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River and riparian areas are important foraging habitat for insectivorous bats. Numerous studies have shown that aquatic insects provide an important trophic resource to terrestrial consumers, including bats, and are key in regulating population size and species interactions in terrestrial food webs. Yet these studies have generally ignored how structural

River and riparian areas are important foraging habitat for insectivorous bats. Numerous studies have shown that aquatic insects provide an important trophic resource to terrestrial consumers, including bats, and are key in regulating population size and species interactions in terrestrial food webs. Yet these studies have generally ignored how structural characteristics of the riverine landscape influence trophic resource availability or how terrestrial consumers respond to ensuing spatial and temporal patterns of trophic resources. Moreover, few studies have examined linkages between a stream's hydrologic regime and the timing and magnitude of aquatic insect availability. The main objective of my dissertation is to understand the causes of bat distributions in space and time. Specifically, I examine how trophic resource availability, structural components of riverine landscapes (channel confinement and riparian vegetation structure), and hydrologic regimes (flow permanence and timing of floods) mediate spatial and temporal patterns in bat activity. First, I show that river channel confinement determines bat activity along a river's longitudinal axis (directly above the river), while trophic resources appear to have stronger effects across a river's lateral (with distance from the river) axis. Second, I show that flow intermittency affects bat foraging activity indirectly via its effects on trophic resource availability. Seasonal river drying appears to have complex effects on bat foraging activity, initially causing imperfect tracking by consumers of localized concentrations of resources but later resulting in disappearance of both insects and bats after complete river drying. Third, I show that resource tracking by bats varies among streams with contrasting patterns of trophic resource availability and this variation appears to be in response to differences in the timing of aquatic insect emergence, duration and magnitude of emergence, and adult body size of emergent aquatic insects. Finally, I show that aquatic insects directly influence bat activity along a desert stream and that riparian vegetation composition affects bat activity, but only indirectly, via effects on aquatic insect availability. Overall, my results show river channel confinement, riparian vegetation structure, flow permanence, and the timing of floods influence spatial and temporal patterns in bat distributions; but these effects are indirect by influencing the ability of bats to track trophic resources in space and time.

ContributorsHagen, Elizabeth M (Author) / Sabo, John L (Thesis advisor) / Fisher, Stuart G. (Committee member) / Grimm, Nancy (Committee member) / Schmeeckle, Mark W (Committee member) / Stromberg, Juliet C. (Committee member) / Arizona State University (Publisher)
Created2010
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Though the connection between terrestrial riparian consumers and the adjacent aquatic food web has been well-studied in a variety of systems, gaps with respect to several habitats remain. The Colorado River Basin represents many of these untested habitat characteristics: it contains large, controlled rivers in an arid environment that are

Though the connection between terrestrial riparian consumers and the adjacent aquatic food web has been well-studied in a variety of systems, gaps with respect to several habitats remain. The Colorado River Basin represents many of these untested habitat characteristics: it contains large, controlled rivers in an arid environment that are often canyon-bound. These characteristics, however, are not unique to the Colorado River Basin. Dams and arid lands are becoming increasingly common around the world, stressing the importance of understanding the function of riparian areas within the Colorado River Basin and basins like it. Stable isotopes, including the more recent application of deuterium, can be used to elucidate trophic linkages between rivers and their riparia. Though dams may harm aquatic insect populations, it is possible that they also make aquatic insects a stable, constant food source to the riparian biological community. This dissertation demonstrates that aquatic emergent insects are a reliable, and therefore important, food source for arid land riparian consumers along regulated rivers. However, the importance of aquatic emergent insects to riparian consumers may vary across sites, even within the same river basin. To explore this variation, the diet of a common riparian lizard species Urosaurus ornatus (Ornate Tree Lizard) can be used as an indicator of cross-ecosystem connectivity. This dissertation demonstrates linkages between two differing river segments and U. ornatus, showcasing its ability as an indicator of connectivity across a diversity of systems. Within the Colorado River Basin, the Grand Canyon provides an opportunity to study a variety of riparian consumers across a gradient of habitat parameters and dam effects. This dissertation demonstrates the manifold connections between large, regulated rivers and arid riparian consumers, ranging from lizards, to bats, to, for the first time, mice. Monsoons have differing effects on river-riparian communities in this basin, potentially related to intact tributary confluences. Lastly, this dissertation demonstrates that hydropeaking reduces river-riparia connectivity by reducing aquatic insect emergence. This dissertation seeks to improve understanding of the linkages between river and their riparia to aid in the management of arid riparian areas affected by dams worldwide.
ContributorsLupoli, Christina Alexandra (Author) / Sabo, John L (Thesis advisor) / DeNardo, Dale F (Committee member) / Kennedy, Theodore A (Committee member) / Muehlbauer, Jeffrey D (Committee member) / Yackulic, Charles B (Committee member) / Arizona State University (Publisher)
Created2021