Bibliography: leaves 186-209.

Climate change is shifting the seasonal timing of many biological events, and the possibility of non-parallel shifts in different taxa has raised concerns about phenological decoupling of interacting species. My thesis investigates interactions between climate, phenology, and pollination, using the plants and pollinators of Rocky Mountain meadows as a study system. Interannual variation in timing of snowmelt since the 1970s has been associated with changes in the assemblages of concurrently flowering species in these meadows, suggesting that plant species differ in their phenological responses to climate. Differences between plants and pollinators in responsiveness to changing climate could, in principle, cause early-flowering plants to flower too early in warm years, before pollinators are active. In fact, I found only transient evidence for pollinator deficits in one early-flowering species (Mertensia fusiformis), even in an early-snowmelt year. However, the assemblage of pollinators visiting M. fusiformis does change predictably over the season, with likely consequences for selection on floral morphology in years when pollen is limiting. Hence, early- and late-flowering populations may evolve in response to phenology of the pollinator community. Differences between plant and pollinator phenologies appear to be due to generally lower temperature thresholds for development in plants, combined with microclimate differences between the soil and the above-ground nests of some pollinators. Phenological decoupling between plants and pollinators seems possible but unlikely to be catastrophic, since many taxa possess adaptations to temporally variable environments. Nevertheless, for many species, adaptation to novel climates will entail evolutionary change, and species interactions can influence evolutionary trajectories. For species affected by increasing late-summer drought, earlier flowering may be advantageous. However, in laboratory experiments, bumble bees avoid rare, unfamiliar flower types, causing simulated plant populations to fail to adapt to changing conditions. Overall, my work emphasizes the importance of the interplay between species interactions and environmental change.

Climate change is shifting the seasonal timing of many biological events, and the possibility of non-parallel shifts in different taxa has raised concerns about phenological decoupling of interacting species. My thesis investigates interactions between climate, phenology, and pollination, using the plants and pollinators of Rocky Mountain meadows as a study system. Interannual variation in timing of snowmelt since the 1970s has been associated with changes in the assemblages of concurrently flowering species in these meadows, suggesting that plant species differ in their phenological responses to climate. Differences between plants and pollinators in responsiveness to changing climate could, in principle, cause early-flowering plants to flower too early in warm years, before pollinators are active. In fact, I found only transient evidence for pollinator deficits in one early-flowering species (Mertensia fusiformis), even in an early-snowmelt year. However, the assemblage of pollinators visiting M. fusiformis does change predictably over the season, with likely consequences for selection on floral morphology in years when pollen is limiting. Hence, early- and late-flowering populations may evolve in response to phenology of the pollinator community. Differences between plant and pollinator phenologies appear to be due to generally lower temperature thresholds for development in plants, combined with microclimate differences between the soil and the above-ground nests of some pollinators. Phenological decoupling between plants and pollinators seems possible but unlikely to be catastrophic, since many taxa possess adaptations to temporally variable environments. Nevertheless, for many species, adaptation to novel climates will entail evolutionary change, and species interactions can influence evolutionary trajectories. For species affected by increasing late-summer drought, earlier flowering may be advantageous. However, in laboratory experiments, bumble bees avoid rare, unfamiliar flower types, causing simulated plant populations to fail to adapt to changing conditions. Overall, my work emphasizes the importance of the interplay between species interactions and environmental change.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 246-266). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 87-90). Also available on the Internet.

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains ix, 89 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 82-88).

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 87-90). Also available on the Internet.

The structural organisation of species-rich plant-pollinator networks is important to understanding their ecology and evolution and is essential for making informed conservation and restoration decisions. This thesis reports on a study located at different altitudes in nine tributary valleys of the Sacred Valley, Vilcanota Highlands, Peru. The assemblages of flower visitors were described and the plant-flower visitor matrices were analysed and compared to those found from other montane systems. Additionally, the thesis also addressed how the European honeybee (Apis mellifera) fits into these communities. Previous studies have predicted that abundance, diversity, and importance of hymenopterans as pollinators decrease with increasing altitude, where they are replaced by Lepidoptera and Diptera. Contrary to other temperate montane areas, Hymenoptera were more diverse at higher elevations. Diptera was the most abundant functional group overall but did not significantly increase in abundance with altitude as predicted. Species richness of visited plants reached a maximum at the highest altitudes. Using ordination analysis, hummingbirds, honeybees, flies and beetles were identified as major functional groups of flower visitors with significantly different visitation profiles. Nestedness analysis revealed that the plant-flower visitor networks had a similar structure to other published networks, consisting of core groups of generalist plants and animals which interacted with one another and with specialised flower visitors and plants, respectively. The core species varied in identity between valleys, but were usually the species in greatest abundance, implying that the networks were abundance structured. In addition, 85% of the interactions were observed only in single valleys. This context specificity may have implications for the conservation of plant-pollinator interactions in the Sacred Valley. Comparisons of the pollinator efficiencies of honeybees, hummingbirds, native bees and moths to Duranta mandonii (Verbenaceae) demonstrated significant variation among flower visitors in rates of visitation, pollen removal ability and contribution to fruit set. This variation was not correlated: hummingbirds were by far the most frequent visitors but removed virtually no pollen and did not contribute to fruit set. Despite the taxonomic diversity of flower visitors, the main pollinators were large native bumblebees and honeybees. Results highlighted the importance of measuring efficiency components when documenting plant-pollinator interactions, and also demonstrated that visitation rates may give little insight into the relative importance of flower visitors. Overall, the study showed that Apis was the most generalist flower visitor and a dominant core species within networks. However, although Apis visited a relatively large proportion of the flora compared to native taxa, they only intensively utilised a small proportion of available plant species. No evidence was found from the surveys to suggest that honeybees used interference competition and displaced other species. It was suggested that because specialised rare species are frequently dependent on a core of generalist taxa honeybees may play an important role for the possibilities of rare species to persist. However, perhaps the greatest threat to biodiversity and the persistence of plant-flower visitor communities in the Sacred Valley is from the destruction and fragmentation of habitats and from facilitative interactions between native and alien plants, mediated through visitation from honeybees

Species exist in complex biotic environments, engaging in a variety of antagonistic and cooperative interactions. While these interactions are generally recognized to be context-dependent, varying in outcome in the presence of other interactions, studies tend to focus on each interaction in isolation. One of the main classes of species interaction is mutualism, in which partner species gain a net benefit from their interaction. However, mutualisms are beset by a variety of species that can reduce or even eliminate the benefits of mutualism through exploitation of and competition for the resources and services offered by mutualists. These exploiter species potentially threaten the ecological stability of mutualisms and may alter selection on mutualistic traits. Thus, understanding the ecology and evolution of mutualisms requires consideration of interactions with exploiter species. In this dissertation, I investigated the effects of exploiter species on mutualisms between plants and pollinators using a combination of eco-evolutionary modeling, optimization theory, and behavioral studies. Using two adaptive dynamics models of coevolution in exploited pollinating seed parasite mutualisms, I found that exploiters reduce mutualist densities and select for more parasitic mutualists. Nevertheless, the models demonstrate that intraspecific competition for host resources and host defense of those resources restrict the ecological conditions that lead to extinction of the mutualism, as well as the chances of evolution to extinction. Thus, exploiters are unlikely to be the threat to mutualisms that has been assumed previously. On the other hand, in another type of exploitation, exploitative predators may pose a greater threat to investment in mutualism than has been presumed. Through both optimal foraging theory and behavioral experiments on bumble bees, I found that the risk from ambush predators can change pollinator floral preferences when predators preferentially use high-quality flowers to locate their prey. This research suggests that predators of mutualists may have important top-down effects and that further research is needed to investigate the effects of exploitative predators on selection on mutualist traits.

This study investigates the distribution and functional guild structure of the bee community in hardwood stands of Algonquin Provincial Park under different logging regimes, assessing both the role of different aspects of the habitat in affecting this distribution and structure, as well as the use of different sampling techniques. The distribution of bee individuals and species was most dependent on the abundance of raspberry (Rubus strigosus), an important floral and nesting resource. Also of importance were total floral resources, microclimate, and habitat heterogeneity. The functional guild structure of the bee community, which was relatively resilient to habitat variation, was related to a greater variety of factors, reflecting wide-ranging behaviours and requirements of different guilds. Malaise traps, pan traps and nets varied in their effectiveness at collecting different bee genera and a high percentage of species were collected only with one trap type. Malaise traps performed relatively poorly in forested environments, though very well in more disturbed, open habitats. Pan traps and nets performed better in forested environments. Trap nests were an inefficient sampling technique in forests, but were effective at collecting some species of cavity-nesting bees. These findings underline the importance of raspberry for bee communities of northern hardwood forests, and the importance of heterogeneity, both of habitat types and sampling techniques, to attain the highest species richness of bees.