Recharge has been conducted very efficiently for twenty-five years near Roger and Ina roads along the Santa Cruz River using reclaimed water. This project seeks to determine the composition of river vegetation due to the release of the reclaimed water, and as a corollary, to examine the effects of channelization on the vegetation of the Santa Cruz River. Using belt and line transects the vegetation along the Santa Cruz River was surveyed. Treatment with effluent was found to increase plant density, diversity, richness, cover, and incidence of exotic plants. Channelization was found to increase only plant richness and incidence of exotic plants. Furthermore, effluent encouraged the growth of tree plant types while channelization discouraged such growth. Recommendations were made regarding future release of effluent into the Santa Cruz River and future attempts to restore the once prolific, willow-cottonwood forests and mesquite forests.

The Sonoran Desert surrounding Tucson, Arizona is the dominant matrix in a region undergoing a transition from desert matrix to urban matrix with little emphasis placed on preserving this native ecosystem intact. Instead, patches of desert, remnants, are cut off the desert matrix and surrounded by a variety of land uses including residential, transit, and commercial. 31 sites within the City of Tucson were surveyed and the site's plant species richness, woody cover, herbaceous cover, and disturbance percentage measured. The plants found on-site were classified into native or exotic, annual or perennial, and woody or herbaceous, and further broken down into growth form. Results indicated a significant correlation between a site's area and its percent disturbance, as well as correlations between its native vegetation and area.

Nectarivorous birds are represented by three major radiations: hummingbirds, honeyeaters, and sunbirds. These lineages share a number of convergent features in ecology, morphology, physiology, and behavior, and have served as important models in the study of foraging strategies and energetics. Because their diet is rich in water and sugar but poor in nitrogen and electrolytes, nectarivores provide a striking opportunity for evaluation of physiological constraints. My research emphasizes a novel aspect of the water-energy interaction: water overingestion in nectar-eating birds. The dual purpose of my dissertation research was to investigate the physiological mechanisms that allow nectar-eating birds to cope with exceedingly high ingestion of water and to elucidate the consequences of ingesting and processing large quantities of water for energy intake and for the maintenance of balance of important metabolites such as glucose. In nectar-eating birds, water overabundance in food has the potential effect of constraining energy procurement by overwhelming osmoregulatory processes and limiting digestive function. My research has allowed the development of an integrated quantitative description of gut and kidney function under the broad range of water loads and hydration conditions that birds can experience in the wild. Understanding limits to water processing will provide general insights into how animals are designed, on how aspects of design constrain their ecological performance, and into how aspects of design in one physiological system can impose limits on other systems. The osmoregulatory processes of nectar-eating birds highlight the relevance of understanding the impact that events taking place in the gut can have for feeding behavior, and renal and metabolic function. Adopting a broadly comparative approach to understanding the interaction between feeding behavior, digestion, and osmoregulation is pertinent because is unclear whether the many extreme physiological characteristics of hummingbirds that have traditionally been assumed to be associated with a nectar-feeding habit are shared by other nectar-eating birds. In my dissertation research I have begun to examine the similarities, and have found some important differences, in the responses of two major radiations of nectar-eating birds to their sugary and watery diets.

Although bees are herbivorous insects, they are seldom studied as such. My dissertation research characterizes the interactions between a guild of solitary cactus-specialist bees and the cacti they visit, examining these bees both as herbivores and as pollinators. I first examined the reproductive biology of two species of Ferocactus as background for the pollination study. Both F. cylindraceus and F. wislizeni were obligate outcrossers, and neither species was pollen-limited. Fruit set was high in both species, and reproductive output was limited by architectural constraints. Whereas most other herbivorous insects are antagonists of the plants they feed on, bees are usually regarded as mutualists (pollinators) of their host plants. However, not all floral visitors are pollinators, and pollen-foraging specialists have been postulated by some to be particularly antagonistic to the plants they visit. To test whether cactus-specialist bees are actually mutualists of the cacti they visit, I examined both the quantity and quality components of pollinator effectiveness of bees visiting F. cylindraceus and F. wislizeni. Despite the generalized morphology of the flowers of these plants, there were very few floral visitors other than three species of cactus-specialist bees. Flowers of both species were pollinated almost exclusively by cactus-specialist bees, primarily Diadasia rinconis. I also tested the pollen preferences of four species of cactus bees. Bees were offered flowers from their normal host cactus in which the stamens had been removed and replaced with novel pollens. Novel cactus pollens were accepted to some degree by all four species, but Diadasia rinconis and D. opuntiae accepted more novel non-cactus pollens than did either Lithurge apicalis or Idiomelissodes duplocincta. Both species of Diadasia showed significant acceptance of Sphaeralcea (Malvaceae) pollen, thought to be the ancestral host plant for the genus Diadasia. Caged, naive D. rinconis bees did not initiate nesting when presented with Sphaeralcea flowers alone; nesting began immediately when cactus flowers were offered. Once nesting was underway, most D. rinconis bees switched to Sphaeralcea if cactus flowers were removed. In both D. rinconis and D. opuntiae, there were striking differences in pollen preferences among individuals.

Food-for-protection mutualisms, interactions between two species in which one species provides protection from aspects of the biotic environment in exchange for a nutritional reward, show an exceptional degree of context dependency. The occurrence, strength, and outcome of these interactions often depend on the ecological context in which they take place. However, the causes and consequences of such context-dependent variation remain poorly understood. The protection mutualism involving lycaenid butterflies and ants provides an opportunity to explore many aspects of the ecology and evolution of interspecific interactions including the importance and predictability of ecological factors that produce context-dependent investment or outcomes in interspecific interactions. Ant-tended lycaenid larvae produce carbohydrate-rich secretions that are collected by attendant ants. In exchange for this food reward, ants may confer developmental benefits and protect larvae from predators and parasitoids. Both participants in this mutualism are capable of responding to changing ecological conditions and, thus, can quickly alter their level of investment or decision to participate in the interaction. In Appendix A, I present the results of field work that illustrate that ant tending provides the lycaenid butterfly, Hemiargus isola, with effective protection from parasitoid attack and enhanced larval survival. Lycaenids on plants from which ants were excluded were almost twice as likely to be parasitized as were lycaenids feeding on plants to which ants had access. In Appendix B, I present the results of laboratory experiments that show that the tentacular organ signal employed by H. isola is a generalized signal, conveyed by either a simple, tactile stimulus or a secretion of low volatility, which evokes an alarm response in attendant ants. Furthermore, I provide evidence to suggest that the function of the tentacular organ signal is context dependent and mediates lycaenid investment in the mutualism. In Appendix C, we present the results of laboratory experiments that demonstrate that altering the ratio of carbohydrate and protein resources available to ants influences their decision to participate in the mutualism with H. isola. Significantly more ants from colonies fed a low carbohydrate/high protein diet tended lycaenids relative to ants fed a high carbohydrate/low protein or high carbohydrate/high protein diet.

Past studies of zebra finch song development have revealed conflicting predictors of song choice. This study sought to clarify the qualities of (1) the relationship between the chick and tutor and (2) the behavior of the tutor that might affect song choice by the pupil. The study subjects were born and raised in an aviary where the free social interactions of all individuals in the colony were possible. A cross-fostering design was used within the aviary, so that chicks would not only have exposure to the male that raised him, but also to his genetic father (if different than his rearing father) and to several other adult males. The results were surprising. (1) Chicks cross-fostered to nests within the same aviary as their parents' nest were found to recognize and learn their genetic father's song after fledging despite their lack of exposure to him in the nest. Also, (2) simply being a father or a mated male was not a significant predictor of song tutor choice, while the quality of being an attentive father or mate was. On a less surprising note, (3) the male that raised the chick was copied more than other adult males, as was the genetic father. Additionally, (4) brothers raised together inhibited song similarity in one another, which supports the finding of "fraternal inhibition" found by Tchernichovski and Nottebohm (1998). Two song copying measures were used and compared, and cross-correlation was used to validate the methods of quantifying song copying behavior. Extensive behaviorial observations of the colony members were made in order to gain a reliable measure of the behavioral tendencies of the tutors for use as predictors of song choice. When given a choice that begins to approach the degree of choice in the wild, juvenile zebra finches revealed the sensitivity of their genetic template to their father's song and the importance of the behavior of the song tutor for choosing song.

Nectarivory has evolved independently eight times among birds. In the neotropics specialized nectarivory evolved in hummingbirds and flowerpiercers (genus Diglossa). Flowerpiercers are nectar-robbers of hummingbird-pollinated plants. Because flowerpiercers and hummingbirds are found in the same habitats feeding on the nectar of the same flowers, they provide us with a unique opportunity to understand the pressures that nectarivory imposes on animals. Flowerpiercers present beaks that have a long hook at the tip of their maxilla. The hook is used to hold tubular flowers in place while they stab them by projecting their lower mandible. Then, they insert their tongues in the puncture and extract nectar. I investigated the following questions: (1) What is the function of the flowerpiercer's hook, and which are the consequences of its evolution? (2) Are the digestive traits of flowerpiercers convergent with those of hummingbirds? (3) How do digestive traits affect sugar selection by nectar feeding birds? And (4) What are the effects of Diglossa baritula's physiology and behavior over its annual cycles? I found that nectarivorous flowerpiercers evolved from a frugivorous ancestor with a hookless beak. The evolution of a hooked bill allowed flowerpiercers to become efficient nectar-robers, but hindered their efficiency to feed on fruit. Using a phylogenetically informed approach, I found that the digestive traits of flowerpiercers and hummingbirds are not convergent. Unlike hummingbirds which have astounding intestinal sucrase activity levels, flowerpiercers had low sucrase activity. Nectar intake in D. baritula seems to be limited by its ability to digest sucrose. I also found that sugar preferences in nectar-feeding birds are concentration-dependent. At lower concentrations birds preferred hexoses, whereas at higher concentrations they preferred sucrose. Although nectar composition and concentration are often discussed as two different floral traits, they have a synergistic effect on the sugar preferences of nectar-feeding birds. D. baritula individuals exhibit biannual reproductive and molting cycles that are synchronized with flower and fruit abundance in the mountains of Mexico. The ability to rob nectar appears to have molded the evolution of the most important morphological, physiological and behavioral traits of D. baritula.

Symbiosis is a prevalent phenomenon among organisms throughout the tree of life, including the insects which often harbor maternally transmitted bacteria. Aphids engage in symbiotic interactions with several maternally transmitted bacteria, and many are known to associate with microbes known as secondary symbionts. These bacteria are typically not essential from the aphid's perspective, and until recently little was known about their roles in aphid biology or the coevolutionary histories of these symbioses. I have addressed these mysteries in this dissertation, through use of molecular and experimental analyses. My findings reveal that secondary symbionts are diverse and infect members of numerous aphid and insect taxa. Though they are maternally transmitted, their distributions can be attributed to occasional horizontal transmission among species. Consequences of symbiosis were observed at genomic levels, with "T-" and "U-type" symbionts exhibiting accelerated evolution in their 16S rRNA sequences. The "R-type" symbiont, in contrast, has not experienced accelerated substitution rates, though it does show a recent trend toward increased AT content, as observed for other symbiotic bacteria. Molecular and phylogenetic evidence presented in this dissertation suggest that secondary symbionts are generalists, capable of infecting numerous aphid hosts. Here, I also present experimental evidence in support of this hypothesis, demonstrating that two of three horizontally transferred symbionts are passed on maternally, at high efficiency, in a novel host, Acyrthosiphon pisum. However, not all efficiently transmitted symbionts would be expected to persist in populations of A. pisum, as some reduce aphid fitness. Finally, evidence obtained from my research and previous experimental and theoretical studies suggests that secondary symbionts should improve aphid fitness, though benefits may not accrue in all environments. Here, I examine the effects of temperature on the fitness effects induced by R-, T-, and U-type symibionts, finding that the R- and T-types confer benefits in aphids exposed to high temperatures, compared to slight and even non-existent effects on A. pisum reared under permissive temperatures. The U-type reduced fitness of aphids reared under high temperatures, revealing a potential cost to symbiont infection that could help to explain intermediate infection frequencies.

I used two sampling techniques, visual line transects and pitfall traps, to compare the numbers and species richness of lizards in four vegetative communities representative of the Sonoran Desert region: exotic grasslands, native grasslands, oak woodlands and desertscrub. I found similar numbers of lizards and species richness in three of the four communities, but I detected more lizards using transects than pitfall traps in the oak woodland community. On a per area basis, I detected significantly more lizards with transects than with pitfall traps in all four communities (P = 0.018). I compared capture success using three different pitfall traps. Overall, I found no differences between capture success in black and white plastic 19-1 buckets (Chi square = 0.58, df = 1, P > 0.05) or between white buckets and number 10 cans stacked three deep (Chi square = 0.60, df = 1, P > 0.05). I did find that one species (Sceloporus magister) was captured more often in black buckets than in white buckets (Chi square = 5.33, df = 1, P < 0.05). Pitfall traps were significantly more expensive (P = 0.02) than transects in terms of materials, installation and data collection. I did not obtain sufficient recaptures of any species in the pitfall traps to generate population or survivorship estimates using the programs RELEASE, SURGE, or JOLLY. I calculated the effort necessary to obtain sufficient recaptures to make those estimates using pitfall traps. I also calculated the effort needed to obtain similar estimates using transects in each vegetative community. Recommendations for sampling days for the two methods varied considerably depending on the species and the vegetative community. If managers need mark-recapture data or detailed information on individual lizards, pitfall traps should be used. However, if managers do not need detailed information, I recommend using transects to sample lizard populations because they are less expensive, less time-consuming, and provide similar information on the relative abundance and species richness of lizard populations.

I utilize a variety of methods, from field studies of selection to phylogenetic systematics, to study the historical processes involved in the evolution of reproductive structures of milkweeds (Asclepias L. (Asclepiadaceae)). In an experimental study of a natural population of Asclepias tuberosa L., I explore the mechanisms by which pollinators select on the arrangement of flowers on a plant. I present an evolutionary model for the manner in which pollinators select on inflorescence design (the number of flowers in inflorescence units), considering reproductive success gained through both male and female function. In this model, the maximum fitness is achieved when proportional changes in male and female reproductive success with changes in inflorescence-unit size are balanced. The model is used to predict optimal inflorescence-unit size in Asclepias tuberosa, which roughly match inflorescence-unit sizes observed in nature. In studies of selection on plant reproductive characters in natural populations, the pollinators responsible for selection remain unidentified or are inferred from floral morphology. In the same experimental population of Asclepias tuberosa in which I studied selection on inflorescence design, I measured the effectiveness of all common pollinators. Although A. tuberosa possesses characteristics of butterfly-pollinated plants, and many butterfly species are found at its flowers, the most effective pollinators are bees. Furthermore, the most effective pollinators in the study population varied between years. These results suggest that inferences about the identity of effective pollinators should be based on careful measurements of effectiveness over several seasons. In order to study factors that affect the evolution of reproductive characters like inflorescence design in this large genus, it is desirable to employ a phylogenetic hypothesis of the relationships among Asclepias species. I present such an analysis based on morphological data. My results suggest that some of the North American species of Asclepias are more closely related to African species in other genera than to other North American species of Asclepias. Also, most infrageneric groups currently recognized are not monophyletic. Several novel infrageneric groupings are well-supported by my results. I also present analyses of the evolution of growth form and flower "horns" based on an explicit phylogenetic hypothesis.