Phylogenetic structure measures patterns of evolutionary history within communities – are some communities composed of species more distantly or closely related than expected by chance? Due to common descent, closely related species are more ecologically similar, and so degrees of relatedness in a community may be good predictors of its ecology, more so than the number of species. Whether we are speaking of how phylogenetic structure arises as a consequence of ecological processes, or how phylogenetic structure affects the functioning of communities, the role of consumer organisms has received less attention than the role of resources. In this thesis, I ask what are the consequences and causes of phylogenetic structure of a potentially multi-level community, focusing on the underappreciated effects of consumer-resource interactions. In Chapter 2, I show how phylogenetic diversity of plant communities predicts the diversity and abundance of arthropods captured in a long-running biodiversity experiment better than species richness alone. In Chapter 3, I show how phylogenetic diversity and species richness interact to explain herbivore damage at a whole community level. In Chapter 4, I explore how phylogenetic structure of old field plant communities differs in plots of contrasting disturbance history, and speculate as to what factors – such as herbivory – may have contributed to these differences. In Chapter 5, I present a model which incorporates competition – through both resources and consumers of a focal trophic level – and environmental filtering, two factors which are thought to impact phylogenetic structure through their influence on ecological similarity. I show that environmental filtering interacts with competition to determine the coexistence of similar species, and that consumers may have different effects than do resources. My dissertation provides new insight into the importance of consumers in ecological communities, both through their effect on, and through their response to, patterns of evolutionary history in their prey.

Phylogenetic structure measures patterns of evolutionary history within communities – are some communities composed of species more distantly or closely related than expected by chance? Due to common descent, closely related species are more ecologically similar, and so degrees of relatedness in a community may be good predictors of its ecology, more so than the number of species. Whether we are speaking of how phylogenetic structure arises as a consequence of ecological processes, or how phylogenetic structure affects the functioning of communities, the role of consumer organisms has received less attention than the role of resources. In this thesis, I ask what are the consequences and causes of phylogenetic structure of a potentially multi-level community, focusing on the underappreciated effects of consumer-resource interactions. In Chapter 2, I show how phylogenetic diversity of plant communities predicts the diversity and abundance of arthropods captured in a long-running biodiversity experiment better than species richness alone. In Chapter 3, I show how phylogenetic diversity and species richness interact to explain herbivore damage at a whole community level. In Chapter 4, I explore how phylogenetic structure of old field plant communities differs in plots of contrasting disturbance history, and speculate as to what factors – such as herbivory – may have contributed to these differences. In Chapter 5, I present a model which incorporates competition – through both resources and consumers of a focal trophic level – and environmental filtering, two factors which are thought to impact phylogenetic structure through their influence on ecological similarity. I show that environmental filtering interacts with competition to determine the coexistence of similar species, and that consumers may have different effects than do resources. My dissertation provides new insight into the importance of consumers in ecological communities, both through their effect on, and through their response to, patterns of evolutionary history in their prey.

Phylogenetic structure measures patterns of evolutionary history within communities – are some communities composed of species more distantly or closely related than expected by chance? Due to common descent, closely related species are more ecologically similar, and so degrees of relatedness in a community may be good predictors of its ecology, more so than the number of species. Whether we are speaking of how phylogenetic structure arises as a consequence of ecological processes, or how phylogenetic structure affects the functioning of communities, the role of consumer organisms has received less attention than the role of resources. In this thesis, I ask what are the consequences and causes of phylogenetic structure of a potentially multi-level community, focusing on the underappreciated effects of consumer-resource interactions. In Chapter 2, I show how phylogenetic diversity of plant communities predicts the diversity and abundance of arthropods captured in a long-running biodiversity experiment better than species richness alone. In Chapter 3, I show how phylogenetic diversity and species richness interact to explain herbivore damage at a whole community level. In Chapter 4, I explore how phylogenetic structure of old field plant communities differs in plots of contrasting disturbance history, and speculate as to what factors – such as herbivory – may have contributed to these differences. In Chapter 5, I present a model which incorporates competition – through both resources and consumers of a focal trophic level – and environmental filtering, two factors which are thought to impact phylogenetic structure through their influence on ecological similarity. I show that environmental filtering interacts with competition to determine the coexistence of similar species, and that consumers may have different effects than do resources. My dissertation provides new insight into the importance of consumers in ecological communities, both through their effect on, and through their response to, patterns of evolutionary history in their prey.

Phylogenetic structure measures patterns of evolutionary history within communities – are some communities composed of species more distantly or closely related than expected by chance? Due to common descent, closely related species are more ecologically similar, and so degrees of relatedness in a community may be good predictors of its ecology, more so than the number of species. Whether we are speaking of how phylogenetic structure arises as a consequence of ecological processes, or how phylogenetic structure affects the functioning of communities, the role of consumer organisms has received less attention than the role of resources. In this thesis, I ask what are the consequences and causes of phylogenetic structure of a potentially multi-level community, focusing on the underappreciated effects of consumer-resource interactions. In Chapter 2, I show how phylogenetic diversity of plant communities predicts the diversity and abundance of arthropods captured in a long-running biodiversity experiment better than species richness alone. In Chapter 3, I show how phylogenetic diversity and species richness interact to explain herbivore damage at a whole community level. In Chapter 4, I explore how phylogenetic structure of old field plant communities differs in plots of contrasting disturbance history, and speculate as to what factors – such as herbivory – may have contributed to these differences. In Chapter 5, I present a model which incorporates competition – through both resources and consumers of a focal trophic level – and environmental filtering, two factors which are thought to impact phylogenetic structure through their influence on ecological similarity. I show that environmental filtering interacts with competition to determine the coexistence of similar species, and that consumers may have different effects than do resources. My dissertation provides new insight into the importance of consumers in ecological communities, both through their effect on, and through their response to, patterns of evolutionary history in their prey.

Awarded second place in Biological Sciences for GPSC Student Showcase

Interference competition is widely considered to structure ant communities. Competition’s effect, however, may be contingent upon disturbance or the abiotic environment. The interaction of temperature and competition is implicit in a wide body of ant community research; however, very few studies have experimentally manipulated these variables. To investigate the role of competition and temperature on ant communities, I (i) employed null models to investigate how species partition their spatial, temporal, and thermal environments in disturbed and undisturbed forests, (ii) used pairwise behavioral experiments to construct a Markov chain model to predict relative abundance patterns and correlated behavioral indices to species co-occurrence patterns, and (iii) conducted a shade, physiological thermal tolerance, and fully factorial shade and removal experiment to investigate the interaction of competition and temperature on ant community structure. The results of these studies are summarized below. First, I took advantage of a natural experiment, the 2002 Biscuit Fire, to investigate how species partition their temporal, thermal, and spatial environments in disturbed and undisturbed forests with null models. I found that most sites displayed a high degree of temporal niche overlap and species aggregation along the thermal axis. Half of the sites, however, had regular spacing of the temperature at which species obtain maximum activity. Species co-occurrence patterns in space modulated with diurnal temperature variations. Unburned sites had more spatial segregation of species than burned sites. Overall, it appears as though species activity is regulated, at least in part, by the thermal niche axis, and ant communities may repeatedly assemble and disassemble throughout the day. Second, I used data from pairwise behavioral experiment to generate transition probabilities for a Markov chain model. Assuming the landscape represents a large number of patches, the model predicted the relative abundance of an assemblage. I compared Markov chain predictions of relative abundance to relative abundance measurements on the local and regional scale. I used the same pairwise behavioral data to predict species co-occurrence values in three sites. Neither model accurately predicted community patterns. The only significant result was the Markov chain prediction of bait occurrence on the local scale; however, the relationship was opposite of the prediction. Finally, I conducted a shade experiment to investigate how communities respond to an altered thermal environment and associated their response to results from physiological thermal tolerance experiments. I then conducted a fully-factorial shade and Formica moki removal experiment to investigate if thermal responses were mediated by competitive effects. The addition of shade tables greatly reduced temperatures in the field, and Temnothorax nevadensis abundance was consistently lower in shade treatments. Decreased abundance at shade stations did not appear to be an indirect effect of F. moki activity. Physiological thermal tolerance was strongly associated with changes in abundance in shade treatments: the lower a species thermal tolerance, the greater its positive change in abundance after shade additions. The only species with a strong foraging response to F. moki removal was T. nevadensis, a species who was often cooccurred with F. moki on baits. I did not find evidence for the interaction of competition and temperature, and it appears as though physiological differences strongly influence the foraging activity of Siskiyou ant communities.

Scarce knowledge of Neotropical small mammal communities prevents experimental inquiry on the mechanisms structuring these communities. In this study, I examined patterns of local assembly of the small mammal communities on the eastern slopes of El Cielo Biosphere Reserve (ECBR) in Tamaulipas, Mexico, at two spatial scales. At the landscape level I tested patterns of species co-occurrences between four sites with a null model. At the local level I addressed floor microhabitat use, vertical structure use and temporal partitioning. I studied these niche axes at two adjoining forest types, Tropical Subdeciduous Forest (TSDF) and Cloud Forest (CF), that had different structural complexity. Total trapping effort consisted of 19,712 trapnights distributed over three years. In 1,365 capture events I recorded 789 individuals representing 14 species. Abundant species, mostly Peromyscus species that are of intermediate body size, co-occurred less often than expected by chance, whereas rare species, mainly Reithrodontomys species of small size, occurred at random over study sites. This pattern suggests that species interactions might be responsible for this non-random structure. Both the TSDF and CF had striking differences in both microhabitat use and temporal partitioning. In the TSDF common species (>8 individuals) organized along a microhabitat gradient from grassy/open areas to closed forest areas. Temporal partitioning for the whole community was less than expected by chance with use of an ad hoc null model. Species from ecotone/open areas avoided use of middle portions of the night whereas the single forest species concentrated activity in this period. So, it is plausible that predator avoidance strategies might have higher impact on temporal partitioning as compared to competitive interactions. In high contrast the CF community was codominated by two Peromyscus species that overlapped heavily in both their microhabitat use and diel activity patterns. Ecological separation of these two species probably occurs along a niche axis not considered in my study or might be facilitated by their body mass difference. Overall, I provide the first account of community patterns for small mammals at ECBR. These patterns can provide the basis for experimental manipulations to ascertain mechanisms responsible for structure at these communities.

Questions surrounding the causes and consequences of diversity lie at the centre of community ecology. Understanding the mechanisms by which species diversity is maintained motivates much experimental and theoretical work, but this work often focuses on fluctuation-independent mechanisms. Variability in habitat suitability is ubiquitous through space and time however, and provides another important path through which species diversity can be maintained. As a result, considering environmental variability has value for conservation and management. Finally, differences through space and time in the mechanisms that promote and maintain diversity produce spatially varying patterns of diversity. Spatial variation in different forms of diversity (species (SR), phylogenetic (PD), and functional diversity (FD)) creates difficult decisions about prioritization and reserve locations. This thesis uses experimental, observational, and theoretical methods to explore the causes and consequences of diversity. I show that variation in space and time has important implications for species coexistence and diversity maintenance. In microbial nectar communities, temperature variation through space and time alters the importance of priority effects on community assembly. Using models of warming temperatures in annual plant communities I show that considering temporal partitioning of flowering (a strategy to minimize competition) introduces constraints on phenological shifts: this has implications for phenological monitoring programs. Finally, I show that variability in the timing of fire events in Mediterranean shrublands contributes to coexistence between life forms, suggesting that it should be considered for fire management. In the final two chapters, I focus on conservation prioritization. Comparisons of species richness and evolutionary diversity through space in the Cape Floristic Region of South Africa show that existing reserves protect Proteaceae richness, but fail to capture evolutionary distinct species. More generally, in the final chapter I suggest that SR and PD should be congruent through space when species are of similar ages, regions are depauperate, or ranges are discontinuous.

Questions surrounding the causes and consequences of diversity lie at the centre of community ecology. Understanding the mechanisms by which species diversity is maintained motivates much experimental and theoretical work, but this work often focuses on fluctuation-independent mechanisms. Variability in habitat suitability is ubiquitous through space and time however, and provides another important path through which species diversity can be maintained. As a result, considering environmental variability has value for conservation and management. Finally, differences through space and time in the mechanisms that promote and maintain diversity produce spatially varying patterns of diversity. Spatial variation in different forms of diversity (species (SR), phylogenetic (PD), and functional diversity (FD)) creates difficult decisions about prioritization and reserve locations. This thesis uses experimental, observational, and theoretical methods to explore the causes and consequences of diversity. I show that variation in space and time has important implications for species coexistence and diversity maintenance. In microbial nectar communities, temperature variation through space and time alters the importance of priority effects on community assembly. Using models of warming temperatures in annual plant communities I show that considering temporal partitioning of flowering (a strategy to minimize competition) introduces constraints on phenological shifts: this has implications for phenological monitoring programs. Finally, I show that variability in the timing of fire events in Mediterranean shrublands contributes to coexistence between life forms, suggesting that it should be considered for fire management. In the final two chapters, I focus on conservation prioritization. Comparisons of species richness and evolutionary diversity through space in the Cape Floristic Region of South Africa show that existing reserves protect Proteaceae richness, but fail to capture evolutionary distinct species. More generally, in the final chapter I suggest that SR and PD should be congruent through space when species are of similar ages, regions are depauperate, or ranges are discontinuous.

The boreal peatlands that cover much of western Canada are immense reservoirs of organic carbon and nitrogen, serving as sinks for atmospheric carbon, as well as providing habitat for flora and fauna, and nutrient cycling. These ecosystems are generally believed to be nitrogen limited. Due to regional increases in industrial activities associated in the Athabasca Oil Sands Region (AOSR), atmospheric deposition of nitrogen is projected to increase, with unknown effects on peatland functioning. The results of this study provide baseline data for a nitrogen fertilization experiment with an accurate site description of the entire peatland complex to provide reference for the experiment. This study also examines patterns in production and nitrogen usage along a wet to dry gradient. My main question was if species assemblages could be sorted into communities and how these were related to environmental gradients. In chapters three and four I asked how production and nitrogen usage and storage varied along a moisture gradient. In chapter two, four communities were identified as being independent with clear indicator species. These communities had differences in abiotic factors formed clear gradients across the peatland, influencing the distribution of species arrangements in the peatland complex. Sphagnum angustifolium thrived in all four communities and across the entire range of gradients. This species is a foundation of species of bogs and poor fens and was studied in more detail in chapters 3 and 4. In chapter three, I found that primary production of S. angustifolium increased from dry to wet along the moisture gradient. Cranked wires used to measure linear growth became less reliable in wetter habitats, missing over 50 % of growth measure by innate time markers. Capitula increased in biomass throughout the course of the growing season, suggesting that after vertical elongation, S. angustifolium begins to accumulate branches and leaves in the capitula to close the growing season. Chapter four, evaluating nitrogen requirements found that while primary production of S. angustifolium increased from dry to wet, tissue quality of the growth decreased along this gradient. Despite the lower tissue quality, wet habitats had higher nitrogen requirements to support growth rates. Inputs of atmospheric deposition fulfilled <5% of annual N requirements and nitrogen saturated capitula in the beginning of the season was found to be an important source of nitrogen for growth, as capitula nitrogen storage declined over the season. Of the total nitrogen assimilated into annual growth, the percent lost a year later was similar across the moisture gradient; more nitrogen is stored in the wet habitats, strictly due to higher amounts initially assimilated. The results of this study suggest that in drier peatland habitats, there is an insufficient supply of water to deliver nitrogen and to support continuous growth during the growing season. Consequently, in wetter habitats, production is limited by nitrogen while in drier habitats it is limited by climate.