Xylem vessels have long been proposed as a key innovation for the ecological diversification of angiosperms by providing a breakthrough in hydraulic efficiency to support high rates of photosynthesis and growth. However, recent studies demonstrated that angiosperm woods with structurally ‘primitive’ vessels did not have greater whole stem hydraulic capacities as compared to vesselless angiosperms. As an alternative to the hydraulic superiority hypothesis, the heteroxylly hypothesis proposes that subtle hydraulic efficiencies of primitive vessels over tracheids enabled new directions of functional specialization in the wood. However, the functional properties of early heteroxyllous wood remain unknown. We selected the two species of Canellales from Madagascar to test the heteroxylly hypothesis because Canellaceae (represented by Cinnamosma madagascariensis) produces wood with vessels of an ancestral form, while Winteraceae, the sister-clade (represented by Takhtajania perrieri) is vesselless. We found that heteroxylly correlated with increased wood functional diversity related mostly to biomechanical specialization. However, vessels were not associated with greater stem hydraulic efficiency or increased shoot hydraulic capacity. Our results support the heteroxylly hypothesis and highlight the importance integrating a broader ecological context to understand the evolution of vessels.

Xylem vessels have long been proposed as a key innovation for the ecological diversification of angiosperms by providing a breakthrough in hydraulic efficiency to support high rates of photosynthesis and growth. However, recent studies demonstrated that angiosperm woods with structurally ‘primitive’ vessels did not have greater whole stem hydraulic capacities as compared to vesselless angiosperms. As an alternative to the hydraulic superiority hypothesis, the heteroxylly hypothesis proposes that subtle hydraulic efficiencies of primitive vessels over tracheids enabled new directions of functional specialization in the wood. However, the functional properties of early heteroxyllous wood remain unknown. We selected the two species of Canellales from Madagascar to test the heteroxylly hypothesis because Canellaceae (represented by <em>Cinnamosma madagascariensis</em>) produces wood with vessels of an ancestral form, while Winteraceae, the sister-clade (represented by <em>Takhtajania perrieri</em>) is vesselless. We found that heteroxylly correlated with increased wood functional diversity related mostly to biomechanical specialization. However, vessels were not associated with greater stem hydraulic efficiency or increased shoot hydraulic capacity. Our results support the heteroxylly hypothesis and highlight the importance integrating a broader ecological context to understand the evolution of vessels.

Free-living vertebrates likely encounter many stressors throughout their lifetime, from fighting off a predator to coping with unpredictable weather. As a result, vertebrates will mount an acute response to the stressors. Here, we outline previous research conducted in behavioral endocrinology and stress physiology as it relates to our research. We then discuss our study with white-crowned sparrows (Zonotrichia leucophrys) in Tioga Pass Meadow, in which we examined how the acute stress response affects foraging behavior 24 hours after a stressor. In birds that underwent a stress series, we found there to be a significant 57% decrease in foraging behavior 24 hours following the stressor. Additionally, we found no significant difference in foraging of unstressed birds during this same time frame. Our findings suggest that the acute stress response in this species causes a reduction in foraging activity 24 hours following a stressful event.

Human domination of global nutrient cycles is profoundly altering our planet. Yet on coral reefs, the effects of changing nutrient regimes have likely been over-simplified. This dissertation investigates the complexity of animal-nutrient interactions at the organismal level and explores how the outcomes of these interactions cascade through levels of biological organization. To do so, I examined the effects of nitrogen (N) and phosphorus (P) on corals and macroalgae, and how these effects in turn influenced reef communities and entire ecosystems. I show that P consistently increases coral growth rates while N has variable, often negative, effects on coral growth. The majority of this variability was explained by the contrasting responses of corals to ammonium, which had negligible effects on coral growth, versus nitrate, which consistently had negative effects on corals. Experimental manipulations of nutrient regimes revealed that these effects could be attributed, in part, to increased damage to the photosynthetic components of the corals’ endosymbionts. Nitrogen and P-enrichment also impacted macroalgae, increasing the nutrient content of algal tissue and in turn, consumption patterns of herbivorous fishes. Initial phase parrotfishes and juvenile surgeonfishes increased their feeding rates on algae rich in N and P respectively. However, adults from both species were irresponsive to algal nutrient content. At the community level, the effects of N and P on corals, algae and herbivory were linked to the development of distinct benthic communities. Algae cover was lower and coral growth rates higher around reef structures that were consistently enriched with N and P excreted by sheltering fishes. At the ecosystem level, I found that the responses of corals to N and P enrichment were similar to those of other nutrient-sharing mutualists. Across terrestrial and marine environments, I show that N and P enrichment consistently decouples mutualism performance, benefiting one partner at the expense of the other. Thus, collectively this dissertation demonstrates that the impacts of global nutrient loading resonate from single organisms through whole ecosystems.

Our understanding of the natural world is constantly evolving and strengthening as more observations are made and experiments are performed. For example, we understand that tree stems grow toward the light (positive phototropism; Darwin 1880, Loehle 1986, Christie et al. 2013) and against gravity (negative gravitropism; Knight 1806, Hashiguchi et al. 2013). We also know that plants respond to mechanical stimulus and perturbation (thigmotropism; Braam 2005). Genes and their resulting proteins have been described to uncover some of the mechanisms for these environmental responses, but relatively speaking, we have just scratched the surface (Wyatt et al. 2013). While the discovery of the molecular mechanisms responsible for these behaviors is certainly dependent on the ever-improving lab technology available, every molecular discovery is dependent on a macroscopic observation. In this manuscript I present the two novel macroscopic observations I made on members of Araucaria in the urban forest. The first describes a hemisphere-dependent lean in A. columnaris, and the second provides genetic and morphological evidence that hybrids exist between A. columnaris and A. heterophylla. Araucaria columnaris (J.R. Forst.) Hooker, or the Cook Pine is a conifer with a narrow native range that has been cultivated worldwide and grows unlike any other tree known. The initial observation we made was that trees in California and Hawaii lean south, and trees in California lean to a greater extent than trees in Hawaii. Measuring 250 trees in 16 regions worldwide, however, produced statistically significant evidence for a hemisphere dependent directional leaning pattern. Trees in the northern hemisphere lean south, and trees in the southern hemisphere lean north. Additionally, the lean becomes more pronounced at greater distances from the equator. We also gathered morphological and genetic evidence in the California urban forest that A. columnaris and A. heterophylla (Salisb.) Franco are hybridizing. Many individuals have intermediate characteristics of both species, which originally led me to believe that hybrids exist in cultivation. After analyzing several individuals with microsatellite genetic markers, I have enough evidence to conclude that hybrids between A. columnaris and A. heterophylla exist. This is an important observation mainly for municipalities and arborists interested in properly identifying trees in the urban forest. Knowing the proper identity of trees is imperative to informing decisions about their protection or removal. As we continue to ask questions about the inner workings of nature we will continue to gain a better appreciation for what we still do not know. The evidence provided in this manuscript better informs our future questions about a leaning pattern in A. columnaris and about the history of the cultivation of Araucaria.

Lionfish (Pterois spp.), an invasive species native to the Indo-Pacific, have permanently established themselves throughout the greater Caribbean, Gulf of Mexico, and regions of the Western Atlantic ranging from as far north as North Carolina to central Brazil. As their fundamental range expands, lionfish threaten to migrate into estuarine environments as they have been found to tolerate low salinities and an eclectic range of temperatures. The physiological capacity of invasion was assessed by quantifying the visual ecology of lionfish utilizing corneal electroretinography (ERG) as well as their metabolic scope and hypoxia tolerances under various temperature-oxygen-regimes utilizing intermittent-flow respirometry. Seasonal changes in temperature-dissolved oxygen levels consistent with Atlantic/Gulf of Mexico inshore estuaries not only exceed the physiological tolerances of lionfish, but also constrain metabolic scope at sub-lethal levels by significantly limiting maximum metabolic rate across all temperatures. Median Scrit values were 33%, 39%, 46%, and 54% at 15, 20, 25, and 30℃ respectively. Luminous sensitivities, temporal resolutions (Flicker fusion frequency), and spectral sensitivities scaled similarly with other estuarine piscivores indicating lionfish possess a visual system that can function effectively within estuarine photic conditions. Overall, visual characteristics of estuaries will not pose as a significant barrier to lionfish, but minimum winter temperatures and hypoxia will pose controlling and limiting factors substantially preventing further inshore invasion. However, caution should still be advised as lionfish may capitalize on specific temporal and spatial scales that provide suitable habitat quality and abundance of prey items. Further insight is needed to forecast the effects of temperature-dissolved oxygen on lionfish metabolic-scope.

Over the past 20 years both morphological and molecular phylogenies have been proposed for extant and extinct members of the family Felidae. However, there remain several discrepancies, particularly within the genus Panthera and the position of Panthera atrox. Consequently, morphologic characters from the skull and dentary were analyzed within Panthera (including all extant and one extinct taxa) to gain a better understanding of pantherine phylogeny. Multiple specimens of each taxon were analyzed, including: P. leo, P. tigris, P. onca, P. pardus , Uncia uncia, and Neofelis nebulosa. Four outgroups were used; Crocuta crocuta, Metailurus ssp., Proailurus lemanensis, and Pseudaelurus validus. From each phylogeny created, despite the outgroup, apparent grouping between Panthera leo, P. tigris, and P. atrox was present. Therefore, P. atrox is likely more closely related to the African lion and the tiger than the jaguar, in contrast to what has been recently suggested.

The genus Aneides (Caudata: Plethodontidae) is an arboreal salamander with a prehensile tail and a distribution that spans North America. It is hypothesized that adaptations for arboreality will be visible in the osteology of the sacral vertebra either by qualitative analysis or linear and morphometric analysis in comparison with other plethodontid salamanders. This study demonstrates that while qualitative and quantitative analyses are successful at making genus-level distinctions between taxa, identification to lower taxonomic levels remains inconclusive. Linear morphometrics and dorsal Procrustes landmarks were the most successful metrics to identify known taxa. Two unidentified fossil salamander sacral vertebrae from Oregon Caves National Monument are examined with the same techniques and are tentatively identified as Hydromantes based on qualitative similarities to modern Hydromantes specimens, as the quantitative analyses were unable to confidently diagnose the unknown specimens.

Hydration is a critical element for many physiological processes in vertebrates, such as protein production, innate immunity, and behavioral processes such as daily activity and thermoregulation. Few studies have directly assessed the effect of hydration on these animals in nature. While it seems intuitive that drought is stressful to animals, studies examining drought are typically observational and fail to assess how the hydration state of these animals influences their physiology and behavior. We tested for an effect of hydration on several physiological and behavioral parameters in Northern Pacific rattlesnakes (Crotalus oreganus oreganus) by experimentally manipulating hydration levels in the field. Two treatment groups were created: one of these received supplemental hydration twice a month from May to September (hydrated) while the other did not (control). Pregnant females were brought to the lab before parturition to collect data on litter characteristics. We radio-tracked snakes to examine any effects on movement, measured SVL and mass of each snake throughout the study for assessment of body condition, and collected blood samples for stress hormone physiology. Finally, we used intra-coelomic temperature data loggers to track body temperature data for each individual snake every two hours. Our results suggest that supplemental water and thus hydration has a significant effect on reproduction as all four hydrated females gave birth to a litter, while no control females gave birth. We saw no effect on movement parameters; however, males had larger home ranges and moved a larger total distance than females, regardless of hydration status. Interestingly, body condition was significantly higher in hydrated snakes, suggesting that hydrated individuals were acquiring more food than control snakes. We saw no effect on stress hormone physiology. There was no influence of hydration on any behavioral parameters such as time spent above or below ground, or time spent in a particular body position. Finally, there was a significant interaction of treatment group and sex on seasonal body temperature. Hydrated females had higher mean body temperatures than all other treatment group and sex combinations. However, all hydrated females were also pregnant, which confounds this result. Similar results were seen when body temperature was analyzed by time of day. Females overall had higher body temperature than males. These results suggest that hydration may have a profound influence on reproduction and has the potential to affect body condition and thermoregulation. The lack of an effect on movement and stress physiology should not be overlooked, however. This study is the first to experimentally manipulate hydration in free-ranging rattlesnakes and one of the few to manipulate hydration in vertebrates. More studies are needed to support a pivotal role of hydration in physiology and behavior of reptiles and we encourage the use of experimental field manipulations to answer these questions.

To gain a better understanding of the role of steroid hormones in vertebrate reproduction, we quantified steroid hormone concentrations in a free ranging population of the Northern Pacific rattlesnake, Crotalus oreganus. Plasma steroid hormone concentrations were quantified for both male and female snakes throughout the active season (Mar-Oct). We measured testosterone (T), 5α-dihydrotestosterone (DHT), and corticosterone (B) concentrations in male and female snakes. 17β-estradiol (E2) and progesterone (P) were measured in females only. We also observed breeding behaviors (e.g. consortship, courtship, and copulation) in the field and measured testis and follicle size in male and female snakes from museum collections. Our results indicate that C. oreganus in central California utilizes a bimodal pattern of breeding, with mating and agonistic behavior occurring in the spring and the late summer/fall. Each breeding season corresponds with elevated or highly variable androgen (T and DHT) levels. Several female snakes had high E2 concentrations in the spring and fall, coincident with vitellogenesis and mating. Females with high E2 concentrations also had high T and DHT concentrations. Corticosterone concentrations in males are not related to either time of year or concentrations of any other hormones quantified. This suggests that the breeding season in this population may not demand a significant increase in energy mobilization by glucocorticoids. Measurements of testis volume show that testes are regressed in the spring when the majority of breeding was observed in this population and reach peak volume in August and September during spermatogenesis. Multiple regression analyses revealed that in female snakes, P is positively correlated with T and DHT, and E2 is correlated with T. Since these results are strictly descriptive, experimental studies are needed to identify the functional significance of these results.