Previous observations of light levels and phytoplankton abundances along the Oregon coast demonstrated that phytoplankton attenuated light sufficiently to potentially limit the growth of intertidal macrophytes and therefore structure local intertidal communities. Inspired by this observation, in spring 2004, I initiated a study to quantify the direct and indirect benthic...
This study investigated whether a device commonly used to measure settlement of mussel larvae for ecological studies, the Tuffy™, functions uniformly whether placed in a bed of filamentous algae or on bare rock. During the summers of 2004 and 2005, the number of mussel larvae settling on Tuffys in patches...
Two of the most powerful ways in which humans have altered ecosystems are by increasing productivity and changing the densities of important consumers. The bottom-up effects of productivity and the top-down effects of consumers have been identified as primary determinants of biological diversity, though the links between them remain unclear....
Most vertebrates exhibit seasonality in many life history traits. Such seasonal rhythms are temporally organized via the transduction of environmental cues (e.g., photoperiod, temperature) into appropriate endocrine signals. However, among ectothermic vertebrates that undergo continuous winter dormancy, temperature is the only environmental cue available for synchronizing seasonal rhythms. Most intriguing...
Animal signaling systems frequently utilize multiple traits to produce and transmit a signal. These system elements may span multiple levels of organization. Functional integration of these traits may be expected to generate concordance in evolutionary pattern among system elements, such that evolutionary change in one system component is correlated with...
Interface habitats are considered valuable natural systems, tightly linked to adjacent habitats through the flow of matter and energy. However, there is limited research on mechanisms of connectivity such as movement of organisms and particulate matter and ways in which anthropogenic disturbance to interface habitats may affect immediate and adjacent...
Previous attempts to understand the factors affecting the energetic cost of locomotion have found a direct link between the energetic cost and the mechanical work done during periods when the limb is in contact with the ground. However, when the limb is not in contact with the ground during the...
Over 150 years ago, C. Bergmann observed a within-species pattern of increasing body size as elevation and latitude increased. Bergmann’s data came from numerous endothermic taxa, but the pattern has since been documented among numerous poikilotherms and invertebrates. The ferocious waterbug Abedus herberti Hidalgo (Hemiptera: Belostomatidae) lives in isolated populations...
This dissertation focuses on the importance of pelagic subsidies in the Northeast Pacific to rocky shore community regulation. My results document the patterns of pelagic subsidy supply, determine if those subsidies are correlated with community structure, and examine if community regulation differs between areas of high- and low-subsidies. Understanding how...
Many members of the Phylum Cnidaria are mutualistic with unicellular dinoflagellates belonging to the genus Symbiodinium. Corals are the most widely recognized example of these associations due to their key ecological importance in coral reef ecosystems where they serve as the structural and trophic foundation of these rich ecosystems. Coral...
Accurate chromosome segregation and cell cleavage are critical to maintaining genomic integrity. Both events involve the spindle apparatus, but the exact mechanics is as puzzling as the contradicting models proposed in the last two centuries. In this dissertation, current prevailing models of chromosome segregation and cell cleavage are tested using...
Cnidarians, such as anemones and corals, engage in an intracellular symbiosis with
photosynthetic dinoflagellates. Corals form both the trophic and structural foundation of
reef ecosystems. Despite their environmental importance, little is known about the
molecular basis of this symbiosis. In this dissertation we explored the cnidariandinoflagellate symbiosis from two perspectives:...
Environmental stress can negatively affect the ability of organisms to reproduce. Energetic trade-offs exist in all organisms, and under stress, energy may be allocated away from reproduction and towards physiological defense and repair mechanisms. The rocky intertidal environment is ideal for investigating the influence of environmental stress, as organisms are...
While there are many more species of reptiles in the tropics than in temperate
latitudes, relatively little is known about the natural history of tropical species of
snakes. Even basic information, such as reproductive ecology and behavior, is lacking. Patterns of reproduction in tropical species differ from patterns in temperate...
My thesis explored the effects of and potential mediating mechanisms for an important environmental stressor, ultraviolet-B (UVB) radiation. UVB radiation has negative effects on organisms in both terrestrial and aquatic systems. I used meta-analysis to quantify the effects of UVB radiation on a diversity of aquatic organisms (Chapter 2). UVB...
Predators are fundamentally important for regulating and driving prey population dynamics as well as structuring ecological communities. Over-exploitation of marine resources has caused dramatic depletions of predatory fish species and shifts in marine community composition, with attendant declines in productivity and diversity of marine ecosystems. Despite the important ramifications of...
The benefits of reproduction are clear, but there are also costs. Much is known about the costs of reproduction in females, but only recently have male costs been investigated in any depth. These costs of reproduction may be minimized by appropriately modifying behavior, but there has been little research on...
The phantom midges (Diptera: Chaoboridae) are a relatively small fly family composed of 50 extant species in six genera. Larvae are of interest to limnologists and ecologists because of their tolerance to toxicants, predatory avoidance strategies, and the role chaoborids play in zooplankton community dynamics. Relative to mosquitoes, systematists have...
An ancient pheromonal signal is found in aquatic courting salamandrids and terrestrial courting plethodontids, two highly divergent salamander families. In the aquatic courting salamandrids Cynops pyrrhogaster and C. ensicauda, the decapeptide sodefrin is cleaved from a larger 189 amino acid Sodefrin Precursor Factor (SPF) protein and released from a gland...
How complex traits evolve continues to be a major focus of evolutionary
investigation. A current topic of debate is the hypothesis that the phenotypic
integration of complex traits gives rise to evolutionary constraints. I studied two color
traits in the common garter snake, Thamnophis sirtalis, that show a high level...
Breeding ecology and behavior were investigated in a field study of three sympatric anuran amphibians in the Oregon Cascade Mountains: the western toad (Bufo
boreas), the Cascades frog (Rana cascadae) and the Pacific treefrog (Hyla regilla). A comprehensive study of the western toad mating system was conducted at three populations...
Factors affecting the persistence of mussels (Mytilus californianus) and their associated epibiont species were studied along the central Oregon coast. Interactions between mussels and their algal epibionts (Endocladia
muricata) varied in sign and strength with environmental conditions. In extreme temperatures mussel—epibiont interactions determined survival of individual mussels,
and persistence of...
This dissertation focuses on science relevant to the design and implementation of marine reserves. The chapters explore a range of topics related to among-site variation in population, community, and ecosystem dynamics. My results demonstrate the value and feasibility of integrating this knowledge into more comprehensive conservation and management approaches. While...
The influence of large-scale processes on natural communities has become one of the central issues of modern ecology. I combined field and laboratory studies to investigate the effects of variation in coastal upwelling on rocky intertidal communities along the central Oregon coast. I examined whether the growth of intertidal barnacles...
The earth is undergoing a “biodiversity crisis” characterized by loss of populations, species, genetic diversity, and ecosystem services. Part of this crisis consists of population declines, extinctions, and increased incidence of deformities in amphibians. It is unknown whether deformities contribute to these declines. Many cases of population declines in amphibians...
The vascular system of Aplysia californica is a simple visceromotor system with three main arteries innervated by a small pool of identified neurons. I used this system to
study the functions of neuropeptide transmitters and their actions on neural and muscle tissues. A central finding of this study is that...
Ultraviolet-B radiation (UVB) is an abiotic stressor in both terrestrial and aquatic systems. The stratospheric ozone layer, depleted due to anthropogenic activities and the cause of elevated UVB at earth's surface over the last four decades, is predicted to recover by 2065. However, UVB levels in aquatic systems may continue...
Mutualistic associations between cnidarians, such as corals, and photosynthetic
dinoflagellate algae provide the trophic and structural foundation of coral reef
ecosystems. In many cases, this intracellular mutualism is highly specific and must be
established anew for each generation of host corals. The ability to maintain partner
specificity across generations implies...
Studies were conducted within a 12-mile radius of Camp Sherman, Oregon, in the Deschutes National Forest during the spring and summer of 1965 and the spring of 1966, with one follow-up visit in the summer of 1967. The feeding and foraging activities of Eutamias amoenus and Citellus lateralis were observed,...
Investigations about the feeding ecology of a consumer
can facilitate prediction of its effects on prey populations
and the biological community. The aspects of feeding
ecology that are important to predicting consumer effects
include foraging movements, feeding preference and
selectivity, and the effects of physical factors on foraging
behavior and...
1. Distribution: A general map of distribution is given in the introduction, showing the range of the genus as a whole. A second, composite map, provides collection localities for the three species studied. Other maps indicate sites of collection for each individual species, including nests of P. longicaudus and P....
Along the central and southern Oregon coast and on San Juan Island, Washington, the lined chiton Tonicella lineata is very abundant in the lower intertidal levels on rocky shores. It is usually found on
encrusting coralline algae which, with epiphytic diatoms, make up the major portion of its diet. On...
An investigation was undertaken to determine the role that temperature might play in limiting the distribution of the mountain beaver, Aplodontia rufa. A field study was carried on from August, 1965, through August, 1966, in the coast mountains of Benton County, Oregon, and consisted of measuring the annual temperature cycle...
Studies of geographic variation are central to understanding ecological and evolutionary processes. Geographic variation in the shell of the black abalone (Halioth cracherodii), a marine intertidal gastropod, involves both
clinal and local variation along the eastern Pacific coast in the number and size of tremata (=respiratory pores) on the shell....
Contemporary environmental change encompasses massive biodiversity loss and
increasing numbers of emerging diseases worldwide. As part of a global biodiversity
crisis, amphibians are disappearing at unprecedented rates. Batrachochytrium
dendrobatidis is an emerging infectious pathogen prominently associated with many
declines. Chapter 1 reviews the past decade of research on this system...
Habitat selection behavior was investigated as a proximate mechanism influencing spatial distributions of three species of anuran larvae. Rana cascadae, Hyla regilla, and Bufo boreas overlap in distribution in lakes and ponds of the Cascade Mts. and were chosen to provide a comparative basis for analyzing habitat selection behavior. Major...
There is little, if any, direct fossil evidence of the cardiovascular, respiratory, reproductive or digestive biology of dinosaurs. However, a variety of data can be used to draw reasonable inferences about the physiology of the carnivorous theropod dinosaurs (Archosauria: Theropoda). Extant archosaurs, birds and crocodilians, possess regionally differentiated, vascularized and...
A water bird census was taken at three points on Upper Klamath Lake at weekly intervals extending over a period from September 9, 1936 to May 29, 1937. A total of 24,319 birds was recorded in field records and included thirty-two species. Totals of birds by weekly field trips show...
A fluke found in the intestine of the red-legged frog, Rana
aurora Baird and Girard, was identified as Brachycoelium lynchi
Ingles 1936. The life cycle of this fluke was studied and found to
be of the lecithodendriid type rather than brachycoeliid. Instead
of having one intermediate host, as is the...
The Mount Jefferson Primitive Area is one of three High Cascade wilderness areas in Oregon. It is second in size among these, covers approximately 136 square miles, and with the addition of a large roadless area in Warm Springs Indian Reservation represents the only one of these areas in Oregon...
This thesis describes studies that investigated 1)
the effects of courtship on the neuroendocrine system of
female rough-skinned newts, Taricha granulosa, and 2)
whether the observed courtship-induced neuroendocrine
changes affected female sexual receptivity.
Sexual behaviors of female T. granulosa changed
dramatically during courtship. Initially, females
exhibited unreceptive behaviors to a...
In this dissertation I study evolutionary patterns at genes encoding antimicrobial peptides (AMPs) in frogs. AMPs are short, amphipathic, cationic, secreted proteins that kill bacteria and other pathogens through a non-catalytic mechanism that involves
binding to and disrupting the microbial cell membrane. In many animal taxa, positive selection is much...
A 15-month field study was made on the reproductive cycles of
the prosobranch gastropods Nucella lamellosa, Nucella emarginata,
Searlesia dira and Amphissa columbiana on the Oregon coast.
Amphissa columbiaria and Searlesia dira were collected from Boiler
Bay, Nucella emarginata from Seal Rock and Nucella lamellosa
from inside Yaquina Bay.
All...
Chemoreception is one of the dominant sensory modalities for many species of salamanders (reviewed in Chapter 2). At least seven of the ten currently recognized salamander families are known to respond to some sort of chemical cue. These responses are as varied as delaying hatching, seeking refuge, or initiating aggressive...
An investigation was undertaken to determine if respiratory
changes might occur in conjunction with migrations of the rough-skinned
newt, Taricha granulosa (Skilton) in and out of ponds in the
Willamette Valley. A field study was carried on from December
1964 through October 1965 to investigate certain physical and
chemical parameters...
Ultraviolet-B radiation (UV-B) has been suggested as a factor contributing to global amphibian population declines. While ambient UV-B levels damage the eggs and embryos of some amphibian species, few studies have addressed how UV-B affects other life history stages or sublethal responses. My dissertation focuses on (1) investigations of sublethal...
Many species have complex life cycles in which a dispersive larval stage is
followed by a relatively sedentary adult stage. For such species, reproductive output
is often high and large variation in survivorship throughout early life-history phases
(eggs and larvae) can lead to dramatic fluctuations in recruitment which may in...
Many marine fish populations are severely declining due to over-fishing, loss of both juvenile and adult habitats, and accelerating environmental degradation. Fisheries management and the implementation of marine protected areas (MPAs) and other conservation tools are currently hindered by large gaps in knowledge about larval dispersal and its subsequent effects...
The respiratory and metabolic biology of dinosaurs is poorly, if at all, reflected in the fossil record. By comparing anatomical features of modern taxa that are functionally linked to specific biology with the remains of theropod dinosaurs (Archosauria: Theropoda) and early birds, we may reasonably infer the physiology of long...
Ecosystems are facing increasing threats from human related activities, such as overfishing, pollution, habitat destruction, species invasions, and diseases, among others. While oceanic islands provide natural laboratories to understand ecological and evolutionary process, they are also particularly vulnerable to these impacts, given their usual isolation from the mainland and the...