While pollinators and leaf herbivores have been a focus of research for decades, floral antagonists have been studied significantly less. Since floral antagonists can be as common as leaf herbivores and have strong impacts on plant reproduction, it is important to understand the role of floral antagonists in the ecology and evolution of flowers. I conducted four experiments to better understand the relationship between plants, floral traits, floral antagonists, and other plant-insect interactions. First, I manipulated resources (light and soil nutrients) that are known to have impacts on plants and floral traits to test how they affect floral antagonists and other plant-insect interactions. Plentiful resources increased the proportion of floral antagonists to visit flowers, but also increase tolerance of floral antagonists. Second, I manipulated flower bud gallers, a species-specific floral herbivore that destroys flowers, to test how it affected other plant-insect interactions, floral traits, and plant reproduction. Plants with flower bud gallers tended to have more pollinator visits, but this effect is due to a shared preference by gallers and pollinators for similar plants. Third, I manipulated florivory to examine how it affects subsequent plant-arthropod interactions, floral traits, and plant reproduction. Florivory had systemic effects on other plant-insect interactions, including leaf herbivores, and shifted the plant mating system towards more selfing. Additionally, I tested how several floral antagonists respond to floral attractive and defense traits to understand which floral traits are important in mediating antagonisms. Finally, I manipulated florivory, pollination, and nectar robbing to test for effects of multiple floral interactions on subsequent plant-insect interactions, floral traits, and plant reproduction. There were significant many-way interactions between the three treatments on subsequent plant-insect interactions and reproduction, indicating that the effect of one interaction depends on what other interactions are present. Understanding the role that floral antagonists play in plant ecology can help scientists determine which interactions are most important, and may help determine why some floral traits exist in their current state. Together, this work represents some of the most comprehensive research on the community consequences of floral antagonists, as well as the interplay between floral traits and floral interactions.

Human activities potentially threaten key ecological processes, or "ecosystem functions", mainly through the habitat conversion associated with urbanization and agriculture. Although ecosystem functions can clearly be disrupted in severely degraded systems, it is not clear how those functions vary along the entire gradient of human activity at scales most relevant to global environmental change. To address this question, I used two remotely sensed indices of ecosystem function, as measured by the normalized difference vegetation index (NDVI) and thermal infrared radiation (TIR), to derive estimates of primary productivity and evapotranspiration, respectively, at 1-km resolution across multiple vegetation types in southern Canada. After controlling for the variation in NDVI and TIR related to the climatic gradient, I related these indices to measures of anthropogenic activity (road density, extent of natural cover, and protected areas status). While NDVI and TIR are both strongly related to climate and vegetation type, much of the residual variation in NDVI (up to 67%) and TIR (up to 55%) is related to human activity. Ecosystems in areas of intense human impact are generally less productive and exhibit less water cycling (i.e., energy-transforming) efficiency, but I found no evidence of threshold effects in the response of ecosystem function to increasing human impact. Ecosystems in protected areas (parks and reserves) have significantly higher productivity and, to a lesser extent, higher evapotranspiration, which suggests increased solar energy-transforming capacity. These relationships are strongest at coarse spatial scales and are generally consistent within different vegetation types. The magnitude of these effects along the entire gradient of human activity is substantial.

One of the most obvious patterns in ecology is the geographic variation in species richness over broad spatial scales. However, despite observations of these patterns of richness for two centuries, mechanisms for the patterns remain controversial. This thesis is a study of the broad-scale biodiversity patterns of plants and the potential mechanisms behind those patterns. Richness-climate relationships often account for >80% of the spatial variance in richness. However, it has been suggested that richness-climate relationships differ significantly among geographic regions, and that there is no globally consistent relationship. Since there is little point in arguing about mechanisms before the patterns they predict have been documented, I investigated the global patterns of species and family richness of angiosperms in relation to climate. One hypothesized mechanism that predicts strong and consistent richness-climate patterns is the Physiological Tolerances hypothesis. This hypothesis predicts that the number of species found in a given location is a function of the number that can tolerate the climatic conditions in that place. Using global angiosperm family richness distributions and climatic data to estimate the climatic tolerances of plant families, I examined the relationships of potential family richness patterns to both climatic gradients and observed patterns of family richness. Observed family richness was not strongly related to potential family richness. However, both richness and potential richness were related to climate, but in different ways. Potential family richness necessarily sets an upper limit on observed richness levels, but observed richness did not generally reach that limit. In other words, there are generally many more species that can tolerate the climate in a particular area than actually occur there. A second hypothetical mechanism predicting strong consistent richness-climate patterns, the Energy-Diversity or Species-Energy hypothesis, suggests that for a species to persist in an area, there must be sufficient energy available in that area to support enough individuals of that species to maintain a viable population. Thus species richness will depend upon the number of individuals, which in turn depends upon energy availability. Using tree counts from 15 forest sites along a latitudinal gradient running from James Bay, Canada to Costa Rica, I tested whether a series of direct correlative links existed from climate to tree density to tree species richness. Despite a positive (but not statistically significant) correlation between AET and richness, the tree density per site was negatively correlated with energy. (Abstract shortened by UMI.)

No description available.

No description available.

<p> In Arctic Alaska, Dolly Varden <i>Salvelinus malma </i> is highly valued as a subsistence fish; however, little is known about oceanic dispersal or ecology. This study addresses this knowledge gap, by using a fisheries independent method, pop-up satellite archival tags (PSATs). In spring of 2012 and 2013, we attached 52 PSATs to Dolly Varden in a river in northwestern Alaska, which flows into the Arctic Ocean, to examine the marine dispersal, behavior and habitat occupancy of this species. Tagged Dolly Varden demonstrated two types of dispersal, including offshore and nearshore dispersal. The offshore type was the first documented northwesterly dispersal and occupancy of Outer Continental Shelf (OCS) areas of the Russian Chukchi Sea. While occupying this area, tagged Dolly Varden demonstrated affinity for the first 5 m of the water column, diel patterns in depth occupancy, and dive depths of up to 50 m, while experiencing a thermal environment of generally 3&ndash;7&deg;C. During the nearshore dispersal type, Dolly Varden transited in coastal areas of northwest Alaska, likely returning to their natal rivers to spawn. While in nearshore areas, tagged Dolly Varden always occupied shallow waters (&lt; 6 m), and experienced a rapidly changing thermal environment (&plusmn; 15&deg;C), including some waters temperatures cooler than -1&deg;C. This study demonstrates that PSATs offer an alternative and effective platform with which to study several aspects of large adult Dolly Varden dispersal and ecology in areas where it is not practical or feasible to capture these fish, such as in coastal and offshore regions of Arctic Alaska. Additionally, the results of this study have increased our knowledge of the summer marine distribution, behavior and thermal environment of Dolly Varden in Arctic regions of Alaska, and this knowledge is important to several stake holders for the conservation of this important subsistence species.</p>

<p> Arctic Grayling (<i>Thymallus arcticus</i>) are widely distributed on the Arctic Coastal Plain (ACP) of Alaska, and are one of the few upper level consumers in streams, but the trophic pathways and food resources supporting these fish are unknown. Grayling migrate each summer into small beaded streams, which are common across the landscape on the ACP, and appear to be crucial foraging grounds for these and other fishes. I investigated prey resources supporting different size classes of grayling in a beaded stream, Crea Creek, where petroleum development is being planned. The specific objectives were to measure terrestrial prey subsidies entering the stream, quantify prey ingested by Arctic Grayling and Ninespine Stickleback (<i>Pungitius pungitius </i>), determine if riparian plant species affect the quantity of terrestrial invertebrates ingested by grayling, and determine if prey size and type ingested were a function of predator size. Results indicated that small grayling (&lt; 15 cm fork length (FL)) consumed mostly aquatic invertebrates (caddisflies, midges, and blackflies) early in the summer, and increasing quantities of terrestrial invertebrates (wasps, beetles, and spiders) later in summer, while larger fish (> 15 cm FL) foraged most heavily on stickleback. Riparian plant species influenced the quantity of terrestrial invertebrates entering the stream, however these differences were not reflected in fish diets. This study showed that grayling can be both highly insectivorous and piscivorous, depending upon fish size class, and that both aquatic and terrestrial invertebrates, and especially stickleback, are the main prey of grayling. These results highlight the importance of beaded streams as summer foraging habitats for grayling. Understanding prey flow dynamics in these poorly studied aquatic habitats, prior to further petroleum development and simultaneous climate change, establishes essential baseline information to interpret if and how these freshwater ecosystems may respond to a changing Arctic environment. </p>

Presence and composition of Eragrostis Lehmanniana was measured on 75 permanent transects every 3-8 years between 1958-1989 on the Santa Rita Experimental Range, Arizona. The number of transects occupied and average composition increased rapidly over this period. A repeated measures analysis of two soil groups with different water holding capacity and permeability revealed that the rate of increase of E. Lehmanniana was different between the groups. Repeated measures analysis of five grazing intensities revealed that the rate of E. Lehmanniana increase was different among intensities. It appears that the highest intensity had the highest rate of increase. The influence of grazing on E. Lehmanniana spread was also expressed by the lack of difference in relative composition measured in 1989 between ten livestock enclosures and adjacent grazed areas. This research suggests that E. Lehmanniana will spread and dominate with an average of 89 mm of summer precipitation in 40 days; a lower regime than estimated by other research.

I examined movements and habitat use by desert mule deer (Odocoileus hemionus crooki) and collared peccary (Dicotyles tajacu) in the Rincon Mountain District of Saguaro National Monument (SNM) from February 1988 through December 1989. Movements and habitat use by mule deer were closely associated with the distribution of free-standing water during the driest seasons of the year. Deer responded to losses of ephemeral water sources in SNM by leaving the monument to obtain water. Four of 5 peccary herds supplemented their natural diet by visiting houses and/or restaurants on a daily or twice daily basis. The addition of water and supplemental food sources was a deliberate effort by homeowners to attract wildlife onto their property. The current pattern of habitat islands interspersed with low density housing (1 house/2-4 ha) is an effective and highly desirable buffer zone between the monument and the more heavily developed urban areas 3.2 km west of the park.

Measurements of tree characteristics were used as indicators of overstory structure on four oak woodland sites in southeastern Arizona. Three areas harvested at different times and intensities were compared with an undisturbed area to assess effects of harvesting on various structural attributes of woodland overstories. Structural vegetation changes affect habitat quality and thus wildlife populations in modified areas. Significant differences were found for some woodland structural characteristics between harvested areas and an undisturbed area. Structural changes persist, as prolific coppice sprouting produces shrub-like trees, which appear to take a relatively long time to reach mature height and form. Managers might be able to moderate impacts of harvests on woodland structure by adjusting harvest intensity, and multiple-use management objectives for some species of wildlife still might be met.