The dynamics of ecological populations and communities are predominantly governed by three ecological processes, environmental filtering, species interactions and dispersal, and these processes may vary with heterogeneity of the environment. In my PhD research, I investigated how ecologists conceptualize landscape heterogeneity, and how these three ecological processes may vary with spatial and temporal environmental heterogeneity. I conducted my empirical work in Alliaria petiolata, a non-native invasive species in North America, at the Koffler Scientific Reserve at Joker’s Hill in Ontario, Canada. The thesis contains six chapters, where chapters 2 – 5 are structured as stand-alone manuscripts. In chapter 2, I conducted a quantitative review to link the metacommunity concept (which combines the above-mentioned three processes) with different conceptual models of landscape spatial heterogeneity. I found that 78% of metacommunity studies were not explicit about the underlying model of landscape heterogeneity, though there was a significant association between the implied model of landscape heterogeneity and the observed metacommunity model. In chapter 3, I quantified dispersal of Alliaria petiolata, assessed the spatial structure of rosette and adult density, and compared the effects of the different processes on rosette and adult density. Seed dispersal followed a lognormal distribution (μ = 0.01, σ = 0.65). Both adults and rosettes exhibited significant spatial structure up to 2 m. Propagule pressure and interactions among life stages were significant processes shaping rosette density, whereas propagule pressure was the only important process shaping adult density. In chapter 4, I investigated patterns, determinants and demographic consequences of herbivory in A. petiolata. I found that patterns, determinants and demographic consequences of herbivory may vary between life stages and habitat types. One striking finding was that herbivory incidence in A. petiolata may strongly depend on plant life stage, possibly due to a defense–fitness trade off. In chapter 5, I tested whether intra-specific interactions in A. petiolata shift with temporal environmental heterogeneity (seasonality). I found significant negative density-dependent survival in summer and positive density-dependent survival over winter. I suggested that predictions of the stress gradient hypothesis at the intra-specific level are applicable to seasonal variation in environmental stress.

The fragmentation of natural habitat caused by anthropogenic land use changes is one of the main drivers of the current rapid loss of biodiversity. In face of this threat, ecological research needs to provide predictions of communities' responses to fragmentation as a prerequisite for the effective mitigation of further biodiversity loss. However, predictions of communities' responses to fragmentation require a thorough understanding of ecological processes, such as species dispersal and persistence. Therefore, this thesis seeks an improved understanding of community dynamics in fragmented landscapes. In order to approach this overall aim, I identified key questions on the response of plant diversity and plant functional traits to variations in species' dispersal capability, habitat fragmentation and local environmental conditions. All questions were addressed using spatially explicit simulations or statistical models. In chapter 2, I addressed scale-dependent relationships between dispersal capability and species diversity using a grid-based neutral model. I found that the ratio of survey area to landscape size is an important determinant of scale-dependent dispersal-diversity relationships. With small ratios, the model predicted increasing dispersal-diversity relationships, while decreasing dispersal-diversity relationships emerged, when the ratio approached one, i.e. when the survey area approached the landscape size. For intermediate ratios, I found a U-shaped pattern that has not been reported before. With this study, I unified and extended previous work on dispersal-diversity relationships. In chapter 3, I assessed the type of regional plant community dynamics for the study area in the Southern Judean Lowlands (SJL). For this purpose, I parameterised a multi-species incidence-function model (IFM) with vegetation data using approximate Bayesian computation (ABC). I found that the type of regional plant community dynamics in the SJL is best characterized as a set of isolated “island communities” with very low connectivity between local communities. Model predictions indicated a significant extinction debt with 33% - 60% of all species going extinct within 1000 years. In general, this study introduces a novel approach for combining a spatially explicit simulation model with field data from species-rich communities. In chapter 4, I first analysed, if plant functional traits in the SJL indicate trait convergence by habitat filtering and trait divergence by interspecific competition, as predicted by community assembly theory. Second, I assessed the interactive effects of fragmentation and the south-north precipitation gradient in the SJL on community-mean plant traits. I found clear evidence for trait convergence, but the evidence for trait divergence fundamentally depended on the chosen null-model. All community-mean traits were significantly associated with the precipitation gradient in the SJL. The trait associations with fragmentation indices (patch size and connectivity) were generally weaker, but statistically significant for all traits. Specific leaf area (SLA) and plant height were consistently associated with fragmentation indices along the precipitation gradient. In contrast, seed mass and seed number were interactively influenced by fragmentation and precipitation. In general, this study provides the first analysis of the interactive effects of climate and fragmentation on plant functional traits. Overall, I conclude that the spatially explicit perspective adopted in this thesis is crucial for a thorough understanding of plant community dynamics in fragmented landscapes. The finding of contrasting responses of local diversity to variations in dispersal capability stresses the importance of considering the diversity and composition of the metacommunity, prior to implementing conservation measures that aim at increased habitat connectivity. The model predictions derived with the IFM highlight the importance of additional natural habitat for the mitigation of future species extinctions. In general, the approach of combining a spatially explicit IFM with extensive species occupancy data provides a novel and promising tool to assess the consequences of different management scenarios. The analysis of plant functional traits in the SJL points to important knowledge gaps in community assembly theory with respect to the simultaneous consequences of habitat filtering and competition. In particular, it demonstrates the importance of investigating the synergistic consequences of fragmentation, climate change and land use change on plant communities. I suggest that the integration of plant functional traits and of species interactions into spatially explicit, dynamic simulation models offers a promising approach, which will further improve our understanding of plant communities and our ability to predict their dynamics in fragmented and changing landscapes. / Die Fragmentierung von Landschaften umfasst die Zerschneidung und den Verlust von Flächen mit natürlicher Vegetationsentwicklung und ist eine der Hauptursachen für den gegenwärtigen drastischen Verlust an Biodiversität. Diese Dissertation soll zu einem besseren Verständnis der Vegetationsdynamik in fragmentierten Landschaften beitragen. Damit verbunden ist das Ziel, Vorhersagen über die Reaktion von Pflanzengemeinschaften auf Fragmentierung zu verbessern. Diese Vorhersagen sind notwendig, um gezielte Naturschutzmaßnahmen zur Verminderung eines weiteren Verlustes an Biodiversität umsetzen zu können. In Kapitel 2 der Dissertation wird mit einem Simulationsmodell untersucht, wie sich die Ausbreitungsdistanz von Samen auf die lokale Artenzahl von Pflanzengemeinschaften auswirkt. Dabei zeigte sich, dass längere Ausbreitungsdistanzen die lokale Artenvielfalt sowohl erhöhen, als auch verringern können. Der wichtigste Einflussfaktor war dabei die Artenvielfalt der über-geordneten Pflanzengemeinschaft, in der die betrachtete lokale Gemeinschaft eingebettet war. Im dritten Kapitel wird die Konnektivität zwischen Pflanzengemeinschaften in Habitat-fragmenten, d.h. der Austausch von Arten und Individuen durch Samenausbreitung, im Unter-suchungsgebiet in Israel analysiert. Dafür wurde ein zweites räumliches Simulationsmodell mit statistischen Verfahren an Felddaten angepasst. Der Vergleich des Modells mit den Daten wies auf eine sehr geringe Konnektivität zwischen den Habitatfragmenten hin. Das Modell sagte vorher, dass innerhalb von 1000 Jahren 33% - 60% der Arten aussterben könnten. In Kapitel 4 wird zuerst analysiert, welche Prozesse die Verteilung von funktionellen Eigenschaften in Pflanzengemeinschaften bestimmen. In einem zweiten Schritt wird dann unter-sucht, wie sich funktionelle Eigenschaften von Pflanzengemeinschaften mit dem Niederschlag und der Fragmentierung im Untersuchungsgebiet in Israel verändern. Der Zusammenhang zwischen den Eigenschaften Pflanzenhöhe, sowie spezifischer Blattfläche und der Fragmentierung änderte sich nicht entlang des Niederschlagsgradienten. Im Gegensatz dazu, änderte sich der Zusammenhang zwischen der Samenmasse bzw. der Samenzahl und der Fragmentierung mit dem Niederschlag. Aus den Ergebnissen der ersten Teilstudie wird deutlich, dass Naturschutzmaßnahmen, die natürliche Habitate stärker vernetzen sollen, die Diversität, sowie die Zusammensetzung der übergeordneten Artengemeinschaft berücksichtigen müssen, um Verluste an Biodiversität zu vermeiden. Die Verknüpfung eines räumlichen Simulationsmodells mit Felddaten in der zweiten Teilstudie stellt einen neuen und vielversprechenden Ansatz für die Untersuchung der Auswirkungen verschiedener Management-Szenarien dar. Die dritte Teilstudie ist die erste Analyse der gemeinsamen Auswirkungen von Klima und Fragmentierung auf funktionelle Pflanzen-eigenschaften und zeigt die hohe Bedeutung der Untersuchung von Synergie-Effekten verschiedener Umweltfaktoren. Für zukünftige Forschung legt diese Dissertation nahe, funktionelle Eigenschaften und Konkurrenz zwischen Arten in räumlichen Simulationsmodellen zu berücksichtigen, um das Verständnis von Artengemeinschaften in fragmentierten Landschaften noch weiter zu verbessern.

A central issue in climate change research is to identify what species will be most affected by variations in temperature, precipitation or CO2 and via which underlying mechanisms. Dynamic global vegetation models (DGVMs) have been used to address questions of habitat shifts, extinctions and changes in carbon and nutrient cycling. However, DGVMs have been criticized for assuming full migration and using the most generic of plant functional types (PFTs) to describe vegetation cover. My doctoral research addresses both of these concerns. In the first study, I added two new tropical PFTs to an existing regional model (LPJ-GUESS) to improve vegetation representation in Central America. Although there was an improvement in the representation of some biomes such as the pine-oak forests, LPJ-GUESS was still unable to capture the distribution of arid ecosystems. The model representations of fire, soil, and processes unique to desert vegetation are discussed as possible explanations. The remaining three chapters deal with the assumption of full migration, where plants can arrive at any location regardless of distance or physical barriers. Using LPJ-GUESS, I imposed migration limitations by using fat-tailed seed dispersal kernels. I used three temperate tree species with different life history strategies to test the new dispersal functionality. Simulated migration rates for Acer rubrum (141 m year-1) and Pinus rigida (76 m year-1) correspond well to pollen and genetic reconstructed rates. However, migration rates for Tsuga canadensis (85 m year-1) were considerably slower than historical rates. A sensitivity analysis showed that maturation age is the most important parameter for determining rates of spread, but it is the dispersal kernel which determines if there is any long distance dispersal or not. The final study demonstrates how northerly refugia populations could have impacted landscape recolonization following the retreat of the last glacier. Using three species with known refugia (Acer rubrum, Fagus grandifolia, Picea glauca), colonization rates were faster with a northerly refugia population present. The number of refugia locations also had a positive effect on landscape recolonization rates, which was most pronounced when populations were separated. The results from this thesis illustrate the improvements made in vegetation-climate models, giving us increasing confidence in the quality of future climate change predictions.

The factors influencing habitat selection by juveniles of species within the family Unionidae (i.e., unionids), between post-larval detachment from a fish host and burrowing into the substratum, are largely unknown. Bed shear stress (τw) has been proposed as a critical factor. A laboratory wall jet apparatus generated τw to assess the response of juvenile Epioblasma triquetra, Villosa iris, Lampsilis fasciola, and Ligumia nasuta. The relationships between juvenile unionids, τw, and chemical and physical parameters were also examined in the field. There was a significant relationship between unionid resuspension and τw in the laboratory (resuspension when τw > 0.26 Pa), and adhesion behaviour required greater critical τw. Near-bed velocity and D50 grain size predicted sphaeriid clam density (a proxy for juvenile unionids) in the field. Laboratory experiments confirmed predictions that juvenile unionids cannot establish beyond a critical τw, demonstrating the importance of hydrodynamics in dispersal and for developing unionid conservation measures. / NSERC and Species At Risk Research Fund Ontario (MNR) to J.D.A.

Das Tierreich zeichnet sich durch eine große Diversität an Sozialsystemen aus, die von einer einzelgängerischen Lebensweise bis hin zum Leben in komplexen sozialen Gruppen reicht. Diese Variation in Sozialsystemen liefert den perfekten Rahmen um die evolutionäre Entwicklung von sozialen Merkmalen zu untersuchen. Ein besonders erfolgsversprechender Ansatz besteht darin, eng verwandte Arten, die sich durch einen unterschiedlichen Grad der Vergesellschaftung auszeichnen, miteinander zu vergleichen. Die Charaktersierung von Sozialsystemen wird für verschiedene taxonomische Gruppen unterschiedlich gehandhabt. Bei Vögeln wird das Sozialsystem normalerweise durch das Brut- und das soziale Paarungssystem charakterisiert. Die meisten Vogelarten sind paarlebend, aber man findet auch komplexere Gruppen welche im Allgemeinen durch das Verbleiben der Jungen am Aufwuchsort und kooperatives Brüten charakterisiert sind. Bisher wurden verschiedene Hypothesen im Zusammenhang mit Demographie, Ökologie, Lebensgeschichte und Verwandtschaftsverhältnissen vorgeschlagen um den Übergang von Paarbrütern zu kooperativen Brutsystemen in Vögeln erklären. Kurzfuß-Stelzenrallen (Mesitornis variegata) sind mittelgroße, am Boden lebende Vögel, die zur Familie der Mesitornithidae gehören. Diese Vogelfamilie ist endemisch in Madagaskar und beinhaltet zwei weitere allopatrische Arten, welche sich hinsichtlich des Grades der Vergesellschaftung unterscheiden: Die Einfarb-Stelzenralle (Mesitornis unicolor) des östlichen Regenwaldes welche in Paaren brütet und die Monias-Stelzenralle (Monias benschi) des südlichen Dornenwaldes welche in Gruppen lebt und kooperativ brütet. Die Kurzfuß-Stelzenralle hingegen kommt im westlichen Trockenwald vor und lebt für gewöhnlich in Paaren oder kleinen Gruppen von denen angenommen wird, dass es sich um Familiengruppen handelt, wobei allerdings nur wenig Informationen über das Brutsystem vorhanden ist und bisher keine Studie die genetischen Verwandtschaftsverhältnisse innerhalb der kleinen sozialen Einheiten untersucht hat. Das Hauptziel dieser Arbeit war es erstens die verschiedenen Komponenten des Sozialsystems der Kurzfuß-Stelzenrallen zu beschreiben, ein Art für welche bisher angenommen wurde das sie kooperativ brütet, deren Jungen jedoch Nestflüchter sind und prinzipiell nur wenig elterliche Fürsorge benötigen. Zweitens sollten die proximaten und ultimativen Ursachen untersucht werden, die dieses Sozialsystem geformt haben könnten. Um dieses Ziel zu erreichen habe ich genetische, morphologische, räumliche sowie Verhaltensdaten von 10 bis 15 sozialen Einheiten von M. Variegate während fünf Feldsaisonen (Oktober 2009 bis April 2012) im Kirindy-Wald im Westen von Madagaskar gesammelt. Das Ergebnis dieser Studie zeigt, dass die Kurzfuß-Stelzenralle in sehr kohäsiven stabilen Paaren oder kleinen Familien lebt, die durch eine verspätete Abwanderung der Jungtiere entstehen, und dass nur die Elterntiere sich um die Aufzucht der Brut kümmern. Außerdem versorgen die Eltern ihre Jungen entgegen bisherigen Vermutungen in den ersten zwei Lebensmonaten intensiv mit Nahrung, und auch darüber hinaus bis zum 12. Lebensmonat obwohl mit viel geringerer Häufigkeit. Diese lange Periode der elterlichen Fürsorge hängt wahrscheinlich mit der langsamen Entwicklung der Jungtiere hinsichtlich der für die Nahrungssuche erforderlichen Fertigkeiten zusammen. Die hohe Kohäsion sozialer Einheiten mit inter-individuellen Abständen von selten mehr als drei Metern steht eher mit einer Strategie der Raubfeindvermeidung als einer Strategie zur Verhinderung des Fremdgehens in Verbindung. Dennoch kann die hohe Kohäsion zwischen Paarpartnern das streng monogame Paarungssystem erklären. Die Untersuchung des Abwanderungsverhaltens hat ergeben, dass männliche Nachkommen länger in ihren Familien bleiben als weibliche, was mit der beobachteten langsameren Fluktuation der erwachsenen männlichen Population und dem Vorhandensein von „Stiefmüttern“ in einigen Familien übereinstimmt. Darüber hinaus konnte ich durch den Vergleich von Paaren mit und ohne Nachwuchs zeigen, dass Familienleben für die Eltern hinsichtlich der Effizienz der Nahrungsbeschaffung und hinsichtlich der Investitionen in zukünftige Reproduktion kostspielig ist. Dies könnte die Intoleranz der Eltern gegenüber älteren Nachwuchs erklären, welche ich beobachten habe. Zusammenfassend kann gesagt werden, dass die Einschränkungen bezüglich unabhängigen Brütens und einzelgängerischen Umherstreifens in Kombination mit der langsamen Entwicklung der Fähigkeiten die im Zusammenhange mit der Nahrungsbeschaffung stehen und elterliche Kosten wichtige Faktoren sind, welche das Abwanderungsverhalten der Jungtiere, die Bildung von Familien und die Familienstabilität in dieser Art erklären. Zusätzlich beeinflusst die Gefahr von Raubfeinden, die mit der starken Kohäsion innerhalb sozialer Einheiten einhergeht, das Paarungssystem bei Kurzfuß-Stelzenrallen und legt eine Verbindung zwischen genetischer Monogamie und Raubfeindruck bei sozial monogam lebenden Arten nahe. Basierend auf einem Vergleich mit den anderen Arten der Familie der Mesitornithidae könnte das Brutsystem der Kurzfuß-Stelzenralle als Übergansstadium zwischen einem allein auf den beiden Elternteilen basierenden und einem kooperativen Brutsystem erachtet werden in dem einige Jungen fähig wären Hilfe zu stellen, aber von den Eltern daran gehindert werden.

Freshwater ecosystems face unprecedented levels of human-induced stresses and it is expected that the invasion of non-indigenous species will cause the greatest loss of biodiversity in lakes and rivers worldwide. Bythotrephes longimanus is a predatory invertebrate that invaded North America in the early 1980s, first being detected in the Great Lakes, and then moving to a number of inland lakes in Ontario and the northern United States. Using experimental and survey-based approaches, I tested several hypotheses concerning the effects of Bythotrephes on native zooplankton community structure and function. My results indicate that Bythotrephes reduces total abundance, biomass, and richness of zooplankton, especially cladoceran taxa, throughout the ice-free season. As a result of high predation pressure by the invader, total seasonal and epilimnetic zooplankton production was also substantially reduced in invaded lakes, which may have important consequences for the transfer of energy to fish and other taxa that feed on zooplankton. Interestingly, there was some evidence that zooplankton shifted their reproduction in time and space to avoid Bythotrephes, which may buffer the effects of the invader on food web functioning. Other measures of ecosystem function were relatively unaffected by the invasion of Bythotrephes. In addition, Bythotrephes may interact in unexpected ways with other anthropogenic stressors, and act to slow down the process of recovery by preying on species that maintain community abundance during acidification, but also affecting species attempting to recolonize historically acidified lakes. Although dispersal of zooplankton may maintain some of the ecosystem functions provided by zooplankton communities, loss of biodiversity may be a permanent result of invasion. The effects of the continued spread of invasive species across the landscape may be profound, as the invader Bythotrephes has demonstrably altered zooplankton communities and may reduce the ability of freshwater ecosystems to respond to future environmental change and maintain ecosystem functioning. / Thesis (Ph.D, Biology) -- Queen's University, 2007-07-19 14:56:57.102

The impact of agricultural practices on wood turtle (Glyptemys insculpta) movements and survivorship was investigated in a fragmented agri-forest landscape over two years. Agricultural activities and machinery contributed to the death of 20% of radio-tracked turtles. Annual survivorship of adults was 0.904 and 0.868 and for juveniles it was 0.815 and 0.831 for 1998 and 1999, respectively. Mutilation rates in adults were 90% +/- 3% in both years; in contrast, the maximum rate in juveniles was 57%. Setting the cutting height of disc mowers to 100 mm would increase harvest yields, reduce wear on machinery, decrease soil erosion, and reduce turtle mortality and mutilation rates. The concepts of integral, statistical, and linear range are introduced as distinct estimators of turtle movements. Since integral ranges include all habitats critical to survival, they provide an important contribution to our knowledge of imperiled species. Statistical ranges are stable and easily promote within and between study comparisons. Linear ranges quantify migratory and ranging movements. Thread-trailing techniques were used to record the fine-scale movements of six adult male G. insculpta translocated to an experimental hayfield patch-matrix. Although patch size had no effect on move length or path sinuosity, habitat structure did. Paths were generally straighter and move length longer in the harvested portion of a hayfield. Apparent habitat boundaries were shown to be permeable. Subjects exhibit three movement phases: agitation dispersal, local search, and ranging. Thus, G. insculpta exhibit predetermined movement patterns and move to maximize the likelihood of locating resources, while minimizing the probability of revisiting previously searched areas. Recent changes in agricultural practices and machinery are having a decidedly negative impact on G. insculpta. This study provides new insights into the movements of G. insculpta. Such knowledge will be an es

No description available.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

A central issue in climate change research is to identify what species will be most affected by variations in temperature, precipitation or CO2 and via which underlying mechanisms. Dynamic global vegetation models (DGVMs) have been used to address questions of habitat shifts, extinctions and changes in carbon and nutrient cycling. However, DGVMs have been criticized for assuming full migration and using the most generic of plant functional types (PFTs) to describe vegetation cover. My doctoral research addresses both of these concerns. In the first study, I added two new tropical PFTs to an existing regional model (LPJ-GUESS) to improve vegetation representation in Central America. Although there was an improvement in the representation of some biomes such as the pine-oak forests, LPJ-GUESS was still unable to capture the distribution of arid ecosystems. The model representations of fire, soil, and processes unique to desert vegetation are discussed as possible explanations. The remaining three chapters deal with the assumption of full migration, where plants can arrive at any location regardless of distance or physical barriers. Using LPJ-GUESS, I imposed migration limitations by using fat-tailed seed dispersal kernels. I used three temperate tree species with different life history strategies to test the new dispersal functionality. Simulated migration rates for Acer rubrum (141 m year-1) and Pinus rigida (76 m year-1) correspond well to pollen and genetic reconstructed rates. However, migration rates for Tsuga canadensis (85 m year-1) were considerably slower than historical rates. A sensitivity analysis showed that maturation age is the most important parameter for determining rates of spread, but it is the dispersal kernel which determines if there is any long distance dispersal or not. The final study demonstrates how northerly refugia populations could have impacted landscape recolonization following the retreat of the last glacier. Using three species with known refugia (Acer rubrum, Fagus grandifolia, Picea glauca), colonization rates were faster with a northerly refugia population present. The number of refugia locations also had a positive effect on landscape recolonization rates, which was most pronounced when populations were separated. The results from this thesis illustrate the improvements made in vegetation-climate models, giving us increasing confidence in the quality of future climate change predictions.