance were measured beginning in 1951. Non-metric multidimensional scaling (NMDS) revealed distinct periods of community assembly that we categorized as distinct early, mid, and late successional communities. We used an index of species co-occurrence (the checkerboard score) and found that early successional communities were largely random, while mid and late successional communities were characterized by nonrandom co-occurrence of species. Alpha and gamma richness increased, and species turnover rate also increased. Specific species relative abundance showed typical patterns of species abundance when classified by their successional status. We conclude that facilitation was the predominant mechanism at the landscape scale, while tolerance was more of a driver on a smaller local scale. We found no evidence of inhibition. Succession at the scale we have documented is difficult to study, because of the long times required to document change. More successional studies of this nature will benefit the field of community assembly and ecology as a whole.</p>