The evolution of wind pollination (anemophily) has occurred at least 65 times in the flowering plants and over 10% of angiosperm species are wind pollinated. However the pollination and mating of anemophily species is poorly understood, particularly in comparison with animal-pollinated species. My thesis employs a range of approaches and tools to examine the evolution and ecology of wind pollination. These include comparative analyses, theoretical modeling, field and glasshouse experiments, the use of genetic markers and quantitative genetics. Experimental studies on diverse taxa were used to address questions concerned with the efficacy of outcrossing mechanisms, the ecological and demographic context of pollination and mating, and the plasticity of sex allocation. Comparative analyses indicated that wind pollination is correlated with unisexual flowers, reduced ovule number, small unshowy flowers, an absence of nectar, and open habitats. These analyses also demonstrated that anemophily originates more often in lineages with unisexual flowers. This suggests that wind pollination evolves in diclinous taxa as a mechanism of reproductive assurance because autonomous selfing is mechanically precluded. Empirical data on stigmatic pollen loads in 19 anemophilous species challenge the widespread assumption that anemophilous plants commonly have uniovulate flowers because they capture few pollen grains. Further, a model based on floral costs and the aerodynamics of pollen capture demonstrated that when flowers are inexpensive it is optimal to produce many flowers each with few ovules, because this allows more efficient sampling of the airstream. Manipulative field experiments on seven Carex species indicated that neither monoecy nor protogyny, two putative outcrossing mechanisms, are effective at limiting selfing. Based on these results I suggest that geitonogamy can provide reproductive assurance in anemophilous species with unisexual flowers. Field experiments and the application of sex-specific markers in Rumex nivalis revealed that the local neighbourhood of maternal plants affects pollination intensity and progeny sex ratios. Finally, I demonstrated that plant density in Ambrosia artemisiifolia affects stigmatic pollen loads but not outcrossing rates. Through a quantitative genetics experiment in A. artemisiifolia, I detected significant genetic variation for plasticity in sex allocation, potentially enabling adaptive adjustment of sex allocation to local environmental conditions.

The development of biofilms at solid-liquid interfaces has been investigated extensively, whereas the yield of planktonic cells from biofilms has received comparatively little attention. The detachment of single cells from biofilms has been attributed mainly to the erosive action of flowing liquid or the dispersal of cells from within biofilm microcolonies. The result has been an underestimation of the active role that biofilms can play in microbial proliferation through the production and release of planktonic cells to the environment. In this study, the cultivation of Pseudomonas sp. strain CT07 biofilms in conventional flowcells, glass tubes and a novel CO2 evolution measurement system was utilized to show that biofilm-derived planktonic cell yield was initiated within 6 hours of initial surface colonization and increased in conjunction with biofilm development. The magnitude of the yield was influenced by the metabolic activity of the biofilm, which was in turn dependent on environmental conditions, such as carbon availability. The physiologically active region of the biofilm was responsible for the yield of significant numbers of planktonic cells (~107 CFU.cm-2.h-1), whereas a less active biofilm zone was optimized for survival during unfavourable conditions and shown to be responsible for the subsequent re-establishment of biofilm structure, activity and cell yield. Despite the yield of numerically considerable numbers of planktonic cells (~1010 CFU), a carbon balance revealed that the carbon investment required to maintain this yield was insignificant (~1%) compared to the amount of carbon channelled into CO2 production (~54%). Together, these results indicate that biofilm-derived planktonic cell yield represents an efficient proliferation mechanism and support the view that the biofilm lifestyle affords microbes a dual survival-proliferation strategy, where the dominant strategy depends on the prevailing environmental conditions. An alternative model of biofilm development is presented to account for planktonic cell yield during all stages of biofilm development.

Ecological problems often require multivariate analyses. Ever since Bray and Curtis (1957) drew an analogy between Euclidean distance and community dissimilarity, most multivariate ecological inference has been based on geometric ideas. For example, ecologists routinely use distance-based ordination methods (e.g. multidimensional scaling) to enhance the interpretability of multivariate data. More recently, distance-based diversity indices that account for functional differences between species are now routinely used. But in most other areas of science, inference is based on Fisher's (1922) likelihood concept; statisticians view likelihood as an advance over purely geometric approaches. Nevertheless, likelihood-based reasoning is rare in multivariate statistical ecology. Using ordination and functional diversity as case studies, my thesis addresses the questions: Why is likelihood rare in multivariate statistical ecology? Can likelihood be of practical use in multivariate analyses of real ecological data? Should the likelihood concept replace multidimensional geometry as the foundation for multivariate statistical ecology? I trace the history of quantitative plant ecology to argue that the geometric focus of contemporary multivariate statistical ecology is a legacy of an early 20th century debate on the nature of plant communities. Using the Rao-Blackwell and Lehmann-Scheffé theorems, which both depend on the likelihood concept, I show how to reduce bias and sampling variability in estimators of functional diversity. I also show how to use likelihood-based information criteria to select among ordination methods. Using computationally intensive Markov-chain Monte Carlo methods, I demonstrate how to expand the range of likelihood-based ordination procedures that are computationally feasible. Finally, using philosophical ideas from formal measurement theory, I argue that a likelihood-based multivariate statistical ecology outperforms the geometry-based alternative by providing a stronger connection between analysis and the real world. Likelihood should be used more often in multivariate ecology.

Unraveling the relationships between organisms and patterns of diversity is a central goal of evolutionary biology, pursuant to the aim of reconstructing the history of life. I constructed a hypothesis for species relationships in the shorebird suborder Scolopaci, and mapped onto this framework behavioural and life-history traits to infer their evolutionary history. Relationships were well-resolved and well-supported, although reliable resolution of certain nodes will require additional, independent sources of information. We estimated the Scolopaci ancestor to be monogamous, and care-giving through fledging, but ancestral breeding location and migration distance reconstructions were equivocal. Tests for correlations between parental care and other traits to explain extant species’ trait diversity show that, contrary to previous reports, evolution of Scolopaci diversity was a complex process that cannot be explained by individual character correlations. This study provides important insights into Scolopaci and shorebird evolutionary history, and the general practice of inferring past processes from phylogenetic hypotheses.

The herbivory experienced by non-native invasive plants may depend on their local environments, such as herbivore abundance. In this study, I performed a common garden experiment with plants sampled from 11 populations of Arctium minus, from southern Ontario to near its northern range limit. I also compared performance and herbivory of burdock in open and understory habitats. Finally, I conducted freezing tolerance experiments with the lepidopteran seed predator Metzneria lapella, and palatability tests with plants from different populations. Results suggested that the previously described latitudinal trends in herbivore damage among populations are due to environmental differences rather than genotypic differences among populations. At a local scale, plants of open habitat were less damaged and had better performance than understory plants. Burdock has not escaped damage by herbivores in its invaded range; instead variation among sites in herbivore populations and impacts may significantly affect the invasiveness of this species.

Habitat loss and disturbance due to human activity are major causes of global biodiversity decline. Beyond outright species loss, one potential outcome is modification of species interactions that are integral to ecosystem functioning. To investigate this possibility, I asked whether human activity influences avian frugivory and seed dispersal, bird-fruit interactions that facilitate plant reproduction. On Tobago (West Indies), I compared patterns of frugivory in three adjacent rainforest habitats along a gradient of increasing disturbance: primary forest in a reserve, unprotected intermediate forest outside the reserve, and nearby forest that was moderately disturbed by subsistence resource use. I assessed plant and bird community composition, seedling species, fruit removal, and bird fecal samples, to estimate human effects on seed dispersal and plant recruitment in this ecosystem. Disturbed forest had different species assemblages than primary forest, characterized by more light-demanding plants, more birds, and a shift in the relative abundance of avian feeding guilds: insectivores and frugivores declined, while nectarivores and omnivores increased. Canopy cover declined with disturbance; along with plant abundance, this explained much of the variation in bird species composition. The rate of avian fruit consumption in removal experiments varied considerably but tended to be highest in primary forest. Fecal samples showed that fruit composition of avian diets also varied with disturbance; birds captured in disturbed forest consumed more seeds from light-demanding plants. Seeds in the samples provided evidence of some seed transfer between habitats—from disturbed forest into the reserve and vice versa. Seedling composition was consistent with plant species fruiting in the same study plots, and illustrated some successful recruitment of light-demanding plants in primary forest and shade-tolerant plants in disturbed forest. Notably, the plant community of intermediate forest was more similar to disturbed than primary forest. This suggests that habitat adjacent to areas of human activity can be susceptible to ecological change, even though it does not experience the same direct disturbance. In summary, the unprotected portion of Tobago’s rainforest has a markedly different plant and bird community than the forest reserve, and my results indicate that avian frugivory and seed dispersal can be influenced by moderate human activity.

The C3 photosynthetic pathway uses light energy to reduce CO2 to carbohydrates and other organic compounds and is a central component of biological metabolism. In C3 photosynthesis, CO2 assimilation is catalyzed by ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), which reacts with both CO2 and O2. While competitive inhibition of CO2 assimilation by oxygen is suppressed at high CO2 concentrations, O2 inhibition is substantial when CO2 concentration is low and O2 concentration is high; this inhibition is amplified by high temperature and aridity (Sage 2004). Atmospheric CO2 concentration dropped below saturating levels 25-30 million years ago (Tipple & Pagani 2007), and the C4 photosynthetic pathway is hypothesized to have first evolved in warm, low latitude environments around this time (Christin et al. 2008a). The primary feature of C4 photosynthesis is suppression of O2 inhibition through concentration of CO2 around Rubisco. This pathway is estimated to have evolved almost 50 times across 19 angiosperm families (Muhaidat et al. 2007), a remarkable example of evolutionary convergence. In several C4 lineages, there are species with photosynthetic traits that are intermediate between the C3 and C4 states, known as C3-C4 intermediates. In two eudicot genera, Flaveria (Asteraceae) and Alternanthera (Amaranthaceae), there is evidence that these species represented an intermediate state in the evolution of the C4 pathway (McKown et al. 2005; Sanchez-del Pino 2009). The purpose of this thesis is to ascertain the specific benefits to plant carbon balance and resource-use efficiencies of the C3-C4 pathway relative to C3 species, particularly at low CO2 concentrations and high temperatures, factors which are thought to have been important in selecting for C3-C4 traits (Ehleringer et al. 1991). This will provide information on the particular advantages of the C3-C4 pathway in warm, often arid environments and how these advantages may have been important in advancing the initial stages of C4 evolution in eudicots. This thesis addresses the physiological intermediacy of previously uncharacterized C3-C4 species of Heliotropium (Boraginaceae); the water- and nitrogen-use efficiencies of C3-C4 species of Flaveria; and the photosynthetic performance and acclimation of C3, C4 and C3-C4 species of Heliotropium, Flaveria and Alternanthera grown at low and current ambient CO2 levels and high temperature.

Doctor of Philosophy / Division of Biology / Keith B. Gido / This dissertation consists of three research-based chapters which focus on habitat association of prairie stream fishes and how these fish communities influence stream ecosystem properties. Chapter one introduces important concepts used throughout the chapters, and describes my study streams. In chapter two, I identify local habitat factors associated with the diversity and density of fishes in two protected prairie watersheds. Specifically, the relative importance of habitat factors associated with fish communities were evaluated along a stream-size gradient and across multiple seasons and years. I found that species richness was positively associated with pool area and discharge. Redundancy analyses showed common prairie fish species exhibit ontogenetic habitat associations, with adults in deep and juveniles in shallow pools. Chapter 3 addresses how fish species richness in small prairie streams affects whole-stream metabolism and biomass distribution of benthic organic matter, algal and macroinvertebrates. This study was conducted by stocking experimental stream mesocosms that included pool-riffle habitats with three different communities that represent a gradient of species richness of headwater prairie streams from one to three common prairie stream fish species. I illustrated how species influence ecosystems across multiple spatial scales and found that different communities altered the distribution of algal biomass from benthic surfaces to floating mats and from pools to riffles. The objective of the fourth chapter was to quantify how two size classes of herbivorous prairie stream fish species, central stoneroller Campostoma anamolum and southern redbelly dace Chrosomus erythrogaster differentially affect stream ecosystem properties. This study was also conducted in experimental stream mesocosms, where each unit consisted of one riffle and one pool. Using ANOVAs, I found large dace were associated with longer filaments (F = 7.5, P = 0.002, df = 4) and small fishes with less benthic organic matter (F = 4.2, P = 0.02, df = 4). There was no evidence for ontogenetic shifts in diet and likely differences in energetic requirements and behavior drove the differences among treatments. My research finds that small-bodied prairie stream fishes have predictable habitat preferences and effects on stream properties are dependent on species identity, richness and size structure.

Doctor of Philosophy / Department of Biology / Walter K. Dodds / Streams exist in a state of dynamic equilibrium with frequent floods and drought. The frequency and intensity of stream disturbances are projected to increase with greater water withdrawal for agriculture and biofuel production, watershed development, and altered climate. Changes in the hydrologic regime may alter stream ecosystems. I studied how stream communities return after disturbances and how nutrients, consumers, and substrata heterogeneity influence recovery trajectories. Large consumers were excluded from pools following a severe drought to assess how community structure and function returned in their absence. Large consumers reduced algal biomass, primary productivity, and nutrient uptake rates, and delayed macroinvertebrate recolonization. However, grazer effects were temporary and their influence weakened after five weeks. In a second experiment, I assessed the relative influence of grazer density and nutrient loadings on algal recovery from flood. Nutrients had a stronger effect on recovery than grazers, but the strength of each varied temporally. Grazer control decreased and nutrient control increased over time. A third experiment addressed the physical properties of stream substrata on algal development. The relationship among algal accumulation and substrata surface topography was assessed by growing algae on substrata with varying orientation and roughness. Total algal biomass decreased on surfaces with angles > 45 degrees, and peaked at an intermediate roughness (pit depth of [similar to]17 [Mu]m). Rougher surfaces collected more tightly attached (grazer resistant) forms and less loosely attached (grazer susceptible) forms. Individual algal forms responded differently to grazing pressure, nutrient availability, and surface features. I developed a method using Fourier-transform infrared microspectroscopy to measure single-cell physiological responses in benthic algae. Nutrients and consumers were strong regulators of ecosystem succession following disturbance, but nutrient influence was stronger. The influence of nutrients and consumers were context dependent, and changed over the course of recovery. Rougher surfaces increase algal growth and shifted algal assemblages to more grazer resistant forms, which may decrease the influence of large consumers on stream function. Altering the severity and frequency of disturbances can change the trajectory of stream recovery and ultimately change community composition and stream metabolic activity, which may alter ecosystem services such as water purification and recreation.

Forest disturbances and the spatial patterns they create affect ecosystem processes through their influence on forest vegetation from individual trees to landscapes. In the boreal and mixed-wood forests of eastern Canada the main agents of disturbance are logging, fire, and defoliation by the spruce budworm (SBW, Choristoneura fumiferana). These disturbances are similar in that they remove forest biomass and influence forest succession but also distinct in that logging creates patterns that are different than those created by natural disturbances. All disturbances are indirectly linked to each other through their mutual effects on forest spatial structure and succession. Through such feedbacks, spatial disturbance legacies can facilitate or constrain further disturbances, including forest management. Surprisingly, the long term spatial consequences of interactions among multiple natural and anthropogenic disturbances remain largely unexplored. This thesis investigates how, and at what spatial scale, legacies in forest composition and age structure influence natural disturbance dynamics, and how natural disturbances constrain forest management. I address four specific questions: (i) For how long do spatial legacies of different forest management strategies persist on the landscape? (ii) How do interactions among logging, fire, SBW, and succession affect timber availability and long term forest patterns in age and composition? (iii) How do these patterns differ from those created by each disturbance individually? And, (iv) How can management be used to reduce the extent and severity of fires and SBW defoliation through the manipulation of forest structure? The key scientific innovations of this thesis are: (i) Characterization of the duration and influence of spatial legacies on forest disturbances and sustainability; (ii) Development of a dynamic spatial forest simulation model that includes distinct successional rules that respond to different types of disturbance and shifts in disturbance regimes; and, (iii) Development and application of a wavelet-based significance testing framework to identify key scales of expression in forest spatial patterns. These innovations provide a scientific basis for landscape level forest management strategies designed to reduce the long term impacts of defoliating insects and to meet multiple objectives.